This material chemical compatibility lookup is particularly useful because it is important that the valve you select is made from materials that are compatible with the medium being used and remains compatible over the full temperature range that it will operate. Some materials you will see quite commonly in valve descriptions (brass, bronze, cast iron, carbon steel, stainless steel, EPDM, Viton, Nitrile) and others you will only come across when the medium is particularly corrosive or the valve is operating at high or low temperatures.
MATERIALS USED IN VALVE CONSTRUCTION
Any temperatures or pressures quoted are a guide and may change between the exact grade and manuafcturer.
METALS: Metals are predominantly used to manufacture the main valve components such as the body, bonnet, stem, ball, springs etc.
Brass: Generally good corrosion resistance. Susceptible to de-zincification in specific applications; excellent machinability. Primary uses for wrought brass are for ball valve stems and balls, and iron valve stems. A forging grade of brass is used in commercial ball valve bodies and end pieces.
Bronze: is one of the first copper alloys developed in the bronze age and is generally accepted as the industry standard for pressure-rated bronze valves and fittings. Bronze has a higher strength than pure copper, is easily cast, has improved machinability, and is very easily joined by soldering or brazing. Bronze is very resistant to pitting corrosion, with general resistance to most chemicals less than that of pure copper. Historically, bronze alloys have contained lead to improve machinability and leak tightness, but recently are being improved with the release of lead-free alloys for drinking water applications.
Ductile Iron / Cast Iron: has a chemical composition similar to gray iron, but special treatment during the casting process enhances its metallurgical graphite structure to yield higher mechanical properties and improved ductility similar to steel. It is a standard material for bodies and bonnets of ANSI Class 150 and 300 valves.
Carbon Steel: has very good mechanical properties, good resistance to stress corrosion and sulfides. Carbon steel has high and low temperature strength, is very tough, and has excellent fatigue strength. Steel can be easily cast or welded in making ANSI Pressure-Temperature rated valve bodies or structural parts for applications up to 850 degrees F.
304SS: 304 SS is basic 18% chromium, 8% nickel austenitic stainless steel commonly used for valve trim. Its 0.08% max carbon content reduces intergranular corrosion usually associated with carbide precipitation that can occur during welding. It offers excellent resistance to a wide range of corrosives and atmospheric exposures.
316 / 316Ti / 321: 316 SS is chemically similar to 304 SS except with the addition of molybdenum providing better corrosion and pitting resistance and higher strength at elevated temperatures. It is non-magnetic with greater ductility than 400SS. 316SS has excellent corrosion resistance in a wide range of environments, is not susceptible to stress corrosion cracking, and is not affected by heat treatment. Most common uses in valves are stem, body and ball materials.
17-4PH: is similar to 304 SS except it is capable of being heat treated, doubling its strength and making it a good choice for high performance valve trim. 17-4 PH withstands corrosive attack better than any of the 400 series stainless steels and in most conditions its corrosion resistance closely approaches that of 300 series stainless steel. 17-4 PH is primarily used as a stem material for high pressure butterfly and ball valves. It is also used as a metal disk material in Safety valves.
Aluminium: A non-ferrous metal, very lightweight, approximately one-third the weight of steel. Aluminum exhibits excellent atmospheric corrosion resistance, but can be very reactive with other metals. In valves, aluminum is mainly used as for exterior components such as a hand wheels or identification tags.
Aluminium Bronze: Aluminum Bronze is the most widely accepted disc material used in many valves for liquid service. Aluminum bronze is heat treatable and has the strength of steel. Formation of an aluminum oxide layer on exposed surfaces makes this metal very corrosion resistant. Is often used when the the medium is seawater.
Alloy 20: This alloy has higher amounts of nickel and chromium than 300 series stainless steel and with the addition of columbium, this alloy retards stress corrosion cracking and has improved resistance to sulfuric acid. Alloy 20 is widely used in all phases of chemical processing.
Duplex: Higher strength and greater corrosion resistance than standard stainless steels.
Inconel: is nickel-copper-molybdenum alloy with excellent corrosion resistance in a wide range of corrosive media and is especially resistant to pitting and crevice corrosion. Like Monel, it is a favorable choice for seawater applications but with far greater strength. Sometimes used as a spring material in Safety Valves.
Hastelloy: A high nickel-chromium molybdenum alloy, which has outstanding resistance to a wide variety of chemical process environments including strong oxidisers such as wet chlorine, chlorine gas, and ferric chloride. Hastelloy C is also resistant to nitric, hydrochloric, and sulfuric acids at moderate temperatures.
Titanium: Titanium alloys are metals that contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures). They are light in weight, have extraordinary corrosion resistance and the ability to withstand extreme temperatures
The following materials are used in the manufacture of items such as diaphragms and o-ring seals.
Buna N / Nitrile / NBR: (Copolymer of Butadiene and Acrylonitrile) has excellent resistance to petroleum products, lubricants, and water over a wide temperature range of -50 to 200 deg F. Nitrile is a widely used elastomer for hydraulic system o-rings. Buna-N does not have good resistance to outdoor exposure to ozone, sunlight, or weather.
EPDM / EPR: (Ethylene Propylene Diene) exhibits strong resistance to ozone, certain hydraulic fluids, brake fluids, steam, and water over a wide temperature range of -50 to 250 deg F. EPDM has gained increased use in the municipal water industry because of its resistance to water disinfected with chloramines. It has poor resistance to petroleum-based fluids, mineral oils, and solvents.
Flexible Graphite: Flexible Graphite products are ideal for sealing those difficult high temperature applications, chemical applications, and low bolt load applications.
Kalrez: DuPoint Kalrez delivers outstanding performance in aggressive process environments. Withstands attack from more than 1,800 chemicals, solvents and plasmas.
Viton: (Fluorocarbon, FKM) possesses a strong resistance to chemicals and air at high temperature applications to 400 deg F. Viton is high in cost and is used in aircraft, automotive applications where resistance to petroleum oils, silicone fluids, and acids is needed. Viton also has superior chloramine resistance for drinking water applications.
The following are engineering plastics with specific properties, making them useful in the manufacture of valve components such as ball seat rings in ball valves or in the construction of the disk in a Safety valve. Many of the product names are trade names from the various different manufacturers.
Delrin: DuPont Delrin acetal homopolymer resin is a highly-crystalline polymer that has high stiffness and strength without the need for glass reinforcement. When compared to acetal copolymers offered by competitors, Delrin offers higher tensile strength, stiffness, and creep resistance, and significantly outperforms on impact resistance, allowing for thinner and lighter part design. In addition, Delrin offers outstanding low- and high-temperature performance, good colorability, and good mating with metal and other polymers.
PEEK: is a strong and stiff plastic material that is often used in applications where performance at elevated temperatures is required. PEEK has outstanding chemical resistance as well as resistance to steam and hot water.
PVDF: PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low smoke generation during a fire event.
Teflon: non stick coatings
PCTFE: Nonflammability, chemical resistance, near-zero moisture absorption and wide temperature range of -400 to 400 deg F. Sometimes referred to as Kel-F (a discontinued product from 3M).
UHMWPE: Highest impact strength of any thermoplastic.
Vespel: DuPoint Vespel parts and shapes provide high-performance solutions for the toughest sealing, wear, or friction challenges.
PFA: Often used as a coating in valves when used with agressive chemicals.
KEL-F: A trade name for PCTFE.