1. Oxy/Fuel Cutting
Level 1 – chapter 2

2. objectives When we have completed this chapter, you will be able to:
Identify oxyfuel equipment
set up and operate oxyfuel equipment
Light and adjust an oxyfuel torch
Shut down oxyfuel cutting equipment
Explain the hazards and safety concerns of oxyfuel cutting

3. 1.0.0 Introduction
Oxyfuel cutting (OFC), also called flame cutting or burning, is a process that uses the flame and oxygen from a cutting torch to cut ferrous metals.
The flame is produced by burning a fuel gas mixed with pure oxygen.
The flame heats the metal to be cut to the kindling temperature (a cherry red color).

4. 1.0.0 Introduction
Then a stream of high-pressure pure oxygen is directed from the torch at the metal’s surface.
This causes the metal to instantaneously burn or oxidize.
This cutting process results in oxides that mix with molten iron and produce dross.
This oxidation process, which takes place during the cutting operation, is similar to a greatly sped-up rusting process.

5. 1.0.0 Introduction

6. 2.1.0 protective clothing and equipment
Always use safety glasses
Wear protective leather or flame retardant clothing including welding gloves
Wear 8” high-top safety boots
Wear a face shield or snugly fitting cutting goggles. Either the face shield or the lenses of the cutting goggles must be an approved shade #3 or #6 filter.
Use earplugs to protect your ears from sparks

7. 2.2.0 fire / explosion prevention
Never carry matches of gas-filled lighters in your pockets. Sparks can cause matches to ignite or the lighter to explode, causing a serious injury.
Never perform any type of heating, cutting or welding until a hot work permit is obtained. Most work site fires caused by these types of operations are started by cutting torches.
Make sure that any flammable material in the work area is moved or shielded by a fire-resistant covering.
Approved fire extinguishers must be in the area before hot work is started.

8. 2.2.0 fire / explosion prevention
Never release any compressed gas into an area, especially acetylene.
Never release a large amount of oxygen or use compressed oxygen as compressed air. It can cause rapid and uncontrolled combustion
Keep oxygen away from oil, grease, and other petroleum products.

9. 2.2.0 fire / explosion prevention
Acetylene is lighter than air, but is more dangerous than methane. When mixed with air, acetylene will explode at much lower concentrations than any other fuel.
As a standard practice, always clean and then fill any tanks or barrels with water, or purge them with a flow of inert gas before cutting them.

10. 2.3.0 work area ventilation
Always perform cutting or welding operations in a well-ventilated area
Make sure proper safety procedures are followed when working in a confined space
Cutting or welding operations involving zinc (galvanized)or cadmium materials results in toxic fumes.
For long-term cutting or welding of such materials, always wear an approved full face, supplied-air (SAR) that uses breathing air supplied externally of the work area.

11. 3.0.0 oxyfuel cutting equipment
The equipment use to perform oxyfuel cutting includes:
Oxygen and fuel gas cylinders
Gas regulators
Hoses
Cutting torch

12. 3.1.0 oxygen
Oxygen (O2) is a colorless, odorless, tasteless gas that supports combustion.
Combined with burning material, pure oxygen causes a fire to flare and burn out of control.
When mixed with fuel gases, oxygen produces the high-temperature flame required in order to flame cut metals.

13. 3.1.1 oxygen cylinders
Oxygen is stored at more than 2,000psi in hollow steel cylinders
The cylinders come in a variety of sizes based on the cubic feet they hold.
The smallest standard cylinder holds about 85 cubic feet of oxygen.
The largest ultra-high-pressure cylinder holds about 485 cubic feet.

14. 3.1.1 oxygen cylinders
The most common size oxygen cylinder used for welding and cutting operations is the 227 cubic feet cylinder.
The cylinders must be tested every 10 years.

15. 3.1.1 oxygen cylinders
Turning the bronze cylinder valve controls the flow of oxygen out of the cylinder
A safety plug on the side of the valve allows oxygen in the cylinder to escape if the pressure in the cylinder rises too high.
When not is use, always cover the cylinder valve with the protective steel safety cap.

16. 3.1.1 oxygen cylinders

17. 3.2.0 acetylene
Acetylene gas , a compound of carbon and hydrogen, is lighter than air.
It has a distinctive, garlic-like odor.
Because of its instability, acetylene can not be compressed at pressures of more than 15psi when in its gaseous form.
At higher pressure, acetylene gas breaks down chemically, producing heat and pressure that could result in a violet explosion.
When combined with O2, acetylene creates a flame that burns hotter than 5,500 degrees F.

18. 3.2.1 acetylene cylinders
Because of the explosive mature of acetylene gas, it cannot be stored above 15 psi in hollow cylinders.
The acetylene cylinder is filled with porous material that creates a solid cylinder.
The porous material is soaked with liquid acetone, which absorbs the acetylene, stabilizing it for storage at higher pressures.

19. 3.2.1 acetylene cylinders
Because of the liquid acetone inside the cylinder, acetylene cylinders must always be used in the upright position.
If the cylinder is tipped over, stand the cylinder upright and wait at least 1 hour before using it.
Always take care to withdraw acetylene gas from a cylinder at pressure less than 15 psig and at hourly rates that do not exceed 1/7th of the cylinder capacity.

20. 3.2.1 acetylene cylinders
Acetylene cylinders have safety plugs in the top and the bottom of them that melt at 220 degrees
In case of a fire, the plugs will release the acetylene in case of a fire so that the cylinder will not explode.

21. 3.2.1 acetylene cylinders

22. 3.3.0 liquefied fuel gases
Many fuel gases other than acetylene are used for cutting.
They include:
Natural gas
MAPP
Propylene
Propane
Their flames are not as hot as acetylene, but there are cheaper and safer to use.

23. 3.3.0 liquefied fuel gases
MAPP is a chemical combination of acetylene and propane gases.
MAPP burns at temperatures almost has high as acetylene and has the stability of propane.
Propylene mixtures are hydrocarbon-based gases that are stable and relatively safe to use.
They burn at temperatures a round 5,193 degrees F, hotter than natural gas and propane.
Propane is also known as LP. It burns at 4,580 degrees.
Natural gas burns at about 4,600 degrees.

24. 3.3.1 liquefied fuel gas cylinders
Liquefied fuel gases are shipped in hollow steel cylinders.
They can hold from 30 to 225 pounds of fuel.
As the cylinder valve is opened, the vaporized gas is withdrawn from the cylinder.
The pressure of the vaporized gas varies with the outside temperature.

25. 3.3.1 liquefied fuel gas cylinders
If high volumes of gas are removed from a liquefied fuel gas cylinder, the pressure drops, and the temperature of the cylinder will also drop.
A ring of frost can form around the base of the cylinder.
The weight of a cylinder determines how much liquefied gas is left.

26. 3.4.0 regulators
Regulators reduce the high cylinder pressures to the required lower working pressures and maintain a steady flow of gas from the cylinder.
The pressure adjusting screw controls the gas pressure to the torch.
Most regulators contain two gauges:
Cylinder pressure gauge
Working pressure gauge

27. 3.4.0 regulators
Cylinder pressure gauge is the high pressure gauge that indicates the pressure in the gas cylinder.
Working pressure gauge is the low pressure gauge that indicates the pressure being sent to the torch.

28. 3.4.0 regulators
Oxygen regulators are painted green or have green lettering and numbers.
Oxygen have right handed threads on all connections.
The oxygen regulators high pressure gauge scale generally goes up to 3,000 psi.
The low pressure scale generally goes up to 100 psi

29. 3.4.0 regulators
Fuel gas regulators are often painted red or have red lettering or numbers.
All fuel gas regulators are left handed threads on all connections.
As a reminder that the regulator has left-handed threads, a V-notch will be cut around the connections.
The fuel gas regulator’s high pressure gauge scale goes up to 400 psi.
The low pressure gauge scale goes up to 40psi.
The pressure coming out of an acetylene gauge should NEVER exceed 15psi.

30. 3.4.0 regulators

31. Break time
Take 15 min. break.

32. 3.4.1 SINGLE STAGE REGULATORS
Single stage, spring compensated regulators reduce pressure in one step.
It becomes necessary to adjust the spring pressure to periodically raise the output gas pressure (screw in the adjustment screw) as the gas in the cylinder is consumed.
These regulators are the most common.

33. 3.4.1 SINGLE STAGE REGULATORS
Gas From Cylinder
Adjusting Screw
Primary Spring
Flexible Diaphragm

34. 3.4.2 two stage regulators
The two stage, pressure compensated regulator reduces pressure in two steps.
First it reduces the input pressure from the cylinder to a predetermined intermediate pressure.
The intermediate pressure is then adjusted by the pressure adjusting screw.
The delivery pressure to the torch remains constant.

35. 3.4.2 two stage regulators

36. 3.4.3 check valves & flashback arrestors
Check valves and flash arrestors are safety devices for regulators, hoses and torches.
Check valves allow gas to flow in one direction only.
Check valves consist of a ball and spring that open inside a cylinder.
The valve allows gas to move in one direction but closes if the gas attempts to flow in the opposite direction.

37. 3.4.3 check valves & flashback arrestors
Flashback arrestors stop fire.
Flashback arrestors have a flame retarding filter that will allow heat, but not flames, to pass through.
Most flashback arrestors also contain a check valve.
Both check valves and flame arrestors have arrows on them to indicate flow direction.

38. 3.4.3 check valves & flashback arrestors

39. 3.5.0 hoses Hoses transport gases from the regulators to the torch.
The oxygen hoses are usually green with right handed threaded connections.
Hoses for fuel gas are usually red and have left hand threads.
Protect the hoses from molten slag and sparks
Remove the hoses from under the metal being cut. If the hot metal falls on the hose, the hose will be damaged.

40. 3.6.0 cutting torches
Cutting torches mix oxygen and fuel gas for the torch flame and control the stream of oxygen necessary for the cutting jet.
Cutting torches can be one piece or a combination torch.

41. 3.6.1 one piece cutting torch
The one-piece hand cutting torch, sometimes called a demolition torch, contains the fuel gas and oxygen valves that allows the gases to enter the cambers and then flow into the tip where they are mixed.
The torch valves control the fuel gas and oxygen used for preheating the metal to be cut.
The cutting oxygen lever, which is spring loaded, controls the jet of cutting oxygen.
These torches are designed for heavy duty use.

42. 3.6.1 one piece cutting torch

43. 3.6.2 combination torch
The combination torch consists of a cutting torch attachment that fits onto a welding torch handle.
These torches are normally used in light-duty or medium-duty applications.
Fuel gas and oxygen valves are on the torch handle.
The cutting attachment has a cutting oxygen lever and another oxygen valve to control the preheat flame.

44. 3.6.2 combination torch

45. 3.7.0 cutting torch tips
Cutting torch tips, or nozzles, fit into the cutting torch and are either screwed in or secured with a tip nut.
There are one and two piece cutting tips.
The cutting torch tip to be used depends on the base metal thickness and fuel gas being used.
Special tips for gouging and grooving are available.

46. 3.7.1 cutting tips for acetylene
One piece torch tips are usually used with acetylene cutting because of the high temperatures involved.
They can have four, six, or eight preheat holes in addition to the single cutting hole.

47. 3.7.1 cutting tips for acetylene

48. 3.7.2 tips for liquefied fuel gases
Tips used with liquefied fuel gases must have at least six (6) preheat holes.
Because fuel gases burn at lower temperatures than acetylene, more holes are necessary for preheating.
Tips can be one or two piece cutting tips.

49. 3.7.3 special purpose cutting tips
Special purpose cutting tips are available for special cutting jobs.
Sheet metal cutting tip has only one preheat hole
Rivet cutting tips are used to cut off rivet heads, bolt heads, and nuts.
Gouging tips are used to groove metal in preparation for welding.
Flue cutting tips are used for any cutting operation in tight quarters such as boilers.

50. 3.7.3 special purpose cutting tips

51. 3.8.0 tip cleaners and tip drills
Tip cleaners are small round files.
They usually come in a set with files to match the diameters of the various tip holes.
Tip drills are used for major cleaning and for holes that are plugged.
Tip drills are tiny drill bits that are sized to match the diameters of tip holes.

52. 3.8.0 tip cleaners and tip drills

53. 4.0.0 setting up oxyfuel equipment
Transport cylinders to the workstation in the upright position using a hand truck or bottle cart.
Secure the bottles at the work station.
Crack open the cylinder valve to remove any dirt from the valve.

54. 4.0.0 setting up oxyfuel equipment
Attach the regulators using a torch wrench.
Connect the hoses to the regulators.
New hoses contain talc and loose bits of rubber. These materials must be blown out of the hoses before the torch is attached.
Attach the torch with the proper tip for the type and thickness of material being cut. (4.8.0 step 1)

55. 4.0.0 setting up oxyfuel equipment
Close torch valves and loosen the regulator adjusting screws. (4.9.0 steps 2 & 3)
While standing to the side of the cylinder, open cylinder valves slowly ( warning)
Oxygen is opened all the way to engage the back setting valve
Acetylene is opened until there is pressure to the gauges, usually less than 2 complete turns of the hand wheel

56. 4.0.0 setting up oxyfuel equipment
Purge the lines and set the working pressure
Test for leaks using a soap and water solution.
Check all connection thoroughly.
Equipment should be tested for leaks immediately after it is set up and periodically thereafter.
The torch should be checked for leaks each time before use.( pg. 2.31)

57. 5.1.0 oxyfuel flames There are three types of oxyfuel flames;
Neutral flame
Carburizing flame
Oxidizing flame
Neutral flame burns proper proportion of oxygen and fuel gas. Neutral flame is used for all but special cutting operations.

58. 5.1.0 oxyfuel flames
Carburizing flame has a white feather created by excess fuel.
The length of the feather depends on the amount of excess fuel present in the flame.

59. 5.1.0 oxyfuel flames Oxidizing flame has an excess of oxygen.
The inner cones are shorter, much bluer in color and more pointed than a neutral flame.
The excess oxygen in the flame can combine with many metals, forming a hard, brittle ,low strength oxide

60. 5.2.0 backfires and flashbacks
When the torch flame goes out with a loud pop or snap, a backfire has occurred.
Backfires are usually caused when the tip of the torch touches the work surface or a hot piece of slag interrupts the flame.
You can relight the torch immediately after a backfire occurs.

61. 5.2.0 backfires and flashbacks
When the flame goes out and burns back inside the torch with a hissing or whistling sound, a flashback is occurring.
The flame is burning inside the torch.
Immediately shut off the oxygen valve on the torch.
Flashbacks are caused by:
Equipment failure
Overheated torch
Spatter hitting and sticking to the torch tip

62. 5.3.0 igniting the torch
After the cutting equipment has been properly set up, the torch can be ignited and the flame adjusted for cutting.
After donning proper personal safety equipment , flow these steps:
Open the fuel valve on the torch handle ¼ turn.
Use a friction lighter to ignite the flame
Increase the fuel gas until the flame stops smoking
Open the oxygen torch valve and adjust the flame to a neutral flame
Press the cutting oxygen lever and adjust the cutting flame

63. 6.0.0 shutting down oxyfuel equipment
When cutting is complete and the oxyfuel equipment is no longer needed, it must be shut down.
Follow these steps:
Close the valve on the torch
Close the oxygen and fuel gas cylinder valve
Bleed the pressure of the hoses and regulators by opening the torch valves
Back out the regulators adjustment screws until they are loose
Coil up the hoses and store the torch properly to prevent damage

64. 7.0.0 disassembling oxyfuel equipment
Step 1: Check to be sure the equipment has been properly shutdown . This includes:
The cylinder valve is closed
All pressure gauges read zero
Step 2: Remove hoses from the torch
Step 3: Remove the regulators from the cylinders
Step 4: Put protective caps on the cylinders and store cylinders in their proper storage area.
Mark MT and the date near the top of the cylinder with soapstone (8.0.0 step 5)

65. 9.1.0 inspect the cut
A good cut features a square top edge that is sharp and straight, not ragged.
Dross should be minimal and easily removed
The drag lines should be near vertical and not very pronounced
When preheat is insufficient, bad gouging results at the bottom of the cut
Too much preheat will result in the top surface melting over the cut, an irregular cut edge, and an excess amount of dross.

66. 9.1.0 inspect the cut

67. 9.3.0 cutting thin steel Thin steel is 3/16” thick or less
A major concern is distortion caused by heat of the torch.
Move quickly to minimize distortion and:
Step 3: Hold the torch so that the tip is pointing in the direction of travel at 15 to 20 degree angle.

68. 9.5.0 piercing a plate
Before holes or slots can be cut in a plate, the plate must be pierced.
After lighting the torch, hold the tip 1/4” to 5/16” above the metal
Tilt the torch slightly so that molten metal does not blow back onto the tip.
Once the hole is established, begin cutting the metal

69. 9.6.0 cutting a bevel
Bevel cutting is often performed to prepare the edge of steel plate for welding.
Angle iron can be used as a guide.
After the torch is ignited, hold the torch at the desired angle
Begin the cut, pay close attention to the torch angle.

70. 9.8.0 gouging
Gouging is the process of cutting a groove into a surface.
Gouging operations use a special curved tip that produces a low-velocity stream of oxygen that curves up.
It is an effective means to gouge out cracks or weld defects for welding.

71. 10.0.0 portable oxyfuel cutting machine
Machine oxyfuel gas cutters or track burners are basic guidance systems driven by variable speed electric motors.
They enable the operator to cut or bevel straight lines at any desired speed

72. summary Oxyfuel has many uses on job sites.
It can be used to cut plate to size, prepare joints for welding, and disassemble structures.
There is a danger of fire and explosion when using oxyfuel equipment.
These risks are minimized when the oxyfuel operator is well trained.
Be sure you understand and use all safety precautions.

73. Review questions
Answer review questions1-20
Answer trade terms 1-11