ORNL-4830.txt

CFNTRAL RESEARCH LIRRARYG L\ on0

i

cj.

3 445k 0515Lke 5

THE ORNL AUTOMATED ORBITAL PIPE
WELDING SYSTEMS

Peter P. Holz

CUMENT COLLECTION

LIBRARV LOAN COPy

JO NOT TRANSFER O NOTHER PERSO}

OAK RIDGE NATIONAL LABORATORY

OPERATED BY UNION CARBIDE CORPORATION  FOR THE U.S. ATOMIC ENERGY COMMISSION

Printed in the United States of America. Available from
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road, Springfield, Virginia 22151
Price: Printed Copy $3.00; Microfiche $0.95

This report was prepared as an account of work sponsored by the United
States Government. Neither the United States nor the United States Atomic
Energy Commission, nor any of their employees, nor any of their contractors,
subcontractors, or their employees, makes any warranty, express or implied, or
assumes any legal liability or responsibility for the accuracy, completeness or
usefulness of any information, apparatus, product or process disclosed, or
represents that its use would not infringe privately owned rights,

ORNL-4830
UC-80 Reactor Technology

Contract W-7405-eng-26

REACTOR DIVISION

THE ORNL AUTOMATED ORBITAL PIPE WELDING SYSTEMS

Peter P. Holz

JANUARY 1973

OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37830
operated by
UNION CARBIDE CORPORATION
for the
U.S. ATOMIC ENERGY COMMISSION

DRI

3 445k 05151ke 5

|
|
111

|
Contents
) ACKNOWLEDGMENTS ... ... v
N ABSTRACT vii
1. INTRODUCTION AND SUMMARY . .. .. e 1
2. FUNCTIONAL DESCRIPTION .. e e 3
3. SYSTEM COMPONENT S . . 6
7 1 6
Welding Head . ... .. .. e 9
Power SUPDly .. 15
Pendant, Sensor, and Cables . ... ... .. . . . . . 18
Recorder . .o 18
4. ELECTRICAL AND CONTROL SYSTEM . ... .. 21
Programmer-Controller .. .. ... .. . 21
Basic Subdivisions of Programmer Circuitry ... ... ... . . . . 21
. Control Modes . . .. ... 22
’ Current Control . .o e 22
Pulse CUrtent . L. o e 23
’ Torch Oscillator . . ... 23
Tool Speed Control . . ... . 23
Wire Feed Control and AVC .. . 24
Arc Length Control (ALC) ... o 24
Stubber CirCUit . . ... . 25
Gas and Water Interlocks . . ... .. 25
Power Supplies and Power Buses . . . ... ... 25
5. WELDING STUDIES, WELD JOINT DEVELOPMENT. AND WELDING SCHEDULE . ................ 26
6. WELDING SYSTEM OPERATIONS . . .. e e e e 30
Preweld Operations .. ... . e 30
Guidelines for Tacking Consumable Weld Inserts ... ... ... . .. . .. . . i 31
Welding Techniques . . . . .. .o 32
Cleaning of Weld Beads . . .. ... . 32
-~ D eCtS .. 32
RepaiTS o 32
- Weld Schedule Data Sheets . . ... ... 32

1v

Operational Procedure (ORNL Equipment) Checkoff List . .......... ... ... .. ... o . 32
Guidelines for the Welder-Operator’s Visual Observation During Automated Welding . .. .......... . ... .. 36
7. WELDING SYSTEM MAINTENANCE . . . ... 37
8. OPERATOR TRAINING .., 37
9. CUTTING PREREQUISITES — PIPE CUT AND BEVEL PREPARATION DEVELOPMENT ... ....... .. 38
10. COMMERCIAL US. EQUIPMENT SOURCES FOR ORBITAL WELDING SYSTEMS . ................ 39
Appendix A. ORNL WELDING PROGRAMMER-CONTROLLER, CONTROLS AND FUNCTIONS ......... 41
Appendix B. RECOMMENDED FORMAT FOR ESTABLISHING A WELDING PROCEDURE
FORAUTOMATIC WELDING .. ... ... 45

Acknowledgments

I wish to thank the Union Carbide Nuclear Division
Purchasing Department and associates in various fields
of endeavor at the Oak Ridge National Laboratory for
their important contributions to the Automated Pipe
Welding Program. Their combined effort contributed to
the successful design, fabrication, development, and
performance of our systems. Special thanks go to W. O.
Harms, Director’s Division, H. A. Nelms, General
Engineering Division; W. A. Bird, C. C. Courtney, W. R.
Miller, R. L. Moore, and R. W. Tucker, Instrumentation
and Controls Division; G. M. Goodwin, T. R. Housley,
G. C. Nelson, P. Patriarca, R. G. Shooster, G. M.
Slaughter, and J. R. Weir, Jr., Metals and Ceramics
Division; D. R. Frizzell and V. T. Houchin, Plant and
Equipment Division; and S. R. Ashton, R. Blumberg, J.
O. Brown, J. R. Shugart, C. M. Smith, Jr., I. Spiewak,

W. E. Thompson, and T. K. Walters, Reactor Division. |
am particularly indebted to Bird, Goodwin, Houchin,
Housley, Miller, Moore, Nelson, Slaughter, and Smith
for their leadership, technical expertise,and teamwork,
and to Brown, Thompson, and Moore for their assist-
ance in the preparation of the report. I would also like
to give special thanks to Myrtleen R. Sheldon for her
painstaking efforts in final editing of the report.

Special thanks are also due D. C. King, Westinghouse-
Hanford; R. L. Carter, W. J. Martin, and A. C. Rediske,
Bechtel-Hanford; and L. Birch, T. R. Brown, P. R. Kirk,
J. Morgan, and J. E. Wilkins, TVA — Browns Ferry, for
their cooperation in maintenance of the equipment,
field equipment improvements, and feedback of valu-
able operational information and data.

vii

Abstract

The Oak Ridge National Laboratory has developed
and successfully testea an improved automated welding
system that has demonstrated reliable performance in
making nuclear-quality welds on pipes from 3 to 16 in.
in outside diameter. This equipment also shows promise
for remote control of reactor maintenance operations
of pipe cutting, beveling, and welding in high-radiation
zones where personnel cannot enter.

The equipment was adapted from an orbiting auto-
mated pipe welding system originally designed for the
Air Force by the North American Rockwell Corpora-
tion. Automation of the equipment permits complete
welds to be made from preset programs fed into an
electronic programmer-controller. ORNL developed im-
proved controls that can sense changes from feedback
signals and automatically adjust for pipe ovality and for
irregularities in the geometry and wall thickness at the
prepared edges of the pipe joint. The automated
controls also compensate for the difference between
welding upward or downward in the 5G (pipe hori-
zontal) position, as the carriage moves a gas tungsten-
arc torch continuously around the pipe.

The equipment consists of an orbital horseshoe-
shaped carriage that clamps onto a pipe and propels the
welding apparatus around the circumference of a pipe
in conjunction with an automatic welding programmer-

controller that constantly maintains all conditions
necessary to produce code-quality welds. The auto-
mated system has demonstrated that it can consistently
produce high-quality welds, which also makes it attrac-
tive for direct welding applications in the construction
of nuclear plants. To this end, development efforts were
expanded to include pipe welding with the joint
geometries most commonly used in the construction of
stainless steel and carbon steel piping systems. Proce-
dures were developed and shown to give good results
for construction welding of pipe joints fitted with a
consumable weld insert ring placed in the gap of the
open pipe butt joint.

ORNL automated welding systems have been utilized
at the Browns Ferry Nuclear Power Plant, being built
by the Tennessee Valley Authority, and the Fast-Flux
Test Facility, being built by Bechtel for Westinghouse
at Hanford. At both installations the equipment has
reliably produced nuclear-quality welds that meet ASME
Boiler and Pressure Vessel Code, Section III, Nuclear
Vessels, Section 1X, Welding Qualifications, and appli-
cable RDT standards. An experienced welder can learn
to use the equipment in a few days and produce high-
quality welds with practically zero defects about four
times as fast as in manual welding.

1. Introduction and Summary

In 1968 ORNL reviewed the methods and equipment
used to make remote repairs in the high-radiation zones
of several nuclear reactor systems. The study revealed
that each repair had been handled as a special case with
equipment, controls, and techniques devised on the spot
to meet specific needs. No cutting equipment for
remotely removing failed system components or sec-
tions of pipe and no welding equipment for remotely
installing replacement components were commercially
available. Therefore, ORNL engineers sought available
equipment that could be further developed to provide
for remotely controlled operations with consistently
reliable performance. An automated pipe-cutting and
welding system developed for the U.S. Air Force by
North American Rockwell Corporation showed promise
for such development.

With the cooperation of the Air Force, ORNL
obtained some of their prototype equipment and
control units for testing and evaluation. After extensive
testing of the equipment and numerous design im-
provements and change modifications, a completely
automated combination cutting and welding system was
fabricated for use in ORNL’s remote cut-and-weld
maintenance feasibility studies and for the development
of general-purpose automated pipe welding systems.
After additional refinements to welding control circuits,
the modified system demonstrated such good, con-
sistent performance for indirect work that it gave rise to
another objective (which became the goal of the work,
supported by the Liquid-Metal Breeder Program of the
US. Atomic Energy Commission) — a completely
automated welder for direct application in reactor
construction.

The ORNL automated welding system utilizes an
electronic programmer-controller to operate a conven-

tional arc welding power supply and to direct and
regulate welding and cutting attachments mounted on a
compact carriage that drives the working heads around
the pipe circumference. A supplemental hand-operated
pendant control unit provides alternate manual Start
and Stop push buttons. In automatic welding, the
appropriate welding procedure for the type of metal
being joined is dialed into the programmer-controller
and the Start button is pushed: the machine takes over.
produces the weld, and then shuts itself off. The
welder-operator can observe the weld as it is being made
and, when necessary, make minor adjustments to
improve torch tracking or the weld joint sidewall tie-in.

By proper selection and positioning of controls,
automated pipe welding can be programmed to execute
welding equal to that of the best manual welders. In
order for the automated equipment to make perfect
welds consistently, fine tuning of the automated con-
trols is necessary. Therefore it is highly recommended
that the equipment be operated only by skilled welder-
operators who are trained especially for automation and
who have passed stringent tests with automated equip-
ment.

An experienced welder can learn to use the auto-
mated equipment in a few days and thereafter produce
welds with practically zero defects with about four
times the speed usually achieved in manual Heliarc
welding. The time required for the metal around the
welded joint to cool to acceptable low temperatures
between welding passes usually governs weld produc-
tion output. In automated welding, additional time can
be saved because adaptive controls permit high-quality
welds to be made without such careful, exacting joint
preparation and alignment as otherwise would be
required. Manual welding at the construction site must
be performed by specially qualified welders, which
usually means that the construction contractor must
conduct extensive training programs. In addition, nu-
clear-quality welding by hand is slow and is plagued by
a high percentage of rejects.

Prototype systems of the modified design developed
by ORNL were fabricated by industrial vendors and
then were assembled and proof tested by the Labora-
tory. We confirmed that the automated equipment with
feedback circuits to adjust the controls during progress
of the work can properly compensate for pipe ovality
and for irregularity in the geometry and in the wall
thickness at the prepared edges of the pipe joint. Tests
showed that the automated equipment would accu-
rately follow the programmed instructions and maintain
the necessary conditions for high-quality welds. We
evaluated several consumable weld insert ring shapes to
be fitted into the gap of an open-butt joint to allow
maximum tolerance for irregularities in the matching of
pipe ends to be welded, and developed construction
welding procedures for gas tungsten-arc welding with Y
cross-section inserts and with Kellogg-type rectangular
inserts. The equipment was shown to be capable of
making continuous butt welds around the entire perim-
eter of the pipe that consistently met the requirements
of the ASME Boiler and Pressure Vessel Code, Sections
[l and X, and applicable RDT standards. The contin-
uous perimeter weld offers a special advantage in that
the errors and flaws that often result from welding
starts and stops are eliminated.

ORNL built the prototype automated equipment to
demonstrate the feasibility of using this system for
nuclear-quality welds and also to prove the practicality
of automated welding systems in actual daily use. We
delivered automated welding systems to Westinghouse-
Hanford, where Bechtel Corporation personnel quali-
fied the equipment for welding Fast-Flux Test Facility
Project stainless steel pipes. Another automated welding
system was delivered to the Tennessee Valley Authority
at their Browns Ferry Nuclear Plant and is now in use
primarily for welding carbon steel pipe in sizes up
through 14 in. in diameter.

The metallurgical tests and welding research which
established the optimum conditions and procedures for
welding the pipe materials of nuclear systems were a
vital part of the automated welding development
program. The metallurgical and welding research deter-
mined the optimum values for all the variables that
must be controlled to obtain good welds and estab-
lished detailed procedures to be followed in welding
different materials. The automated system was required
to maintain these conditions and follow the procedurcs.

In particular, the electronic instrumentation and con-
trols had to be sufficiently rugged to stand up under
field construction use and still maintain accuracy in
automatically following the predetermined welding
procedure and controlling the important parameters at
the optimum values. One of the key contributions
ORNL made to the field of automated welding was
bringing together and coordinating the efforts of ORNL
experts in these different fields to produce a complete,
automated welding package ready for use in the field.
ORNL also prepared a detailed manual covering proce-
dures for operation and maintenance of the automated
system and provided training for contractor personnel in
the use of the earliest prototypes of the automated
welding equipment.

The automated pipe welding equipment has demon-
strated that it can produce highest-quality welds con-
sistently at reasonable cost and in reduced time
schedules, if the controls are properly set. The optimum
welding parameters will vary with the pipe material,
diameter, wall thickness. end preparation, and tempera-
ture. It is necessary to select and control optimum
values for the weld travel speed, arc current and mode,
arc length, electrode shape and type, and flow rate of
inert gas. Cleanliness and temperature regulation be-
tween welding passes are also important factors in
achieving high-quality welds.

Our work produced operational automated pipe
welding systems for butt welding pipes from 3 to 16 in.
in diameter. However, we encountered difficulties in
trying to apply the system carriage schemes to pipes
larger than 16 in. and were directed by the AEC to
terminate work with large carriages. For large pipe sizes,
we investigated the adaptability of recently developed
commercial automated welding machine systems which
employ a separate clamp-on track from which to orbit
their weld heads about the circumference of the pipe.
With commercial equipment, we performed successful
tests on a 28-in. pipe weld.

Our development work and field tests with automated
pipe welding equipment have stimulated considerable
interest in orbital pipe welding. This interest, however,
seemed to develop most rapidly after our Industrial
Cooperation Conference on Automated Pipe Welding in
February 1971. More than 100 representatives of
industry and utilities attended the conference, and since
that time, several companies have seriously entered the
automated pipe welding field. At the conference,
ORNL revealed a number of unique self-adaptive
controt techniques to ensure repeatable programmed
welding. Exacting control means have since been

patented! and assigned to the Government to make
them available to all manufacturers.

With industrial competition, automated welding
equipment is becoming more advanced and more
economical. For example, in March and April of 1972,
ORNL proof tested an automated commercial system
costing under $40,000 and used it to weld sample joints
of 6-, 10-, 16-, and 28-in. stainless steel pipes. The welds
made with this commercial equipment all met the
requirements of applicable ASME codes and RDT
standards.

This report describes the completed development
program for the ORNL automated orbital pipe welding
system. We have chosen not to report day-to-day
operations and progress but rather have attempted to

t. C. M. Smith, Jr., and W. R. Miller, Self-Adaptive Welding
Torch Controller, U.S. Patent 3,646,309, Feb. 29, 1972, As-
signee — The United States of America as represented by the
U.S. Atomic Energy Commission. (Filed Jan. 26, 1971.)

present the highlights and results of the work. The
report discusses the functional and mechanical aspects
of the ORNL orbital machinery, the electrical and
control systems, the study of weld joint preparation
and optimum geometry, the techniques of the welding
system, and the operator training requirements. The
section on the electrical and control system is relatively
detailed, since, in principle, the operation of any
automated welding system requires the same general
approach to sensing, signal feedback, and automated
response. The description of our control system, there-
fore, is generally applicable to commercial equipment as
well, although specific control means may vary among
manufacturers. The report also gives limited informa-
tion on the commercial automated orbital welding
systems manufactured in the United States as of July
1972.

Appended to the report are detailed sections to cover
all specific controls and functions of the ORNL welding
programmer-controller and a recommended format for
establishing a welding procedure.

2. Functional Description

The ORNL automated welding system consists of a
conventional welding power supply, an electronic con-
trol console called the programmer-controller, and an
orbiting carriage that propels interchangeable welding
or cutting heads around the circumference of the pipe.
All equipment is lightweight, portable, and compact
and can be set up for pipe welding in a few minutes. At
present, there are different orbiting carriages for the
following ranges of pipe (outside) diameters: 3 to 6, 6
to 9, 9 to 12, and 12 to 16 in. (ref. 2). [n these
carriages, starting with the 6- to 9-in. carriage, the
subassemblies and parts are interchangeable, as are the
welding heads; this helps to minimize the spare parts
inventory. Figure 1 illustrates a typical automated

2. Operational models are available for all size ranges except
the 9 to 12 in.

welding system installation, and Fig. 2 shows an
in-process weld on a 12-in. pipe.

The primary objectives of the automatic pipe welding
program are to provide systems producing only highest-
quality welds at low cost and at high welding speeds.
The control and thereby the reproducibility of the
gas tungsten-arc pipe welding operation depends pri-
marily on the proper selections of welding criteria and
weld programming input.

The welding criteria are contingent on the following
prime factors:

1. pipe diameter,
2. pipe wall thickness,

3. type of pipe joint (joint end preparation with or
without insert rings),

4. type of pipe material,

5. temperature of pipe material.

PHOTO Y 106815

fiiPROGRAMMER AR'JDh
8 — RECORDER

T16-300 300
NN w e

‘“c WtLoen

WELD HEAD f
IN CARRIAGE {8

WELDING
MACHINE

Fig. 1. ORNL automated welding system installation prior to carriage placement on 12- to 16-in. pipe.

PHOTO 98593

T

n G

=

)
f
-
) o
o
(=
0
>
-
o
Rl
<

Fig. 2. ORNL welding system in-process 12-in. pipe weld.

The following welding parameters must be pre-
determined and programmed into the automated con-
trols:

[am—

travel speed,

weld current,

arc length (arc voltage control),

diameter and shape of tungsten electrode,

. type and quantity of inert gas,

weld up and down slope,

weld start, overlap, and weld tail-off distance,
weld filler wire and rate of deposit,

pulse current and pulse sequence mode (if used),

© X X N, kW

[Rm—

oscillation — amplitude and frequency (if used),

f—
[S—

. interpass cleanliness and temperature regulation.

The input to the weld programmer provides for
proper “in process” control and sequencing of all the

variables that influence the weld. The most critical
variables, from the standpoint of weld reproducibility,
are those that govern energy input to the weld, namely,
primary current, voltage, travel speeds, and temperature
of the material being welded. We chose to maintain
uniform travel speed. However, the equipment has
provisions for controlling the other variables except
that interpass temperature is controlled by the cooling
time allowed between passes. Wire deposit, when used,
is automatically controlled by the feed rate. The
programmer must also be adapted to exercise automatic
control of the output of a commercial ac-dc rectifier-
type saturable reactor power supply. A Lincoln TIG
300/300 power supply was used in our system.

Some of our systems are provided with multichannel
analog recorders to monitor and record the main
variables in the weld pass. We use a Gulton model
TR-888 recorder. The recorder chart serves as an aid to
weld inspection.

3. System Components

CARRIAGE

The carriage provides a rigid, stable platform on
which the machining head or the welding head can be
mounted, indexed, and operated. Figures 3 and 4 show
the carriage, its components, and subassemblies. The
carriage supplies the drive mechanism to rotate the
platform around the pipe circumference at preset,
reproducible, governor-controlled speeds. The carriage
also has controls to maintain the platform surface at a
nearly constant distance from the pipe surface so that
the arc length controls will perform properly. The
platform maintains its lateral position with respect to
the pipe joint while rotating about the pipe. The
carriage has geared actuator arm assemblies that clamp
securely to the pipe, and its drive rollers are loaded by
special torsion bars to maintain controlled clamping
pressure on the rollers and to compensate for pipe
ovality within allowable commercial pipe specification
limits. The clearance required for operation of the

carriage is 4 ', in. on the pipe radius and 10 %, in.
longitudinally. [Note: The 4 ' -in. radial clearance is
adequate only for cutting and for welding without
automatic arc length controls (electrode-to-work gap
controls). A carriage/weld-head combination with auto-
matic arc length controls requires 5 ¥ in. radial
clearance.]

The basic carriage structure consists of two side pieces
that provide the platform for the head inserts, two end
supports, and the dual arm and idler subassemblies. The
end supports contain the electrical drive and control
connections and switches for the carriage and for the
insert heads; one end support contains the clamping
device, which uses worm gears to position the idler
rollers through slider linkages. The carriage is made to
rotate by a direct drive system from motors mounted at
the two hinge points of the actuating arms within the
rollers. [Note: An exception is the 3- to 6-in. carriage,
where the motors are not concentric with the rollers

)

PREASSEMBLY, Parts Inventory (12 — 16 in.)

Side Piece

Arm Subassembly

End Supports

FIRST SUBASSEMBLY

Idler

Torque Arm
Torsion Arm Support

Driver

SECOND SUBASSEMBLY

Fig. 3. Carriage assembly — preassembly, first subassembly, and second subassembly.

PHOTO 3432-72

PHOTO 3433-72

Travel Push Buttons

THIRD SUBASSEMBLY

Standoffs to Ride Pipe Collar
for 2G Position Pipe Welding

FINAL ASSEMBLY, Elevation View

Stable Platform

View Port

Clamping Device Actuator

Tachmotor Drive

FINAL ASSEMBLY, Plan View

Fig. 4. Carriage assembly — third subassembly and final.
but are installed in canisters at the hinge points of the
arms. Drive power is transmitted to the rollers through
identical gear trains in the arms. The 3- to 6-in. direct
drive system is designed without torsion bars and
torque tubes and therefore offers less tool flexibility
during clamping and rotation. This simplified drive
design cannot be used for larger pipe sizes, however,
because the greater allowable out-of-round tolerances
require more flexibility in the clamping and drive
mechanisms.] Vulcanized high-temperature, abrasion-
resistant Viton rubber coatings on the rollers provide
traction for carriage propulsion. The carriage speed is
adjustable at the programmer.

WELDING HEAD

The welding head has a motorized vertical slide and a
manually adjustable horizontal slide that can be set to
locate the torch electrode accurately with respect to the
cut and beveled edges of a weld joint. Filler wire can be

fed automatically at a preselected rate by means of a
motorized wire feed mechanism. A standard 4-in.-diam.,
2 '5-1b wire spool is used to store enough wire for
multiple weld filler passes. The torch and the wire
feeder are mounted on the vertical slide, and the wire
spool is mounted on the horizontal slide. The welding
head includes inert-gas hose passages to the torch cup
plus power and cooling water lines to the torch head. A
motorized cam drive supported by the vertical slide
oscillates the torch electrode across the weld seam. The
head also contains integral switches for testing the
operation of the wire feed jog (feed and retract), the
oscillator, and the inert-gas flow controls.

The welding head is shown in Figs. 5 to 8. Figure Sisa
top view of the head with the lid in the closed (welding)
position, showing the power and control cable entry to
the head, and Fig. 6 is a side elevation view showing the
hinged lid in the open position. A front elevation view
and a schematic illustration with the lid open are shown
in Figs. 7 and 8 respectively.

PHOTO Y 106816

Fig. 5. Top view of welding head with lid closed (welding position).

10

PHOTO Y106812

Fig. 6. Side elevation view of welding head.

U | PHOTO Y106811

Fig. 7. Front elevation view of welding head mounted in carriage.

ORNL-DWG 72-.12235

HAYDEN VERTICAL DRIVE MOTOR (ALC)

LOCKING NUT — ADAPTER
BALL NUT COUPLING Cf
COMBINATION

3 VERTICAL BALL SCREW
GUIDES {1 PINNED)

HORIZONTAL ADJUSTMENT
VERTICAL SLIDE AND KNOB AND BEVEL GEAR
WIRE FEED POSITION BLOCK
VERTICAL ADJUSTMENT
OSCILLATOR ADJUSTMENT

MECHANISM AND MOTOR

CRANK ARM WITH

TAPER PIN HORIZONTAL ADJUSTMENT LEAD
SCREW WITH BEVEL GEAR
TORCH -
WIRE FEED

FEED MOTOR
.

PUSH BUTTONS AND
ELECTRICAL CONNECTORS

FILLER WIRE \
ON SPOOL

CCNTROL CONNECTOR
(TO MATE ON CARRIAGE)

Fig. 8. Schematic arrangement of welding head. Front elevation, lid off.

11
Horizontal and Vertical Slide Assemblies

Horizontal torch position is adjusted by the hori-
zontal slide, which is actuated through a bevel gear
linkage from a manual positioning knob on the lid top.
The horizontal slide supports all the internal mecha-
nisms of the weld head as well as the filler wire spool.
Two horizontal guide shafts anchored to the weld head
lid maintain the slide in alignment with the head. Three
vertical guide rods and a (vertical) ball-screw drive
couple the vertical slide block and the horizontal slide
at right angles. An arc-voltage-controlled Hayden drive
motor (ALC motor) is used to drive the vertical slide
for maintaining the predetermined torch electrode
distance from the weld joint. [Components attached to
the vertical slide assembly are covered in subsequent
sections.| It is important to note that the entire vertical
block assembly is integral with the horizontal slide and
that, therefore, all torch components move in unison.
The relationship of the horizontal to the vertical slide is
constant in the horizontal plane and varies only in the
vertical plane when actuated by the ALC motor,

The vertical slide block houses the oscillator motor
subassembly and supports the torch block and its
components, the oscillator amplitude adjustment mech-

12

anism, the wire feed positioner bracket block, and the
ball nut of the vertical ball-screw drive. Details are
shown in Fig. 9. The vertical slide block is of aluminum
for strength, and Delrin plastics and Teflon liners are
used for sleeving and attachment parts. Plastics offer
radio-frequency isolation and protection. The block
contains two tapped holes for the wire feeder sub-
assembly attachment bolts.

The oscillator assembly consists of a 24-V dc drive
motor, an adjustable cam, and a bearing-supported
crank arm that attaches to and drives (rocks) the torch
block electrode holder assembly via a tapered pin. The
cam is adjustable for total electrode tip oscillation from
zero to % in. Adjustment is made by turning the
knurled sleeve with respect to the knurled and notched
ring. A spring locks the dial-set oscillation amplitude in
place. The oscillator motor speed can be adjusted to
provide oscillation frequencies of 50 to 360 cpm, as
discussed in detail in Section 4. All welding parameter
lists should include information on the required input
settings for proper oscillation amplitude and frequency
for each weld pass.

The wire feeder bracket block couples with one end
of a plastic wire feeder guide tube through which wire is

PHOTO 3434-72

Torch Components

Torch Block
Torch Block Isolator
Oscillator Crankarm with Taper Pin

VERTICAL TORCH BLOCK — Component Parts

Torch Block Rod Isolator Bushing

Oscillator Motor and Wire Feed Positioning Bracket Block
Oscillator Amplitude Adjustment Mechanism

Vertical Slide Block

Ball Nut Retainer

Wire Feed Positioner Bracket Block

Oscillator Amplitude Adjustment Mechanism

Bearing for Oscillator Crankarm Drive

OSCILLATOR — Subassembly

Oscillator Motar

Fig. 9. Vertical torch biock component details.

introduced to the feeder mechanism. Threaded ferrules
are used to anchor the ends of the guide tube.

A ball nut anchored and nearly centered within the
vertical block allows the ball-screw drive to raise and
lower the block. The screw directly couples to the
motor shaft to raise and lower the ball nut. Three guide
rods, parallel and adjacent to the ball screw, serve to
align and guide the movement of the vertical block.

Wire Feed Mechanism

The wire feed mechanism utilizes the friction on a
wire compressed between two rotating disks to force
the wire to contact with teeth of a ratchet wheel. Wire

13

is advanced or retracted as the wheel rotates, and the
friction force can be varied by the amount of pressure
applied at the exterior cap to compress the disk and the
rotor.

The wire feed system consists of a wire spool
containing a preselected type and size of wire, the guide
tube, the feed mechanism with its 24-V tachometer-
gear-head motor, the ferrule, and the exit nozzle. A
manual adjustment screw to the ferrule in the mecha-
nism housing is used to direct the exit nozzle so as to
properly locate weld filler wire with respect to the weld
puddle.

Figures 10 and 11 show the wire feeder and its main
components. The wire feeder motor shaft rotates the

PHOTO 343572

Fig. 10. Wire feeder — parts of subassembly.

14

ORNL-DWG 72-12236

PLASTIC WIRE

ROTOR AND INSERT GUIDE

BRACKET AND RACE
IN BACK OF ROTOR

BROACHED COUPLING

COVER
MOUNT BRACKET

HOUSING

SPLIT FERRULE

BEARING / EXIT NOZZLE

RACE

~

COVERIN HOUSING

1
OUTLINE WIRE TROUGH

WeLd

WIREL [/ \\ll,f;%——"
Sy BRACKET
NN\

cap RATCHET \\qq—flACE
INSERT !
[0l
O
=4
(@]
@
B2 OFFSET 7™~ _;::fi;.___._q._MQTO35HAFT
f , x|,
o
gf P // om|O
Q e ot =
v o< g
BRACKET % N o
Q /.
~
RACE N QJ
\\\
BRACKET N
~— NN R J
4 /4 7 AY
v . A Y

7N\

WIRE FEEDER MECHANISM CROSS-SECTION

Fig. 11. Wire feeder schematic — parts and functional assembly.

15

rotor-ratchet insert combination. The cap and disk
force the wire against the ratchet teeth until sufficient
pressure is applied on the wire to pull it from the spool
and feed it through the guide tube into the weld
puddle. Thrust bearings are provided for both the disk
and the rotor. The wire is prevented from moving
toward the center of the rotor disk by a shoulder, and
movement of the wire toward the periphery of the disks
is prevented by the outer disk face being canted at 8° to
the rotor disk face. The mechanism is designed to
accommodate wire diameters from %, to ', in. and
feed rates up to 50 in./min,

Torch Head Assembly

The core of the torch head assembly is a copper block
that includes cooling water passages, the power lead,
and the inert-gas connection. A pivot post on the block
couples the torch to the oscillator mechanism. The
block also contains threaded holes for the attachment
of the torch assembly, which can be used with either a
long or a short torch body. The length of the torch
electrode beyond the end of the ceramic cup can be
adjusted by removing the torch body assembly from the
block, loosening the collet locking screw, repositioning
the tungsten electrode, and relocking the screw. Long
torch bodies are used for welding the root and first
fillers of extra-heavy pipe walls and short bodies for
standard or lightweight pipes. The torch assembly is
shown in Fig, 12.

POWER SUPPLY

Most commercially available welding power supply
units of the saturable reactor type are compatible with
our programmer control circuitry and can be employed
as power sources for the automated welding system. We
use a Lincoln model TIG 300/300 power supply, Fig.
13. with minor internal circuit modifications. Inductive
transicnt suppressors and a transistorized current con-
trol amplifier, Fig. 14, have been added to provide for
programmed operation control of the current in the
welder’s saturable reactor. The amplifier replaces the
welder’s magnetic amplifier, which is retained to permit
manual control welding as well. An external switch and
light are mounted on the side panel of the machine to
change from programmed to manual control. The light
is on for programmed operations and flashes on and off
during dc pulse welding.

The welding machine is also provided with controls to
stop or prevent operations at low gas and low cooling
water flows. These protective controls, Fig. 13, are set

ORNL-DWG 72—12237

I TORCH NUT
COLLET
LOCKING SCREW
[
Dlz/ COPPER SPACER
I
l

TORCH BODY

|
r—%_/(SHORT SHOWN)

) COLLET
D\/ (LINDE 13N23)
| TEFLON GASKET, OR
.~ (LINDE 53N85 GASKET)

GAS LENS
(LINDE 45Vv44}

CERAMIC CUP
’ (LINDE 53N6&1)

I
3/32—in. TUNGSTEN
T/ ELECTRODE
|

Fig. 12. Torch assembly.

16

l PHOTO 79539

Low Gas Cutout ™

o -
"J
‘s F

Low Water Cutout

[
N

Fig. 13. Lincoln weld power supply.
Fig. 14.

Power supply — modifications to weld machine circuits.

PHOTO 76558

to downslope welding operations when the flows of gas
or of cooling water fall below the minimum levels. The
controls are normally set for 12 ft® of gas per hour and
‘4 gpm of water, but can be set at other values if
desired. These protectors will also prevent programmed
weld startup if flow values are less than the preset rates.
A pilot lamp for each control lights up to signify
insufficient flows. The gas and water solenoid control
relays, built into the welding machines as standard
equipment, are bypassed for programmed welding
operations. Signal and control wiring is transferred to
replacement relays within the programmer.

Conventional H-20A (AIRCO) water-cooled power
and gas torch leads are used to connect the welding
power supply and the torch in the weld head. A ground
cable is employed to connect the work (pipe) and the
welding machine’s grounding lug.

PENDANT, SENSOR, AND CABLES

The pendant shown in Fig. 15 is a lightweight,
portable, remote-operation station designed to be held
in the weld operator’s hand. In programmed welding,
the pendant permits the operator to observe a weld
from a location close to the weld joint. The pendant
provides weld start, downslope, and instant stop control
and includes a set of push buttons to raise or lower the
torch for preweld torch travel limit checks and for
torch positioning. The buttons also serve to reposition
or adjust the torch-to-work spacing during a weld, and
the pendant’s rheostat dial is available to regulate
current in the manually controlled mode of weld
operation.

All pendant controls are housed within an anodized
aluminum box structure. Electrical leads enter through

PHOTO 3436—72

Fig. 15. Remote-control pendant.

the handle, and a flex grip cable cover is used to avoid
line crimping.

The equipment diagram in Fig. 16 shows all compo-
nents of the welding system, along with the connecting
cables and control leads.

The current sensor shown in Fig. 16 is a current
transformer—thyrector combination housed in an ano-
dized aluminum box. The transformer features a toroi-
dal coil encased in plastic, with a l-in.-diam center
opening passage for the weld cable. The coil, in turn,
connects to the programmer to supply a proportional
feedback signal for precise current control.

Programmer lines include a 120-V (5-A) ac power
supply, a signal control cable to the weld power supply,
a current sensor line, a remote-control pendant cable, a
signal cable to the recorder filter box and recorder, and
the control cable to the weld head. The weld head
control cable also includes a filtered arc voltage return
signal and combination cable shield and ground lines
back to the programmer.

The weld power source includes a 460-V (60-A) ac
supply as well as water and gas supplies. Output lines
include water-cooled power lines and gas lines to the
weld head torch. The welding machine must be
grounded by building equipment ground. A ground
cable, which passes through the current control sensor,
also connects the machine’s alternate terminal to the
work.

RECORDER

An analog recorder can be employed to provide direct
writing trace charting for the programmed welding
variables. The programmer includes a rear apron con-
nector for transmitting tool speed, wire feed rate, and
arc voltage data. A shunt at one of the weld power
source outlet terminals is used to provide a proportional
signal level current input to the recorder. Leads from
the connectors are routed through a noise filter box en
route to the recorder. The multichannel recorder
presently in use, Techni-Rite Electronics model TR-
888, modified to automatically start and stop with the
weld sequence. is shown in Fig. 17.

A highly useful record of amplitude and uniformity
of the variables is obtained by plotting the weld
functions. Deviations from the usual charted patterns
indicate irregularities and often offer clues to the source
of welding problems. Any plotted irregularities can also
be interpolated to precise pipe location for immediate
remedial action subject to the weld inspector’s confir-
mation.

ORNL-DWG 72—-12238

120 V (5 A) ac Supply

> ¢
........................................ g2
Ir 4;5'8& ¢ & \.OQ
! EOELE
<
: U)*?déé‘k%@
|
i é #—
| o il o
| o -—=
| Ll
I B
i m
o ——— —— %) L ___=
, =
s N
| T |
= 5
| 5 | RECORDE
| S TIGWELD POWER SOURCE :
> | d 2 £ l
: | E 3 . t
b "‘& © s jéc j
s \ £ S £ ! °o O
<t b 8::“__’,5) l I NS, @D |
o = - @ ] o O
e ” & = I |
> © I [
= w\\ ®_-—@ : . PENDANT |
M oA {O) y ———— — |
| ( ‘ |
N 1 J
] 00$’b
y, WELD HEAD
UPPER =——==C% T PIPE
TERMINAL — F— (Work Piece)
- - — —- -
| LOWER TERM!NAL—"’{
L/ }
CURRENT l' CARRIAGE
SENSCR |
= L
— EQUIPMENT 7
GROUND GROUND LINE o
(Ul hd
=\«

Fig. 16. Equipment hookup for ORNL weld system.

61

Fig. 17. Multichannel recorder.

PHOTO Y107673

0¢
\
|
\ 21
|

The TR-888 recorder has eight channels. In weld  In normal operation, however, it is enough to record
development work it is often helpful to chart additional the weld speed. wire feed rate, arc voltage, and arc
functions or to chart functions relative to one another. current.

4. Electrical and Control System

PROGRAMMER-CONTROLLER

The function of the programmer is to provide
automatic control of the variables that affect weld
quality. On the basis of parameters manually preset into
the programmer by means of dials and switches, the
programmer-controller responds to data automatically
fed back from sensors which monitor the actual welding
conditions. The settings of the dials and switches,
together with hardware circuitry, comprise a pro-
grammed memory that controls the weld parameters in
a predetermined manner, rate, and sequence. The
feedback information is compared with the preset
values in the programmer memory, and, if one of the
controlled parameters varies from the desired operating
range, corrective action is automatically initiated by the
control system,

The variables controlled are: (1) carriage (tool) speed;
(2) arc length, the distance (gap) between the electrode
and the weld puddle; (3) wire feed rate; (4) welding
current: (5) frequency of torch oscillation; and (6) gas
and water flow to torch.

Control parameters are preset in the programmer by
means of dials and switches located on the front panel,
the rear apron. and the pendant. Appendix A contains
illustrations and tabular listings of the controls and
their functions.

All the controlled variables except the torch oscilla-
tion are monitored by sensors that feed back signals to
the programmer.

The carriage (tool) speed and the wire feed rate are
monitored by tachometers which produce dc feedback
signals having amplitudes proportional to drive motor
speed and polarities corresponding to the direction of
motor rotation.

The welding current is monitored by a current sensor
which, together with its associated circuitry, produces a

unipolarity dc feedback signal proportional to the
current.

The arc voltage is monitored directly and fed back to
the controls of the torch position (ALC), wire feed
(AVC), and stub-out parameters. (“‘Stub-out™ occurs
when the torch touches the weld puddle.) This arc
signal also operates a voltage relay on which contacts
are used as protective interlocks in the control circuitry.

The gas and water flows to the torch are monitored
by flow switches. Contacts on these switches provide
interlocks which protect the welding equipment and
minimize damage to the weld and to the welded
component by preventing startup and/or initiating
shutdown in the event of loss of water or gas flow.

BASIC SUBDIVISIONS
OF PROGRAMMER CIRCUITRY

For purposes of discussion the programmer circuitry
may be considered to be composed of nine basic
subdivisions, as follows:

1. welding cuirent control circuits,
carriage (tool speed) control circuits,
wire feed (rate) control circuits (AVC),
arc length control circuits (ALC),
torch oscillation control circuits,

gas and water flow circuits,

program control circuits,

stub-out circuits,

P AN R

power supplies.

The program control circuits may be further subdivided
into sequence control and sequence timing circuits.
The first six of the above circuit subdivisions are
functionally independent and may, under certain condi-
tions, be operated and tested separately. However,
during programmed welding operations these circuits
respond to the demands of the program control circuits
and are functionally interrelated.

CONTROL MODES

There are two major modes of programmer operation
selectable by panel switch, Manual and Program.

Manual Mode

In this mode the carriage and wire feed may be
operated manually with push-button switches located
on the carriage at speed determined by the setting of
dials on the programmer panel; the weld current can be
manually controlled from the pendant; the torch can be
positioned by manually operated push-button switches
on the pendant; and water flow, gas flow, and torch
oscillation can be tested by operating push-button
switches on the weld head. This mode of operation is
used mainly for initial setup of the system for welding
but is also useful for calibration, maintenance, and
troubleshooting.

Program Mode

In program mode the system performs five preset,
timer-controlled, sequential operations: prepurge, up-
slope, weld, downslope, and postpurge. These opera-
tions are automatically controlled by a stepper relay
and associated relays, switches, and power buses.

Sequence control. The stepper relay has 51 active
positions and a home position. Positions 1 to 5 are used
for prepurge, 6 to 10 for upslope, 11 to 30 for weld, 31
to 39 for downslope, and 40 to 51 for postpurge.
Programmed operations are terminated in the 52d
(home) position.

There are 8 banks of contacts on the stepper relay.
Banks 1 and 2 determine the positions at which the
prepurge, upslope, weld, and downslope and postpurge
operations occur. Stepper banks 3 and 4 determine the
position at which the carriage starts and at which the
wire feed starts and stops. Stepper banks 5 and 6,
together with a Vernistat mounted on the front panel,
provide a means of setting the desired current profile in
34 discrete steps during the upslope, weld, and down-
slope operations. The Vernistat is composed of 34
sliders which are sequentially selected as the stepper
advances through positions 6 to 39 respectively. Each
slider is a potentiometer voltage divider that feeds a

22

reference voltage signal, via a stepper contact, to the
input of the current servo amplifiers. The reference
voltage represents O to 100% of “maximum welding
current.” An additional digital dial is provided on the
front panel to set the maximum welding current to any
value up to 200 A. Thus the maximum weld current
dial sets the upper voltage limit impressed across the
Vernistat voltage dividers. Stepper banks 5 and 6 are
used to operate lights to indicate the position of the
stepper switch throughout the program. A series of
lights above the Vernistat sliders indicates the progres-
sion of timing steps during upslope, weld, and down-
slope operations.

A programmed weld operation can be extended in
any “in-weld” position to permit extended time opera-
tions. A weld can be stopped at any time by pushing an
“Emergency” stop button for immediate stop action or
a “Downslope”™ button that causes the relay to fast-step
to the downslope position and continue programmed
shutdown operations from that point.

Sequence timing. All the timing functions in the
programmer are performed by a unijunction oscillator
and a telephone-type stepping relay combination. Step-
ping rates change throughout the total cycle as the
stepper advances from one sequence to another. This is
accomplished by utilizing several of the stepper contact
decks to change resistors in the unijunction oscillator
RC timing circuit. In this manner, prepurge, upslope,
weld, downslope, and postpurge can all be timed at
different step rates by the same piece of equipment.

CURRENT CONTROL

Welding current is controlled by a saturable reactor in
the welding power supply which responds to a reference
signal supplied by the Vernistat or by the current
control potentiometer on the pendant. The position of
a front panel **Current” switch determines which of
these controls is effective. When the switch is in the
“Manual” position, the reference signal is supplied by
the pendant control, and when the switch is in the
“Program”™ position, the signal is supplied by the
Vernistat. The reference signal is compared to a
feedback signal which is directly proportional to the
actual welding current. The difference in these signals is
obtained by diode bridge circuit arrangement and input
to the first stage of the current control servo amplifier.
The amplified difference obtained from the output of
the servo amplifier is coupled through an isolator
amplifier to a power amplifier. Here it is further
amplified and applied to the input of a driver amplifier
in the welder power supply which indirectly controls
the welding current by controlling the current in the
saturable reactor control winding. The net result of this
action is to maintain the welding current at a value
which is very nearly proportional to the reference signal
voltage supplied by the Vernistat or the pendant
control.

The feedback signal is supplied by a current sensor
through which the welding cable passes. This sensor has
two modes of operation (ac or dc) which are manually
selectable to correspond to the welding current se-
lected. In the dc mode the sensor functions as a
saturable-reactor-type dc transformer in which the
control current is the welding current; in the ac mode it
functions as a current transformer. In both modes the
output is an ac voltage which is rectified by a diode
bridge and filtered to obtain a smooth dc feedback
voltage.

The programmer’s servo isolator and the welder
power and driver amplifiers obtain their supply voltage
from the welder power supply. This voltage is a
rectified half wave (not a smooth dc), and the ground
system for these amplifiers is common to that of the
welder power supply. The servo isolator amplifier,
which consists of an optically coupled diode and
associated circuitry, provides the necessary isolation
between the welder and programmer grounding and
voltage systems.

The welder driver amplifier is basically an emitter
follower with a high current gain. It derives its signal
from an external source and has a faster response, but
otherwise performs the same function as the magnetic
amplifier supplied with the conventional power supply
and retained in the modified Lincoln welder power
supply. A current control switch, located on the side of
the welder power supply. selects either the driver
amplifier for remote (programmer) control or the
magnetic amplifier for local control.

PULSE CURRENT

The welding current pulser is incorporated in the
system to aid in control of the molten puddle for
pulsed and/or out-of-position welding. This unit modu-
lates the welding current serve amplifier at either 40 or
60 cpm and is switch selectable from the front panel.
Pulse amplitude is dialed directly by a potentiometer on
the front panel that is calibrated 0 to 100 A peak to
peak.

The dial light on the maximum current potentiometer
glows alternately bright and dim at the pulse rate
selected. Pulsing is accomplished by modulating the
voltage supplied by the maximum current potentiom-

23

eter to the Vernistat (or manual pendant control) with
a square-wave voltage generated by a relaxation oscil-
lator. The peak-to-peak amplitude potentiometer ad-
justs the amplitude of the modulation voltage.

TORCH OSCILLATOR

The voltage to the oscillator motor is varied by a
Darlington transistor pair to provide control of oscil-
lator speed. An illuminated potentiometer dial on the
front panel calibrated 50 to 360 cpm furnishes the
signal to the Darlington pair. Oscillator amplitude is
adjusted in the weld head by an eccentric cam
mechanism. There is no feedback in the oscillator
circuit. The oscillator is turned on and off by applying
and removing supply voltage to the oscillator amplifier.

TOOL SPEED CONTROL

The tool drive motor is a dc servo motor driven by a
servo amplifier through either the tool forward or tool
reverse relay. The speed of the motor (and the carriage)
is determined by the amplitude of the output voltage
from the servo amplifier. The direction of rotation is
determined by the polarity of the voltage across the
motor which is in tum determined by the position of
the tool reverse relay. The servo amplifier has two
modes of operation, with and without feedback con-
trol. A “Tool Servo” selector switch on the back apron
of the programmer designates the mode of operation.
When this switch is on, a dc voltage from a tachometer
that is an integral part of the drive motor is fed back to
the input of the servo-control amplifier, where it is
compared with the dc signal voltage from the program-
mer, The difference in these voltages is amplified and
fed to the motor. The net effect is to maintain the
speed of the motor constant at a value determined by
the input signal voltage that is dialed into the tool speed
potentiometer on the front pancl of the programmer.
Dialed values apply for forward travel selections;
maximum potentiometer output speed or fast reverse
will automatically occur with reverse tool travel de-
mands. The effect of feedback is to maintain motor
speed at a desired value regardless of changes in load,
line voltage, or amplifier gain. In this mode of operation
the feedback signal from the tachometer is also fed to a
meter on the programmer panel to indicate tool speed.

When the tool servo switch is in the off position, the
feedback circuit is disabled. and the tool speed meter is
switched to read the input signal instead of tachometer
feedback.

WIRE FEED CONTROL AND AVC

When the programmer is in the Manual mode, or
when the AVC wire switch on the programmer front
panel is off, the operation of the wire feed servo system
is similar to that of the tool drive servo system, except
that the speed of the tool drive motor is fixed at
maximum in the reverse direction.

When the programmer is in the Program mode and the
AVC wire switch is on, the input signal to the servo
amplifier (which determines the wire feed rate) is a
function of the arc voltage as well as of the setting of
the wire speed potentiometer and the setting of an arc
volts potentiometer on the programmer front panel.
The response is determined by comparing a set-point
signal proportional to the setting of the AVC volts
potentiometer with the arc voltage between the elec-
trode and the weld puddle. The difference in these
voltages is amplified by the AVC wire module and
applied to the input of the wire feed control amplifier
through contacts in the wire feed forward and reverse
relays and the tool servo switch. The arc voltage signal
is taken directly from the weld electrode and, after
filtering to attenuate RF (radio-frequency) voltage, is
passed through an interlock contact on the contactor
relay and fed to the input of the AVC wire module. The
AVC circuits are adjusted so that the wire feed rate is
one-half that set on the wire speed potentiometer when
the arc voltage is equal to that set on the arc volt
potentiometer. An increase in arc voltage produces a
proportional increase in the wire feed rate. Conversely,
a decrease in the arc voltage produces a decrease in the
wire feed rate. When the AVC wire switch is off, the
output of the AVC wire module is clamped at +30 V dc
and the wire feed rate is insensitive to variations in arc
voltage.

The purpose of this cascade control arrangement is to
regulate the wire feed rate in such a manner as to
maintain the arc voltage as nearly constant as possible
under conditions of varying spacing between the elec-
trode and the weld resulting from pipe eccentricity,
irregularities on the surface of previous passes, and flow
of the weld puddle toward or away from the electrode
due to gravitational or other forces. For example, if,
due to gravity forces, the weld puddle moves toward
the electrode, the arc length and arc voltage decrease. In
general, over the ranges of interest, the arc voltage is
directly proportional to the arc length and is relatively
insensitive to arc current. The AVC system detects a

24

decrease in arc voltage and decreases the wire feed rate
by the amount required to slow down the buildup of
the weld puddle to the point where the desired arc
length and voltage are restored. Conversely, if the weld
puddle moves away from the electrode, the situation is
reversed, and the wire feed rate is increased until the
desired arc voltage is restored.

The AVC system may be used independently or in
conjunction with the arc length control (ALC). The
design intent was that only the ALC control would be
used in the root passes and that both systems would be
operational during filler passes. In the latter cases the
AVC system would provide the fine control and the
ALC system would provide a reset action to keep the
AVC within its operating limits. The system is quite
flexible, however, and the operator may find that under
certain conditions he can obtain better welds by setting
the AVC and ALC controls so that the system operates
in a manner different from that anticipated by the
designer. As is the case for most control systems, the
proper control settings vary with the application and
must be determined in the field.

ARC LENGTH CONTROL (ALC)

The ORNL programmer includes a system (ALC) that
monitors the arc voltage and automatically adjusts the
arc length to a preset value within a prescribed range.
Two front panel dials labeled “High” and “Low’ are
provided to set the arc voltage limits at which corrective
torch motion will start. The center dial, marked
“Average,” is used to set the arc voltage at which
corrective vertical (radial) torch motion will cease.

A printed circuit board in the programmer contains
the circuitry and relays that control a motorized
ball-screw drive in the weld head to reposition the torch
radially with respect to the pipe. The preset control
range provides an area in which the automatic wire feed
rate control can operate. In essence, the ALC system
provides coarse control, and the wire feed rate system
provides a vernier control for maintaining the arc
voltage at a precise value.

ALC also operates in conjunction with the pulsed
current mode and causes the weld puddle to chill on a
regulated basis to maintain a perfectly centered, uni-
form weld bead, regardless of the position of the
orbiting head on the pipe.
The input signal to the ALC system is the same (arc
voltage) signal used as input to the AVC system. After
passing through switches which correct for torch
polarity and an adjustable gain buffer amplifier, the
input signal is compared with the voltdges from the
three (high, average, and low) limit set potentiometers,
and the differences obtained are amplified and used to
operate transistor switching circuits which, in turn,
operate the up and down drive relays that control the
torch position motor. When the up relay is energized,
the motor drives the torch away from the work; when
the down relay is energized, the motor drives the torch
toward the work. The settings of variable resistors
connected between the supply voltage and the motor
determine the motor speed in the up and down
direction. Interlock contacts between the ALC circuit
and the motor disable the ALC action when the
contactor relay is deenergized; however, in the manual
mode of programmer operation, the motor can be run
in either direction to preset the gap between the
tungsten electrode and the pipe surface by manually
operating push-button switches on the pendant which
bypass the contactor interlocks.

STUBBER CIRCUIT

The stubber circuit initiates a programmed shutdown
in the event that the torch touches the weld puddle
(called *‘stubbing™). The signal used to initiate this
action via a plug-in stubber board module inside the
programmer is the same that is used to operate the arc
length control. The effect of stub control is to
automatically initiate a downslope action as though the
operator had anticipated stubbing and pushed the
downslope button on the pendant. This prompt auto-
matic action prevents electrode tungsten contact with
the weld puddle, causing damage to the torch and
contamination of the weld.

25

GAS AND WATER INTERLOCKS

Gas and water interlocks protect the welding equip-
ment and minimize damage to the weld and the welded
components by preventing startup and/or initiating
shutdown in the event of loss of gas or water flow. If
either gas or water flow is lost during the prepurge
programmed sequence, the timer will stop and the
program will halt at that point. However, if such flow is
lost after the weld cycle starts, the programmer will
fast-step to downslope and continue programmed
operations from that point. Both flows are monitored
by a separate flow switch connected in the gas and
water lines. To obtain the required speed of response,
switches having a low internal value in the downstream
side were selected and mounted on the upstream end of
the flexible cables to the welding head, at the gas and
water outlet connections on the welder power supply.

POWER SUPPLIES AND POWER BUSES

The five power supplies in the programmer are as
follows:

. +28 V dc (nominal) unregulated,
+30 V dc regulated,

*£15 V de regulated (ALC),

*15 V dc regulated (pulser),

AR

+40 V dc (nominal) unregulated.

The first four of these are in the programmer and are
energized when the power switch on the programmer
front panel is on. The +40 V dc is supplied from the
welder power supply when the welder contactor is
closed, that is, during the welding cycle.

26

5. Welding Studies, Weld Joint Development,
and Welding Schedule

Early efforts toward developing procedures for auto-
mated welding were often hampered by minor equip-
ment or instrumentation malfunctions. Qur early pro-
gram goals were twofold: to improve system compo-
nents for prolonged operation and, simultaneously, to
seek programmer-controller input settings that would
yield acceptable welds that would be accurately re-
peated by the automated system. The weld joint was
limited to shapes usually employed in manual welding
practices.

In the course of our studies, we found that the
torch-to-work distance control is most critical and were
able to maintain nearly constant torch-to-work spacings
by adding a motorized ball-screw drive on the vertical
slide to move the torch in response to a feedback signal
from the arc voltage. For the ORNL system using gas
tungsten-arc welding, optimum arc voltages range be-
tween 7 and 9 for stainless steel and carbon steel pipe
materials. A variation of 0.1 V in the arc voltage
represents about 5 mils in the arc gap. The nominal arc
gap of 0.1 in. is controlled within +0.025 in, by the new
system.

Many manual welds are made with open butt pipe
joints. The common joint configuration features a
', 6-in. root face and 37 '%4° bevel for each pipe end,
and a %-in. root gap. The use of consumable weld
insert rings to fill this gap between adjacent pipe ends
helped in establishing a root pass welding automatic
control program which yielded consistent, high-quality
welds. The use of consumable inserts offers an addi-
tional advantage in that it is possible to select insert ring
metal compositions which will blend with many pipe
material alloys and provide metallurgical adjustments to
promote crack-free welds. The use of inserts also makes
it easier to handle the problems of mismatching pipe
ends and of irregularities in the root face and/or the
pipe inside diameter. As the weld is formed, ring-face
and cross-section uniformity adjusts and eliminates
puddling problems otherwise caused by geometrically
poor joint matchup.

After several unsuccessful attempts to weld conven-
tional V-groove butt joints we began using modified
J-bevel pipe end preparations (Fig. 18a). In V-groove
butt-joint welding (Fig. 18b), we were unable to attain
uniform and complete penetration for the root pass,
especially with pipes in the 5G (borizontal) position.
The modified J-bevel pipe end preparation was selected

for automated welding applications after we developed
the remote cutting methods for providing such joint
preparations.3

Early gas tungsten-arc welding with the automated
orbital equipment on the modified J-bevel joints,
however, required precise weld joint machining to
obtain matching pipe inside surfaces and pipe wall
thicknesses, as well as near-perfect alignment of the two
joint members and critical selections for the right
amount of filler wire additions. Failure to meet these
requirements resulted in root welds either undercut and
lacking full penetration or over-penetrated with a
resultant heavy convex bead protruding inside the pipe.
Fill pass welding is less difficult, although we noted that
the quality of successive passes depends on prior weld
passes. It is quite simple to lay good fillers over good
root passes or over good prior filler passes, but it is
difficult to repair a poor pass by welding over it
without first machining out the defect. It has been our
experience that special care must be taken to select
proper heat control {weld current and weld speed) for
the first, or for the first two, fill passes over an
acceptable root pass. Too much weld heat will cause
burn-through or drop-through, whereas insufficient heat
will result in lack of fusion or inadequate joint side wall
tie-ins and weld cracking.

It is time consuming and difficult to do precision
machining by remote control, and pipe precision
machining and alignment add greatly to construction
costs. For these reasons, we next concentrated on
experimentation with pipe joint configurations that
permit plain fusion root pass welding either without or
with minimum filler wire additions. Later. we tried
“buttered” washer insert joints (Fig. 18c) for our
remote weld feasibility studies. A buttered insert is
prepared by depositing weld metal around a pipe
interior and then machining the deposit to a washer
shape. It is possible to select welding (fill deposit) wires
of the proper chemistry to adjust the base metal
composition of the pipe for crack-free welding and for
proper fine grain structure interphasing with the base
metal. Weld results were promising; the buttered joint

3. P. P. Holz. Feasibility Studv of Remote Cutting and
Welding for Nuclear Plant Maintenance, ORNL-TM-2712 (No-
vember 1969).

MAXIMUM WALL

l-5/4 i e]

{d)

CRNL--DWG 72-12239

MODIFIED J-BEVEL CLOSED ROOT FACE BUTT “BUTTERED"” WASHER INSERT
~t
~t

72 1/8in. + w <

?n\lq,;,.— —— W [t =

O

—— 3/32 in. o N =
o = ®» - =
—t oN
< Q é
| = N =
s o c
'D —
= = /s
2\{ o
§§

f =} ! =T <

= w . ) o c

=l |y g = | 5| 8lw _.H.

z |53 © = = z 2z I= -,

= <18k = = & F 2 oflo© s =

nlz=Z | OFE iz & © ®
wIE = £z « ol & A
S|<e (b) ol = S|k = -
Qladn €l gl=2
sl=z-~

INTEGRAL WASHER INSERT

b >

Y
3/32 in
A 7/32 in

MAXIMUM WALL

{
:
7

1/8 in.
1/16 + 1/32in.

PIPE ID

PIPE ID + 3/16 in. MINIMUM
0.015 to 0.030 in. MATCH

OPEN ROOT FACE 8UTT

y— 1/8 1+ 1/32 in.

N MAXIMUM WAL L

Z

Sy

1/8 + 1/32 in.

1716+ 1/32in.

Fig. 18. Pipe weld joints. (2) Modified J-bevel; (b) closed root face butt; (¢) “buttered’ washer insert; (d) integral washer insert;

(e) open root face butt, thin wall; {f) open root face butt, thick wall.

Ll
was definitely less dependent upon precision mating
pipe joint geometries and alignment. However, since
buttered joints are expensive to prepare, we resorted
temporarily to integral washer inserts (Fig. 18d); that is,
we simulated buttered insert shapes by machining
heavy-wall-section pipe on the inside surface. Many
tests were run to determine the best criteria for root
width, root face, and (integral) insert dimensioning.
From the results of this work, we then developed
programmed input data for repetitive quality pipe
weldments and formulated guidelines for welding with
commercially available insert shape substitutes for the
integral shaped inserts. All experimental work in studies
to adapt automated orbital welding equipment for
high-quality construction pipe welding applications
concentrated on pipe joints that were suitable for
welding with commercial consumable insert shapes.

Usual construction work pipe welding practice speci-
fies the open-butt V-groove weld joint. The joint shown
in Fig. 18e for pipe wall thicknesses of %4 to % in.
generally calls for a root face of ¢ + ', in.,a 37 ' +
2° bevel, and a "4 * Y4, in. root gap. Similar values
hold for wall thicknesses greater than % in., except the
bevel angle decreases to 10 * 2° starting at the ¥,-in.
wall depth, as shown in Fig. 18f.

With the shift in program goals to adapt the auto-
mated orbital equipment to nuclear construction work,
concentrated efforts were made to attempt to maintain
or adapt the weld joint geometries commonly used in
construction. Based on the aforementioned experience
from our remote applications work, we concluded that
open-butt pipe welding with ORNL equipment would
at best be marginal. We therefore selected commercially
available consumable inserts that would normually fit the
cavity, or opening, between matching joints of an
open-butt pipe joint to permit the contractor to make
weld setups which could be welded either manually or
with automated equipment. Since many contractors
purchase prefabricated, or precut, end-prepped piping,
the capability to utilize automation interchangeably
with manual practice on the same precut ends is
important, especially when introducing automation to
the field construction job. We also realized that
contractors who had manual welders qualified for hand
welding with specific pipe end preparations and con-
sumable insert shapes could insist on qualifying auto-
mated welding for identical ends and inserts in order to
retain manual welding capability for times that the
machines may be down or where construction schedules
compel maximum total productivity. Therefore we
decided to establish data for automated welding with
both rectangular and Y-insert shaped consumable rings.

28

We first investigated welding with Grinnell rings
(Grinnell Corporation, Providence, R.1.). The standard
Grinnell consumable insert for pipes 2 in. or more in
diameter has a cross section Y ¢ in. wide by ¥ in.
deep. Our experimentation indicated best results with
two Grinnell rings stacked together, or for a %-in.-wide,
“ 6-in.-deep cross section. Root welds with single rings
were of uneven internal contour; 5G position welds
with proper contours in the 12 o’clock position
exhibited suckback near the 6 o’clock position.

We next tried welding with *%;,-in. round wire rings
and, later, with wire rings that were drawn and shaped
to square and to rectangular cross sections. Test results
indicated improved root bead control and more con-
sistent penetration and also showed that differences in
the fluidity of the molten carbon steel and stainless
steel pipe materials (at the weld joint) can be compen-
sated with proper consumable insert shape selections.
Best weld results were obtained with “-in.-wide,
*,-in.-deep ring shapes for 6-in. stainless steel (type
304) pipe, and with *,-in.-wide, Y-in.-deep ring
shapes for 6-in. carbon steel pipe type A-53. Respective
pipe inside diameter protrusions were %, in. for
stainless and Y, in. for carbon steel pipes. However,
the rounded corners of ‘“home-made” rectangular-
shaped rings caused the torch-to-work distances to vary,
and the arc voltage control tended to shift as the torch
orbited the pipe. This problem was solved by using
rectangular cross-section rings of the Kellogg geometry.
The Kellogg ring is rectangular, with barely broken
corners (radii between 5 and 10 mils) and is commer-
cially available (Robvon Backing Ring Co., Elizabeth,
N.J.). Pipe end configurations for Kellogg-type rings are
shown in Fig. 19a.

We also tried various pipe end configurations in search
of suitable pipe joint geometries for better-quality gas
tungsten-arc welding with consumable Y-ring inserts
(product of the Weld Ring Company, Bell Gardens,
California). The outward inclined arms of the Y-ring are
designed to be self-aligning with a joint and to fit a
standard ASA 37 ',° pipe end preparation angle to
form an included 75° pipe joint angle. Even within
applicable ASA dimensional standards for commercial
pipe, allowable differences prevail for as-furnished pipe
inside and outside diameters and for wall thicknesses.
Our experience with Y-inserts showed the importance
of first fitting the insert ring to the pipe section with
the larger inside diameter. In practice, however, this
procedure is hard to follow. We decided therefore to
provide each pipe joint section with a minimum root
face and to base axial dimensioning about the inside
diameter of the pipe. A I5-mil root face (plus 20 mils

29

ORNL-DWG 72--12240

O w— W LS
5
or T 20
LIMITING CASE,
FACES MUST HAVE
- SOME CONTACTS
[ae]
603 = 10+ 29
SE N al
o
=) ”
| ’
w
o
- T~
w
o
&
=

L | G—-- PIPE o _ o '

RECT. RING CORNER RADII = 8005,
0.010

RF —w—

SS PIPE CARBON PIPE
d DEPTH 5/32 in. 1/8 in.
w = WIDTH 1/8 in. 5/32 in.
P ID PROTRUSION 3/32in. 1716 in.
RF ROOT FACE 1116+ 1/32 in. 1/16 + 1/32 in.

{a)

G -- PIPE

NN\

UP TO 3/8 in.

ALL DIMENSIONS TYP. AND SYMM.

RF = ROOT FACE = 0.015 * 0.020;,
—0.000

MATING ID’s TO HAVE SOME ROOT

FACE CONTACT. MACHINE I1D.s AS

PIPE REQUIRED.

_—_Q—.—

(b

Fig. 19. Root face butt joint for (¢) Kellogg-type insert and (b} for Y-ring insert. Y-ring insert consumable weld ring
manufactured by the Weld Ring Co., Bell Gardens, Calif.

and minus none) with a 37'% t* 2%° end bevel
provided for consecutive acceptable root-pass Y-insert
welds (Fig. 19b).

We have produced acceptable welds with both Y-ring
and Kellogg ring inserts but prefer the Kellogg rectangular
ring shapes, which provide quality weldments even with
poor pipe end preparation and offset matchup of the
pipe ends to be welded. We were able to produce
satisfactory welds as long as there was a minimum
contact between the respective pipe root faces and the
insert ring; Fig. 19a exemplifies two extreme setups
that were weldable with our equipment. Y-insert
welding requires more precise limits, as shown in Fig. 19b.
ORNL purposely omitted experimentation with con-
sumable EB (Electric Boat Company, Groton, Conn.)
type inserts, because EB insert welding requires pipe
inside diameter matchup within S-mil limits, which is
too expensive to prepare for field construction pipe
welding.

Welding procedure specifications must be prepared
and certified to describe the procedures to be followed
for automated gas tungsten-arc welding of specific pipe
sizes and materials in the 2G, 5G, and 6G welding
positions with specified automated orbital welding
equipment. All welding performed in accordance with
the certified procedure should be done by welder-
operators who have been thoroughly trained in the
operation of the automated equipment and who have
demonstrated their proficiency by having passed tests.

30

Procedure qualifications are referenced in the ASME
Boiler and Pressure Vessel Code, Section 111, Nuclear
Vessels, and are specified in the same Code, Section 1X,
Welding Qualifications, and in Specifications RDT
E15-2T and RDT Fé-5T and supplements to Sections
[IT and IX respectively.

A certified Welding Procedure Qualification Record
must accompany the Welding Procedure Specifications,
and list in detail the following information:

pipe parent material;

electrode and filler material;

shielding gas and flow rate;

pipe joint design and consumable insert data;

heat treatment data;

A i A e

. radiography and liquid penetrant requirements
(NDT);
. results of destructive test sampling, from duplicate

welds in each of the three welding positions: tensile,
root bend, and face bend.

A Welding Parameter Record which lists all the input
selections to the programmer-controller is also required
for each weld. See Appendix B for a sample welding
procedure that is applicable to any automated welding
System.

6. Welding System Operations

PREWELD OPERATIONS

Stored metals will form external oxide coatings which
generally are refractory. Extra power (weld current) is
required to obtain initial weld penetration when metal
surfaces are oxide coated, and even then weld porosity
can be caused by hydration of the oxide. Once
penetration has been achieved, new problems arise
when metal surfaces are coated with oxide. It is
difficult to control the weld puddle, especially at or

near the overhead weld positions, and weld deposits are
uneven, with balling tendencies and void inclusions.

For these reasons, routine cleaning by stainless steel
wire brushing to remove oxide coatings and wiping with
solvent to remove surface dirt and grease traces are
necessary for all welds with automated orbital equip-
ment. Additional draw filing, or grinding, may be
required for filler passes to remove sharp notches or
protrusions and obtain a smooth, blended substrate.

iy

Joint mismatch, one cause for poor root pass welds,
especially in the pipe horizontal position, is most
critical in the “overhead,” or 6 o'clock location. A
slight mismatch of adjacent edges of the joint’s inner
diameter causes the welds to pull out or suck back
metal due to gravity. It is recommended that the
bottom pipe quadrants be matched most precisely for
best welding results, since misfit conditions can be
tolerated to a greater degree in the top quadrant area.
Pipe joint mating surfaces should preferably make
physical contact to both edges of the consumable insert
on fitup. Purge-gas losses are minimized with contacting
surfaces, and needs for filler wire are reduced. Pipe ends
to be joined by welding must be rigidly held in position
during welding to prevent weld-heat-induced pipe move-
ment at the joint due to expansion and contraction.
Pipes may be clamped or tack welded prior to the root
pass.

There is a difference in ionization potential of inert
gases which affects the arc voltage and therefore the
heat input to the weld zone. Helium requires only
about 60% of the welding current required for an
equivalent weld with argon shield gas due to the
increased arc voltage. Different arc plasma shapes result;
argon spreads the weld heat, while helium concentrates
the heat. Since wider argon plasmas give best results for
stainless steel welding, all ORNL work was done with
argon shielding gas. The pipe interiors were purged with
argon usually at approximately 20 cth gas flow. The
exit orifices or flow openings for the purge gas should
be approximately equal in flow capacity to the inlets.

Electrode configuration tests have indicated that
better welds can be obtained by tapering the electrode
to a 30° included angle and providing a minimum
rounded-off apex. Electrode configuration has a strong
influence on the arc heat pattern. The tendency of an
arc to spread to an adjacent area causes the weld nugget
to fuse only intermittently and can cause incomplete
fusion at the joint sidewalls, leaving an uneven surface
appearance on the weld bead. It is practically impos-
sible to lay acceptable fill passes over such defective
weld beads and, of course. not recommended; one must
resort to corrective interpass machining and blending
prior to proceeding with further welding.

The angle of the tip of the electrode determines
where the arc will initiate. Arc emission can occur from
any spot of the heated electrode’s tapered emitting
surface. Weld bead shape can be somewhat varied by
changing electrode tip angles: however, precision, cau-
tion, and care are required even with AVC regulation to
confine the arc emission to the desired direction so that
it will not bump into pipe joint sidewalls. Additional

31

precautions are necessary to prevenl contacting the
electrode with the filler wire during the overlap portion
of the weld. The wire feed motor cutoff point must be
programmed to stop in the initial downslope portion of
the weld current,

Tracking capability of the carriages is adequate for
pipe welding operations on horizontal pipes. The driver
and idler rollers are designed to include two % -in.-wide
metal lands, one at each end of the 6-in.-wide Viton
rubber roll tread surface. Tlie lands project to within
0.005 in. of the rubber surface, so that when the rollers
are clamped to the pipe, the rubber is deformed at the
point of contact to the extent that the metal lands
contact the pipe surface. The traction obtainable from
these rollers drives the carriage around the horizontal
pipe with a maximum deviation of about 3 to 6 mils per
orbit. No compensation is required for this amount of
drift, and no end restraints are required for welding
pipes from horizontal to 15° slope positions.

However, when welding on pipes that slope more than
15° end restraints are required in order to keep the
rollers from slipping. These restraints are either in the
form of split circular ring collars or sprocket chains
which are clamped to the pipe. Nylon or Teflon bearing
surfaces are provided to minimize rotational friction
between the orbiting carriage and the restraint. When
the split circular ring clamps are employed, primarily
for the smaller pipe sizes, plastic buttons are attached
to the carriage end plate to reduce friction. When the
sprocket chain is used, for the larger pipe sizes, we
exchange all standard link pins in the chain for
extension pins to which we mount the plastic roller
buttons to “ride” the carriage end plate. Extension
links may be added or removed to adjust the chains to
fit over a variety of pipe diameters.

All clamping devices for use in stainless steel pipe for
RDT work must be made of stainless steel. Marker gages
must be prepared and applied to properly locate all
restraints uniformly from the weld joint. It is necessary
to tap the links with a hammer to line them up before
tightening the circumferential chain band.

GUIDELINES FOR TACKING
CONSUMABLE WELD INSERTS

A consumable insert ring should always be tack
welded to at least one side of the pipe joint. ORNL
developed special C-clamp jigs to hold the insert in
proper alignment while it is being tack welded, since
proper and uniform spacing relative to the pipe end and
inner pipe diameter is critical, particularly for carbon
steel pipes. The amount of ring material protruding into

the inside diameter of the prepared root face of the
pipe end must be carefully controlled to attain an
acceptable root pass. The insert is supported by the
clamp and held in position over the pipe end; the tack
welds on one side of a joint should be about 1 in. apart,
When tacking an insert to both sides of a pipe joint, the
tack welds should be alternated to the respective pipe
ends, with at least six approximately equally spaced
tack welds around each pipe, or so that they are no
more than % in. apart, whichever distance is smaller.
These spacings should prevent breaking of tacks during
root pass welding. It is important that some filler wire
be used for all tack welds to Y-inserts, since there is a
tendency to burn away part of the thin edge of the Y
while fusion weld tacking the ring to the beveled pipe
edge. For gas tungsten-arc tack welding, the arc current
should be set at approximately 75% of the mean root
pass weld current, or about 80 A at 12 V. Both sides of
the pipe joint insert must be tacked unless clamps are
used to compress the joint for the root pass weld. In
addition, the pipe ends being joined must be rigidly
held in position during welding to prevent movement at
the weld joint due to expansion and contraction forces.

WELDING TECHNIQUES

The basic principle of gas tungsten-arc welding is to
use inert gas to shield the weld puddle of molten metal
and the surrounding area where the temperature is high
enough to cause rapid oxidation by the atmosphere if
not protected. To maintain the inert-gas blanket, the
welding must be performed in a quiet atmosphere
where no air current or drafts exist. [t may be necessary
to shield the area to assure a constant inert-gas
atmosphere for the weld. Before welding, 2 minimum of
6 in. of the internal surface of the joint on each side of
the weld should be blanketed with argon. The volume
of gas for the blanket should be at least five times the
volume of the area to be blanketed, and the blanket
should be’ maintained during welding and until the
temperature of the weld falls below 400°F.

CLEANING OF WELD BEADS

Oxide particles and heavy film should be removed
from the weld bead and base metal in the line of arc
travel before depositing each section or each complete
weld bead. Thorough brushing with a stainless steel wire
brush is usually required.

-

32

DEFECTS

Each weld bead should be visually examined for
cracks, holes, incomplete fusion, lack of penetration,
overlap, undercut, underfill, and other defects. Each
bead should have a smooth surface and contour and
should merge smoothly into previously deposited beads
and base metal; if it does not, repairs should be made.

REPAIRS

Weld defects can be removed by grinding, chipping,
filing, or machining, and appropriate operations should
be performed to obtain a smooth surface before
depositing the next bead.

WELD SCHEDULE DATA SHEETS

Table 1 is a typical data sheet for our system giving
the programmer input information for the root and
subsequent filler pass welds. A final, governing weld
parameter table will be prepared and issued at the time
of procedure qualifications that must be followed to
achieve good weld results. Limits, or tolerances, for
respective data input as normally listed for manual
welding practice are omitted from the parameter data
since the automated controls, when in calibration, will
maintain their built-in tolerances. Calibration proce-
dures and test checks are provided with the instruction
manuals furnished with the equipment.

OPERATIONAL PROCEDURE (ORNL EQUIPMENT)
CHECKOFF LIST

I. Preweld

1. Verify that the pipe joint setup for welding

meets the following criteria:

(a) cleanliness,

(b) proper end preparation for both sides of
the joint,

(c) proper insert — insert spacing and location
within the established dimensional limits,

(d) insert in contact with both pipe ends and
properly tacked.

2. Check purge-gas supply and regulate proper
purge flow to the work piece.

3. Check water flow and torch purge-gas flow to
the weld machine. Gas flow should be 14 cfh
minimum and water flow should be about Y
gpm at approximately 20 psi. Use pressure
regulators to protect water hoses, passages, etc.

Weld 3-2-15

Date 5-25-71

Pipe size 3 in.

Material type 304 SS

Joint type Single V Kellogg

Carriage size 3—6 in.

Pipe position 2G

Table 1. ORNL Weld System Welding Parameter Data Sheet

33

3-in. sched-40 pipe; 0.216-in. nominal wall thickness

rectangular insert

Torch gas Argon, 15 cfh

Backup gas Argon, 20 cfh

Filler wire type 308L SS
Filler wire diam 0.045 in.
Electrode shape 0.035 in. flat
Electrode projection (in.) 1/4
Cup 7 o

AVC 7.3-8.5-9.5

Wire feed snout type Solid

Program Check

Oscillator On
AVC wire On
Program On
Current On
Upslope Set
Contactor On
Welder On

Tool servo (rear panei)-On

Weld servo (rear panel)-On

Weld Passes

Control box settings?
R 1 2 3 4 5 6 7 8 9

1. Tool speed? 16 |16 |16 [16 |16 |16

2. Wire speed® (in./min) 35 25 25 25 25

3. Oscillator speed (cpm) 80 80 80 80 80

4. Tool start position 4 4 4 4 4

5. Wire start position 6 6

6. Wire stop position 26 26 26 26 26 26

7. Weld time (sec) Manual Downslope

8. Down slope (sec) 9 9 9 9 9 9

9. AVC wire control (V) 13.5 [13.5] 13.5( 13.5( 135} 13.5
10. Maximum weld current (mean amperes){ 100 {100 [ 100 | 100 .| 100 | 100
11. Actual current reading
12. Slider position No. 1 (% max current) |40 40 40 40 40 40
13. Slider position No. 2 (% max current) |70 70 70 70 70 70
14. Slider position No. 3 (% max current) |100 [100 | 100 | 100 | 100 | 100
15. Slider position No. 34 (% max current)|0 0 0 0 0 0
16. Weld current pulse amplitude (A) 16542 16542 16542 16542 16542 16542
17. Weld current pulse rate (cpm) 68 68 68 68 68 68

Weld tool settings

18. Oscillator amplitude (dial setting) 0 1 1 1 1 1
19. Electrode included angle (°) 30 {30 30 30 30 30
20. Electrode diameter (in.) Y % *3%_ 335 35 3%
21. Arc gap (in.) 11_6 16 1i6 % i% ‘l_lé
22. Start location; clock position 1 11 1 11 1 11

@A 10% variation in current is permissible to compensate for permissible joint tolerances.

bNumber 16 setting equivalent to 3.7 in./min.

“True readings = 50% data input.
Position the carriage component on the pipe,
and align the torch head slot directly over the
joint.

. Use Allen wrench to tighten carriage arms to

pipe. Note: Torque an equal amount on each
arm until rollers are snug and even. Torque
required is approximately 75 in.-lb. Do not
over-torque.

. Connect the control cable to carriage.

7. Check the six cable connections on rear of the

10.
11.

12.
13.

14.

15.

programmer.

. Turn on power to programmer. This activates

power to the carriage.

. Check operation of the carriage, forward and

reverse. Forward speed is regulated from the
programmer by adjusting the tool speed con-
trol, which reads inches per minute travel. Pull
knob out, set desired speed, then push knob in
to lock. Reverse speed is a constant, fast speed
and has no adjustment. Note: Always be aware
of the control cable position and do not let it
hang on some obstruction because this will
damage the connector wiring,

Turn power off at programmer.

Install the weld head assembly into the car-
riage. Do not force it in place, as the wiring
connector may be slightly misaligned.

Raise cover on the weld head.

Turn power back on to programmer. This
activates power to the weld head and carriage.

Check out the oscillator component of the

weld head.

(a) The oscillator speed control is regulated
from the programmer. Pull knob out,
adjust speed, push knob in to lock. Indica-
tion is given in cycles per minute.

(b) The swing or travel distance is regulated
by the control knob on the oscillator
component in the weld head. The maxi-
mum swing spans % in.

(c) Activate oscillator to check by pushing
control button on the weld head.

Check out the wire feed component of the

weld head.

(a) Check parameter table for correct wire
material and size.

(b) Wire feed speed is regulated from the
programmer. Pull knob out, adjust control

16.

17.
18.

to desired speed, push knob in to lock.
Indication in inches per minute.

(¢) Match the alignment mark on the wire
feeder cap with the first mark on the
cover piece. This permits the wire to
manually advance into the feeder’s gear
drive. Now tighten the cap by rotation
until the cap’s alignment mark matches
the second alignment mark on the cover.
This provides proper gear tooth tension on
the wire for motorized wire travel through
the feeder. Verify wire advance by push-
ing forward wire travel button on weld
head.

(d) Push the wire retract button on the weld
head momentarily to verify reverse wire
travel.

(e) Position the filler wire directly at the
outlet of the feeder’s nozzle.

Turn power on to the weld machine to check
the torch cover gas and water flow — approxi-
mately 14 cfh gas and approximately ', gpm
water.

Turn power off to weld machine.

Check out the torch head.

(a) See parameter table for proper size of
electrode, electrode angle , and tip.

(b) Position electrode in torch extension and
tighten, Tungsten tip to protrude about ',
in. beyond the ceramic torch cup.

(c) Screw extension into torch head and
tighten.

(d) Check electrode and extension piece to be
sure desired depth can be reached by the
electrode in the pipe joint. Use Teflon
spacer between the extension piece and
the ceramic cup if needed. If more depth
is desired, use a copper spacer between the
torch head and the extension piece. Do
not use Teflon between torch head and
extension piece. Spacers should be used to
allow the electrode to touch bottom of
joint on root pass. This will leave % in.
movement upward or raising length for fill
passes.

19. Check the horizontal and vertical adjustments

of the weld head.

(a) The horizontal adjustment is made by
rotating a knob on the outside cover of
the weld head assembly, which moves and
21.

22.

23.

24.

locates the components of the weld head
to the desired area of the pipe joint. When
the*electrode is in the center of the joint,
the horizontal adjustment should be in its
midrange, or at the center of its move-
ment. If necessary, relocate the carriage to
acquire this position,

The vertical adjustment is motor driven,
with the controls located on the remote
weld pendant control. The motor is
mounted on the outside cover of the weld
head. The motor shaft alignment is criti-
cal, and all caution should be taken not to
abuse the motor housing or its holddown
clamp.

Energize both manual pendant controls
and check to see that both directions, up
and down, are working correctly .
Adaptive vertical control is maintained
during welding operation through pro-
grammer sensing circuits. AVC control
settings for the programmer are listed on
the weld parameter data sheet.

(b)

(¢)

(d)

. Reverse wind the carriage one revolution to get

the cables in proper position to unwrap from
around the pipe during the weld operation.
Clear any obstructions that may tend to
interfere with the cable.

Rewind carriage about 2 in. past start point
and then move it forward about 1 in. in weld
direction to remove any possible slack in the
gears that might cause a rough start on the
weld pass.

If wire feed is to be used, check the guide
nozzle position. The direction of the wire
should be guided directly from the nozzle end
into the weld puddle. Wire should not touch
the weld surface or joint sides before it
reaches the puddle. Wire should enter the
extreme front area of the weld puddle. A set
screw is used to lock the nozzle in position.

Use the weld parameter data sheet to make all
settings on the programmer.

Set all welding machine switches and selectors
to the proper positions indicated:

Remote current control - On
Mode selector — Straight dc (—)
Soft start - Off

Spark — Start only

35

25.
20.
27.

28.

Current range selector — Medium

Side switch (program control position} - Up
(light is on during welding)

Fine adjustment control — #10
Gas afterflow — #50 (max)
Gas welding selector — Other types welding
Spark intensity — #10 (max)
Close weld head cover and lock.
Turn weld machine power on.

Locate remote power control pendant close to
work area.

Welding operation is now ready to begin.

I. Welding Operation

1.

The following items have been checked.

(a) The electrode position has been placed so
that the initial arc will strike on the joint
side if oscillation is used.

If oscillation is required, the span of the
electrode will not touch the joint sides.

(b)

Oscillation of the weld torch helps to
assure fusion into the sidewall. When used
in combination with current pulsing, oscil-
lation will also help to maintain a stable
weld puddle. The oscillation amplitude
can be varied up to % in. width, and the
oscillation frequency can be controlled.

Oscillation amplitude (side interference)
checks should be made prior to each pass
by depressing the OSC button on the weld
head lid body.

The electrode gap from tip to work has
been set at approximately '4 in., and the
adapting vertical control

(¢)

settings have
been entered on the programmer.

Press start button on the pendant control.

. Observe through port in carriage to check weld

operations. Always keep pendant control close
by to be able to push the downslope button or
the stop button in case of an emergency.

Whenever possible, stop the welding operation
by pushing the downslope button on the
remote pendant control. This action protects
the good weld already made. If the stop
button is used, the weld can be damaged by
the filler wire sticking to the puddle area
and/or the purge gas being cut off too quickly.

5. Downslope the weld operation after each
complete orbit is made.

6. Reverse wind the carriage to properly arrange
the cables around the pipe prior to each weld
pass.

7. Always overlap the previous start point on the
reverse wind so that on the next start, all slack
in the drive gears will be out and no backlash
motion of the carriage will affect the weld
head. Stagger subsequent weld starts by at
least 1-in. spacings.

8. Lift the cover on the weld head and check the
electrode angle and tip. A close watch on the
arc voltage will also indicate when an electrode
should be changed or reshaped.

9. Position of starts should preferably be some-
where between 10 and 2 o’clock. Viewing
through the weld head’s viewport is easier; it
permits adjustments in an area least vulnerable
to operator regulation assists.

10. Follow weld parameter sequence selection

recommendations.

GUIDELINES FOR THE WELDER-OPERATOR’S
VISUAL OBSERVATION
DURING AUTOMATED WELDING

As mentioned previously, it is recommended that
skilled manual welders be selected for training to
operate the ORNL automated orbital pipe welding
system. The welder’s experience is invaluable, not only
in properly assembling and locating the torch, etc., but
also in detecting minor discrepancies that might occur
during operation. Lack of proper remedial action by the
operator can ruin a weld.

Ideally, each weld system should include a recorder to
plot variables such as torch travel rate, welding current,
arc voltage, and wire feed deposit rates. The recorder
chart can be used during operation to detect functional
deviations and to guide and verify the operator’s
corrective action. For automated systems without
separate chart recorders, it is possible to observe the
console voltmeter and the wire feed rate meter to attain
some indications of weld pass quality. Both meters

36

indicate variations in arc length. A root pass weld is not
penetrating the joint fully if voltage readings hold
steady but the feed rate registers only below the
selected rate. Usually, a small increase in welding
current will remedy this situation. If, however, the wire
feeder motor builds up to the selected set rate and
voltage continues to climb, poor welding also results
and the cycle should be stopped at once. Now the
problem will usually be an excessive joint gap formation
with too much push-through in the upper quadrants of
the pipe. filler wire bound up within the wire feeder
drive and not feeding into the weld, or excessive puddle
fluidity in pipe vertical positions causing puddle flow
away from the electrode tip. Investigate the problem
with the machine off. Satisfactory weld fill passes do
not appear to present great problems. The second weld
pass, or first fill pass, requires some special care in
properly adding the filler wire and obtaining weld
buildup without root pass burn-through. Heat input
selections for this and subsequent passes require only
fusion to the previous pass and to the joint sidewalls.
Oscillation of the weld torch helps to assure fusion into
the sidewall, and current pulsing tends to maintain a
stable weld puddle and to smooth out minor weld
puddle perturbations.

Few programmer input changes are required during
the initial fill passes, except to add torch oscillation and
to adjust, or set, the wire feeder exit nozzle to a proper
entry angle with the pipe joint surface. Final fill passes
can be made with increased weld power, wider oscilla-
tion, and increased wire feed. A near 12 o’clock start
position for the first fill pass (for 5G position welding)
generally helps to balance partial distortion of the pipe
created by the root pass.

One procedure for filling local weld areas that have
been purposely ground out to remove weld defects is to
place the carriage about ' in. in front of the area to be
filled, set a short arc gap of about %5, in., and initiate a
weld cycle. After the carriage traverses the recessed
area, the AVC wire feed control will start to automati-
cally add wire as soon as the arc gap increases. If the
localized defect is not too severe, the AVC and wire
feed additive controls will automatically fill the depres-
sion to the level of the surrounding substrate during
subsequent filler passes.

7. Welding System Maintenance

Detailed instructions for mechanical maintenance and
electronic calibration checks are given in the Operation
and Maintenance Manual for ORNL-Furnished Auto-
mated Welding Systems. The Manual also includes a
chapter on “Malfunction Data,” plus suggestions and/or
procedures for corrective maintenance actions, and
disassembly and reassembly directions for the carriage
and the weld head. Guidelines are offered for trouble-
shooting every functional programmer-controller circuit
and for the plug-in cards.

Routine daily maintenance requirements for the
welding equipment include visual checks for obvious
abnormalities and for general cleanliness. The carriage
and weld head should be stored in appropriate dustfree
boxes overnight and whenever not in use. The carriage
arm assemblies should be slightly untorqued to mini-
mize roller pressure against the pipe and thus prevent
permanent Viton-rubber tread deformation where inter-
pass temperature controls for welding call for consider-
able delays between passes.

Biweekly preventive maintenance checks for the
equipment should include programmer calibration
checks, particularly for orbit travel speed and wire feed
rate. Nonroutine carriage maintenance operations
should be conducted as necessitated by operational
needs; troubleshooting procedures recommended in the
Manual should be followed.

Cleanliness is required for proper operation and
maintenance of the equipment. Driver and idler rubber
roll surfaces must be kept clean by wiping with acetone;
chips and dirt must be removed from all crevices; and
bearing surfaces must be coated at all times with a light
film of high-temperature lubricant. The carriage, weld
head, programmer-controller, and, where possible, the
recorder should preferably be kept away from dust,
dirt, and rain. A ventilated, boxed enclosure has been
designed and is available to house the programmer and a
recorder for field operations. Clean air is circulated
through the box to retain a slight pressurization within
the enclosure to seal out dust and dirt.

8. Operator Training

Operator training consists in instructions in the sectup,
calibration, control, operation, and maintenance of the
automated orbital welding and programming equip-
ment. ORNL conducted a two-weck training program
for Bechtel Corporation operating personnel from
Westinghouse-Hanford and for TV A personnel from the
Browns Ferry Nuclear Plant utilizing the Operations
and Maintenance Manual for the Oak Ridge equipment
system as a text to supplement the practical training.
The practical training involved a one-weck period for
becoming acquainted with the equipment followed by a
week of specialist training held in split sessions for both
the weld opcrator and the electronics maintenance
engineer. We purposely requested that the trainees
include someone with a4 broad manual welding back-
ground and someone knowledgeable in automated

electronics system operation and upkeep. The second-
week training sessions involved the mechanical and
metallurgical aspects of weld technology for the welder,
plus electronic control, programming, troubleshooting,
and maintenance for the instrument sysiems specialist.
The welder-operator actually set up and executed a
number of automated welds, while the electronics man
performed controller checks, calibrations, and elec-
tronic repairs. The trainees also received instructions in
the interpretation of mechanical and electrical drawings
for the ORNL system and were issued Manuals and
blueprints at the time of their departure.

The dual-phase training program, theory and practical
work, effectively provided each trainee with a balanced
overall background of automated welding technology
and practice. Exposing the welder trainee to some basic

instrument, programming, and control techniques and
practices, and acquainting the electronics trainee with
actual welding routines helped each to appreciate and
comprehend the specific involvements and problems of
the respective expertises. Good automated welding
practice calls for a “team effort” of specialists. The
instrument man can often provide the welder with

38

adequate controls to maintain certain required torch-to-
work relationships if he is taught to understand what
constitutes the proper weld. Also, a weld operator who
understands how the controls interact, why time delays
occur in control responses, and what control factors
influence repeatability can then select the programming
parameters essential for consistently good welds.

9. Cutting Prerequisites - Pipe Cut and
Bevel Preparation Development

The most important objective in cutting and prepar-
ing pipe ends for welding is to obtain precision
geometrical and dimensional symmetry for mating pipe
ends. This statement holds true for all types of weld
joints. Unfortunately, commercially available pipes are
routinely out-of-round, nonconcentric between inside
and outside diameters, and of uneven wall thickness.
These irregularities make it impossible to rely on
simple, rapid machining operations to establish the ideal
pipe end geometries for weld joints.

ASME Materials Specification, Section 11, Boiler Code
for Piping, describes the allowable dimensional varia-
tions in the diameter and wall thickness of various types
of pipe. Section SB 167, for Nickel-Chrome Alloy Pipe,
for example, permits an allowable eccentricity of pipe
inside and outside diameters up to 10% of the nominal
wall thickness; even comparable SA 106 carbon steel
pipe specifications allow for 12 '4% thickness varia-
tions. Diameters for large piping may vary as much as
% in. All commercial pipe is governed by these
specifications. Our experience indicates that piping
dimensions vary at least as much as, or slightly more
than, the allowable tolerances. Furthermore, the manu-
facturing process of pipes in the mill is based on
squeeze rollers about the pipe’s outside diameter,
resulting in primary, or best, dimensional tolerance
control of the outside diameter and least control of the
inside diameter. The pipe joint to be welded, however,

requires closest matchup tolerances for the root bead
pass at the pipe’s inside diameter and only nominal
control at the outside.

Piping for nuclear work often requires special mill
rolling for above-average material composition control
adherence. Dimensional pipe specifications also require
strict tolerance limits on the diameter and wall thick-
ness but realistically must conform to dimensional
control limits of the manufacturing process. Hence, it
becomes necessary to establish pipe roundness and
inside diameter control by requiring inside diameter and
root face machining. Standard lathes are usually em-
ployed for end preparation ‘in the smaller pipe sizes;
clamp-on, track-operated frame lathes* are often used
to properly prepare ends for the larger pipe sizes. Care
must be exercised to retain the specified pipe wall
thicknesses, and the designer should always specify
sufficiently heavy pipe walls to end up with at least the
minimum required pipe wall thickness after machining.
It is also important that the stress analyst study all joint
configurations to provide allowances for uneven wall
thickness near the finished weld joint and examine the
weld-heat shrinkage-induced pipe contour deformation
at the weld joint.

4. Pipe-end preparation machines are manufactured by the
H&M Pipe Beveling Company, Tulsa, Okla., and by others.

39

10. Commercial U.S. Equipment Sources
for Orbital Welding Systems

To the best of our knowledge, as of July 1972, the
following companies are the only manufacturers of
automated tungsten-gas orbital pipe welding equipment
in the United States:

Astro-Arc Company, Sun Valley, Calif.

CRC-Crose International, Inc., Houston, Tex.
Dimetrics, Inc., North Hollywood, Calif.

Liquid Carbonic Corporation, Des Plaines, I
Magnatech, The DSD Company, East Grandby, Conn.
Rytek, Inc., Santa Fe Springs, Calif.

TekTran Company, Newark, Ohio

Zeta International Engineering, Inc.,
Calif.

Santa Clara,

A number of companies in Europe also market
equipment systems that are quite similar to the Liquid
Carbonic line. The above list includes only companies
producing equipment for orbital torch travel about a
stationary pipe. Most of the major welding equipment
manufacturers build automated, or at least semiauto-
mated, tungsten-gas torch equipment for use in applica-
tions where the pipe rotates past a stationary torch.

The Astro-Arc pipe weld system can accommodate a
pipe range from 4 to 36 in. OD. One guide ring and one
disposable belt are required for each diametral size
increment. Two-section hinged guide rings are available
for use with pipe sizes up to 12 in., and segmented link
tracks are used for 12- to 36-in.-diam pipes. Links are
added or deleted for the in-between pipe diameter sizes,
and all tracks are grooved to seat the inexpensive special
cloth belts. The Astro-Arc carriage, containing the
torch, wire feeder with a 4-in.-diam spool, oscillator,
and orbit motor drive, includes a rugged spring mount-
ing for the belt attachment. The Astro-Arc power
supply is solid state, 200 A GTA, fully transistorized,
and includes an integral liquid-cooling system. Program-
ming includes 1 %4-in. AVC torch travel adjustment at
approximately 60 in./min AVC compensation speed, 10
to 100 cpm oscillation frequency for up to ' -in.-wide
oscillations with independent dwell stop capability per
side, and several modes of pulsed current operation.
The Astro-Arc solid-state programmer is housed directly
on top of the power supply. The system also includes
provisions for future plasma arc attachments.

CRC-Crose International, Inc., is a subsidiary of
Crutcher-Rolfs-Cummings, Inc. Their automatic pipe
welding system employs the gas shielded-arc welding
process with multiple torches mounted to the pipe both
internally and externally. The system also includes an
integral hydraulically powered machine to prepare and
align pipe joints in the field. However, the machinery,
built primarily for large overland pipe lines, is bulky
and very heavy and does not lend itself for highest-
quality nuclear-grade gas tungsten-arc welding.

Dimetrics, Inc., like Astro-Arc, is an independent
company that produces solid-state power supplies and
specialty tube and pipe welding equipment. The com-
pany is presently developing automated chain-driven
orbital pipe welding machinery for interchangeable gas
tungsten-arc or gas metal-arc welding to be marketed to
supplement their standard rolled-work AVC controlled
stationary torch equipment systems. These systems
feature programmer-controlled power supplies in var-
ious power ranges for operation in multiple pulsed
welding modes.

Liquid Carbonic, a subsidiary of the Houston Natural
Gas Corporation, has taken over the manufacture of
automated machinery systems originally developed for
the Navy by the Electric Boat Division of General
Dynamics at Groton, Connecticut. Their APW series
machines employ a split gear to carry a combination
torch. torch oscillator, wire feeder attachment. The gear
is enclosed within a hinged circular housing track, and a
stationary motor mounted to the track orbits the
gear-torch combination about the pipe. The balance of
the system comprises a solid-state control console and a
pulsating arc dyna-surge power supply. The GTA
system will accommodate from 3- to 36-in. pipes.

Magnatech, the DSD Company, entered the tube and
small pipe automated welding field by adapting a
home-built tube welder used in the manufacture of
their precision metal O-ring Turoseals to an inexpensive
orbital welder which they now market commercially.
The equipment is presently limited to gas tungsten-arc
welding of square-cut, butted pipe joints up to 1 %4 in.
in diameter with wall thicknesses up to %4 in. The
automated, programmed fusion welder consists of a
mechanical programmer and a weld head built to
accommodate curved tubes and pipes as well as straight
runs. The equipment incorporates simple mechanical

devices for preparing the weld program and a program
profile cam disk. The programmer plays back the cam
card to obtain the automated control of welding
parameters. The automated system operates in conjunc-
tion with any commercial GTAW power pack. Magna-
tech is presently enlarging their welder line and adding
wire feed and oscillation capabilities to their equipment
in order to handle larger diameters and heavier wall
thicknesses.

Rytek, Inc., recently went out of business, but,
according to its owner, Henry Rygiol, the operation
apparently is being reinstituted as part of the Susque-
hanna Corporation in San Diego, California. Rygiol has
built a number of specialty systems for specific auto-
mated gas tungsten-arc applications.

TekTran is a relatively new joint venture company
formed by the Air Products and Chemicals, Inc., and
North American Rockwell Corporation to market auto-
mated welding systems and testing equipment. TekTran
obtained the detailed drawings and specifications pre-
pared for our ORNL welding system via the National
Technical Information Service to build prototype
machinery for evaluation from manufacturing, opera-
tional, and servicing standpoints. We understand that
TekTran expects to market a series of four automated
orbital welding carriages for pipe sizes ranging from
2', to 24 in. Their system basically resembles the
ORNL horseshoe carriage-weld insert design, but the
four-roller tractor carriage with two motorized drivers
and two free-rolling idler rolls has been changed to a

40

three-roll tractor with each of the rollers motorized.
TekTran’s new line is based around their new 300-A
solid-state, SCR-type weld power supply for both gas
tungsten-arc and gas metal-arc welding. The system will
also feature interchangeable weld insert modules for
operation in both welding modes, with the GMA
process recommended for speedier, heavier bead de-
posits for final filler passes.

Zeta International Engineering, Inc., is the successor
to the Bartley Engineering Company. Their automated
welding system utilizes pulsed gas tungsten-arc welding
and pulsed gas metal-arc welding processes. The major
components of the system are: four welding tractors,
operator’s control console, wire feeder with junction
box, dual weld power supplies, and a solid-state logic
control cabinet. Three of the four tractors clamp onto
the pipe and rotate the torch similar to most automated
tube welders. These tractors are sized to handle piping
Yo to 1Y%, 1% to2'%, and 3 to 5 in. The fourth
tractor, for all pipe sizes above 3 in., uses a tooling ring
which is bolted to the pipe to be welded. A double-row
chain is used on the tooling ring to hold and provide
means to drive the tractor. The weld tractors also have
as options arc voltage control, oscillation, and cold wire
addition. Zeta’s GTAW power supply is a 200-A, 100%
duty cycle, constant current machine, with current
pulsing available as an option. The GMAW power
supply is an Airco model PA-3, modified to make the
Z.1E. system ““turn-key.”
41

Appendix A

ORNL Welding Programmer-Controller,
Controls and Function

This appendix essentially outlines the controls and functions of the welding programmer-controller. Table A-1
lists the controls and functions for the front panel, and Fig. A-1 is a front view of the programmer-controller. Similar
information for the rear panel is given in Table A-2 and Fig. A-2.

1 PHOTO 0613—71

-uv.,

cta » fLanes
istable function generator

.....

........
............
________

. e S Hy

12 av  or IR ESESESiiiiiiiiiiics =iiEsis

23 24
273 8 6] 29| 28 2526

vinnet

N‘

E—

Fig. A-1. Programmer-controller, front view.
42

Table A-1. Welding programmer front panel controls

Functions Related to Welding Current

1. Vernistat welding current programmer

. Maximum current potentiometer (0—-200 dial)
. Current “Program-Manual™ switch

. dc-ac and 200-50 A switches

. Ammeter

[ N C N Y I

Functions Related to Programmer Time

6. Upslope 5—2.5 sec switch
7. Weld time seconds switches
8. Downslope seconds switch
9. Upslope position lamps

10. Weld position lamps

11. Downslope position lamps

Functions Related to Tool Drive

12. Tool speed potentiometer (0—20.0 dial)
13. Tool speed meter
14. Tool start switch

Functions Related to Wire Feed and Arc Voltage

15. Wire speed potentiometer (0-50.0 dial)

16. Wire speed meter

17. Wire start and wire stop switches

18. AVC volts potentiometer (wire feed rate control
set, 0—1000 dial)

19. Arc voltage meter

20. AVC wire On-Off switch

Functions Related to Torch Cross Seam Oscillator

21. Osc speed potentiometer (0—300 dial)
22. Osc On-Off switch

Miscellaneous Functions

23. Gas prepurge lamp

24. Program On lamp

25. Weld On lamp

26. Gas postpurge lamp

27. Program On-Off switch

28. Welder On-Off switch

29. Contactor program-manual switch

30. Power On switch

31. Adaptive vertical controls

32. Pulse amperes potentiometer (10—1 ratio,
01000 dial)

33. Pulse fast/slow switch

34. Torch polarity switch

Sets and indicates programmed weld current with respect to program
position

Selects and indicates maximum weld current (200 A max)

Selects and indicates current control source

Select and indicate ammeter range

Indicates welding current (0—50 A, 0200 A)

Selects and indicates upslope time (2.5 or 5 sec)
Select and indicate weld time (10 to 999 sec)
Selects and indicates downslope time (0 to 9 sec)
Indicate program position

Indicate program position

Indicate program position

Selects and indicates tool speed (0—-20 in./min)
Indicates actual tool speed (0—20 in./min)
Selects and indicates tool start as related to program position

Selects and indicates maximum wire speed (050 in./min)

Indicates actual wire speed (0—50 in./min)

Select and indicate wire start and stop as related to program position
Selects and indicates AVC wire control voltage (06.5—16.5)

Indicates welding arc voltage (030 V)
Selects and indicates normal or AVC wire control

Selects and indicates oscillator frequency (50—-350 cpm)
Selects and indicates oscillator operation

Indicates preweld inert gas purge on

Indicates program on

Indicates weld on

Indicate postweld inert gas purge on

Selects and indicates program on or off (halted)

Selects and indicates welder contactor control on or off (disabled)
Selects and indicates welder contactor manual or programmed operation
Selects and indicates input power on or off

Low, average, high settings for arc voltage controlled torch arc length
Sets weld current pulse amplitude (0—100 A peak to peak)

Selects fast or slow weld current pulse rate (60 or 40 pulses/min)
(+) for ac welding mode
(—) for dc welding mode

43

PHOTO 061771

4
b
b
-
H
:
X0
3

Rear Panel

Fig. A-2. Programmer-controller, top view.
44

Table A-2. Welding programmer rear panel controls

Item Description Function
1 Pilot lamps (2) Welder current control indicators
2 Fuse Welding power supply current control fuse (10 A)
3 Male connector Welding power supply control cable
4 Fuse Power input fuse (5 A SB)
5 Male connector 120-V ac power input cable
6 Fuse Control power fuse (5 A SB)
7 Female connector Welding current sensor cable
8 Fuse Tool drive motor fuse (2 A SB)
9 Switch Tool drive servo On/Off switch
10 Fuse Oscillator motor fuse (1 A SB)
11 Female connector Tool cable
12 Fuse Wire feed motor fuse (2 A SB)
13 Switch Wire feed servo On/Off switch
14 Female connector Remote control cable
15 Female connector Recorder cable
16 Switch Arc voltage control {manual or automatic)

a?

45

Appendix B

Recommended Format for Establishing a Welding
Procedure for Automatic Welding

The information in this section is intended to assist newcomers to automated welding in setting up procedures
for automated systems. Qur experience in training and in working with people not familiar with automated welding
technology indicated the need for simple guide lines along with a list of available procedures for both nondestructive
and destructive examinations of welds. A sample welding procedure is given along with a typical list of general
welding parameters (Table B-1). Figures B-1 and B-2 illustrate a joint geometry for weld joints and details of
insert tack-weld sequencing respectively.

Sample Welding Procedure Record for Type Welds
A. SCOPE

This procedure record describes the criteria for automated gas tungsten-arc welding of Sched. _ (Mat’l )
(Type ) piping using the (Name of automated system). This procedure is based on use of
the (type) consumable insert with an internal (type gas) purge and cold wire feed in
the G and____ G positions. The procedure is detailed here for__in. diam. Sched. ___ pipe, and with
attached data tables (one for each size) applies also to other specified pipe sizes. All welding performed in
accordance with this procedure, which meets the requirements of Section [X of the ASME Code and RDT
Standards E 15-2T and F 6-5T (supplements to the ASME Code), must be done by welder-operators who have
demonstrated their proficiency by passing the qualification tests and receiving thorough training in the
operation of the automated equipment.

B. SAMPLE PROCEDURE RECORD FOR WELD #

1. Preweld Preparation
Reference: ASME Boiler and Pressure Vessel Code, Section IH, “Nuclear Vessels™

a.  General specifications. ASME Boiler and Pressure Vessel Code, Section IX, “Welding Qualifications,”
and RDT Standards E 15-2T and F 6-5T, “Requirements for Nuclear Components™ and “Welding
Qualifications”

b. Base metal
i.  Specification - ASTM A 312-64, “Specification for Seamless and Welded Austenitic Stainless
Steel Pipe.”
ii. Grade — type 304.
iii. Form and “P” number - seamless pipe, ASME Section IX “P”” No. 8.
iv.  Thickness — 0.280 in. nominal.
v. Diameter — 6.625-in. nominal outside.

c. Filler metal
i.  Specification - ASME-AWS Specification SFA-5.9, *‘Specification for Corrosion-Resisting
Chromium and Chromium-Nickel Steel Welding Rods and Bare Electrodes.”
ii.  Classification and chemical composition — ER 308.
iii. F and A numbers per Code Section 1X — type ER F7 (Table Q11.2), Weld Metal Analysis No. =
A7 (Table QI1.3).
46

Table B-1. Welding parameters — XYZ machine system?

Weld# X and type X Torch gas, flow X , X cfh Pass sequence -
Date X Backup gas, flow X , X cfh

Pipe-size, sched_X_ , _XF Filler wire diam., type_x_ , X -
Mat'l X ,type X Electrode diam. X , shape X

Joint type X Electrode proj. from cup X

Pipe position(s) X , X, | Cup# X Insert info: X

Weld passes =

Weld tool settings Root | 1 2 3 4 5 6
Torch height above pipe surf., in. X X -
Electr. tip to wire distance, in. X X -
Oscillator amplitude, in. X X |——p—a| X |—>
Wire feed retract (set at) in. X X -

Weld start (clock position on pipe) 11 1 11 1 11 1 11

Programmer control box settings

Arc voltage, V dc (Av.)

Y
>

Wire feed rate, in./min

Carriage drive rate, in./min

Carriage drive mode

P e | ] A
EA I B B
Y
>

Oscillation, cpm

Dwell time, left side, sec

Dwell time, right side, sec

Carriage drive start delay, sec X X >
Wire feed start delay, sec X X -
Wire feed upslope, sec X -
Wire feed delay, sec X -
Prepurge timer, sec X I
Postpurge timer, sec X :
Weld current, pulse high, A X X X |———T—»| X X
Pulse time, high, sec X X X |————e—— N | g
Pulse low current, A X X X |———] X X
Pulse time, low, sec X X X |————t—| X | =
[nitial current set, A X o
Current upslope time, sec X >
Current downslope time, sec X I
Total weld time, min and sec X X - X [=—> .
Arc voltage set, high, low X o X 4 - < | —

@X marks the spaces where specific values are to be provided.

47

ORNL-DWG 72-12241

16

/-

P 1/2 N, o]

Y-INSERT

—0.000

0.015 * 0.020

o

0.010 in.
MAXIMUM
MISMATCH

INSIDE OF PIPE MAY BE
MACHINED FOR THE
DISTANCE SHOWN, |F
NECESSARY, IN ORDER
TO HOLD THE LAND
AND ROQOT FACE TO
SPECIFIED DIMENSIONS

i L g PIPE_ _ il _ _

Fig. B-1. Joint geometry for weld joints, weld preparation.

ORNL—-DWG 72—-12242

+1/16 in. \'\/'

: 44 -

w c c 0

w - T.= =
083 |z w +
ol |® =
;g é +|_ +| _P !
¥ . - 4
¢32 e < S ;
L| = | X
i BN N

e Y

ieind b U

. £ )%

TACK WELD INSERT DETAIL

Fig. B-2. Tack-welding insert detail.

48

iv. Size — 0.045-in.-diam wire (on 1 '4-1b spools).

v. Form — continuous length wound on 4-in. spools.

vi. Wire surface — smooth finish, free of slivers, scratches, depressions, scale, or any foreign matter
that would affect weld quality.

vii. Storage — in original sealed containers or subsequently wrapped in plastic and sealed.

viii. Manufacturer — Airco Welding Products, heat No. W06753.

Shielding gas. Welding-grade argon at 20-cfh flow rate.

Backing gas. Welding-grade argon at 20-cfh flow rate during welding; prepurge prior to welding as
described in paragraph 2(a)iii.

Consumable inserts. Y-type consumable insert rings manufactured by WeldRing Company, Inc., of
Bell Gardens, California, and conforming to ASME-AWS Specification SFA-5.9, Classification ER
308.

Cleaning. The welding groove and adjacent area must be free of scale, rust, oil, grease, or any foreign
material that would affect the quality of weld metal or the operation of the welding equipment.
Before assembling the joint to be welded, the mating surfaces and adjacent areas must be wiped with
clean, lint-free cloths saturated with an approved solvent, acetone.

Weld groove type. Single Vee with 0.015- to 0.035-in. root face.
Joint geometry. Per attached Fig. B-1.

Joint preparation. Machine and/or grind to dimensions and finishes shown in attached Fig. B-1.

Weld joint setup.

i.  Pipe mismatch — per Para. NB-4425, ASME Section I, except uniform mismatch limited to
0.010 in., as detailed in Fig. B-1.

ii. Assembly and fixtures — the necessary clean fixtures must be provided to align and support joint
during welding, along with the necessary purge seal fixtures to prevent contamination of the
backing gas.

iii. Tack welding — as shown in Fig. B-2, mating ends of the pipe are to be tack welded to each
other, with an appropriately placed insert. Tack welding is to be done with a torch
coupled to a power supply using the following conditions:

current upslope time, sec

weld current, A

arc voltage, V

weld time, sec

current downslope time, sec

The following steps should be followed in the tack-welding sequence:
1. clean pipe and ring with acetone and lint-free rags.
manually align insert to proper position on one pipe section,
mark overlap point on insert,
cut off excess insert,
tack insert together using above conditions,
position insert between pipe sections,
clamp or restrain pipe sections, causing insert to seat firmly against the pipe-wall bevel,
tack at approximately %-in. intervals, alternating sides of the insert to avoid breaking
of tacks during root-pass welding.

e AT

iv. Welding positions — 5G for weld # (procedure verified for 2G position).
v.  Method of restraint — not applicable if the test joint was tack welded prior to welding.

49

. Welding process, current, and equipment

i.
ii.
- iii.

Process - - gas tungsten-arc, argon shielded.
Process control - automatic.
Current -- direct current, electrode negative (straight polarity). Ground cable, No. 2 gage,

connected from “Ground Terminal on power supply to work piece. Power
supply also grounded to “building ground.”

Current source — power supply.

Arc starter — high frequency.

Welding torch — with gas lens and gas cup size No.___.

Electrode - ¥%,-in.-diam nominal 2% thoriated tungsten, AWS classification EWTh-2, to
AWS Specification A 5.12-69, “Specification for Tungsten-Arc Welding Electrodes.”
Flowmeter — suitable for controlling the flow of argon within *1 cfh, actual setting for
pressure, 50 psig.

Gas lines - metal and plastic.

m. Preheat and interpass temperature

i.
ii.
2. Welding

Preheat temperature - 60 to 100°F: none required for record weld.
Interpass temperature 60 to 250°F, as determined by Tempilstik measurement.

a. General considerations

i.
1.
ii.

Welding parameters — as shown in Table B-1.

Electrode geometry and setting — as shown in Table B-1.

Welding technique - - The basic principle of gas tungsten-arc welding is to shield the weld
puddle of molten metal and the surrounding area with argon or some similar type of gas
while the temperature is high enough to cause oxidation by the atmosphere if not
protected. Therefore, it is necessary to perform all welding in a quiet atmosphere where no
air currents or drafts exist in the immediate vicinity of welding. [t may, in other locations,
be necessary to shield the area from drafts to assure a constant inert-gas atmosphere for the
weld.

Before welding starts, a minimum of 3 in. of the internal surface of the joint on each side of
the weld should be blanketed with argon. The back side of the joint should be purged with a
minimum of 20 cfh of argon for at least 10 min prior to root-pass welding and for at least 5
min prior to the first two fill passes. The volume of gas for the blanket should be at least
five times the volume of the area being blanketed. This area is to remain blanketed during
welding, and until the temperature of the weld falls below 250°F.

b. Procedures — equipment setup — The required procedure must be determined by the conditions
encountered in the piping system where welding is to be done.

c. Procedures — root pass welding

1.

The following preparations should be completed:

(a) An insert tacked into the pipe joint as shown in Fig. B-2.

(b) The joint set up per previously listed setup instructions.

(c) The track and/or carriage set per previous instructions; cables and hoses connected, ctc.

Double check on the following:

(a) Ground cable connected to machine “ground” and to pipe.

(b) Travel clearance available for carriage orbit. Sufficient clearance between supporting
structures, flanges, bosses, etc., and welding head 360° around the pipe.

Turn on primary ac power. Turn on circuit breaker on programmer-controller control panel.

Refer to Table B-1 and dial listed settings into the programmer.

Manually operate the following switches for final preoperational checks:

(a) AVCjog “up” and “down.”

(b) Wire feed, forward and retract.

(c) Carriage, forward and reverse,

50

vi. Set AVC head, torch and electrode.

vii. Push “Sequence Start Button.”

viii. Once arc starts, introduce manual torch set adjustments, if necessary.

ix. When the root pass is complete, overlap about Y, to ' in., exercise proper operator
judgment for proper tie-in; then operate “downslope” button to taper the weld and then
terminate it to be followed by the preset postpurging.

x. Refer to the inspection procedure and interpass temperature requirements before starting
with fill passes.

d. Procedure followed (interpass operations)

i.  Cleaning of weld beads — remove oxide particles and heavy film from weld bead and base
metal in line of arc travel before depositing each subsequent weld bead. Use only clean wire
brushes with stainless steel bristles and clean lint-free rags with approved solvent, acetone,
or equal.

ii. Examination for defects — visually examine each bead for cracks, holes, incomplete fusion,
lack of penetration, overlap, undercut, underfill, and other defects. Each bead to have a
smooth surface and contour and merge smoothly into previously deposited beads and/or
base metal.

iii. Repair of defects — remove weld defects by grinding, chipping, or filing before depositing
the next bead.

NOTE: PERFORM OTHER CODE REQUIRED INSPECTIONS, TF APPLICABLE.

e. Procedure for fill-pass welding;

i.  Refer to Table B-1 and dial listed settings into the programmer.

ii. Test check oscillation relative to amplitude setting and torch positioning within the weld
groove,

ili. Reposition the AVC head, torch, and electrode.

iv. Position the wire feed as required.

v.  Operate the “Sequence Start Button,” etc.

vi. Cover passes — the weld operator shall exercise best judgment to determine how many fill
passes will be required for completing a pipe weld. The cover passes, or cap passes, must
blend with the pipe outside diameter to form a circular, or slightly convex, overall weld
contour.

C. REFERENCE GUIDE FOR NONDESTRUCTIVE AND DESTRUCTIVE EXAMINATION LISTINGS

1. Nondestructive Examination

d.

Visual examination — Described in ORNL Standard Procedure, Section 9, of Inspection Engineering
Quality Assurance Procedures.

Radiographic examination — ORNL Standard Procedure Section 3, Appendix 2, of Inspection
Engineering Quality Assurance Procedures.

Liquid-penetrant examination — ORNL PE-NDT-1 (which conforms with ASME Code Section III
ASME E165 and RDT F3-6T).

2. Destructive Examination

d.

Metallographic examination (not required by ASME Code or RDT standards; however procedures
have been developed by ORNL for quality assurance and are available, if needed.

Root and face bend tests — ASME Code Section 1X.
Tensile tests — ASME Code Section IX and ASTM E8-65T.
Dimensional examination — ASME Code Section 111, ASME Code Case 1331-7, and RDT E 15-2T.
51

INTERNAL DISTRIBUTION

ORNL-4830
UC-80 Reactor Technology

1. G. M. Adamson 69. H. C. McCurdy
2. S.R. Ashton 70-74. 1. R. McGuffey
3. S. E. Beall 75. R. E. MacPherson
4. M. Bender 76—80. C. L. Matthews
5. W. A. Bird 81. W. R. Miller
6. R. Blumberg 82. R. L. Moore
7. 1. 0. Brown 83. H. A. Nelms
8. R. H. Bryan 84. G. C. Nelson
9. J. R. Buchanan 85-94. P. Patriarca
10. W. B. Cottrell 95. 1. N. Robinson
11. C. C. Courtney 96. M. W. Rosenthal
12. F. L. Culler 97. M. R. Sheldon
13. M. H. Fontana 98. R. G. Shooster
14. A.P. Fraas 99. I. R. Shugart
15—17. D. R. Frizzell 100. M. J. Skinner
18. R. M. Fuller 101-110. G. M. Slaughter
19. W. R. Gall 111. C. M. Smith, Jr.
20-29. G. M. Goodwin 112. I. Spiewak
30. D. L. Gray 113. D. A. Sundberg
31. W. L. Greenstreet 114. W, E. Thompson
32. A. L. Grindell 115. D. B. Trauger
33. W.O. Harms 116. R. W. Tucker
34. R.F. Hibbs(Y-12) 117. T. K. Walters
35. E. C. Hise 118. A. M. Weinberg
36. H. W. Hoffman 119. J. R. Weir
37—61. P. P.Holz 120. G. D. Whitman
62. V. T. Houchin 121, F.J. Witt
63. T. R. Housley 122. G.T. Yahr
64. M. I. Lundin 123-125. Central Research Library
65. R.N. Lyon 126. Document Reference Section
66—67. R. M. McClung 127—148. Laboratory Records Department -
68. H. E. McCoy 149. Laboratory Records ORNL RC
EXTERNAL DISTRIBUTION
150. L. Birch 151. T.R. Brown
Tennessee Valley Authority Tennessee Valley Authority
: Browns Ferry Nuclear Plant Browns Ferry Nuclear Plant
P.O. Box 2000 P.0O. Box 2000

Decatur, Ala. 35601

Decatur, Ala. 35601

152-155.

156-158.

159.

160-161.

162.

163—-164.

52

R. L. Carter, Bechtel Corporation
50 Beale St.

San Francisco, Calif. 94119
D. C. King

Westinghouse Hanford Co.
Hanford Engineering Lab.
P.O. Box 1970

Richland, Wash. 99352

P. R. Kirk

Tennessee Valley Authority
Browns Ferry Nuclear Plant
P.0. Box 2000

Decatur, Ala. 35601

W. J. Martin

Bechtel Corporation
Hanford Engineering Lab.
P.O. Box 9

Richland, Wash. 99352

J. Morgan

Tennessee Valley Authority
Browns Ferry Nuclear Plant
P.O. Box 2000

Decatur, Ala. 35601

A. C. Rediske

Bechtel Corporation
Hanford Engineering Lab.
P.O.Box 9

Richland, Wash. 99352

165.

166167,

168.

169—171.

172—173.

174—190.

191.
192.

193407,

L. Rousseau

Welding Engineer -
Westinghouse Hanford .
1212 Building, 300 Area

P.O. Box 1970 .
Richland, Wash. 99352

E. Thompson

Liquid Metals Engineering Center

P.O. Box 1449

Canoga, Calif. 91304

J. E. Wilkins

Tennessee Valley Authority

Browns Ferry Nuclear Plant

P.O. Box 2000

Decatur, Ala. 35601

Directorate of Licensing, USAEC
Washington, D.C.

Directorate Regulatory Standards
USAEC, Washington, D.C.

Manager, Technical Information Center
AEC, ORO

Patent Office, AEC, ORQ

Research and Technical Support Division
AEC, ORO

Given Distribution as shown in TID-4500
under Reactor Technology category
(including 25 copies — NTIS) N