Oxy-Acetylene
Oxy-Acetylene welding equipment consists of two large tanks (one containing the oxygen and the other containing the acetylene), a regulator assembly at the top of each tank, a pair of hoses leading from the regulators to the torch handle and the torch handle itself. The first thing to do is adjust the line pressure, which is controlled by the large wing nut on the front of each regulator. Close both valves on the torch handle (one controls the oxygen and the other controls the acetylene). Then slowly open the large valves at the top of the tanks. It’s a good practice to stand to one side when doing this because the sudden pressure could blow out the face of a defective gauge and send parts flying.
Next, open one valve on the torch handle about a half turn, then screw the regulator wing nut in or out until the line pressure reads about 5psi. Close the valve, and then adjust the other line to the same pressure.
Use a No. 2 or No. 3 welding tip, and begin by experimenting with a piece of scrap metal. The basic idea is to use the torch to create a small puddle of molten metal on the work, then put the end of the welding rod into the puddle. This melts the rod, causing it to mix with the molten metal, which bonds the two pieces together. If you do that correctly, you will have made a good weld. If you don’t apply enough heat to get the work to puddle, but instead quickly melt the rod onto the work, the weld will not hold.
If you apply too much heat to a single spot you’ll melt away the work entirely, leaving a large hole. Good technique involves adjusting the torch to the correct intensity for the thickness of the work, creating a good puddle, and moving the puddle along at the correct rate as you feed the correct amount of rod. Although we're describing gas welding, the same type of puddling must also occur with arc or MIG welding. A feel for that comes only with practice.
No matter how you try, you cannot make a good weld unless you correctly adjust the torch. The difference between them is caused by the relationship between the amount of oxygen and acetylene, which is controlled by the two valves on the torch handle. The flame you’re after is the neutral flame which comes just as the acetylene feather of the carburizing flame disappears into the inner cone.
The correct intensity is determined by the thickness of the work and by how rapidly you move the puddle along. Beginners tend to do better with a lower flame because it allows them to work more slowly.
Angle the flame toward the work with the rod coming in from the opposite direction. Once the puddle forms move the torch in circular or semicircular patterns across the weld as you slowly advance the puddle.
Continue to feed the rod, but don’t force it into the work or it’ll stick. When things start flowing correctly, you’ll know it’s right.
OSHA’s Welding Standard
Specific requirements for assuring the safety of welding, cutting, and brazing operations are covered under OSHA Standard 29 CFR 1910.252. Below are some selected requirements of the standard:
• Compressed gas cylinders must be kept away from radiators and other heat sources and stored upright in a well ventilated, dry location at least 20 feet from highly combustible materials such as oil. Cylinders should be kept away from elevators, stairs, or other spaces where they can be knocked over or damaged.
• Piping systems must be tested and proved gastight at 1 1/2 times the maximum operating pressure, and shall be thoroughly purged with air, before being placed in service. Service piping systems must be protected by pressure relief devices.
• Hoses showing leaks, burns, worn places, or other defects must be repaired or replaced.
• Cutters and welders must be suitably trained in the safe operation of their equipment and the safe use of the process.
• The welder should be enclosed in an individual booth, or by non-combustible screens, that are painted with a finish of low reflectivity such as zinc oxide or lamp black (to absorb ultraviolet radiation). Other people next to the welding area must be protected by noncombustible or flameproof screens or be required to wear appropriate goggles. The booths or screens should permit circulation of air at the floor level.
• All movable fi re hazards in the vicinity of welding operations must be taken to a safe place. If all the fire hazards cannot be moved, guards must be used to contain the heat, sparks, and slag.
• Suitable fi re extinguishing equipment must be maintained ready for instant use.
• Firewatchers are required whenever welding or cutting is performed in a location where other than a minor fire might develop. A fire watch must be maintained for at least 1/2 hour after completion of welding or cutting operations to detect and extinguish possible smoldering fires.
• No welding, cutting, or other hot work shall be performed on used drums, barrels, tanks, or other containers until they have been thoroughly cleaned (a purge with an inert gas is also recommended).
• Eye protection must be used during all arc welding or arc cutting operations, gas welding, oxygen cutting, resistance welding, or brazing operations (the proper shade number should be selected).
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• When a welder must enter a confined space through a manhole or other small opening, an attendant with a pre-planned rescue procedure must be stationed outside to observe the welder at all times and to put the rescue operation into effect, if necessary.
• Special ventilation and/or respirators are required in confined spaces, for cleaning compounds, when fluorine compounds, zinc, lead, beryllium, cadmium, and mercury are encountered, and when cutting stainless steel.
• Warning labels are required for all filler metals and fluxes containing fluorine compounds (fluorides).