Valve Terms and Meanings

ABS:
Acrylonitrile Butadien Styrene. A rugged plastic compound typically used for housings, some external valve parts. A form of ABS is also used for low-pressure air piping systems in harsh environments.

AFLAS:
An elastomer used for high temperature/high purity or highly aggressive applications; particularly suited to ozone-treated water. Aflas® is a trademark of 3M.

ASQ:
American Society for Quality

ASTM:
American Society for Testing and Materials.

BCF:
Bead and crevice free. Also known as fusion. A means of connecting pipes, valves and fitting via heat fusion, with a perfectly smooth internal joint.

BS, BSP:
British Standard, British Standard Piping. A piping specification.

BUNA or BUNA-N:
Nitrile rubber, used to make o-rings and other seals used in valves. Buna-N is the least expensive type of seal, and it lacks the chemical compatibility of other more costly elastomers.

CHEMRAZ:
A fluorinated elastomer used for high temperature/high purity or highly aggressive applications. Chemraz® is a trademark of Greene-Tweed.

CNC:
Computer numerically controlled. Popular type of control system for vertical machining centers, lathes, injection molding machines, and other tools used to fabricate a valve.

Corzan, CPVC:
Chlorinated polyvinyl chloride. While not as popular as PVC, it is able to withstand higher temperatures. Plast-O-Matic is an authorized vendor of Corzan® CPVC, a brand name of Noveon Corp .

CSA:
Canadian Standards Association.

DIVERTER:
A three-way valve; the flow can be diverted from one outlet to another, or different inlets can be selected and sent to a common outlet.

EPDM:
Ethylene propylene diene monomer. A popular rubber seal material, compatible with a wide range of chemicals.

FLANGE:
A type of pipe fitting that attaches via nuts and bolts.

FLARE:
A type of pipe fitting that uses a socket and a type of union nut to form a connection with minimal crevice, for ultrapure processes. Usually seen on fluoropolymer or natural polypropylene valves.

GPM:
Gallons per minute. Expresses volume of flow.

GPP:
Glass-filled polypropylene. Offers the chemical resistance of polypropylene, with glass fibers added for strength.

HALAR:
Ethylene-chlorotrifluoroethylene. Plast-O-Matic uses this material for some external components; it is also a valve body material for high temperature/high purity applications.

IAPD:
International Association of Plastics Distributors. Formerly NAPD, National Assoc. etc.

ISA:
The Instrumentation Systems and Automation Society. Formerly Instrument Society of America.

KALREZ:
A fluorinated elastomer used for high temperature/high purity or highly aggressive applications. Kalrez® is a trademark of DuPont Dow Elastomers.

KYNAR:
Brand of Polyvinylidene flouride. A dense, high-purity plastic that is used in critical applications, such as semiconductor manufacturing. Plast-O-Matic is an authorized reseller of Kynar® PVDF. Kynar is a trademark of Atofina.

NATURAL:
Describes resins, frequently PP or PVDF, that have not had colorants, fibers, or other components added prior to processing. Sometimes mistakenly interchanged with “virgin.”

NC:
Normally-Closed. Describes a valve that is “fail-safe” to the closed position. This is usually accomplished by a spring built into the valve.

NEMA:
National Electrical Manufacturers Association. Used in valve terminology to define the level of external resistance an enclosure or solenoid coil is suited for. e.g.: NEMA 1 is dusttight, NEMA 9 is explosion proof, etc.

NO:
Normally-Open. Describes a valve that is “fail-safe” to the open position. This is usually accomplished by a spring built into the valve.

NPT:
“National Pipe Thread.” A specification for tapered pipe threads from ANSI (American National Standards Institute). Actually taken from American National Standard Taper Pipe Threads. When listed as NPT-F, indicates female ends.

O-RING:
A type of seal. An O-ring is a round elastomeric ring, ideally suited to be a compressed, static seal between non-moving parts. O-rings can be used as a face seal on a valve, and used on rotating shafts inside a valve.

PECTFE:
Ethylene-chlorotrifluoroethylene. Plast-O-Matic uses this material, in HALAR brand, for some external components; it is also a valve body material for high temperature/high purity applications.

PET or PETRA:
Polyethylene terephthalate. (PETRA is a brand) Used on certain housings.

PP or PPL, Polypropylene:
A lightweight plastic that offers relatively high purity characteristics at a price well below PVDF or PTFE. Impervious to many chemicals.

PSI:
Pounds per square inch. Used to indicate the amount of pressure in a given piping system.

PTFE:
Polytetrafluoroethylene. A type of fluorinated thermoplastic with outstanding chemical resistance, low leachability, and excellent lubricity.

PTFE BELLOWS:
A sealing mechanism that is made of PTFE, formed in a bellows shape, used on many Plast-O-Matic solenoid valves.

PVC:
Polyvinyl chloride. This is the most popular material used for plastic piping systems.

PVDF:
Polyvinylidene flouride. A dense, high-purity plastic that is used in critical applications, such as semiconductor manufacturing. Plast-O-Matic is an authorized reseller of Kynar® PVDF. Kynar is a trademark of Elf-Atochem.

PVF:
Pipes, valves, fittings. Used to describe a segment of the plastics industry, or distributors who specialize in these products.

REGRIND:
Thermoplastic that has been processed once, then is placed in a grinder to be shredded/pelletized for re-molding. In injection molding, runners etc. are often re-ground. No thermoplastic can be successfully reground and remolded indefinitely; eventually the molecular bond begins to break down and the plastic is no longer usable.

ROLLING DIAPHRAGM:
A type of seal, also senses pressure. This is a diaphragm formed in a convoluted shape. It gets its name because as the stem moves, the diaphragm “rolls” at the convolution. It is frequently used in a manner similar to a u-cup, that is, to seal the gap between a linear moving shaft and the valve body.

SOLENOID VALVE:
A valve that uses an electromagnetic coil for actuation.

SPIGOT:
A type of fitting, essentially a section of pipe fused cleanly into a valve. This protruding pipe is then fused into the piping system. Usually found in high purity systems.

TEFLON:
This is the brand name for a number of fluorinated polymers manufactured by E.I. DuPont de Nemours. Many valve manufacturers use this term illegally, when in fact their products are not Teflon® but generic PTFE, PFA etc.

TEMPRITE:
This is a formulation of Corzan® CPVC that is used for injection molded valve bodies.

THERMOPLASTIC, THERMOSET:
Two basic types of plastic resins. Thermoplastics are resins that can be reground after molding, and molded again. Thermosets can be molded once only. They tend to be denser materials for special purposes. PVC is a thermoplastic. A PVC valve could conceivably be reground, then molded into a coffee mug. The resin used on a solenoid coil is a thermoset. A good analogy is paraffin wax vs. paraffin paste; both are petroleum products, but the wax can be melted and reformed while the lubricant cannot. Just as paraffin cannot be melted and reshaped indefinitely, no thermoplastic can be successfully reground and remolded indefinitely. Eventually the molecular bond begins to break down and the plastic is no longer usable. In another popular analogy, thermosets are often compared to an egg; once the egg is hard boiled it can’t be returned to a liquid and recooked as sunny side up.

U-CUP:
A type of seal. A u-cup is an o-ring formed into a u-shaped channel. Liquid or air pressure “inflates” the u-cup and affects a seal. The u-cup is used in instances where an o-ring is not desirable.

VIRGIN:
Describes thermoplastic resins that have no “regrind” in the processing mix. Sometimes mistakenly interchanged with “natural.”

VITON:
A fluorinated elastomer used in making o-rings and other seals. Viton® is a trade mark of DuPont Dow Elastomers.

WOG:
Water/Oil/Gas. Describes a common type of brass valve.

X-VALVE:
A Plast-O-Matic term used to describe any type of custom valve. “Q-valve” is used to describe custom ball valves.

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