Page 79 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

PIPING 2.29

and should be obtained from individual manufacturers. Those that are available shall con-
form to the following standards:
1. ASTM D-2665: PVC Fittings
2. ASTM D-2852: Styrene Fittings
3. ASTM D-2661: ABS Fittings
4. ASTM D-2609: PE Fittings

Unions
Unions are fittings used when it is necessary to easily separate piping, usually for the
purpose of removing a piece of equipment (such as a pump) without having to take apart
a joint. A union is a screwed fitting. These fittings should conform to the following
standards:
1. ANSI B 16.39: Unions, Steel or Malleable Iron
2. ANSI B 16.41: Unions, Brass or Bronze

JOINTS

A joint is required each time it is necessary for piping to be connected either to itself, a
fitting, or a piece of equipment. It must be able to withstand the greatest possible pressure
exerted upon it by either the design or test pressure of the individual system. Piping systems
use both pressure and nonpressure piping. The same joints may be utilized for similar pip-
ing on any system.
Most plumbing codes refer to recognized standards that govern the methods and mate-
rials used to fabricate each type of joint. The selection of the jointing methods will be
determined by the type of pipe used, the type of fittings available for the pipe, the highest
pressure expected in the system, and the possible need for disassembly.

METALLIC PIPE JOINTS

Caulked

The caulked joint is used only for piping with hub and spigot ends. After the spigot end is
placed inside the hub, a rope of oakum or hemp is packed into the annular space around
the spigot end, until it reaches 1 in from the top. (For AR pipe, the packing is hydrous
magnesium aluminum silicate reinforced with fiberglass.) Then, a 1-in thickness of molten
lead is poured into the annular space on top of the rope. The lead is then pounded further
into the joint by a caulking iron until it is at a level 1/8 in below the rim of the hub. In use,

the hemp or oakum swells when it absorbs water and further increases the joint’s ability
to resist leaking.
There are no widely recognized standards that govern the fabrication of caulked joints.
Requirements controlling installation are often provided in plumbing codes.

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