Welding 10 - Module 5: Oxy-acetylene Start-up, Shut-down,
and Cutting
Outcome: Develop and apply a systematic routine for setting up and putting
away oxy-acetylene equipment.
a. Describe and perform the accepted start-up and shut-down procedures for
the oxy-acetylene system, which includes valves, regulators, torches, tips,
types of flames, and safety precautions.
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Reading Guide
Describe the hazard associated with mixing oil and pure
oxygen________________________________________________________________________________________
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Why should n area be well
ventilated?____________________________________________________________________________________
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Describe the PPE for use with oxyacetylene cutting and
welding_______________________________________________________________________________________
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Why are oxygen and acetylene tanks set-up away from the welding/cutting area?
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What precaution should be taken when opening cylinder valves?
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Why should an acetylene cylinder valve be opened less than a full turn of the valve?
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What is the purpose of purging oxygen and acetylene lines prior to lighting the
torch?
Oxy-acetylene start-up, shut-down
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Describe the proceure used to establish a neutral flame
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Describe the procedure used to light a torch
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Describe the procedure used to shut down an oxyacetylene outfit
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How to operate an oxyacetylene torch
Safety Considerations
Welding is a practical and satisfying art; however, oxyacetylene welding is
potentially dangerous activity. Severe and fatal burns and violent building
destroying explosions can result from inattention and carelessness. Familiarize
yourself with safety procedures and weld safely!
Before using an oxyacetylene set, ensure that flammable
materials such as grease, oil, paint, sawdust etc are cleared
from the area and work pieces. Oil and grease can
spontaneously ignite and burn violently in the presence of
pure oxygen. For this reason it is important to wear clean, oil
and grease free clothing.
The fluxes, filler rods and base metals
heated during welding and brazing all
release toxic fumes and acetylene gas is
highly explosive so ensure adequate
ventilation before welding. Acetylene is often
described as having a sweet garlic like smell.
If you can smell it in the air and don't know
where it is coming from, evacuate the area
immediately. Call the fire department from a
phone *outside* of the area as a phone can
set off vapours. In confined spaces,
respirator masks designed for welding can
be used. For the home welder, an outdoor
area is probably the most practical, though
the weld site should be protected from winds
as this will disperse the heat of the flame.
Never weld on containers that have
previously contained toxic or flammable
substances. Do not weld inside enclosed
spaces or in tanks where the only ventilation
comes from above - you might suffocate.
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Leather gloves with long
cuffs and heavy work boots
are recommended. Falling
droplets of metal will
instantly burn through
running shoes and continue
burning through the
operator’s foot. Long pants
and shirt sleeves should be
worn. Do not role up pant
legs as the cuffs could catch
sparks. Leather aprons and
flame proof jackets can be
used to protect the
operator. Many operators
use a baseball cap put on
backwards to prevent
sparks from lodging in hair
or going down the neck of
their shirt. Eye protection is
also necessary. Gas
welding does not
generate the same UV as
arc welding but sparks and infra-red radiation are still very dangerous. Safety
gear such as shaded protective goggles should be adjusted before lighting. For
brazing and light welding "shade 5" goggles can be used. Note, gas welding goggles
and arc welding masks are not the same!
Before using an oxyacetylene setup, ensure that a fire
extinguisher in good working order is present. Water
does not work on grease fires, however a bucket of
water can be handy for putting out small wood fires
and quenching parts. A wet cloth can also be used to
extinguish a flame on a hose or fitting. Sand can also
be used to put out fires. It is also generally handy to
have at least one pair of heavy pliers around for
moving hot things if necessary. Be sure your
workspace is well organized before starting. Have
tools laid out where they can be easily reached and
make sure there are no tripping hazards. A fireproof
surface should be used for welding. Steel table tops
and fire bricks are commonly used.
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Ensure that the tanks are secured vertically on a cart or chained to a wall. If the
cylinders were to fall over and the valve broken off the top, the highly pressurized
gases inside will convert the cylinders into rockets capable of smashing through
walls. On your oxyacetylene torch system there will be three types of valves the tank
valve, the regulator valve, and the torch valve. There will be one of them for each
gas. The gas in the tanks or cylinders is at high pressure. Oxygen cylinders are
generally filled to something like 2200 PSI. The regulator converts the high pressure
gas to a low pressure stream suitable for welding. Never attempt to directly use
high-pressure gas. Do not use pressurized oxygen for blowing dirt out or cleaning
clothing. The oxygen can saturate the material making it eight times more
flammable!
Know how to contact
emergency services at
whatever site you are
working.
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Lighting an Oxyacetylene Torch
The link below will take you to a Website with a series of videos which deal
with setting up an oxyacetylene outfit. Review these videos and then read the
step by step guide below:
Video Guides:
Lighting and shutting down an oxyacetylene torch
Step by Step Guide
Here are the steps:
1. Read the safety rules
2. Reread the safety rules
3. Ensure that the hoses are untangled and kept well clear of the flame. It is a
good practice to give the hoses a quick inspection for cracks and abrasion
before use. Generally, tanks are set up behind the welding area and hoses run
backwards away from the weld site to minimize chances of sparks hitting
hoses.
4. Make sure that the regulator valves are turned all the way out and the
torch valves are closed.
5. Open both tank valves. The valves should be opened slowly to minimize the
impact of unleashing highly compressed gases on the regulators. The
operator should not stand directly in front of the regulator gauges as
malfunctioning gauges can blow outwards. The oxygen tank valve is a
backstop valve and should be opened all the way in order to completely seal.
The acetylene valve should only be opened a 1/2 turn. This step ensures that
theacetylene valves are easily accessible shutdown in case of an emergency.
6. Turn both regulator valves inwards until you reach the desired pressure.
o For welding with a smaller tip (size 5), use 5 PSI for the oxygen and 5
PSI for the acetylene. For other tips consult a welding reference. For
larger sized tips it is important to make sure that you do not draw
more than 1/7 capacity of the acetylene tank per hour.
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For cutting, use 15 PSI for the oxygen and 8 PSI for the acetylene.
7. It is recommended that you purge the gas lines before use to ensure that no
oxygen is in the acetylene line and vice versa. (The hoses may explode if
there is fuel gas and oxygen mixed inside the hose.) Ensure that you have
adequate ventilation. For a 20 foot hose, open the torch valve for 5 seconds
to allow oxygen to bleed from the line acetylene line. For a longer hose,
consult a welding reference. Close the torch valve and repeat for the other
line.
8. If the setup has not been used in a while you may wish to check for leaks.
With the torch valves closed and the regulators open, shut off the tank valves
and observe the line pressure for several minutes. If the pressure falls, there
is a leak in the system. Bubble solution can be used to test connections for
leaks. Never use a setup with a leak!
9. Open the acetylene torch valve a very small amount (1/4 turn) and light with
a striker.
10. Once the flame is lit, open the acetylene valve just until the flame stops
smoking. You should get a flame about 8 inches long with a toothy
splintering end.
11. Now open the oxygen valve until the flame loses its feather around its inner
core, but no farther than this amount. This is called a "neutral" flame. The
mixture of oxygen and fuel gas combines to produce exhaust gases that do
not chemically alter the metal to be welded or brazed.
o
NOTE: DO NOT SET THE ACETYLENE REGULATOR VALVE HIGHER THAN 15 PSI!
If you do, the acetylene am explosively decompose into carbon and hydrogen gas.
Oxyacetylene Shut-Down Procedures
To shut down the torch, close the acetylene torch valve first, then the oxygen.
Then close both the tank valves. Turn on the torch valves again, one at a time,
to bleed any remaining pressure and then close them again. Lastly, turn the
regulator valves out all the way.
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Resources
Lighting and shutting down an oxyacetylene torch
Safetycare videos may be downloaded, at no charge, from any computer in the Sun
West School Division
http://www.safetycare.com/videos_3/usa/montie/welding.html
ESBA - Safe Cutting and Welding with Oxy Fuel You Tube Video
Acetylene Safety Information
http://supporting-paa.wikispaces.com/Containers+-+welding+on%C2%A0
Welding and cutting on containers
Oxyacetylene shut down procedure animation
http://en.wikipedia.org/wiki/Oxyacetylene
CCOHS Welding ventilation
CCOHS storing gas cylinders
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