A number of factors, such as the application, operating conditions, nature of the medium, etc., influence the selection of valve materials.
The following are examples of common valve components.
Cast Iron
Cast iron can be used for low pressure valves with operating temperatures ranging from -15 to 200 degrees Celsius and nominal pressures not exceeding PN16.Medium applicable for water, gas, etc.
Aluminium is a non-ferrous metal that is extremely lightweight, weighing roughly one-third as much as steel. Aluminium has an exceptional resistance to atmospheric corrosion, but it is highly reactive with other metals. Aluminium is predominantly used for external components such as hand wheels and identification marks in valves.
Copper
The thermal and electrical conductivity, corrosion resistance, wear resistance, and ductility are some of the most essential properties of wrought copper materials. Copper wrought performs well in high-temperature applications and can be readily soldered or brazed. Generally, wrought copper is only used for fixtures.
Bronze
One of the earliest alloys developed during the Bronze Age – is the industry standard for pressure-rated bronze valves and fittings. Bronze has greater strength than pure copper, is readily cast, has enhanced machinability, and can be soldered or brazed with ease. Bronze is extremely resistant to pitting corrosion and has a broad chemical resistance.
Silicone bronze possesses the ductility of copper but a significantly higher strength. Copper has equal or greater corrosion resistance than silicon bronze. Silicon bronze, which is commonly used as the stem material in pressure-rated valves, is more resistant to stress corrosion fracture than common brasses.
Aluminium Bronze
The most popular material for butterfly valve discs, aluminium bronze is heat-treatable and has the strength of steel. The formation of an aluminium oxide layer on exposed surfaces enhances the corrosion resistance of this metal. Not recommended for damp systems with a high pH.
Brass
Brass is generally resistant to corrosion. In certain applications susceptible to dezincification; exceptional machinability. Principal applications for wrought brass include ball valve stems and spheres, as well as iron valve stems. In commercial ball valve bodies and end sections, a forging-grade brass is used.
Grey Iron
An iron, carbon, and silicon alloy that is readily cast and has excellent pressure tightness in its as-cast state. Grey iron has superior dampening properties and is simple to manufacture. It is the standard material for Class 125 iron body valve bodies and bonnets. In certain environments, grey iron has greater corrosion resistance than steel.
Ductile Iron
The composition of ductile iron is comparable to that of grey iron. Special processing modifies the metallurgical structure, resulting in enhanced mechanical properties; certain grades are heat-treated to enhance ductility. Ductile iron has the strength properties of steel and is employed for class 250 (as well as class 125 in larger quantities) using the same casting techniques as grey iron. Ductile iron is ideal for medium and low pressure valves with operating temperatures ranging from -30 °C to 350 °C and nominal pressures not exceeding PN40. It is compatible with liquids such as water, sea water, gas, and ammonia.
Carbon Steel
Excellent mechanical properties; highly resistant to stress corrosion and sulphides, Carbon steel has strength at both high and low temperatures, is extremely durable, and has exceptional fatigue strength. Utilised predominantly in gate, globe, and check valves for applications up to 454 deg. C, as well as one, two, and three-piece ball valves. Can be forged or cast, with forgings being superior for larger diameters and classes of the highest quality. Medium suitable for water, natural gas, compressed air, liquefied gas, oil, saturated steam, and superheated steam, among others.
Titanium alloy
Titanium alloy is primarily utilised in valves for powerful corrosive fluids.
Cast copper alloy
Cast copper alloy is primarily used in the valves of oxygen pipelines and sea water pipelines where the operating temperature ranges from -273 to 200 degrees Celsius.
Nickel-Coated Ductile Iron
Nickel coatings are widely accepted for chemical processing applications. The tensile strength of these coatings ranges from 50 to 225 ksi. The hardness of a material is indicative of its resistance to abrasion and erosion to a certain extent. As a disc coating, nickel plating is commonly specified for butterfly valves. For industrial and petroleum ball valves, carbon steel valve components are coated with electroless nickel plating (ENP) that is preferable to stainless steel in hardness but has similar corrosion properties.
Monel
A nickel-copper alloy that is primarily utilised as interior decoration on all types of valves. One of the most specified materials for seawater and saltwater corrosion resistance. Additionally, Monel is highly resistant to strong caustic solutions.
Stellite
Stellite is a cobalt-based alloy that is one of the most versatile hard-facing alloys. Extremely heat, abrasion, corrosion, impact, galling, oxidation, thermal stress, and erosion resistant. Stellite can be polished to a high sheen and is utilised in steel valve seat rings. Stellite's hardness is unaffected by thermal treatment; it is typically applied using transfer plasma-arc.
Hastelloy C
A high nickel-chromium molybdenum alloy with exceptional resistance to a broad range of chemical process environments, such as strong oxidizers like wet chlorine, chlorine gas, and ferric chloride. Additionally, Hastelloy C is resistant to nitric, hydrochloric, and sulfuric acids at moderate temperatures.