Chapter
17
Oxyfuel Welding and Cutting
Equipment, Setup, and Operation
OBJECTIVES
After completing this chapter, the student should be able to:
• Identify all of the components and equipment found in a typical oxyfuel
welding station.
• Demonstrate the proper assembly, testing, lighting, adjusting, and
disassembling of an oxyfuel system.
• List the proper safety procedures for setting up and operating an oxyfuel
system.
KEY TERMS
acetylene (C2H2)
backfire
Bourdon tube
carburizing flame
combination welding
and cutting torch
creep
cutting torch
cylinder pressure
diaphragm
flashback
flashback arrestor
gauge
leak-detecting solution
line drop
methylacetylenepropadiene (MPS)
neutral flame
oxidizing flame
oxyacetylene
oxyfuel gas torch
purged
regulators
safety disk
safety release valve
seat
spark lighter
two-stage regulators
valve packing
working pressure
INTRODUCTION
Oxyfuel welding is one of the oldest welding processes. It was referred to as gas
welding, although the process today is referred to as oxyacetylene or oxyfuel
welding. Oxyfuel refers to the fact that many fuel gases other than acetylene
(C2H2) can be used, although acetylene is still the most popular fuel gas.
387
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388
CHAPTER 17
Oxyfuel welding, cutting, brazing, hard surfacing, heating, and other similar processes use the same
basic equipment. The same safety procedures must
be followed for each process when storing, handling,
assembling, testing, adjusting, lighting, shutting off,
and disassembling this equipment. Oxyfuel processes
are safe only when all of the proper setup and operating procedures have been followed. Improper or careless work habits can cause serious safety hazards.
Although numerous manufacturers produce
a large variety of gas equipment, it all works on the
same principle. Much of the basic equipment is common to all oxyfuel processes, and some parts, such
as cylinders, regulators, hoses, hose fittings, safety
valves, and torches, may be interchangeable. When
welders are not sure how new equipment is operated,
they should seek professional help. A welder should
never experiment with any equipment.
All oxyfuel processes use a high-heat, hightemperature flame produced by burning a fuel gas
mixed with pure oxygen. The gases are supplied in
pressurized cylinders. The cylinder gas pressure must
be reduced by using a regulator to lower working gas
pressure. The gas flows from the regulator through
flexible hoses to the torch. Valves on the torch body are
opened and adjusted to control the gas flow through
the torch to the tip. At the torch tip the gases have
been mixed to produce a properly combusting flame.
Acetylene is the most widely used fuel gas because
of its high temperature and concentrated flame, but
about 25 other gases are available. The regulator
and torch tip are usually the only equipment change
required to use another fuel gas. The flame adjustment and operating skills required are often different,
but the storage, handling, assembling, and testing are
the same. When changing gases, make sure the tip
can be used safely with that gas.
OXYFUEL EQUIPMENT
Because of the similarities in the way equipment is
operated and assembled, the following information
can be easily applied to all oxyfuel welding systems.
Pressure Regulators
All pressure regulators reduce the high cylinder or system pressure to the proper lower working pressure. It
is important that the regulator keep the lower pressure
constant over a range of flow rates. Some of the various
types of pressure regulators are low-pressure regulators,
high-pressure regulators, single-stage regulators, dualstage regulators, cylinder regulators, manifold regulators, line regulators, and station regulators. Although
they all work the same, they are not interchangeable.
CAUTION
Although all regulators work the same way, they cannot be safely used interchangeably on different types
of gas or for different pressure ranges without the
possibility of a fire or an explosion.
Regulator Operation
A regulator works by holding the forces on both
sides of a diaphragm in balance, Figure 17-1. As the
REGULATOR
SPRING
HIGH-PRESSURE
VALVE
ADJUSTING SCREW
CYLINDER
VALVE
2200 LB
10 PSIG
FLEXIBLE
DIAPHRAGM
HOSE
TORCH VALVE
THROUGH VALVE OF CYLINDER
TO INPUT OF REGULATOR
FIGURE 17-1
Force applied to the flexible diaphragm by the adjusting screw
through the spring opens the high-pressure valve. © Cengage Learning 2012
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
389
first spring is preset at the factory to reduce the
cylinder pressure to 225 psig (0.35 kg/cm2g). The
second spring is adjusted like other regulators. Because
the second high-pressure valve has to control a maximum pressure of only around 225 psig (0.35 kg/cm2g),
it can be larger, thus allowing a greater flow.
2200 LB
10 PSIG
Pressure Gauges
THROUGH VALVE OF
CYLINDER TO INPUT
OF REGULATOR
There may be one or two pressure gauges on a regulator. The working pressure gauge shows the regulated
pressure being controlled for the torch, and the cylinder pressure gauge shows the remaining cylinder pressure, Figure 17-5. The working pressure gauge shows
the pressure at the regulator, which is not exactly the
same as the actual pressure at the torch tip. The torch
tip pressure is always a little less than the working
pressure due to some line drop. Line pressure drop
is the greater on small diameter lines and on longer
line lengths than it is on larger diameter and shorter
line lengths, Table 17-1. The line drop is caused by the
resistance of a gas as it flows through a line.
FIGURE 17-2 When the gas pressure against the
flexible diaphragm equals the spring pressure, the highpressure valve closes. © Cengage Learning 2012
pressure-adjusting screw is turned inward, it increases
the force of a spring on the flexible diaphragm and
bends the diaphragm away. As the diaphragm is
moved, the small high-pressure valve is opened, allowing more gas to flow into the regulator. The gas pressure cancels the spring pressure, and the diaphragm
returns back to its original position, closing the highpressure valve, Figure 17-2. When the regulator is used,
the gas pressure on the back side of the diaphragm is
reduced, the spring again forces the valve open, and gas
flows. The drop in the internal pressure can be seen on
the working pressure gauge, Figure 17-3.
Because some small single-stage pressure regulators have difficulty maintaining the proper working
pressure under high flow rates, two-stage regulators
were developed. Two-stage regulators have two sets
of springs, diaphragms, and valves, Figure 17-4. The
NOTE: The high-pressure gauge on a regulator shows
cylinder pressure only. This gauge may be used to indicate the amount of gas that remains in a cylinder. However, the cylinder pressure of liquefied gases, such as
CO2, propane, and methylacetylene-propadiene (MPS),
will remain fairly constant as the gas is used as long
as some liquid remains in the cylinder. Therefore, the
cylinder pressure on these cylinders cannot be used to
determine the quantity of remaining gases. The only
way to accurately determine the amount of remaining
gases in these cylinders is to weigh them.
9 PSIG
2200 LB
10 PSIG
THROUGH VALVE OF
CYLINDER TO INPUT
OF REGULATOR
FIGURE 17-3
A drop in the working pressure occurs when the torch
valve is opened and gas flows through the regulator at a constant
pressure. © Cengage Learning 2012
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390
CHAPTER 17
STEM-TYPE SEAT MECHANISM
INLET PRESSURE AIDS IN SEALING
PRECISION MACHINED NOZZLE
STAINLESS STEEL
DIAPHRAGM
BRONZE INLET FILTER
KEEPS OUT DIRT AND
FOREIGN MATERIALS
ADJUSTING SPRING
DESIGNED FOR
PRECISE PRESET
EXTERNAL RELIEF
VALVE SYSTEM
FIGURE 17-4
Two-stage oxygen regulator. Thermadyne Industries, Inc.
CYLINDER
PRESSURE
GAUGE
WORKING
PRESSURE
GAUGE
SAFETY
RELEASE
VALVE
FIGURE 17-5
Safety release valve on an oxygen regulator.
Thermadyne Industries, Inc.
Regulator Pressure* for Hose Lengths
ft (m)
Tip Pressure
psig (kg/cm2 G)
1 (0.1)
5 (0.35)
10 (0.7)
10 ft (3 m)
25 ft (7.6 m)
50 ft (15.2 m)
75 ft (22.9 m)
100 ft (30.5 m)
1 (0.1)
5 (0.35)
2.25 (0.15)
6.25 (0.4)
3.5 (0.27)
7.5 (0.52)
4.75 (0.35)
8.75 (0.6)
6 (0.4)
10 (0.7)
11.25 (0.75)
12.5 (0.85)
13.75 (0.95)
15 (1.0)
10 (0.7)
*These values are for hoses with a diameter of 1/4 in. (6 mm); larger or smaller hose diameters or high flow rates will change these pressures.
Table 17-1 Regulator Pressure for Various Lengths of Hose
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
SPRING
THIN DISC
SAFETY RELEASE VALVE
FIGURE 17-6
REGULATOR BODY
REGULATOR BODY
BALL
391
Pressure release valves.
Regulator Safety Pressure Releases
Regulators may be equipped with either a safety
release valve or a safety disk to prevent excessively
high pressures from damaging the regulator. A
safety release valve is made up of a small ball held
tightly against a seat by a spring. Excessively high
pressures will push the ball back away from the seat,
safely releasing potentially explosive pressure. The
release valve will reseat itself after the excessive
pressure has been reduced.
A safety disc is a thin piece of metal held
between two seals, Figure 17-6. Excessively high pressures will cause this disk to rupture or burst, releasing the pressure. Rupture disk safety devices are
one-time-use devices. They release all of the cylinder
pressure once ruptured; they do not reseat after the
pressure is lowered to a safe level as the safety release
valves do. If a rupture disk opens, it must then be
replaced before the regulator can be used again.
SAFETY DISC VALVE
© Cengage Learning 2012
on the working side, resulting in damage to the diaphragm, gauge, hoses, or other equipment.
CAUTION
Regulators that creep excessively or beyond the safe
working pressure must not be used.
A gauge that gives a faulty reading or that is
damaged can result in dangerous pressure settings.
Gauges that do not read “0” (zero) pressure when the
pressure is released, or those that have a damaged
glass or case, must be repaired or replaced.
CAUTION
All work on regulators must be done by properly
trained repair technicians.
Regulator Safety Practices
The regulator pressure-adjusting screw should be
backed off each time the oxyfuel system is being shut
down. This is done to release the spring and diaphragm pressures, which, over time, may cause damage. Keeping a spring compressed and the diaphragm
stretched can cause the spring to weaken and the diaphragm to be permanently distorted.
In addition, when the cylinder valve is reopened,
some high-pressure gas can pass by the open highpressure valve before the diaphragm can close it. This
condition may cause the diaphragm to rupture, the
low-pressure gauge to explode, or both.
High-pressure valve seats that leak result in a
creep or rising pressure on the working side of the
regulator. This usually occurs when the gas pressure
is set but no gas is flowing. If the leakage at the seat is
severe, the maximum safe pressure can be exceeded
CAUTION
Regulators should be located far enough from the
actual work that flames or sparks cannot reach them.
Leak Detection
A leak-detecting solution should be purchased premixed. Leak-detecting solution must be free flowing so that it can seep into small joints, cracks, and
other areas that may have a leak. The solution must
produce a good quantity of bubbles without leaving a
film. The solution can be dipped, sprayed, or brushed
on the joints.
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392
CHAPTER 17
CAUTION
Some detergents are not suitable for O2 because of
an oil base. Use only O2-approved leak-detection
solutions on oxygen fittings.
Regulator Fittings
Both regulators and gas cylinder fittings have a variety of different designs for various types of gases to
ensure that regulators cannot be connected to the
wrong gas or pressure, Figure 17-7. A few adapters
are available that will allow some regulators to be
attached to a different type of fitting, provided that
the gas type and pressure are similar. For example,
adapters are available for an external left-hand acetylene regulator fitting to an internal right-hand cylinder fitting, or vice versa. Both of these cylinders
contain a low-pressure fuel gas. Other adapters are
available that will allow argon or mixed gas regulators
to fit a flat washer-type CO2 cylinder fitting. Both of
these cylinders contain a high-pressure inert or semiinert gas, Figure 17-8.
The connections to the cylinder and to the hose
must be kept free of dirt and oil. Fittings should screw
together freely by hand and require only light wrench
pressure to be leak tight. If the fitting does not
tighten freely on the connection, both parts should be
cleaned. If the joint leaks after it has been tightened
with a wrench, the seat should be checked. Examine
the seat and threads for damage. If the seat is damaged, it can be repaired by a manufacturer-authorized
regulator repair shop. Severely damaged connections
must be replaced.
The outlet connection on a regulator is either a
right-hand fitting for oxygen or a left-hand fitting for
fuel gases. A left-hand threaded fitting has a notched
nut, Figure 17-9.
Regulator Use and Servicing
There are no internal or external moving parts on a
regulator or a gauge that require oiling, Figure 17-10.
(A)
(B)
(C)
(D)
FIGURE 17-7
(A) Acetylene cylinder valve (left-hand thread). (B) Oxygen cylinder valve. (C) Argon cylinder valve.
(D) Carbon dioxide (CO2) cylinder valve. Larry Jeffus
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
393
NOTE: NO OIL
FIGURE 17-10
Never oil a regulator.
Thermadyne Industries, Inc.
(A)
(B)
FIGURE 17-8
If the adjusting screw becomes tight and difficult
to turn, it can be removed and cleaned with a dry, oilfree rag. When replacing the adjusting screw, be sure
it does not become cross-threaded. Many regulators
use a nylon nut in the regulator body, and the nylon is
easily cross-threaded.
When welding is finished and the cylinders are
turned off, the gas pressure must be released and the
adjusting screw backed out. This is required both by federal regulation and to prevent damage to the diaphragm,
gauges, and adjusting spring if they are left under a load.
A regulator that is left pressurized causes the diaphragm
to stretch, the Bourdon tube to straighten, and the
adjusting spring to compress. These changes result in a
less accurate regulator with a shorter life expectancy.
Cylinder to regulator adapter. Larry Jeffus
DESIGN AND SERVICE OF
WELDING AND CUTTING
TORCHES
The oxyacetylene hand torch is the most common
type of oxyfuel gas torch used for welding and cutting. The hand torch can be purchased as either a
combination welding and cutting torch or a cutting torch only, Figure 17-11 and Figure 17-12. The
FIGURE 17-9 Left-hand threaded fittings are identified
with a notch. Larry Jeffus
CAUTION
Oiling a regulator is unsafe and may cause a fire or
an explosion.
FIGURE 17-11
A torch body or handle used for
welding or cutting. Thermadyne Industries, Inc.
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394
CHAPTER 17
Torch Care and Use
FIGURE 17-12
A torch used for cutting only.
© Cengage Learning 2012
The torch body contains threaded connections for
the hoses and tips. These connections must be protected from any damage. Most torch connections are
external and made of soft brass that is easily damaged.
Some connections, however, are more protected
because they have either internal threads or stainless
steel threads for the tips. The best protection against
damage and dirt is to leave the tip and hoses connected when the torch is not in use. Because the hose
connections are close to each other, a wrench should
never be used on one nut unless the other connection
is protected with a hose-fitting nut, Figure 17-14.
The hose connections should not leak after they
are tightened with a wrench. If leaks are present, the
seat should be repaired or replaced, Figure 17-15. The
valves should be easily turned on and off and should
stop all gas flowing with minimum finger pressure.
FIGURE 17-13 A combination welding and cutting
torch kit. Thermadyne Industries, Inc.
combination welding and cutting torch offers more
flexibility because a cutting head, welding tip, brazing
tip, or heating tips can be attached to the same torch
body, Figure 17-13. Combination torch sets are often
used in schools, automotive repair shops, auto body
shops, small welding shops, or any other situation
where flexibility is needed. The combination torch sets
are usually more practical for portable welding since
the one unit can be used for both cutting and welding.
Dedicated cutting torches are usually longer than
combination torches. The longer length helps keep the
operator farther away from heat and sparks. In addition, thicker material can be cut with greater comfort.
Most manufacturers make torches in a variety
of sizes for different types of work. There are small
torches for jewelry work and large torches for heavy
plates. Specialty torches for heating, brazing, or soldering are also available. Some of these use a fuel-air
mixture. Fuel-air torches are often used by plumbers
and air-conditioning technicians for brazing and soldering copper pipe and tubing.
There are no industrial standards for tip size identification, tip threads, or seats. Therefore, each style, size,
and type of torch can be used only with the tips made
by the same manufacturer to fit the specific torch.
FIGURE 17-14 One hose fitting will protect the threads
when the other nut is loosened or tightened. Larry Jeffus
FIGURE 17-15
The torch valves should be checked
for leaks, and the valve packing nut should be tightened if
necessary. Larry Jeffus
Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
To find leaking valve seats, set the regulators to a
working pressure. With the torch valves off, spray the
tip with a leak-detecting solution. The presence of
bubbles indicates a leaking valve seat.
No gas should leak past the valve stem packing.
To test for leaks around the valve stem, set the regulator to a working pressure. With the valves off, spray
the valve stem with a leak-detecting solution and watch
for bubbles, indicating a leaking valve packing. The
valve stem packing can now be tested with the valve
open. Open the valve and spray the stem and watch
for bubbles, which would indicate a leaking valve
packing. If either test indicates a leak, the valve stem
packing nut can be tightened until the leak stops.
After the leak stops, turn the valve knob. It should
still turn freely. If it does not or if the leak cannot be
stopped, replace the valve packing.
The valve packing and valve seat can be easily
repaired on most torches by following the instructions given in the repair kit. On some torches, the
entire valve assembly can be replaced if necessary.
WELDING AND HEATING
TIPS
Because no industrial standard tip size identification
system exists, the student must become familiar with
the size of the orifice (hole) in the tip. The larger the
395
FIGURE 17-16 A variety of tip styles and sizes for one
torch body. Larry Jeffus
diameter of the hole in a welding tip, the higher the
heating capacity. The heating capacity of a tip determines the thickness range it can be used on. Comparing the overall size of tips and, therefore, their heating
capacity can be done only for tips made by the same
manufacturer for the same type and style of torch,
Figure 17-16. Learning a specific manufacturer’s system is not always the answer because on older, worn
tips the orifice may have been enlarged by repeated
cleaning.
Tip sizes can be compared to the numbered drill
size used to make the hole, Table 17-2. The sizes of
tip cleaners are given according to the drill size of the
hole they fit. By knowing the tip cleaner size commonly used to clean a tip, the welder can find the
same-size tip made by a different manufacturer. The
tip size can also be determined by trial and error.
Tip Cleaner Standard Set
Use
Cleaner
Smallest
Largest
1 .................
2 .................
3 .................
4 .................
5 .................
6 .................
7 .................
8 .................
9 .................
10.................
11.................
12.................
13.................
For
Drill
77-76
75-74
73-72-71
70-69-68
67-66-65
64-63-62
61-60
59-58
57
56
55-54
53-52
51-50-49
77 .0160 "
(0.4064 mm)
49
.0730"
(1.8542 mm)
Table 17-2 Tip Cleaner Size Compared to Drill Size as Found
on Most Standard Tip-Cleaning Sets
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396
CHAPTER 17
Tip Care and Use
Torch tips may have metal-to-metal seals, or they
may have O rings or gaskets between the tip and the
torch seat. Metal-to-metal seal tips must be tightened
with a wrench. Tips with an O ring or a gasket are
tightened by hand. Follow the torch manufacturer’s
recommendations. Using the wrong method of tightening the tip fitting may result in damage to the torch
body or the tip.
Dirty welding and cutting tips can be cleaned
using a set of tip cleaners or tip drills, Figure 17-17.
Using the file provided in the tip-cleaning set, file
the end of the tip smooth and square, Figure 17-18.
Next, select the size of tip cleaner that fits easily into
the orifice. The tip cleaner is a small, round file and
FIGURE 17-19
cleaner.
Cleaning a tip with a standard tip
© Cengage Learning 2012
should be moved in and out of the orifice only a few
times, Figure 17-19. Be sure the tip cleaner is straight
and that it is held in a steady position to prevent it
from bending or breaking off in the tip. Excessive
use of the tip cleaner tends to ream the orifice, making it too large. Therefore, use the tip cleaner only as
required. Once the tip is cleaned, turn on the oxygen
for a moment to blow out any material loosened during the cleaning.
Backfires
A backfire occurs when a flame goes out with a loud
snap or pop. A backfire may be caused by the following:
FIGURE 17-17
Tools used to repair tips. Larry Jeffus
• Touching the tip against the workpiece
• Overheating the tip
• Operating the torch when the flame settings are
too low
• Loose tip
• Damaged seats
• Dirt in the tip
The problem that caused the backfire must be
corrected before relighting the torch. A backfire may
cause a flashback.
Flashbacks
FIGURE 17-18
Standard set of tip cleaners. Larry Jeffus
A flashback occurs when the flame burns back
inside the tip, torch, hose, or regulator. A flashback
produces a high-pitched whistle. If the torch does
flashback, close the welding torch oxygen valve at
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
once, and then close the torch fuel valve. The order
in which the valves are closed is not as important as
the speed at which they are closed. A flashback that
reaches the cylinder may cause a fire or an explosion.
Closing the torch oxygen valve stops the flame
inside at once. Then the fuel-gas valve should be
closed and the torch must be allowed to cool off
before repairing the problem. When a flashback
occurs, there is usually a serious problem with the
equipment, and a qualified technician should be
called. After locating and repairing the problem, blow
gas through the tip for a few seconds to clear out any
soot that may have accumulated in the passages. A
flashback that burns in the hose leaves carbon deposits inside that may explode and burn in a pressurized
oxygen system. Replace any hose that has been damaged by a flashback.
397
have reverse flow valves built into the torch body, but
most torches must have these safety devices added.
If the torch does not come with a reverse flow valve,
it must be added to either the torch end or regulator
end of the hose.
A reverse flow of gas can occur through the torch
if it is not turned off or the pressure is not properly
bled off. When bleeding off the gas pressure, open one
valve at a time so that the gas pressure in that hose
will be vented into the atmosphere and not through
the torch into the other hose, Figure 17-21. A reverse
flow valve will not stop the flame of a flashback from
continuing through the hoses.
CAUTION
If both valves are opened at the same time, one gas
may be pushed back up the hose of the other gas.
Reverse Flow Valves
The purpose of the reverse flow valve is to prevent
gases from accidentally flowing out of one hose
through the torch body and then into the other hose.
If the oxygen and fuel gases are allowed to mix in the
hose or regulator, they might explode. The reverse
flow valve is a spring-loaded check valve that closes
when gas pressure from a backflow tries to occur
through the torch valves, Figure 17-20. Some torches
BALL
Flashback Arrestors
A flashback arrestor will stop both reverse gas flow
and the flame of a flashback, Figure 17-22. The flashback arrestor is designed to quickly stop the flow of
gas during a flashback. These valves work on a similar
principle as the gas valve at a service station. They are
very sensitive to any back pressure in the hose and
stop the flow if any back pressure is detected.
SPRING
Servicing the Reverse Flow Valve
and Flashback Arrestor
GAS WILL NOT
FLOW THIS WAY
GAS WILL
FLOW THIS WAY
Both devices must be checked on a regular basis to see
that they are working correctly. The internal valves may
become plugged with dirt or they may become sticky
and not operate correctly. To test the reverse flow valve,
you can try to blow air backward through the valve. To
test the flashback arrestor, follow the manufacturer’s
recommended procedure. If the safety device does not
function correctly, it should be replaced.
Hoses and Fittings
FIGURE 17-20
Reverse flow valve only.
© Cengage Learning 2012
Welding hoses are molded together as one piece. Fuel
gas hoses are red and have left-hand threaded fittings.
Oxygen hoses are green and have right-hand threaded
fittings. Hoses are available in four sizes: 3/16 in.
(4.7 mm), 1/4 in. (6 mm), 5/16 in. (8 mm), and 3/8 in.
(10 mm). The size given is the inside diameter of the
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398
CHAPTER 17
FUEL VALVE
MIXING CHAMBER
OXYGEN
OXYGEN VALVE
FUEL GAS
OXYGEN
OXYGEN
FIGURE 17-21 Gas may flow back up the hose if both valves are opened at the same time when the
system is being bled down after use. Installing reverse flow valves on the torch can prevent this from
occurring. ESAB Welding & Cutting Products
(C)
(A)
(B)
(D)
FIGURE 17-22
(A) Acetylene. ESAB Welding & Cutting Products (B) Oxygen combination flashback
arrestors and check valves. ESAB Welding & Cutting Products (C) Replacement cartridge for flashback
arrestor. ESAB Welding & Cutting Products (D) Torch designed with flashback arrestors and check valves
built into the torch body. Thermadyne Industries, Inc.
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
399
hose. Larger diameter hoses offer less resistance to
gas flow and should be used when long hose lengths
are required. The smaller sizes are more flexible and
easier to handle for detailed work.
The three sizes of hose end fittings available are
A (small), B (standard), and C (large). The three sizes
are made to fit all hose sizes.
Hose Use and Servicing
When hoses are not in use, the gas must be turned off
and the pressure bled off. Turning off the equipment
and releasing the pressure prevents any undetected
leaks from causing a fire or an explosion. Turning the
system off and bleeding off the pressure eliminates
the danger of a fire or explosion if the hoses are accidentally damaged or cut while not in use and you are
not there to quickly shut off the gas.
Hoses are resistant to burns, but they are not
burn proof. They should be kept out of direct flame
and sparks and away from hot metal. You must
be especially cautious when using a cutting torch.
If the hose becomes damaged, the damaged section should be removed and the hose repaired with
a splice. Damaged hoses should never be taped to
stop leaks. Hoses should be checked periodically for
leaks. To test a hose for leaks, adjust the regulator
to a working pressure with the torch valves closed.
Wet the hose with a leak-detecting solution by rubbing it with a wet rag, spraying it, or dipping it in a
bucket. Then watch for bubbles, which indicate that
the hose leaks.
The hose fittings can be replaced if they become
damaged. Several kits are available that have new
nuts, nipples, ferrules, a ferrule crimping tool, and
any other supplies required to replace the hose ends,
Figure 17-23. To replace the hose end, the hose is
first cut square. The correct-size ferrule is inserted.
Then both the hose end and nipple are sprayed with
a leak-detecting solution. This will help the nipple
slide in more easily. Screw the nipple and nut on a
torch body. This will hold the nipple deep inside the
nut, and the body will act as a handle for leverage as
the nipple is pushed inside the hose, Figure 17-24.
After the hose is slid up to the nut, crimp the ferrule
until it is tight. The crimping tool should be squeezed
twice, the second time at right angles to the first, Figure 17-25. When the crimping is complete, install the
hose on a torch and regulator. Then adjust the regulator to a working pressure and spray the fitting with a
leak-detecting solution. Watch for any bubbles, which
indicate a leaking fitting.
FIGURE 17-23
Hose repair kit. Western Enterprises,
a Scott Fetzer Company
FIGURE 17-24
Screwing the hose nut onto a fitting
will help when pushing the nipple into the hose.
Larry Jeffus
FIGURE 17-25
Crimping hose ferrule. Larry Jeffus
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400
CHAPTER 17
OXYFUEL EQUIPMENT
SETUP AND OPERATION
It is always recommended that you read and follow
the equipment manufacturer’s safety and operation
manual before using oxyfuel equipment for the first
time. Copies of these manuals are available from the
manufacturer, supply houses, and/or on the Internet.
The following method of assembling, testing, lighting,
and adjusting the flame and disassembling an oxyfuel
welding set is designed to guide you safely through
the process.
CAUTION
Always stand to one side. Point the valve away from
anyone in the area and be sure there are no sources
of ignition when cracking the valve.
3. Attach the regulators to the cylinder valves, Figure 17-30A. The nuts can be started by hand and
then tightened with a wrench, Figure 17-30B.
4. Attach a reverse flow valve or flashback arrestor, if the torch does not have them built in,
Figure 17-31. Occasionally test each reverse
Setting Up an Oxyfuel
Torch Set
The following steps can be used to assemble almost
any manufacturer’s oxyfuel equipment if the original
manual is not available.
1. Safety chain the cylinders separately to the cart
or to a wall, Figure 17-26. Then remove the valve
protection caps, Figure 17-27.
2. Crack the cylinder valve on each cylinder for a
second to blow away dirt that may be in the valve,
Figure 17-28.
CAUTION
If a fuel-gas cylinder does not have a valve hand
wheel permanently attached, you must use a nonadjustable wrench to open the cylinder valve. The
wrench must stay with the cylinder as long as the cylinder is on, Figure 17-29.
FIGURE 17-26
Safety chain cylinder. Larry Jeffus
FIGURE 17-27 Unscrew the valve protector caps. Put
the caps in a safe place as they must be replaced on empty
cylinders before they are returned. Larry Jeffus
FIGURE 17-28 Cracking the oxygen and fuel cylinder
valves to blow out any dirt lodged in the valves. Larry Jeffus
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
401
(A)
(A)
(B)
(B)
FIGURE 17-30 Attach the oxygen regulator (A) to
the oxygen cylinder valve. Using a wrench (B), tighten
the nut. Larry Jeffus
(C)
FIGURE 17-29 (A) Small combination wrench.
(B) Large combination wrench. (C) T-wrench.
ESAB Welding & Cutting Products
FIGURE 17-31
flow valve by blowing through it to make sure
it works properly and follow the manufacturer’s
recommendation on proper flash arrester
maintenance.
5. Connect the hoses. The red hose has a left-hand
grooved nut and attaches to the fuel-gas regulator.
Attach reverse flow valves. Larry Jeffus
The green hose has a right-hand nut without
grooves and attaches to the oxygen regulator.
6. Attach the torch to the hoses, Figure 17-32. Connect both hose nuts finger tight before using a
wrench to tighten either one.
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402
CHAPTER 17
CAUTION
Tightening a tip the incorrect way may be dangerous
and might damage the equipment.
Turning On and Testing Oxyfuel
Welding Equipment
The following steps can be used to turn on and test
any manufacturer’s oxyfuel equipment.
FIGURE 17-32
Connect the free ends of the oxygen
(green) and the acetylene (red) hoses to the welding torch.
Larry Jeffus
1. Back out the regulator pressure adjusting the
screws until they are loose, Figure 17-34.
2. Standing to one side of the regulator, open the
cylinder valve slowly so that the pressure rises on
the gauge slowly, Figure 17-35.
FIGURE 17-34 Back out both regulator adjusting
screws before opening the cylinder valve. Larry Jeffus
FIGURE 17-33 Select the proper tip or nozzle and
install it on the torch body. Larry Jeffus
7. Check the tip seals for nicks or O rings, if used,
for damage. In most cases tips that have O ring–
type seals are hand tightened, and tips that have
metal-to-metal seals are wrench tightened, but it
is best to check the owner’s manual, or a supplier,
to determine if the torch tip should be tightened,
Figure 17-33.
FIGURE 17-35
cylinder valve.
Stand to one side when opening the
Larry Jeffus
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
403
CAUTION
If the valve is opened quickly, the regulator or gauge
may be damaged, or the gauge may explode.
Open the oxygen valve all the way until it is sealed at
the top, Figure 17-36.
3. Open the acetylene or other fuel-gas valve one
quarter turn, or just enough to get gas pressure,
Figure 17-37. If the cylinder valve does not have
a hand wheel, use a nonadjustable wrench and
leave it in place on the valve stem while the gas
is on.
CAUTION
The acetylene valve should never be opened more
than one and a half turns so that in an emergency it
can be turned off quickly.
Open one torch valve and point the tip away from
any source of ignition, including the cylinders, regulators, and hoses. Slowly turn in the pressure adjusting
screw until gas can be heard escaping from the torch.
The gas should flow long enough to allow the hose to
FIGURE 17-37
Open the cylinder valve slowly.
Larry Jeffus
be completely purged (emptied) of air and replaced
by the gas before the torch valve is closed. Repeat this
process with the other gas.
4. After purging is completed, and with both torch
valves off, adjust both regulators to read 5 psig,
Figure 17-38.
5. Spray a leak-detecting solution on each hose
and regulator connection and on each valve
stem on the torch and cylinders. Watch for
bubbles, which indicate a leak. Turn off the cylinder valve before tightening any leaking connections, Figure 17-39.
CAUTION
VALVE STEM
Connections should not be overtightened. If they do
not seal properly, repair or replace them.
BACK SEATING
SEAL
SAFETY
RELEASE
DISC
MAIN SEATING
SEAL
FIGURE 17-36 Cutaway of an oxygen cylinder valve
showing the two separate seals. The back seating seal
prevents leakage around the valve stem when the valve is
open. Larry Jeffus
FIGURE 17-38
Adjust the regulator to read 5-psig
working pressure. Larry Jeffus
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404
CHAPTER 17
This flame has the highest temperature and may put
oxides in the weld metal.
Lighting and Adjusting
an Oxyacetylene Flame
The following steps can be used to light and adjust
manufacturers’ oxyacetylene equipment.
FIGURE 17-39
Spray fittings with a leak-detecting
solution. Larry Jeffus
1. Wearing proper clothing, gloves, and gas welding
goggles, turn both regulator adjusting screws in
until the working pressure gauges read 5 psig. If
you mistakenly turn on more than 5 psig, open
the torch valve to allow the pressure to drop as
the adjusting screw is turned outward.
2. Turn on the torch fuel-gas valve just enough so
that some gas escapes.
CAUTION
Leaking cylinder valve stems should not be repaired.
Turn off the valve, disconnect the cylinder, mark the
cylinder, move it outdoors or to a very well-ventilated area, and notify the supplier to come and pick
up the bad cylinder, Figure 17-40.
Types of Flames
There are three distinctly different oxyacetylene flame
settings. A carburizing flame has an excess of fuel gas.
This flame has the lowest temperature and may put
extra carbon in the weld metal. A neutral flame has
a balance of fuel gas and oxygen. It is the most commonly used flame because it adds nothing to the weld
metal. An oxidizing flame has an excess of oxygen.
CAUTION
Be sure the torch is pointed away from any sources
of ignition or any object or person that might be
damaged or harmed by the flame when it is lit.
3. Using a spark lighter, light the torch. Hold the
lighter near the end, Figure 17-41, of the tip but
not covering the end, Figure 17-42.
CAUTION
A spark lighter is the only safe device to use when
lighting any torch.
DANGER
OR
TCHES,
ING, MA
K
O
S
NO SM
T
H
OPEN LIG
FIGURE 17-40
Identify any cylinder that has a prob-
FIGURE 17-41
lem by marking it.
Larry Jeffus
lighter.
Correct position to hold a spark
Larry Jeffus
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Oxyfuel Welding and Cutting Equipment, Setup, and Operation
405
FIGURE 17-42 Spark lighter held too close over the
end of the tip. Larry Jeffus
NEUTRAL FLAME
HEAT
COOL GASES
HEAT
FIGURE 17-43
Enough cool gas flowing through the
tip will help prevent popping. Larry Jeffus
4. With the torch lit, increase the flow of acetylene
until the flame stops smoking.
5. Slowly turn on the oxygen and adjust the torch to
a neutral flame.
This flame setting uses the minimum gas flow
rate for this specific tip. The fuel flow should never
be adjusted to a rate below the point where the
smoke stops. This is the minimum flow rate at which
the cool gases will pull the flame heat out of the tip,
Figure 17-43. If excessive heat is allowed to build
up in a tip, it can cause a backfire or flashback. The
maximum gas flow rate gives a flame enough flow
so that, when adjusted to the neutral setting, it does
not settle back on the tip. This will help keep the tip
cooler so it is less likely to backfire, Figure 17-44.
Shutting Off and Disassembling
Oxyfuel Welding Equipment
The following steps can be used to shut down and
disassemble any manufacturer’s oxyfuel equipment.
1. First, quickly turn off the torch fuel-gas valve.
This action blows the flame out and away from
FIGURE 17-44 Explosion-proof light fixtures suitable
for a manifold room. Cooper Crouse-Hindsâ
the tip, ensuring that the fire is out. In addition,
it prevents the flame from burning back inside
the torch. On large tips or hot tips, turning the
fuel off first may cause the tip to pop. The pop
is caused by a lean fuel mixture in the tip. If you
find that the tip pops each time you turn the fuel
off first, then do not turn off the fuel first, but turn
the oxygen off first. Turning the oxygen off first
will prevent the pop. Be sure that the flame is out
before putting the torch down.
2. After the flame is out, turn off the oxygen valve.
3. Turn off the cylinder valves.
4. Open one torch valve at a time to bleed off the
pressure.
5. When all of the pressure is released from the system, close both torch valves and back both regulator adjusting screws out until they are loose.
6. Loosen both ends of both hoses and unscrew
them.
7. Loosen both regulators and unscrew them from
the cylinder valves.
8. Replace the valve protection caps.
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406
CHAPTER 17
SUMMARY
The oxygen and acetylene welding equipment and
process have been around for hundreds of years. It was
one of the first practical welding processes. Oxyacetylene welding was the only practical welding process
for many years. During this time it was occasionally
used to manufacture and repair metal sections several
feet thick. The heat that welders had to endure making
such large welds was almost unbearable. Fortunately,
many other welding processes are available, so welders
do not have to be nearly roasted alive to make oxyacetylene welds. Today, oxyfuel welding is used only
on thin sheet metal.
Although changes in equipment and procedures
have relegated this once popular welding process to
the brink of extinction for commercial applications, it still flourishes in small shops, art studios,
automotive repair services, home and farm shops,
and so on. There are several reasons for it remaining popular. For example, none of the other welding systems can cut, weld, and heat using the same
equipment. Another reason it is taught in schools
is because learning it can serve as a great basis for
learning other welding processes. Many welders and
welding educators believe that learning oxyacetylene welding first makes learning other welding processes much easier.
REVIEW QUESTIONS
1. Why is acetylene the most popular fuel gas used
for oxyfuel welding?
2. What do pressure regulators do?
3. List five various types of pressure regulators.
4. Why are two-stage regulators used sometimes
and not a single-stage regulator?
5. Why is the pressure at the torch tip always lower
than the pressure shown on the working pressure
gauge?
6. When does the high-pressure regulator gauge not
show an approximate quantity of remaining gas
in the cylinder?
7. Which type of safety pressure release reseals once
the excessive pressure has been released?
8. Why should the regulator pressure adjusting
screw be backed off each time the oxyfuel system
is being shut down?
9. What qualities must a leak-detecting solution
have?
10. Why do gas cylinders have different design fittings?
11. Why is it unsafe to use oil on a regulator?
12. What is the advantage of using a combination
welding and cutting torch?
13. What is the advantage of using a long dedicated
cutting torch?
14. What should be done if the hose connections leak
after they are tightened?
15. Can the size of a welding tip be used to determine
the tip heating capacity?
16. What may occur if the wrong method of tightening the tip fitting is used?
17. How can dirty welding tips be cleaned?
18. List five possible causes of a welding tip backfiring?
19. What is a flashback?
20. What does a flashback arrestor do?
21. Why would you use a larger diameter welding
hose?
22. Why must the welding hose be kept out of the
direct flame and sparks and away from hot metal?
23. What must you read before using oxyfuel equipment for the first time?
24. When setting up an oxyfuel torch set, why should
you crack the cylinder valve on each cylinder before
you attach the regulators to the cylinder valves?
25. List the safety precautions for lighting and adjusting an oxyacetylene flame.
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.