Page 93 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

PIPING 2.43

FIGURE 2.16 Solvent cement joint.

wire with multiple loops around the outside of the plain end of the pipe. The wire will con-
duct electricity and has two leads, called pigtails, about 2 ft long. The pipe and wire are then
placed into the socket of a fitting. These leads are connected to a carefully controlled source
of electricity provided by the pipe manufacturer for this purpose. When the electricity is
turned on, the wires inside the joint are heated, causing those portions of the pipe and the
fittings contacting each other to melt and fuse together. After the electricity is turned off, the
plastic hardens, creating a watertight joint. The embedded wires become part of the joint.
The leads are cut off to complete the process. The fused butt joint is made by separately
heating the pipe ends to the melting point and then bringing them together. When the joint
hardens, a leakproof seal is formed.
There are no widely recognized standards that govern the fabrication of this joint. The
manufacturer’s instructions must be carefully followed.
This rigid pressure joint is suitable for all above-ground and underground installations.
Refer to Fig. 2.17 for illustrations of heat-fused joints.

JOINTS FOR FRP PIPING

Tapered Adhesive Joint
This type of joint, illustrated in Fig. 2.18, is made by machine tapering the outside of the
male pipe and inserting it into a matching bell-shaped female end. An adhesive spread on
the male section secures the joint. A coupling with tapers at each side is used to join two
lengths of tapered male pipe ends. A straight coupling (used with straight pipe ends) with
no taper is also available.

Butt and Strap Joint
This type of joint, illustrated in Fig. 2.19, is made by squaring and deburring each end of
the pipes to be joined. The ends are aligned and then the outside is wrapped with layers of
glass mat and cloth saturated with resin. The width of the wrapping depends on the pressure
rating of the pipe.

Elastomeric Compression Joint
The joint shall conform to ASTM D-3212.

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