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Plastic and Plastic-Lined Piping


1.0 Scope

This specification defines the minimum requirements to cover the materials, design, fabrication, inspection and testing of plastic and plastic-lined piping.  It covers thermoplastic piping, thermoplastic lined ferrous metal piping, and reinforced thermosetting resin pipe (RTRP). 2.0 References

The following documents are considered part of this specification. Use the edition of each referenced document in effect on the date of the publication of this specification.

ASME – American Society of Mechanical Engineers

ASME B31.3 Process Piping

ASTM – American Society of Testing and Materials

ASTM D 2563 Standard Specification for Classifying Visual Defects in Glass-Reinforced Plastic Laminate Parts
ASTM D 3035 Standard Specification for Polyethylene (PE) Plastic Pipe (DR-PR) Based on Controlled Outside Diameter
ASTM F 1545 Standard Specification for Plastic-Lined Ferrous Metal Pipe, Fittings, and Flanges

AWWA - American Water Works Association

AWWA C950 Fiberglass Pressure Pipe
AWWA M-45 Fiberglass Pipe Design Manual

In the event of a conflict among the above listed standards or between the standards and other instructions listed in the specifications and drawing, it should be the Suppliers responsibility to notify the Buyer in writing for a resolution of the conflict prior to starting work.

3.0 Documentation

Temperature, pressure, and fluid service conditions will be supplied by Buyer.
Pipe Installer - The pipe should only be installed by qualified contractors approved by the pipe Manufacturer.

The following data should be submitted to Buyer for approval:

  • Product information including pipe specifications, MSDS sheets, installation instructions, and detailed joining procedures.
  • Verification that the pipe is suitable for the service.
  • Pipe inspection and testing procedures.
  • Pipe transportation and storage information and details.

4.0 Design

Thermoplastic, Reinforced Thermosetting Plastic (RTRP) and plastic lined pipe should conform to the referenced standards.

Plastic piping should not be used in aboveground flammable materials, combustible liquid or critical water services (Plastic pipe cannot be used above ground in hydrocarbon or other critical services because, in the event of a fire, the pipe will burn; the pipe may also have inadequate resistance to mechanical damage).

Proposals to use plastic pipe in hazardous chemical service should be submitted for approval by Buyer.
To determine the external design pressure for plastic pipe installed underground, underwater, or in other situations which cause external pressure, a safety factor of four must be applied to the critical buckling pressure considering all imposed loads.

Plastic-lined piping should have flanged joints.  Joint design should be per the following:

  • Nonflammable or non-combustible service - The liner should be molded or shaped (lapped over the flange faces) to provide the gasket for the joint.
  • Flammable materials, combustible liquid or hazardous liquid service - The flanged joint should be designed to prevent leakage under exposure to heat sufficient to destroy or melt the lining material.  Vented piping should not be used.

Maximum allowable deflection of thermoplastic and RTRP pipe, at maximum operating pressure, should be defined by pipe manufacturer, taking into account applicable live and dead loads.

Pipe lengths should not exceed 20 ft (6 m) for plastic linings, in order to limit differential thermal expansion between the pipe and the lining.

For plastic pipe, the flexibility of the filament winding process allows pipe to be produced in any length from 10 to 40 ft as required.

Temperature limits for plastic and plastic-lined pipe should be as follows:

Material
Temperature Limitation(1)
Minimum
Maximum(2)
°F °C °F °C
PP (Polypropylene) 30 –1 210 99
PVDC (Polyvinylidene Chloride) 40 5 160 71
PTFE (Polytetrafluoroethylene) –20 –29 500 260
FEP (Perfluoro (Ethylene-Propylene) (Copolymer) –20 –29 300 149
ETFE (Ethylene-tetrafluoroethylene) –20 –29 300 149
PFA (Perfluoroalkoxy) –20 –29 500 260
PVDF (Polyvinylidene Fluoride) 0 –18 275 135
Notes:
(1)  For exposure to corrosive environments, the recommendation of the pipe manufacturer should be submitted for review and approval by the Buyer.
(2)  Values represent maximum design temperature of contained fluid.

5.0 Installation

Installation (including joint make-up) should be in accordance with Manufacturer's specification. Plastic spacers are permitted between plastic-lined pipe and other types of flanged equipment in non-flammable or non-combustible service.  Spacers longer than 1/2 in. (13 mm) should be armored.  Spacer locations should be indicated on As-Built drawings.

Polyethylene piping should be joined by heat fusion welding only.  Flanges should be used, as required, to connect dissimilar systems.

Mechanical joints that incorporate O-ring seals are acceptable for RTRP piping.  Bell and spigot joints using elastomeric seals are acceptable for underground RTRP pipe.

6.0 Inspection and Testing

Inspection of thermoplastic and thermoplastic-lined pipe and fittings should be per ASTM F 1545.
RTRP pipe should be inspected and tested per AWWA C950.

After installation, plastic piping should not be hydrostatically tested until all fusion joints have cooled to ambient temperature and all solvent cemented joints or adhesive bonded joints have fully cured.

7.0 Preparation for Shipment

Protection of openings.  After completion of inspection, all pipe and fittings should be prepared for shipment as follows:

  • Flanges should be protected over the entire gasket surface with wood and hardboard protectors bolted hand tight with at least four bolts.
  • Socket welding-end connections should be fitted with wood or plastic plugs or caps.

Thermoplastic pipe should be shipped on racks or an equivalent that will give continuous support and prevent sagging or draping.



Tags: plastic lined piping