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 connections 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 following 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 petroleum 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 installation. 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 are greater in thermoplastic systems 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 components 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 connections, and for installation of valves and other individual system 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, pressure 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 thermoplastic 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 recommended.

9.   Hydraulic Shock (water hammer; surge pressure) in thermoplastic piping systems can burst pipe, fittings, and valves. Anticipated surge pressures should be calculated and included in maximum internal pressure ratings of system components (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 thermoplastic piping products for systems to transport or store compressed air or gases, or the testing of     thermoplastic piping systems with compressed air or gases in above or below ground locations. The use of Spears^® products in compressed air or gas systems automatically voids Spears^® warranty for such products, and their use against our recommendation 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 misapplication, incorrect assembly, and/or exposure to harmful substances or conditions.

Individual Materials Overview

Thermoplastics

PVC — Poly Vinyl Chloride

PVC is one of the most specified thermoplastics for piping system components, including, valves, fittings, flanges, and many specialty products. PVC has excellent chemical and corrosion resistance to a broad range of fluids including water, deionized water, most mineral acids, alkaloids, salts, and paraffinic hydrocarbon solutions.  PVC is not recommended for use with chlorinated or aromatic hydrocarbons, esters, or polar solvents such as ketones.  Spears^® PVC materials conform to ASTM Cell Classification 12454 (formerly designated as Type I, Grade 1). The maximum recommended service temperature of PVC products is 140° F (60° C).

Glass Reinforced PVC — Fiberloc^®

Fiberloc^® is a registered trademark of PolyOne Corporation. Fiberloc^® is a glass fiber reinforced PVC composite material. While maintaining the traditional properties of PVC, Fiberloc^® increases its strength, stiffness, and dimensional stability from glass fiber reinforcement. The maximum recommended service temperature of Fiberloc^®  products is 140° F (60° C).

CPVC — Chlorinated Poly Vinyl Chloride

Chlorinated PVC is used for higher temperature applications than PVC, especially for handling hot corrosive liquids. With similar chemical and corrosion resistance to PVC, increased chlorine content gives CPVC superior thermal resistance. CPVC is not recommended for use with chlorinated or aromatic hydrocarbons, esters, or polar solvents such as ketones. Spears^® CPVC materials conform to ASTM Cell Classification 23447 (formerly designated as Type IV, Grade 1). The maximum recommended service temperature of CPVC products is 200° F (93° C).

Glass Reinforced CPVC

This special composite compound has the basic properties of  CPVC with additional strength, stiffness, and dimensional stability from glass fiber reinforcement. The maximum recommended service temperature of glass reinforced         CPVC products is 200° F (93° C).

PP — Polypropylene

Polypropylene is used in a variety of Spears^® valves where different chemical resistance and lower temperature impact resistance is required as compared to PVC or CPVC. The excellent impact resistance characteristics of polypropylene make this polymer the choice for Spears^® valve handles. Spears^® PP products carry a maximum recommended service temperature of 180° F (82° C).

Glass Reinforced PP

Glass reinforced polypropylene is used in numerous valves and valve accessories where additional strength or stiffness is required over standard PP materials while maintaining basically the same range of chemical resistance.

PTFE / PFA) — Polytetrafluoroethylene / Perfluoroalkoxy Resin

PTFE is a ram extrusion processed while PFA is a melt-processed fluoroplastic. These fluoroplastics are virtually inert to most chemicals, acids, alkaloids, and solvents. Due to their low coefficient of friction, these materials are considered “self-lubricating” making them an excellent choice for valve seats, bearings and thrust washers. Spears^® proprietary processing of PTFE with other materials allows low friction characteristics to be built into a variety of thermoplastic components used in Spears^® valves.  Fluoroplastics are serviceable to 500° F (260° C).

PTFE/HDPE

Spears^® proprietary composition of PTFE and high-density polyethylene is used in a variety of valve seats, bearing washers, and other valve components requiring durability and improved lubricity. The chemical resistance of HDPE is somewhat higher than that of LDPE and generally exceeds that of PVC and CPVC. HDPE has excellent resistance to acids, alkaloids, and alcohols. In comparison to PVC and CPVC, HDPE is somewhat less resistant to aliphatic hydrocarbons and has more limited resistance to oxidizing agents.  HDPE is serviceable to 230° F (110° C).

Low Extractable PVC

Low Extractable is a special PVC material developed for use in UPW (Ultra-Pure Water) and other high purity applications.  Independently tested,  Low Extractable PVC provides superior resistance to regular PVC for leaching of anion, cation, and numerous trace metals when subjected to 18.2 megohm deionized water while maintaining ease of installation.  Low Extractable has the same basic chemical resistance as regular PVC.

Elastomers

EPR (EPDM) — Ethylene propylene rubber

Used in O-ring seals, EPR is recommended for water, chlorinated water, dilute acids and alkaloids, alcohols, and has excellent resistance to ozone.  EPR is not recommended for petroleum oils, di-ester lubricants, strong acids, or strong alkaloids. The maximum recommended service temperature of EPR is 300° F (149° C).

 FKM — Fluoroelastomer

Fluoroelastomer are special purpose fluorocarbon-based synthetic rubber categorized under ASTM designation of “FKM”.  The FKM O-Ring is commonly referred to as a “Viton^® O-ring” Elastomers. However, “Viton^® “ is only one of many FKM brand names and is registered trademarks of DuPont Performance Elastomer L.L.C.  Spears^® uses general purpose Type 1 FKM O-Ring with a minimum of 66% fluorine content for the best balance of overall properties.  FKM exhibits a very broad range of chemical resistance, including petroleum oils, di-ester based lubricants, silicate fluids and greases, halogenated hydrocarbons, and mineral acids. FKM is not recommended for ketones, amines, anhydrous ammonia, hot hydrofluoric or chlorosulfonic acids, or automotive brake fluids. The maximum recommended service temperature of FKM is 400° F (204° C).

Nitrile (Buna-N) — Nitrile elastomer

Used in O-ring seals, nitrile elastomers are recommended for petroleum oils and fluids, silicone oils and greases, di-ester based lubricants, ethylene glycol-based fluids, and cold water. Nitrile is not recommended for phosphate ester hydraulic fluids, halogenated hydrocarbons, strong acids, ketones, ozone or automotive brake fluids. The maximum recommended service temperature of nitrile is 275° F (135° C).

FFKM (Aegis™, Kalrez^® - Perfluoroelastomer 

Aegis™ is a trademark of ISC Freudenberg-NOK, Kalrez^® is a registered trademark of DuPont-Dow Elastomers.  These specialty materials are virtually inert and provide the greatest range of chemical resistance found in an elastomer. However, be aware that perfluoroelastomers are substantially more expensive than other elastomer compounds. Perfluoroelastomer are serviceable to 600° F (360° C) and performance is limited at very low temperatures.

 CSM (Hypalon^®) - Chlorosulfonated Polyethylene 

Hypalon^® is a registered trademark of DuPont-Dow Elastomers. CSM is a close match to neoprene, but it has improved chemical resistance. This specialty compound offers good abrasion resistance with superior resistance to weather, ozone, sunlight and oxidation. CSM has excellent resistance to alcohols, alkaloids, and acids, as well as very good color stability with moderate resistance to oils and gasoline. CSM is not recommended for use with aromatic solvents. CSM has limited flexibility at low temperatures and relatively poor compression set. As a result, CSM is not generally manufactured as O-rings. CSM is serviceable to 300° F (149° C). Hypalon^® is offered as an alternative diaphragm elastomer in Spears^® Diaphragm Valves.

 PFA/FEP Encapsulated O-rings   

O-ring encapsulation places a Teflon^® PFA or FEP material around an FKM elastomer core to provide very high chemical resistance. However, this is not without a trade-off. The PFA/FEP encapsulation is far less resilient than an elastomer and may not perform as well in certain O-ring applications. PFA/FEP encapsulated O-rings should be used only where an elastomer O-ring cannot meet requirements.

 Elastomer Backed PTFE 

Used in Spears^® PTFE Diaphragm Valves, this chemically bonded laminate provides the chemical resistance of PTFE with improved resilience from a thick elastomer backing for greater sealing capability than solid PTFE Diaphragms.  Use of heavier, high grade EPDM or FKM backing materials eliminates the need for “gas barrier” PTFE Diaphragm designs.

Metals

Zinc Plated Steel 

Zinc plated carbon steel is the standard for general purpose bolts, nuts and fasteners. Zinc plated steel provides good corrosion resistance for most dry environment applications and normal operating conditions.

Stainless Steel   

Stainless Steel provides superior corrosion resistance than natural or plated carbon steels. Common grade is 18-8, which is excellent for general purpose use in nuts, bolts and fasteners. SS302 and SS304 are commonly used in a variety of sheet stock or deep drawn metal components. SS316 is the preferred choice for harsh chemical and corrosion environments and is used in the majority of Spears^® industrial valves and accessories where stainless steel is required.

SS316 — Type 316 Stainless Steel

Used in special valve components, nuts, and bolts, SS316 is one of the highest chemical and corrosion resistant stainless steels available.

SS316L - Low Carbon Type 316 Stainless Steel 

This specialty stainless steel provides extended chemical resistance over SS316 due to its lower carbon content.  SS316L is used exclusively in all Spears^® Butterfly Valve stems.

PTFE Coated SS316L

Where very high chemical resistance is needed, Spears^® offers a special PTFE coated, low carbon type 316 stainless steel Butterfly Valve stem. This tough, chemically bonded coating makes the stem virtually inert to most chemicals without loss of function or reliability.

 Special Alloys (Titanium, Hastelloy^® , Alloy 20, etc.)

A variety of specialty metals can be obtained on a custom order basis for use in Spears^® products where specific chemical or corrosion resistance is required and specified by user. Please note that custom components generally require extended lead time and may have significant costs.

Temperature Pressure De-rating for PVC, CPVC & PP Thermoplastic Materials

Elevated temperature fluid mediums require a de-rating of thermoplastic pipe maximum internal pressure ratings at 73° F. To determine the maximum internal pressure rating at an elevated temperature, simply multiply the pipe pressure rating at 73° F by the percentage specified for the desired temperature.

                PLEASE NOTE — Valves have different elevated temperature ratings than pipe & fittings. See individual valve recommendations

Typical Physical Properties of PVC, CPVC & PP Thermoplastic Materials

The following table lists typical physical properties of PVC, CPVC and PP thermoplastic materials. Variations may exist depending on specific compound and product.

* Glass filled PP will have slightly different values with higher tensile strength.

 )