and the appearance and quality of the weld are unsatisfactory.

SECURING OXYGAS WELDING EQUIPMENT. - To extinguish the oxygas flame and to secure equipment after completing a job, or to interrupt work temporarily, take the following steps:

1. Close the MAPP-gas needle valve first, then close the oxygen needle valve to extinguish the flame.

2. Close both the oxygen and the MAPP-gas cylinder valves. Leave the oxygen and MAPP-gas regulators open temporarily.

3. Open the MAPP-gas needle valve on the torch and allow gas in the hose to escape (5-15 seconds) to the outside atmosphere. Do not allow gas to escape into a small or closed compartment. Close the MAPP-gas needle valve.

4. Open the oxygen valve on the torch and allow gas in the hose to escape (5-15 seconds). Close the valve.

5. Close both oxygen and MAPP-gas cylinder regulators by backing out the adjusting screws until they are loose.

Follow the above procedures whenever your work is interrupted for an indefinite period. When work is to stop for only a few minutes, you do not have to secure the cylinder valves nor drain the hose; however, for any indefinite work stoppage, follow the entire extinguishing and securing procedures. For overnight work stoppage in areas other than the shop, it is safer to remove the pressure regulators and the torch from the system. Double-check the cylinder valves to make sure they are closed securely.

Maintenance of Gas-Welding Equipment

Welding equipment must be kept up if it is to work well for a long time. You do not have to make repairs to welding equipment; but when repairs are needed, see that the equipment is removed from service and turned in for repair. You are responsible for various duties in the maintenance and care of oxygas welding equipment. This section identifies some of the common types of maintenance duties that you can expect to perform.

Ensure welding torches are kept away from oil and grease. At times, the needle valve may fail to shut off when hand-tightened in the usual manner. If so, do not use a wrench to tighten the seat in the valve stem. When foreign matter cannot be blown off the seat, remove the stem assembly and wipe the seat clean before reassembling. Be sure and keep the mixer seat free of dust, dirt, and other foreign matter.

Before a new torch is used for the first time, check the packing nut on the valves to make sure it is tight. Some manufacturers ship torches with these nuts loose.

Welding tips get rough treatment at times. So keep the orifice smooth and clean if you want the tip to work well. When cleaning a welding tip, do not enlarge or scar it. Remove carbon deposits and slag regularly.

Avoid dropping a tip because the seat that seals the joint may be damaged. The flame end of the tip may receive mechanical damage if you let it contact the welding work, the bench, or the firebricks. This damage can roughen the end of the tip and cause the flame to burn with a "fishtail."

Special welding tip cleaners have been developed to perform this service satisfactorily. The cleaner consists of a series of broachlike wires that correspond in diameter to the diameter of the tip orifices. These wires are packaged in a holder that makes their use safe and convenient. Some welders prefer to use a number drill that is the size of the tip orifice to clean welding tip orifices. A number drill must be used carefully, so the orifice is not enlarged, bell-mouthed, reamed out of round, or otherwise deformed.

The flame end of the tip must be clean and smooth. Its surface must be at right angles to the center line of the tip orifice for a flame that is shaped correctly. A 4- inch mill file is used to recondition this surface.

Should the end of the torch tip become rough and pitted and the orifice become bell-mouthed, recondition the tip. Place a piece of emery cloth, grit side up, on a flat surface; hold the tip perpendicular to the emery cloth; then rub it back and forth just enough to true the surface and to bring the orifice back to its original diameter.

If there is leakage around the TORCH VALVE STEM, tighten the packing nut, and repack it if necessary. For repacking, make sure you use only packing recommended by the manufacturer of the torch. DO NOT USE ANY OIL. If the valve stem