Page 92 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

2.42 CHAPTER TWO

JOINTS FOR PLASTIC PIPING

Plastic piping can be joined by a variety of methods. All of the joints, except the solvent
cement type, are similar to those used for metallic pipes.
1. Solvent cement
2. Heat fusion
a. Butt joints
b. Socket joints
3. Flanged
4. Insert-type mechanical fittings
5. Threaded
6. Threaded-type mechanical fittings
7. Grooved joints
8. Dresser-type joints
9. Mechanical stab-type coupling
10. Elastomeric compression couplings
11. Adapter fittings from plastic pipe to other piping
12. FRP piping
a. Tapered adhesive joint
b. Butt and strap joint

Solvent Welding
Also known as solvent cementing, this process can be used only with specific types of plastic
pipe and fittings with plain and socket ends. Specific solvents and cements can be used only
with specific plastic pipe types.
The cement used to fabricate the joint reacts chemically with the pipe and fitting and
dissolves the material it contacts. It is spread on the male section, which is then inserted
in the female portion of the joint. The dissolved portions in contact with each other flow
together and, when dry, are fused into a single mass, producing a leakproof joint.
There are different standards governing the solvent cement depending on the pipe used.
They are:

1. No standard: PVDF
2. ASTM D 2235: ABS
3. No standard: PP
4. ASTM D 2855: PVC
5. ASTM D 2846 or ASTM F 493: CPVC
This process produces a rigid pressure joint that is suitable for any type of installation
for which the piping itself is acceptable. Refer to Fig. 2.16 for an illustration of a solvent
welded joint.

Heat Fusion
This joint can be used only with specific types of plain end thermoplastic plastic pipe and
fittings manufactured for this purpose. The socket joint is fabricated by first placing a fitted

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