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Thermoplastic Valves Product Guide & Engineering Specifications

Materials

Made in the U.S.A. Suitable for Oil-Free air handling to 25 psi, not for distribution of compressed air or gas Page 714

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Spears

Thermoplastic Piping System Materials

Benefits of Spears

Thermoplastic System Materials

Unlike metal, plastics never rust, scale, or pit — they virtually

last forever. Thermoplastics are abrasion resistant, chemical and

corrosion resistant, nonconductive, lightweight, and operate at

lower friction-loss levels than metals. Moreover, plastics are

nontoxic and environmentally safe. Adding these benefits with

ease of installation at substantially lower costs, thermoplastic

piping system components are the proven choice for years of

maintenance free system operations.

Joining Methods for Spears

Thermoplastic Systems

Spears

thermoplastic piping system products are designed

around primary components manufactured from PVC, CPVC

or PP materials and their glass filled varieties. PVC and CPVC

materials can be easily joined by solvent cement welding plus

threaded, flanged or mechanical coupled connections. Spears

PP products are joined by using flanged or threaded connec-

tions featuring Spears

patented Special Reinforced (SR)

female plastic threads.

Material Considerations in

Application and System Design

PVC, CPVC and PP thermoplastic piping system components

will give years of trouble free service with proper attention to

application and system design. To avoid problems, the follow-

ing key points must be considered when selecting materials

for an application and in designing a system for their use.

1. Fluid incompatibility of certain chemicals, especially petro-

leum distillates and derivatives, can cause environmental

stress cracking in different thermoplastic compounds.

Chemical compatibility of all valve or system components,

including solvent cements, must be verified before installa-

tion. Verification of fluid compatibility is at the discretion

of the user.

2. Temperature-pressure relationships must be considered.

Product pressure ratings are based on use of water mediums

at 73°F. In general, product pressure ratings must be de-rated

as temperature increases (see Temperature Pressure Table for

individual valves).

3. Expansion and contraction is greater in thermoplastic sys-

tems than in metal systems. As a result, system design must be

flexible to allow for movement. Use of Spears

Thermoplastic

Expansion Joints is recommended.

4. Extreme heat or cold where internal fluids may freeze or

where temperatures may exceed thermoplastic design limits

must be avoided, including consideration of storage locations.

5. Direct sun exposure results in high thermal heat absorption,

especially in darker color thermoplastic materials. A white

water-based exterior latex paint can be applied to reduce

heat buildup.

6. Lower impact resistance of thermoplastic system com-

ponents than that of metal systems requires avoidance of

sharp, pointed objects in both above and below ground

installations, including mounting devices and backfilling

operations.

7. Proper installation is essential. Special attention must be

given to technique and instructions for making solvent

cemented connections, threaded connections, flanged connec-

tions, and for installation of valves and other individual sys-

tem components. System design must also take into account

support, thrust blocking, transition to different materials and

other installation related factors.

8. Threaded joints require several considerations. First, pres-

sure capacities of threaded system components should be

de-rated to 50% of the rating for corresponding type and

size of thermoplastic pipe. NOTE: Valves have individual

pressure ratings and do not require de-rating for threaded

connections. Second, as with internal fluids, certain paste

sealants may cause environmental stress cracking in ther-

moplastic materials, and compatibility should be verified

before use. Finally, the leading cause of thread joint failures

is from over tightening female thermoplastic threads. Use

of Spears

Special Reinforced (SR) Threads is recom-

mended.

9. Hydraulic Shock (water hammer; surge pressure) in ther-

moplastic piping systems can burst pipe, fittings, and valves.

Anticipated surge pressures should be calculated and included

in maximum internal pressure ratings of system compo-

nents (specified “Non-Shock” pressure rating for valves).

Safeguards should be incorporated in system design to vent

pressures and eliminate entrapped air. Fluid velocities should

not exceed a maximum of 5 feet per second in thermoplastic

systems.

10. Non-liquid transport — WARNING: Spears

Manufacturing

Company DOES NOT RECOMMEND the use of ther-

moplastic piping products for systems to distribute or store

compressed air or gases. The use of Spears

products in

compressed air or gas systems automatically voids Spears

warranty for such products, and their use against our recom-

mendation is entirely the responsibility and liability of the

installer. Spears

Manufacturing Company will not accept

responsibility for damage or impairment from its products, or

other consequential or incidental damages caused by misap-

plication, incorrect assembly, and/or exposure to harmful

substances or conditions.