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NCCER Welding Unit 2.  Oxyfuel cutting is a process that uses the flame and oxygen from a cutting torch to cut ferrous metals.  Flame is produced by.

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Presentation on theme: "NCCER Welding Unit 2.  Oxyfuel cutting is a process that uses the flame and oxygen from a cutting torch to cut ferrous metals.  Flame is produced by."— Presentation transcript:

1 NCCER Welding Unit 2

2  Oxyfuel cutting is a process that uses the flame and oxygen from a cutting torch to cut ferrous metals.  Flame is produced by mixing a fuel gas with pure oxygen.  The flame heats the metal and then a flow of oxygen is used to cut the metal which produces dross. (The cut metal fragments)  Fast and easy way to cut metal…Not the most precise

3  Always use safety cutting glasses with the proper shade. (shade filter of at least 3 to 6)  Wear protective clothing…sleeves, leathers, and gloves  Always wear 8’’ or taller high top safety boots.

4  Ake sure any flammable material in the work area is moved or shielded from the source of an open flame. ‘  Make sure fire extinguishers are in working order and located in an well seen area.  Before cutting tanks or barrels, check to see if they have contained any flammable material. Always clean and fill with water, or purge them with a flow of inert gas to displace any oxygen.

5  Always perform cutting operations in a well ventilated area.  If the material contains any kind of mercury, lead, or zinc coating always wear an approved full face, supplied air respirator. This will prevent you from breathing toxic fumes.

6  Oxygen 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.  Oxygen is stored at more than 2,000 psi in hollow steel cylinders.  These cylinders must be tested every 10 years.

7  Acetylene gas is a compound of carbon and hydrogen and is lighter than air. It is formed by dissolving calcium carbide in water.  It has a strong, garlic like odor which is added so the gas can be detected.  It is very unstable and will explode easily under pressure, this is why it must never exceed 15 psi when in a gaseous form.  When combined with oxygen, acetylene creates a flame that burns hotter than 5,500 degrees.

8  Because of its explosive nature, acetylene cannot be stored above 15 psi in a hollow cylinder.  To solve this problem, acetylene cylinders are filled with a porous material that creates a solid, instead of a hollow cylinder.  Acetylene cylinders must always be stored in the upright position and if one is ever tipped over, stand the cylinder upright and wait at least one hour before using.  Acetylene cylinders have safety fuse plugs in the top and bottom of the cylinder that melt at 220 degrees. These prevent the tank from exploding.

9  Many fuel gasses other than acetylene can be used in oxyfuel cutting.  They include natural gas, methylacetylene propadiene(MAP gas), propylene, and propane.  Flames are not as hot, but may be cheaper or safer to use.  MAP gas is mixture of acetylene and propane.  Propylene mixtures are stable and shock resistant and burn at around 5,193 degrees.

10  Liquified fuel gases are shipped in hollow steel cylinders.  Can hold up to 225 pounds of liquid fuel gas.  If high volumes of gas are removed from a liquid fuel gas cylinder, the pressure will drop, and the temperature of the cylinder will also drop.  A ring of frost can sometimes form around the base of the cylinder.

11  Regulators are attached to the cylinder and reduce the pressure from the tank before it gets to the torch handle. Also helps maintain a steady flow of gas from the cylinder.  Oxygen regulators have green markings and always have right handed threads. Will read up to 3000 psi on its high pressure gauge.  Acetylene regulators are red and have left hand threads. A v-notch is cut on the nut for a reminder. The high pressure gauge will read up to 400 psi.

12  2 types… One piece cutting torch and a combination torch  Combination torch is what we use.  Consists of a cutting torch attachment that connects to a welding torch handle.  The fuel gas and oxygen valves are on the torch handle.  These are used in light to medium duty jobs.

13  The cutting tip to be used depends on the base metal thickness and fuel gas being used.  Special tips are also made for gouging or grooving.  Rivet cutting heads are used to cut of rivets, bolts, and nuts.

14  A variety of fixed and portable motorized cutting equipment is available for straight and curved cuts.  CNC machines like the Torchmate are used to cut metal using a computer driven system.  Portable track cutting machines (track burners) can be used in the field for straight or curved cuts and beveling.

15  As a safety precaution, always check equipment periodically for leaks before using.  The torch should be checked before every use.  We can use soapy water to check for leaks, if bubbles form… then a leak is present.

16  There are 3 types of oxyfuel flames:  Neutral flame- burns equal amount of oxygen and acetylene. Used for all cutting operations  Carburizing flame- has a white feather caused by excess fuel. Length of feather depends on amount of excess gas.  Oxidizing flame- has an excess of oxygen, inner cone is shorter and much bluer in color, more pointed than a neutral flame

17  Once finished cutting, always remember to shut down the torch for safety reasons.  First step in shutting down is to always close the fuel gas and oxygen valves.  Once everything is shut down, always wrap up the hose to eliminate any tripping hazards.

18  Once cylinders become to low to use, we should prepare them to be changed out.  Remove the regulator and replace the cylinder cap on top of the cylinder.  Mark MT(empty) and the date near the top of the cylinder using soapstone.

19  Thin steel is 3/16” thick or less. Distortion can be caused when cutting due to the heat and thinness of the steel.  To minimize distortion, move as quickly as you can without loosing the cut.  Hold the torch tip so that it is traveling in a 15 to 20 degree angle.

20  Washing is a term used to describe the process of cutting out bolts or rivets.  Washing tips can also be used to remove items such as blocks, angles, or channels that are welded onto a surface.

21  Gouging is the process of cutting a groove into a surface.  Uses a special kind of cutting tip.  Not as effective as washing tips but

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