Page 62 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

2.12 CHAPTER TWO

PLASTIC PIPE AND PIPING MATERIALS

This section will discuss various commercially available plastic piping materials and their
properties.
Plastics, because of their unique chemical resistance and other characteristics, are
widely used as raw material for both piping and elastomeric sealing and gas-keting com-
pounds. It is no longer justifiable to think of plastic pipe as merely a cheap substitute for
other piping materials. Plastic has become the material of choice for piping systems used to
convey various liquids, chemicals, pharmaceuticals, liquid fuels, and fuel gases, and those
used for underground sewer water.
Plastic pipe is available in a great variety of compositions. When used for plumbing
systems, the restrictions imposed by the applicable code will be the single most important
determining factor in the use and selection of any plastic pipe material.
Plastic pipe is manufactured in two types: thermoset (TS) and thermoplastic (TP).
Thermoset piping is permanently rigid; examples are epoxy and phenolics. Thermoplastic
material will soften when subject to any degree of heat and reharden upon removal of the
heat. This will affect the strength of the pipe. Therefore, extreme care must be used when
selecting the material type and support system for the material.
In general, the advantages of plastic pipe are excellent resistance to a very wide range
of sanitary and chemical effluent and aggressive soils, long laying lengths, good flow
characteristics, and economical initial system costs. Disadvantages are poor structural
stability requiring close support, susceptibility of some materials to changes resulting
from exposure to ultraviolet rays or sunlight, poor fire resistance, lowering of pressure
ratings with elevated temperature, and production of toxic gases released by some materi-
als when burning.

KEY PROPERTIES OF PLASTIC PIPE

The advantages of plastic pipe include:

1. Resistance to a very wide range of sanitary and chemical effluents
2. Resistance to aggressive soils
3. Availability in long lengths
4. Light weight
5. Low resistance to fluid flow
6. Generally low initial cost
Disadvantages include:
1. Poor structural stability requiring additional support
2. Susceptibility of some types of plastics to physical changes resulting from exposure to
sunlight
3. Generally low resistance to solvents
4. Poor fire resistance
5. Lowered pressure ratings at elevated temperature
6. Production of toxic smoke and gases, which are released upon combustion of some
types of plastic pipe

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