Except when Safety valves are discharging, the only parts that are wetted by the process fluid are the inlet tract (nozzle) and the disc. Since safety valves operate infrequently under normal conditions, all other components can be manufactured from standard materials for most applications. There are however several exceptions, in which case, special materials have to be used, these include:

• Cryogenic applications.
• Corrosive fluids.
• Where contamination of discharged fluid is not permitted.
• When the valve discharges into a manifold that contains corrosive media discharged by another valve.

The principal pressure-containing components of Safety valves  are normally constructed from one of the following materials:

• Bronze - Commonly used for small screwed valves for general duty on steam, air and hot water applications (up to 15 bar).
• Cast iron - Used extensively for ASME type valves. Its use is typically limited to 17 bar g.
• SG iron - Commonly used in European valves and to replace cast iron in higher pressure valves (up to 25 bar g).
• Cast steel - Commonly used on higher pressure valves (up to 40 bar g). Process type valves are usually made from a cast steel body with an austenitic full nozzle type construction.
• Austenitic stainless steel - Used in food, pharmaceutical or clean steam applications.

For extremely high pressure applications, pressure containing components may be forged or machined from solid.

For all safety valves, it is important that moving parts, particularly the spindle and guides are made from materials that will not easily degrade or corrode. As seats and discs are constantly in contact with the process fluid, they must be able to resist the effects of erosion and corrosion. For process applications, austenitic stainless steel is commonly used for seats and discs; sometimes they are 'stellite faced' for increased durability. For extremely corrosive fluids, nozzles, discs and seats are made from special alloys such as 'monel' or 'hastelloy'.

The spring is a critical element of the safety valve and must provide reliable performance within the required parameters. Standard safety valves will typically use carbon steel for moderate temperatures. Tungsten steel is used for higher temperature, non-corrosive applications, and stainless steel is used for corrosive or clean steam duty. For sour gas and high temperature applications, often special materials such as monel, hastelloy and 'inconel' are used.

Ball Valves

Gate Valves

Bellow Seal Valve

Water Pump Control Valves

Forged Steel Valves