MAGM 200 Introduction to Agriculture Mechanics Flame Cutting

2. Oxy-Fuel Gas Cutting(OFC) A process that uses flame heat to raise the temperature of metal to its kindling point and then applies a high pressure stream of oxygen to �Blow Out� the molten metal Kindling point is the point at which rapid oxidation (combustion) begins to occur (steel � 1,600�). OFC can be used on any iron based alloy.

3. OFC Eye Protection Goggles or other suitable eye protection must be used when flame cutting. The eyes must be protected with the proper shade lens.

4. Cutting Torches The torch mixes the fuel gas and oxygen much like an oxy-fuel welding torch. This mixed fuel is used to create a high temperature preheating flame.

5. Cutting Tips Usually made of a copper alloy but some are chrome. The diameter of the center cutting orifice determines the thickness of the material that can be cut. Use the manufactures tip guide to choose the correct size Some tips are specific to the type of fuel gas being used. Generally the different fuel requires different size and numbers of preheat holes. Tips also come in various shapes and configurations as well as size to better adapt to different situations.

6. Setting Up a Cutting Torch The oxygen and acetylene cylinders must be securely chained to a cart or wall before the safety caps are removed. After removing the safety caps, stand to one side and crack (open and quickly close) the cylinder valves, being sure there are no sources of possible ignition that may start a fire. Cracking the cylinder valves is done to blow out any dirt that may be in the valves. Visually inspect all of the parts for any damage, needed repair or cleaning.

7. Setting Up a Cutting Torch Attach the regulators to the cylinder valves and tighten them securely with a wrench. Attach a reverse flow valve or flashback arrestor if the torch does not have them built in Occasionally test each reverse flow valve by blowing through it to make sure it works properly.

8. Setting Up a Cutting Torch If the torch you will be using is a combination type torch attach the cutting head at this time. Last, install a cutting tip on the torch. Before the cylinder valves are opened, back out the pressure regulating screws so that when the valves are opened the gauges will show zero pounds working pressure. Stand to one side of the regulators� face as the cylinder valves are opened slowly.

9. Setting Up a Cutting Torch The oxygen valve is opened all the way until it becomes tight, but do not over tighten, and the acetylene valve is opened no more than one-half turn. Open one torch valve and then turn the regulating screw in slowly until 2 psig to 4 psig, shows on the working pressure gauge. Allow the gas to escape so that the line is completely purged.

10. Setting Up a Cutting Torch If you are using a combination welding and cutting torch the oxygen valve nearest the hose connection must be opened before the flame adjusting valve or cutting lever will work. Close the torch valve and repeat the purging process with the other gas. Be sure that there are no sources of possible ignition that may result in a fire. With both torch valves closed, spray a leak-detecting solution on all connections including the cylinder valves. Tighten any connection that shows bubbles.

11. Cleaning a Cutting Tip Turn on a small amount of oxygen. This procedure is done to blow out any dirt loosened during the cleaning. The end of the tip is first filed flat, using the file provided in the tip cleaning set. Try several sizes of tip cleaners in a preheat hole until the correct size cleaner is determined. It should easily go all the way into the tip.

12. Cleaning a Cutting Tip Push the cleaner in and out of each preheat hole several times. Tip cleaners are small round files. Excessive use of them will greatly increase the hole size.

13. Lighting a Torch Set the regulator working pressure for the tip size. If you do not know the correct pressure for the tip, start with the fuel set at 5 psig and the oxygen set at 25 psig. Point the torch tip upward and away from any equipment or other students. Turn on just the acetylene valve and use only a spark lighter to ignite the acetylene. The torch may not stay lit. If this happens, close the valve slightly and try to relight the torch.

14. Lighting a Torch If the fame is small, it will produce heavy black soot and smoke. In this case turn the flame up to stop the soot and smoke. The welder need not be concerned if the flame jumps slightly away from the torch tip. With the acetylene flame burning smoke free, slowly open the oxygen valve and by using only the oxygen valve adjust the flame to a neutral setting.

15. Lighting a Torch When the cutting oxygen lever is depressed, the flame may become slightly carbonizing. This may occur because of a drop in line pressure due to the high flow of oxygen through the cutting hole. With the cutting lever depressed, readjust the preheat flame to a neutral setting.

16. Hand Cutting Position - Steady / Braced - Comfortable - Free Movement Use non-dominant hand to support extension tubes. Use dominant hand to hold end and control oxygen lever. Angle tip slightly towards direction of travel for straight cuts and at 90 degrees for circles or angled cuts.

17. Hand Cutting Keep inner pre-heat cones 1/8 inch from workplace As materials reach kindling point, depress oxygen lever and slightly raise the tip.

18. Distortion The bending and twisting of metal from being heated Two methods to control - Make two parallel cuts on the plate at the same speed and time - Stitch Method

19. Homework