Using Gas Welding
Equipment
Ag I
Ag Mechanics
Unit 2
Competencies to be Developed
Identify major parts of propane and
oxyacetylene welding equipment
Change oxygen and acetylene cylinders
Turn on and adjust oxyacetylene controls
Light and adjust oxyacetylene torches
Shut off and bleed oxyacetylene
equipment
Check for leaks in gas equipment
Introduction
Many gases will burn, making them both
dangerous and beneficial
Burning gases are used in ag mechanics
to do many things
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Heat, cut, weld
Weld: to join by fusion
Fusion: melting together
Introduction
Gas: any fluid substance that can expand
without limit.
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This expandable nature also means that a
gas can be compressed
Compress: apply pressure to reduce in
volume
Compressed Gas
Dangerous because it is under pressure
and trying to get free
If the gas is flammable there is the
additional danger that it may explode or
burn out of control
Fortunately, we have suitable equipment
and techniques available to use
compressed, combustible gasses safely
Acetylene and Propane
Most popular for heating, cutting and
welding metals
They must be mixed with oxygen from the
air or pure oxygen from tanks before they
will burn.
Refer to unit 1 for Reducing Hazards in
Agricultural Mechanics
General Precautions with
Compressed Gases
Wear safety glasses at all
times
Store fuel gas cylinders
separately from oxygen
cylinders
Keep gas cylinders
upright and chained
Do not bump or put
pressure on pipes,
connections, valves,
gauges or other
equipment connected to
compressed gas
cylinders
When connections are
opened or cylinders are
changed check for leaks
before using equipment
Never use grease or oil
on equipment—
spontaneous or instant
fires may result
Follow procedures for
turning systems on and
off
Work only in areas that
are free of materials that
burn
General Precautions with
Compressed Gases
Screw caps on all
cylinders that do not
have regulators
Keep equipment or
cylinders that may
discharge gas pointed
away from the
operator and other
people
Never leave clothing
were it can become
saturated by oxygen
and fuel gases
Learn to recognize the
odors of combustible
fuels
Protect gas cylinder
storage areas with locked
link fences or concrete
enclosures.
If gas equipment catches
fire, immediately turn off
the gas at the tanks. If
this is not practical or this
action does not
extinguish the gas fires,
evacuate the area and
call for help.
Gas Burning Equipment
Shops have either a manifold or portable rig setup
Manifold: pipe with two or more outlets
Rig: self contained piece of apparatus
assembled to conduct an operation
Oxyacetylene: a shortened version of the words
oxygen and acetylene
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It refers to equipment and processes where the two
gases are used together
Shops may also use propane and oxygen
torches and propane furnaces
Oxyacetylene Equipment
Major parts
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Cart
Cylinders
Valves
Regulators
Gauges
Hoses
Torch assemblies
Torch
Mixes gases and discharges them to
support a controllable flame
Cylinder
Long, round tank with extremely thick
walls built to hold gases under great
pressure
Valves and Regulators
Control the flow of gas
Gauge
Measures and indicates the pressure in
the hose, tank or manifold
Hoses
Flexible lines that carry the gases
Made of rubber reinforced with nylon or
there material to withstand high pressure
and heavy use
Red= acetylene
Green= oxygen
The Rig
Acetylene Side
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Acetylene cylinder
Red or brown
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Cylinder valve
Red cylinder pressure
gauge
Regulator
Hose pressure gauge
Red hose
Acetylene valve on
torch
Oxygen side
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Oxygen cylinder
Green cylinder
pressure gauge
Regulator
Hose pressure gauge
Green hose
Oxygen valve on torch
Torch mixing chamber
Torch tip
Setting Up
Acetylene
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Left hand threads
Color coded red (brown in our shop)
Oxygen cylinders
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Right hand threads
Color coded green
Before attaching regulators to cylinders, crack the
cylinder by turning the gas on and off quickly to blow out
any dust
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When attaching regulators, hoses, gauges or torch
connections, the connectors must be threaded in the
correct direction. The red color coding and opposite threads
for acetylene are means of preventing the accidental mixing
of acetylene and oxygen except in the torch its self.
Setting Up
All connections are gas tight when
screwed on properly
Caution!! Oxygen and acetylene valves on
torches seal with light finger pressure.
Over tightening will damage the seats of
the valves. A seat is the point where the
movable part of the valve seat seals off
the gas.
Turning On the Acetylene and
Oxygen
Use the following sequence to turn on the gases.
DO NOT STAND IN FRONT OF GAUGES
WHILE THE GAS IS BEING TURNED ON!!!
Step 1: Close the acetylene valve on the torch
Step 2: Close the oxygen valve on the torch
Step 3: Turn the acetylene regulator handle
counter clockwise until no spring tension is felt
Step 4: Turn the oxygen regulator handle
counter clockwise until no spring tension is felt.
Turning on Oxygen and Acetylene
Step 5: Open the oxygen cylinder valve slowly until the
pressure gauge responds. Open the valve all the way.
Step 6: Open the acetylene cylinder valve slowly half a
turn
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NEVER open the acetylene cylinder more than half a turn. This
is so it can be shut off quickly in the case of emergency.
Step 7: Open the oxygen torch valve an 1/8 of a turn.
Turn the oxygen regulator handle clockwise until the
pressure gauge reads 10 psi
Step 8: Open the acetylene torch valve an 1/8 of a turn.
Turn the acetylene regulator handle clockwise until the
pressure gauge reads 5 psi. Close the acetylene valve.
Turning on Oxygen and Acetylene
Step 7 & 8 purge the lines and set
regulators to a safe starting pressure
Purge the lines: remove undesirable gases
This makes the unit pressurized and ready
to go.
Testing for Leaks
Leak test should be performed when first setting
a rig up, when cylinders are changed or if the
odor of acetylene is present when the rig is not
in use
Leaks should be tested for using a small amount
of water and nondetergent hand soap
The solution should be rubbed around fittings
and any other places that a leak may exist using
a 1” paint brush
If a leak exist it will cause the soap solution to
bubble
Lighting and Adjusting Torches
Two types- welding and cutting
To light
Open the acetylene valve an eighth of a turn
Use a spark lighter to ignite the torch
 NEVER use matches or a lighter!
 DO NOT point the torch directly into the lighter
 DO NOT point the torch towards other people
Open the acetylene valve slowly until the flame is ¼” off
the tip of the torch, increase or decrease the flow until
the flame just touches the tip
 This flame is called a carbonizing flame.
Carbonizing flame is one with excess acetylene.
Lighting and Adjusting Torches
Turn the oxygen valve on slowly and
watch the inner flame shorten. Continue to
add oxygen until the long, inner flame just
fits the cone.
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This is a neutral flame
Neutral flame: one with the correct balance of
acetylene and oxygen.
This flame is correct for heating, cutting, and
welding
Lighting and Adjusting Torches
If additional oxygen is added, the cone
becomes sharp and the flame noisy. This
is an oxidizing flame or one with an excess
of oxygen.
It is hottest type of flame but not
recommend for anything but special types
of applications
Shutting Off Torches
Torches become a fire hazard if the
procedure is not followed when shutting
them off.
Use gentle pressure on torch valves to
keep from damaging their soft internal
parts.
First close the acetylene valve
Close the oxygen valve last
Bleeding Lines
Removing all gas from the lines and equipment
Procedure
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Turn off the acetylene at the cylinder
Turn off the oxygen at the cylinder
Open the acetylene valve at the torch until both regulators return
to zero. Close the acetylene valve at the torch
Open the oxygen valve at the torch until both regulators return to
zero. Close the oxygen valve at the torch
Turn all regulator handles counterclockwise until they are easy to
turn
Coil the hoses over the cart handles
Store the rig in a suitable place.
REVIEW POP QUIZ
1. What color are acetylene hoses?
2. What color are oxygen hoses?
3. Acetylene should be at what pressure to light the
torch?
4. What is used to check for gas leaks?
5. What material is used to reinforce gas hoses?
6. What two gases are used in the agricultural
mechanics shop?
7. What is used to compress gases?
8. How far should the acetylene tank valve be opened?
9. Why are compressed gases dangerous?
10. Define the term rig.