Valve Stem for Industrial Valves

Our products include various grades of ferrous and non-ferrous metals and their alloy materials.
The material used to make the valve parts is selected according to the following factors:
(1) Pressure, temperature and characteristics of the working medium.
(2) The force of the part and its role in the valve structure.
(3) It has good processability.
(4) Under the above conditions, there must be lower costs.

1. Valve body, bonnet and gate
The valve body, bonnet and gate (or wedge) are one of the main components of the valve and are directly subjected to the medium pressure. The materials used must comply with the pressure and temperature rating of the valve. The commonly used materials are as follows:
(1) Gray cast iron: Gray cast iron is suitable for water, steam, air, gas, natural gas, oil and other media with a nominal pressure p N ≤ 1.0 MPa and a temperature of -10 to 200 °C.
(2) Malleable cast iron: suitable for water, steam, air, natural gas, oil and other media with a nominal pressure p N ≤ 2.5MPa and a temperature of -30 ~ 300 °C.
(3) Ductile iron: suitable for water, steam, air, natural gas, oil and other media with p N ≤4.0MPa and temperature -30~350°C.
(4) Acid-resistant high-silica ductile iron: suitable for corrosive media with nominal pressure p N ≤ 0.25 MPa and temperature below 120 °C.
(5) Carbon steel: suitable for water, steam, air, hydrogen, ammonia, nitrogen, natural gas, petroleum products and other media with a nominal pressure p N ≤ 32.0 MPa and a temperature of -30 to 425 °C.
(6) Copper alloy: suitable for water, seawater, oxygen, air, natural gas, oil and other media with p N ≤ 2.5 MPa, and steam medium with temperature of -40 to 250 °C.
(7) High temperature copper: Suitable for steam and petroleum products with a nominal pressure p N ≤17.0 MPa and a temperature not exceeding 570 °C. The specific selection must be in accordance with the valve pressure and temperature specifications.
(8) Low temperature steel, suitable for nominal pressure p N ≤ 6.4 MPa, temperature not lower than -196 ° C ethylene, propylene, liquid natural gas, liquid nitrogen and other media.
(9) Stainless acid-resistant steel, suitable for medium pressure p N ≤ 6.4MPa, temperature not exceeding 200 ° C nitric acid, acetic acid and other media.

2. Valve stem
The valve stem (or spindle) is subjected to tension, pressure and torsion during the opening and closing of the valve, and is in direct contact with the medium, and there is relative frictional movement between the valve and the packing. Therefore, the valve stem material must have sufficient strength and impact toughness at a specified temperature, a certain degree of corrosion resistance and scratch resistance, and good processability.
Commonly used stem materials are as follows.
(1) Carbon steel
For water and steam media with low pressure and medium temperature not exceeding 300 °C, ordinary carbon steel is generally used.
For water and steam medium with medium pressure and medium temperature not exceeding 450 °C, high quality carbon steel is generally used.
(2) Alloy steel
For medium and high pressure, media temperature does not exceed 450 ° C natural gas, petroleum and other media; for high pressure, media temperature does not exceed 540 ° C water and other media; for high pressure, media temperature does not exceed 570 ° C steam and other media.
(3) Stainless acid-resistant steel
Non-corrosive media and weak corrosive media for medium and high pressure, media temperature not exceeding 450 °C. For corrosive media, stainless steel and precipitation hardened steel are suitable.
(4) Heat resistant steel
For high temperature valves with media temperature not exceeding 600 °C, martensitic heat resistant steel and austenitic heat resistant steel may be used.

3. Stem nut
The stem nut directly receives the axial force of the stem during the opening and closing of the valve, so it must have a certain strength. At the same time, it is threaded with the valve stem, requiring a small coefficient of friction, no rust and no seizure.
(1) Copper alloy
Copper alloy has a small friction coefficient and does not rust, and is one of the materials currently widely used.
(2) steel
When working conditions do not allow the use of copper alloys, carbon steel or stainless acid-resistant steel can be used.