1. Oxyfuel Welding and Cutting Equipment, Setup, and Operation
Chapter 30
Oxyfuel Welding and Cutting Equipment, Setup, and Operation

2. Objectives
Describe how to maintain the major components of oxyfuel welding equipment
Explain the method of testing an oxyfuel system for leaks
Demonstrate how to set up, light, adjust, extinguish, and disassemble oxyfuel welding equipment safely

3. Introduction
Oxyfuel welding, cutting, brazing, hardsurfacing, heating, etc.
Use the same basic equipment
Cylinders
Regulators
Hoses
Hose fittings
Safety valves
Torches
Tips

4. Introduction (cont'd.)
All oxyfuel processes use a high-heat, high-temperature flame
Produced by burning a fuel gas mixed with pure oxygen
Gases are supplied in pressurized cylinders
Regulators reduce gas pressure from the cylinder
Gas flows through flexible hoses
Torch controls flow
Acetylene is the most widely used fuel gas

5. Pressure Regulators Reduce a high pressure to a lower working pressure
Kept constant over a range of flow rates
Various types
Low-pressure regulators, high-pressure regulators, single-stage regulators, dual-stage regulators, cylinder regulators, etc.
Not interchangeable

6. Regulator Operation
Regulators work by holding the forces on both sides of a diaphragm in balance
Gas pressure on back side of diaphragm is reduced
Two-stage regulators
Keep pressure constant at very low or high flow rates
Two sets of springs, diaphragms, and valves

7. FIGURE 30-1 Force applied to the flexible diaphragm by the adjusting screw through the spring opens the high-pressure valve.
© Cengage Learning 2012

8. Regulator Gauges One or two gauges on a regulator Line drop
One regulator gauge shows working pressure
Shows pressure at regulator and not at the torch
Second gauge shows cylinder pressure
Line drop
Caused by resistance of a gas flow

9. Regulator Safety Pressure Release Device
Safety release valve or safety disc
Prevent excessive pressure from damaging the regulator
Safety release valve
Made of a ball held against a seat by a spring
Safety disc
Thin piece of metal held between two seals
Must be replaced if used

10. Cylinder and Regulator Fittings
Ensure regulator is not connected to wrong gas or pressure
Common adapters
Left-hand male acetylene cylinder fitting to a right-hand female regulator fitting
Argon or mixed gas male to a female flat washer-type CO2 fitting
Considerations
Keep fittings free of dirt and oil
Screw together freely by hand
Replace damaged connections

11. Regulator Safety Precautions
Key points
Back off adjusting screw at shut down to prevent damage
Creep is rising pressure on working side of regulator
If leakage at the seat is severe: maximum safe pressure can be exceeded on working side
Results in damage to diaphragm, gauge, hoses, etc.
Do not use regulators that creep excessively

12. Regulator Care and Use Considerations
No internal or external moving parts on a regulator or a gauge require oiling
Adjusting screw becomes tight and difficult to turn: remove and clean with a dry, oil-free rag
Replacing adjusting screw: be sure it does not become cross-threaded
Welding is finished and cylinders are turned off: gas pressure must be released and adjusting screw backed out

13. Welding and Cutting Torches: Design and Service
Oxyacetylene hand torches
Most common type of oxyfuel gas torch used
Combination welding and cutting torches
More flexible
Straight or dedicated cutting torches
Longer than combination torches
Most manufacturers make torches in a variety of sizes for different types of work

14. Mixing the Gases Two methods for mixing oxygen and fuel gas
Two gases mixed completely before leaving tip
One method uses equal pressures
Gases are mixed in a mixing chamber
Second method uses higher oxygen pressure
Gases are mixed in an injector chamber

15. FIGURE 30-18 Schematic drawing of an oxyacetylene welding torch.
© Cengage Learning 2012

16. Torch Care and Use Considerations
Torch body contains threaded connections for the hoses and tips
Wrench should never be used on one nut unless the other connection is protected
Hose connections should not leak after they are tightened
Valves should be easily turned on and off
Bubbles around the valve stem indicates a leaking valve packing

17. FIGURE One hose-fitting nut will protect the threads when the other nut is loosened or tightened. Larry Jeffus.

18. Welding and Heating Torch Tips
Key points
No industrial standard tip size identification system
Students must learn various tip sizes
Tip sizes: comparable to numbered drill sizes
On some torch sets: each tip has its own mixing chamber

19. Torch Tip Care and Use Considerations
Tips may have metal-to-metal seals or an O-ring or gasket between the tip and the torch seat
Tighten metal-to-metal seal tips with a wrench
Tips with an O-ring or gasket can be tightened by hand
Dirty tips can be cleaned with tip cleaners
Damaged tips or tips with cleaners broken in them can be reconditioned

20. Backfires Backfire Flame goes out with a loud snap or pop Causes:
Touching the tip against the workpiece
Overheating the tip
Flame settings are too low
Loose tip
Damaged seats
Dirt in the tip

21. Flashbacks Flame is burning inside the tip, torch hose, or regulator
Produces a high-pitched whistle
Close oxygen valve and then close fuel valve
Allow torch to cool
Usually indicates a serious problem with the equipment

22. Reverse Flow and Flashback Valves
Reverse flow valve
Prevents gases from flowing through the torch into the wrong hose
If gases are allowed to mix in the hose or regulator they might explode
Flashback arrestor
Will do the job of a reverse flow valve
Will also stop the flame of a flashback

23. Care of the Reverse Flow Valve and Flashback Arrestor
Considerations
Both devices must be checked on a regular basis
Internal valves may become plugged with dirt
Test reverse flow valve: blow air backwards through the valve
Test flashback arrestor: follow manufacturer's recommended procedure
Replace of not functioning correctly

24. Hoses and Fittings Characteristics
Siamese hoses are molded together as one piece
Other hoses may be taped together
Fuel gas hoses must be red and have left-hand threaded fittings
Oxygen hoses must be green and have right-hand threaded fittings
Hoses are available in four sizes

25. Hose Care and Use Considerations
Hoses not in use: gas must be turned off and pressure bled off
Hoses are resistant to burns: not burn-proof
Hoses should be checked for leaks
Hose fitting can be changed if damaged
To replace hose end: hose is cut square

26. Types of Flames Oxyacetylene flame settings Carburizing flame
Excess of fuel gas
Neutral flame
Balance of fuel gas and oxygen
Oxidizing flame
Excess of oxygen

27. Leak Detection Leak-detection solution Solution can be:
Premixed or concentrate
Must be free flowing
Good quantity of bubbles without film
Solution can be:
Dipped
Sprayed
Brushed

28. Figure 30-36 Safety chain cylinder. Larry Jeffus.

29. FIGURE Connect the free ends of the oxygen (green) and the acetylene (red) hoses to the welding torch. Larry Jeffus.

30. FIGURE 30-43 Select the proper tip or nozzle and install it on the torch body. Larry Jeffus.

31. FIGURE Back out both regulator-adjusting screws before opening the cylinder valve. Larry Jeffus.

32. FIGURE 30-45 Stand to one side when opening the cylinder valve
FIGURE Stand to one side when opening the cylinder valve. Larry Jeffus.

33. FIGURE 30-48 Adjust the regulator to read 5 psig (0
FIGURE Adjust the regulator to read 5 psig (0.35 kg/cm2g) working pressure. Larry Jeffus.

34. FIGURE 30-50 Identify any cylinder that has a problem by marking it.
Larry Jeffus

35. Manifold Systems
Used when there are a number of work stations or a high volume of gas will be used
Must be located at least 20 feet or more from work
Rooms used for manifolds can be also used for cylinder storage
Piping for high-pressure side of the manifold must be steel, stainless steel, or alloyed copper
Should be tested for leaks at a half times operating pressure

36. Manifold Operation Considerations
Clean pipes with oil-free, noncombustible fluid before regulators are attached
Install regulators and purge the system with nitrogen
Fill pipes with oxygen or fuel gas
Set line pressure as low as possible

37. Summary You will work with experienced welders
After you have developed skills and found a welding job
These welders have developed many good shortcuts
Safe way of setting up and testing a system should always be followed
Always refer to the manufacturer's operating instructions and safety recommendations