1. Using Gas Welding Equipment
Ag I
Ag Mechanics
Unit 2

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

3. Introduction
Many gases will burn, making them both dangerous and beneficial
Burning gases are used in ag mechanics to do many things
Heat, cut, weld
Weld: to join by fusion
Fusion: melting together

4. Introduction Gas: any fluid substance that can expand without limit.
This expandable nature also means that a gas can be compressed
Compress: apply pressure to reduce in volume

5. 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

6. 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

7. 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

8. 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.

9. Gas Burning Equipment
Shops have either a manifold or portable rig set-up
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
It refers to equipment and processes where the two gases are used together
Shops may also use propane and oxygen torches and propane furnaces

10. Oxyacetylene Equipment
Major parts
Cart
Cylinders
Valves
Regulators
Gauges
Hoses
Torch assemblies

11. Torch
Mixes gases and discharges them to support a controllable flame

12. Cylinder
Long, round tank with extremely thick walls built to hold gases under great pressure

13. Valves and Regulators
Control the flow of gas

14. Gauge
Measures and indicates the pressure in the hose, tank or manifold

15. 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

16. The Rig Acetylene Side Oxygen side Acetylene cylinder Cylinder valve
Red or brown
Cylinder valve
Red cylinder pressure gauge
Regulator
Hose pressure gauge
Red hose
Acetylene valve on torch
Oxygen side
Oxygen cylinder
Green cylinder pressure gauge
Regulator
Hose pressure gauge
Green hose
Oxygen valve on torch
Torch mixing chamber
Torch tip

17. Setting Up Acetylene Oxygen cylinders
Left hand threads
Color coded red (brown in our shop)
Oxygen cylinders
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
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.

18. 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.

19. 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.

20. 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
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.

21. 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.

22. 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

23. 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.

24. 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.
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

25. 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

26. FLAMES

27. 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

28. Bleeding Lines Removing all gas from the lines and equipment Procedure
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.

29. 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.