12.

Cylinders, cylinder valves, couplings, regulators, 23. The numbers and markings stamped into cylinders
hoses, and apparatus shall be kept free from oily or shall not be tampered with.
greasy substances. Oxygen cylinders or apparatus 24. No person, other than the gas supplier, shall attempt
shall not be handled with oily hands or gloves. A jet to mix gases in a cylinder. No one, except the owner
of oxygen must never be permitted to strike an oily of the cylinder or person authorized by the owner,
surface, greasy clothes, or enter a fuel oil or other shall refill a cylinder.
storage tank. 25. No one shall tamper with safety devices on cylin-
13. A cradle, boat, or suitable platform shall be used ders or valves.
when transporting cylinders by a crane or derrick. 26. A hammer or wrench shall not be used to open cyl-
Slings or electric magnets shall not be used for this inder valves. If valves cannot be opened by hand,
purpose. Valve-protection caps shall always be in the supplier shall be notified.
place on cylinders designed to accept a cap. 27. Cylinder valves shall not be tampered with nor
14. Cylinders shall not be dropped, roughly handled, should any attempt be made to repair them. If trou-
or struck or permitted to strike each other violently. ble is experienced, the supplier should be sent a re-
Rough handling, knocks, or falls are liable to dam- port promptly, indicating the character of the trouble
age the cylinder, the valve, or the safety devices and and the cylinders serial number. Suppliers instruc-
cause leakage. tions as to its disposition shall be followed.
15. Valve-protection caps shall not be used for lifting 28. Fuel-gas cylinders shall be placed with valve end up
cylinders from one vertical position to another. Bars whenever they are in use. Liquefied gases shall be
shall not be used under valves or valve-protection stored and shipped with the valve end up.
caps to pry cylinders loose when frozen to the ground 29. Before connecting a regulator to a cylinder valve,
or otherwise fixed; the use of warm (not boiling) the valve shall be opened slightly and closed im-
water is recommended. Valve-protection caps are mediately. The valve shall be opened while standing
designed to protect cylinder valves from damage. to one side of the outlet; never in front of it. Never
16. Unless cylinders are secured on a special truck, crack a fuel-gas cylinder valve near other weld-
regulators shall be removed and valve-protection ing work or near sparks, flame, or other possible
caps, when provided for, shall be put in place before sources of ignition.
cylinders are moved. 30. Before a regulator is removed from a cylinder
17. Cylinders not having fixed hand wheels shall have valve, the cylinder valve shall be closed and the gas
keys, handles, or nonadjustable wrenches on valve released from the regulator.
stems while these cylinders are in service. In multi- 31. Nothing that may damage the safety device or interfere
ple-cylinder installations only one key or handle is with the quick closing of the valve shall be placed on
required for each manifold. top of an acetylene cylinder when it is in use.
18. Cylinder valves shall be closed before cylinders 32. If cylinder valves or fittings are found to have leaks
are moved. that cannot be stopped by closing the valve or fit-
19. Cylinder valves shall be closed when work is ting, the cylinders shall be plainly tagged and taken
finished. outdoors away from sources of ignition. A sign
20. Cylinders shall be kept far enough away from the should be placed near the leaky cylinders warning
actual welding or cutting operation so that sparks, unauthorized personnel not to approach them. The
hot dross, or flame will not reach them, or fire- supplier should be promptly notified, and the sup-
resistant shields shall be provided. pliers instructions for the return of the cylinders
21. Cylinders shall not be placed where they might be- followed.
come part of an electric circuit. Contacts with third 33. Safety devices shall not be tampered with.
rails, trolley wires, or the like shall be avoided. 34. Fuel gas shall never be used from cylinders through
Cylinders shall be kept away from radiators, pip- torches or other devices equipped with shutoff
ing systems, and layout tables that may be used for valves without reducing the pressure through a
grounding electric circuits, such as for arc welding suitable regulator attached to the cylinder valve or
machines. Any practice such as the tapping of an manifold.
electrode against a cylinder to strike an arc shall be 35. The cylinder valve shall always be opened slowly.
prohibited. 36. An acetylene cylinder valve shall not be opened
22. Cylinders shall never be used as rollers or supports, more than one and one-half turns of the spindle, and
whether full or empty. preferably no more than three-fourths of a turn.

144Chapter 5Gas Welding

Manifold Distribution The acetylene manifolds must be equipped with a flash
Where it is necessary to supply a number of work stations arrester, Figs. 5-11 and 5-12, page 146, to prevent flash-
and conserve space, both oxygen and the fuel gas may be back through the manifold into the cylinders. In addition,
supplied by a manifold system, Figs. 5-8, 5-9, and 5-10. each cylinder is connected to the manifold by means of an

Fig. 5-8 Note torch and filler metal angles and location on this
practice plate. Gases are being supplied via a manifold system as
shown in Fig. 5-9. Bench top surface being protected with fire brick. Fig. 5-9 This manifold system is being used to supply
Location: Northeast Wisconsin Technical College McGraw-Hill oxygen and acetylene to the booths on both sided of it.
Education/Mark A. Dierker, photographer Location: Northeast Wisconsin Technical College McGraw-Hill
Education/Mark A. Dierker, photographer

Oxygen Line Fig. 5-10 A typical station outlet for both oxygen
Welded Joint Acetylene Line and acetylene pipelines from the source. Stations for
the attachment of oxygen and acetylene regulators are
placed at convenient points around the shop or plant
where welding or cutting is to be done.

Slope of Pipe in
Oxygen
Direction of Generator
or Manifold
Acetylene Shutoff
Valve

Oxygen Line
Regulator
Acetylene
Line Regulator

Hose Moisture Drain

Hose to Torch

Gas Welding Chapter 5145

 Master Regulator
Individual
Shutoff Valves

Master
Bank Valves

Individual Flash
Arresters

Water Flash
Seal Arrester

Fig. 5-11 An acetylene gas manifold system. Thermadyne Industries, Inc.

To Distributing Line Extra Heavy Brass Pipe and Fittings

Blow-Off Line Shutoff Valve Cylinder Underwriter

Valve Valve Wrench Wall Approved
Acetylene Bracket
Regulator Flash Arrester
A
Brass
Tubing

High
Pressure
Globe
Valve
Acetylene
Cylinder
Water Check
Level Drain Valve
Flash Arrester
Exhaust from
Blow-Off Valve
to Be Piped Outdoors

A Section A - A

Fig. 5-12 Acetylene cylinder manifolds are constructed of extra heavy pipe and
fittings to conform to the regulations of the National Board of Fire Underwriters.

146Chapter 5Gas Welding

 individual pigtail flash arrester and backcheck
valves. There is the full cylinder pressure of
2,000 p.s.i. in the oxygen manifold pipes. The
Master Regulator manifold regulator reduces the pressure to
50 or 75 pounds in the line that goes to the vari-
ous station outlets in the shop. Figures 5-13 and
5-14 present an oxygen manifold installation.
Both types of manifolds have a pressure
regulator for the purpose of reducing and con-
trolling the pressure of the gas to the work
Copper Tubing station. The work station is also equipped with
an acetylene and oxygen regulator for further
pressure control at the welding or cutting
torch, as shown in Fig. 5-10, page 145.
Manifold piping systems for acetylene
or acetylenic compounds should be steel or
wrought iron. Copper can be used for oxygen
piping systems. Manifold systems range from
very simplistic to highly sophisticated automatic
systems for virtually any gas control require-
ment. Where high capacity is required, liquid
vessel systems can be used. Figure 5-15, page
148 shows a sophisticated design, which auto-
matically switches between the primary and
reserve supply with no interruption of service.

Acetylene Generators
Large users of acetylene generate their own gas
Fig. 5-13 Oxygen manifold system. Note master regulator and flexible copper
tubing leading from each tank. Thermadyne Industries, Inc.
in an acetylene generator, Fig. 5-16, page 148.
The carbide-to-water generators are used to
produce acetylene gas for welding and cutting.
Check Valve Small amounts of calcium carbide are fed into
relatively large amounts of water. The water
Black Wrought Iron Pipe
Annealed
absorbs the heat given off by the chemical
High Pressure Globe Valve Copper Tubing reaction, and the gas is cooled and purified
Relief Valve
Set at 150 lbs. Extra Heavy Brass Pipe by bubbling through the water. Generators of
Wall this type can produce up to 6,000 cubic feet of
A Bracket
acetylene per hour.
There are two classes of generators: low
pressure, in which the acetylene pressure is less
Handle
than 1 p.s.i., and medium pressure, in which the
High Pressure acetylene pressure is from 1 to 15 p.s.i. You will
Valves
recall that free acetylene cannot be used at a
pressure higher than 15 p.s.i.
Welded Acetylene generators are not used by in-
Joint dividual companies or schools but are used
by large gas suppliers. The acetylene prod-
uct is then provided to the consumer in
A Section A - A
cylinders. This has been brought about due
Fig. 5-14 An oxygen manifold. It is often convenient to place all of the oxygen to the various regulations that must deal
cylinders at one point where they may be readily handled and to c onnect them with the byproducts, from an environmental
together to an oxygen manifold as illustrated. aspect. Additional concerns come from the

Gas Welding Chapter 5147

 Acetylene welding hose
Hose couplings
Single-purpose cutting torch or welding torch
Cylinders and cart for portability
Flash arrestor and check valves (protective equipment)
Flint lighter to ignite torch
Approved protective equipment shall be installed in an
OAW system to prevent:
Backflow of oxygen into the fuel-gas supply system
Passage of a flashback into the fuel-gas supply system
Excessive back pressure of oxygen in the fuel-gas sup-
ply system
The two functions of the protective equipment may be
combined in one device or provided by separate devices.
Fig. 5-15 An automated manifold system utilizing the larger The protective equipment should be located in the main
capacity liquid storage cylinders. Thermadyne Industries, Inc./ supply line, at the head of each branch line in a mani-
Victor Equipment Company
fold system, or at each location where fuel gas is with-
drawn. The backflow protection should also be provided
to prevent fuel gases from flowing into the oxygen system.
Flashback protection should be provided to prevent flame
from passing into the fuel-gas system or oxygen gas
system.
Much of this equipment is illustrated in Fig. 5-17A
and B. Note that the welding torch comes with a wide
assortment of tips that provide a choice in the volume of
heat desired. When welding or flame cutting, the welder
must wear a pair of protective goggles to prevent harm

A B OU T WEL DIN G

Shrinkage
Factors causing contraction or shrinkage
during welding:
1. Heat input
2. Mass of the structure
Fig. 5-16 A large acetylene generator for commercial supply.
It can use carbide sizes from lump to 14 ND. Source: Rexarc 3. Ambient temperature
4. Cooling rate
5. External and internal restraint

requirement for operating licenses, inspections, and use

of trained operators.

Welding Equipment J OB T IP
Oxyacetylene welding requires the following equipment:
Oxygen regulator The Internet
Acetylene regulator You can go job hunting on the Web.
Oxygen welding hose

148Chapter 5Gas Welding

 Pressure Regulators
The pressure at which oxygen and acetylene is compressed
into cylinders is much too high for direct use in welding
and cutting. Some means must be provided to reduce the
high internal cylinder pressureabout 2,200 p.s.i. in the
case of oxygento the relatively low pressure of 0 to
45 p.s.i. required for welding and cutting. The flame must
also be steady and uniform. This can be accomplished
only if the gas pressures do not fluctuate. Pressure regula-
tors carry out both of these all-importantfunctions. They
reduce the high cylinder pressure to that used for welding,
and they can maintain that pressure without variation dur-
ing the welding operation.
Design Figure 5-20, page 150 illustrates regulator de-
sign. They have a union nipple (A) for attachment to
the cylinders and an outlet connection (B) for the hose
leading to the torch. Two pressure gauges are mounted
on the body of the regulator: one (C) shows the pres-
sure in the cylinder, and the other (D) shows the pres-
sure of the gas being supplied to the torch. The pressure
Fig. 5-17A A travel kit for a medium duty torch for cutting, heat- gauge that shows the pressure in the cylinder is also
ing, welding, brazing, and soldering. Note the cutting tip, welding
tips, heating tip, and ancillary equipment such as storage case.
useful in indicating to the welder the amount of gas
Gentec remaining in the cylinder.
The working pressure is adjusted by means of a hand
screw (E). When this screw is turned to the left, or coun-
terclockwise, the valve mechanism inside the regulator is
shut off, and gas cannot pass through the regulator to the
torch. Turning the pressure-adjusting screw to the right,
or clockwise, presses it against the regulator mechanism.
The valve opens, and gas passes through the regulator to
the torch at the pressure shown on the working pressure
gauge. Any pressure can be set up by turning the han-
dle until the desired pressure is indicated. Figure 5-21,
page 151 illustrates the internal mechanism of a typical
single stage gas regulator.
Safety Precautions The following precautions regarding
the use of regulators should be observed:
Inspect all nuts and connections before use to detect
faulty seats that may cause leakage of gas.
Keep clean and free from oil and grease.
Fig. 5-17B Light duty torch for welding, principally for jewelry Before attaching the regulator, crack the cylinder
and other fine work. Note the various tips and magnetic holder. valve to blow out contaminants.
Smith Equipment Before opening the valve of a cylinder (always open
cylinder valves slowly) to which a regulator has been
attached, be sure that the pressure-adjusting screw
to the eyes from hot particles of metal, sparks, and glare. has been completely released by turning it to the left.
A flint lighter is also required to light the torch. The Failure to do this allows the full cylinder pressure to
equipment is set up for welding in Fig. 5-18, page 150. hit the engaged mechanism of the regulator. Not only
Portable tank outfits are mounted on a truck similar to will the regulator be damaged, but it may also burst
that shown in Fig. 5-19, page 150. and injure the welder.

Gas Welding Chapter 5149

 Regulator Outlet Pressure Gauge Regulator Outlet Pressure Gauge
Cylinder Pressure Gauge Cylinder Pressure Gauge
Hand Wheel Oxygen Cylinder Valve
Cylinder Adjusting
Cap Screw Cylinder
Bursting Cap
Oxygen Disc
Regulator A

Acetylene C
Regulator Valve
Wrench 91/8 Brass
Adjusting
Fusible Mixing
Screw B
Plug Section
D
55 Welding Torch
Acetylene Acetylene
Cylinder Torch Valve
Copper
Valve 12 441/2 E Section
Handle

F
Flame consumes 2.5
Oxygen parts of oxygen to
Torch 1 part of acetylene.
Valve One part of oxygen
is supplied through
Fusible torch, 1.5 parts
Plugs in from surrounding air.
Bottom of Flame temperature
Cylinder 6300F.

Acetylene Cylinder Oxygen Cylinder

Approximate weight full 215 lb Approximate weight full 145 lb
contains approximately 250 ft3 contains 220 ft3 of oxygen.
of acetylene. Pressure of oxygen 2,000 lb per in2.
Pressure of acetylene
about 250 lb per in2. Oxygen Hose
Acetylene cylinders are
filled with a porous filler Acetylene Hose
and acetone in which the
acetylene is dissolved.

Fig. 5-18 Diagram showing cylinders, regulators, hose, and welding torch
properly connected and ready to operate. Torch and/or regulators
need to be equipped with approved flash arrestors and check valves.

D D
C
C

E
E

A
B B
Acetylene Oxygen
Fig. 5-19 Steel handtruck used to carry oxygen and acetylene
tank and welding equipment. A portable outfit offers wide flexibility
in the use of gas welding in both shop and field. Thermadyne Fig. 5-20 Oxygen and acetylene welding regulators for use with
Industries, Inc. individual tanks. Thermadyne Industries, Inc.

150Chapter 5Gas Welding