The Common Materials of Which Valves Are Made

The Common Materials of Which Valves Are Made selection of valves

It pays to know the range of materials from which valves are usually made, and to understand the pressure, temperature, and structural limitations of each material. It may be highly unsafe to use materials for services beyond their recommended maximum.

Valves commonly used in industry fall into the four general material groups shown below. Variants in each of these groups have individual service characteristics.

Bronze

Steam Bronze is widely used in valves and fittings for temperatures up to 450°F. It is an alloy of copper, tin, lead, and zinc.

Special Bronze is a high-grade copper-base alloy used in piping equipment for higher pressures and for temperatures up to 550°F.

Iron

Cast Iron is regularly made in three grades - Cast Iron, Ferrosteel, and High Tensile Iron. These metals are recommended for temperatures up to 450°F.

Cast Iron is commonly used for small valves having light metal sections.

Ferrosteel, stronger than cast iron, is used for valves having medium metal thicknesses.

High Tensile Iron has even greater strength, and is used principally for large size castings.

Malleable Iron

Malleable Iron used in valves is characterized by pressure tightness, stiffness, and toughness, the latter property being an especially valuable one for piping materials subjected to stresses and shock.

Steel

Steel is recommended for high pressures and temperatures and for services where working conditions, either internal or external, may be too severe for bronze or iron. Its superior strength and toughness, and its resistance to piping strains, vibration, shock, low temperature, and damage by fire afford reliable protection when safety and utility are desired. Many different types of steel - cast, forged, alloy - are both necessary and available because of the widely diversified services steel valves perform.

Ductile Iron

Nodular Cast Iron, also known as ductile iron is cast iron with the graphite substantially in spherical shape and reasonably free of flake graphite. This results in a cast iron having high strength and good ductility. The corrosion resistance of nodular iron is approximately the same as that of gray iron. Strength is about 3 times greater.

Stainless Steel

Stainless Steel Castings are heat treated for maximum corrosion resistance, high strength, and good wearing properties. Seating surfaces, stems, and discs of stainless steel are well suited for severe services where foreign materials in the fluids handled could have adverse effects. Stainless steel has excellent resistance to wear, seizure, galling erosion, and oxidation.