happens to be bent or badly worn, replace it with a new stem.

A symptom of LEAKY VALVES is a continuous flow of gases after the valves are closed. Leaky valves are often caused by a dirty or damaged seat. To clean the seat, remove the valve assembly and wipe the seating portions of both the valve stem and the valve body with a clean rag. If the leak continues, try closing the valve tightly several times. When these measures fail to stop the leak, you may have to replace parts, or the valve body may have to be reseated. These repairs should be made only by qualified personnel.

Leaks in the MIXING-HEAD SEAT of the torch cause oxygen and MAPP-gas leaks between the inlet orifices leading to the mixing head. This defect can cause improper mixing of the gases and result in flashbacks. This defect can be corrected by reaming out the seat in the torch head and by truing the mixing- head seat. You may have to send the equipment to the manufacturer for these repairs, since special reamers are required for truing seats.

With regulators, gas leakage between the REGULATOR SEAT and NOZZLE is a common type of trouble. This defect can be detected by a gradual rise in pressure on the working-pressure gauge when the adjusting screw is fully released or is in position after adjustment. Frequently, this trouble, known as CREEPING REGULATOR, is caused by worn or cracked seats. It can also be brought on by foreign matter lodged between the seat and the nozzle. Regulators with leaks across the seats must be repaired at once; otherwise, damage to other parts of the regulator or apparatus may result. Leaks are particularly dangerous in acetylene regulators because acetylene, at very high pressure in the hose, becomes an explosive hazard. To ensure the safety of personnel and equipment, see that regulators with such leaks are removed from service and turned in for repair.

Another important aspect of welding safety is protecting your eyes and the vision of helpers, chippers, or inspectors where someone is soldering or silver brazing. Ensure you are aware of hazards, such as stray flashes, reflected glare, flying sparks, and bits of molten metal. Ensure that you are using the proper eye protective lenses. If you are not sure, ask your crew leader or project supervisor.

For hand protection, you may have to use either gauntlet gloves or mitts. Some of the important safety precautions in working with acetylene and oxygen cylinders are provided below. Quite a number of precautions apply to cylinders, so the following precautions are NOT a complete listing.

Store all cylinders carefully under prescribed storage procedures. Cylinders should be, stored in dry, well-ventilated, well-protected places, away from heat, and away from combustible materials: Do NOT store oxygen cylinders in the same compartment where acetylene or other fuel-gas cylinders are stored. All cylinders should be stored upright, rather than horizontally. If acetylene cylinders are not stored upright (valves at top), they must not be used until they have been allowed to stand upright for at least 12 hours to prevent acetone discharge. This tendency to discharge acetone depends largely upon the type of porous filler; however, 12 hours is ample time, regardless of the condition of the filler.

When the cylinder is empty, the letter E should be written on the cylinder with a piece of soapstone, keel, or crayon. Store empty cylinders separately from charged ones. Storage spaces must have adequate ventilation and must not be exposed to fire hazards, extremes of weather, continuous dampness, or accumulations of snow or ice.

Galvanized Pipe

The term galvanized means that wrought-iron and steel pipe are protected to resist corrosion. Wrought- iron and steel pipe are made in the same manner. Wrought iron is about twice the cost of galvanized steel, and it is used more for waste systems than for water service. Almost all steel and wrought-iron pipe are galvanized on the outside and on the inside at the factory.

Black iron pipe (not galvanized) is cheaper than galvanized pipe. Black iron pipe is suitable for heating (both steam and hot water) and compressed air systems. It is also used for gas and oil pipelines exclusively. Black iron pipe is NOT suitable for use, either in a water-supply system or a drainage system. This is because black iron pipe rusts and causes stoppages or leaks within a short time.

Galvanized wrought iron and steel pipes are cut, measured, and threaded in the same manner. Both types of pipe come in lengths from 18 to 22 feet. The 20-foot length is about average. These pipes are classified into weights, such as standard, heavy, and extra heavy and refer to the wall thickness of the pipe. The wall thickness is a factor that bears directly on the amount of pressure the pipe can withstand. 3-44