wedging action of the tapered thread may cause the fittings to split. Usually there are two or three unused threads on a pipe that is threaded properly. If you follow the above steps and the threads are made properly, the joints will be tight for pressures several times the 150-psi working pressure of the fittings.

Cement-Asbestos Pipe

Cement-asbestos pipe is corrosion-resistant and does not rust or rot. It has a smooth interior surface that is a favorable friction factor. This pipe comes in sizes from 3 to 36 inches in diameter for pressures of 50 to 200 psi and in lengths of 5, 10, and 13 feet. Light in weight, cement-asbestos pipe is easy to handle. It is made with beveled ends, and adapters are available for connecting to pipe made of other materials.

FITTINGS. - In the absence of cement-asbestos fittings, you can use double-bell, cast-iron fittings and make them up as you would with cast-iron pipe, using sulfur compounds or lead.

CUTTING. - Cement-asbestos pipe can be cut to any length or angle with a carpenter's saw or a transite pipe cutter. Or, it can be tapped for threaded service connections by using a water main self-tapping machine. With this machine, the pipe can be tapped, threaded, and a corporation stop installed while the pipe is under water pressure.

Because of the health and environmental hazards associated with cement-asbestos pipe, special cutting and handling kits have been procured by the Navy and

Figure 3-62. - ;Pipe- and bolt-threading machine.

are available through the naval supply system. Whenever cement-asbestos pipe is encountered, the base or unit environmental officer should be contacted. Also, the newest and most up-to-date instructions should be obtained and followed. Since safety procedures governing asbestos-related equipment change, an attempt to outline all the pertinent procedures for working with asbestos are not included in this manual; however, there are two important factors you should keep in mind. First, always wear a breathing filter or mask. Second, use water while cutting to keep the dust from becoming airborne, or use a vacuum to pull dust from the area of the cutting tool.

JOINING. - Joints in cement-asbestos pipe are made with a special coupling with three rubber sealing rings. Three rings are fixed in grooves at the factory, ready for assembly.

Figure 3-63 shows a cutaway view of a completed joint with the three rings in proper position. As each pipe moves into position during assembly, the rubber

Figure 3-63. - Cutaway view of a cement-asbestos pipe joint.