2 Piece Threaded Ball Valve Common Materials And Temperature Requirements

Common Materials and Temperature Requirements for 2 Piece Threaded Ball Valve

When selecting the material for a valve's main components, the physical properties (temperature, pressure) and chemical properties (corrosiveness) of the working medium should be considered. The cleanliness of the medium (presence of solid particles) should also be considered. Furthermore, relevant national and user regulations and requirements should be consulted.

A variety of materials can meet the requirements of valves in various operating conditions. However, proper and rational selection of valve materials can maximize valve life and performance.

Common Temperature Requirements for Stainless Steel Ball Valve Housing Materials:

1. Gray Cast Iron

Gray cast iron valves are used in various industrial fields due to their low cost and wide range of applications. They are typically used with water, steam, oil, and gas as media, and are widely used in the chemical, printing and dyeing, petrochemical, textile, and many other industries where iron contamination is minimal or non-essential.

They are suitable for low-pressure valves with operating temperatures between -15°C and 200°C and nominal pressures PN ≤ 1.6 MPa.

2. Blackheart Malleable Cast Iron

Suitable for medium- and low-pressure valves operating between -15°C and 300°C, with a nominal pressure PN ≤ 2.5 MPa. Applicable media include water, seawater, gas, and ammonia.

3. Ductile Iron

Ductile iron is a type of cast iron in which the flake graphite found in gray cast iron is replaced by globular or spherical graphite. This change in the metal's internal structure gives it superior mechanical properties to those of ordinary gray cast iron without compromising other properties. Therefore, valves made of ductile iron can operate at higher pressures than those made of gray cast iron.

Suitable for medium- and low-pressure valves operating between -30°C and 350°C, with a nominal pressure PN ≤ 4.0 MPa. Applicable media include water, seawater, steam, air, gas, and oil.

4. Carbon Steel (WCA, WCB, WCC)

Cast steel was initially developed to meet production needs that exceeded the capabilities of cast iron and bronze valves. However, due to the overall superior performance of carbon steel valves and their strong resistance to stresses caused by thermal expansion, shock loads, and pipeline deformation, their application range has expanded, often encompassing conditions typically associated with cast iron and bronze valves.

Suitable for medium- and high-pressure valves operating between -29°C and 425°C. 16Mn and 30Mn, for example, operate between -40°C and 400°C and are often used in place of ASTM A105. Suitable media include saturated and superheated steam, high- and low-temperature oils, liquefied gases, compressed air, water, and natural gas.

5. Low-Temperature Carbon Steel (LCB)

Low-temperature carbon steel and low-nickel alloy steel can be used in subzero temperatures, but cannot be extended to cryogenic environments. Valves made of these materials are suitable for media such as seawater, carbon dioxide, acetylene, propylene, and ethylene.

Suitable for low-temperature valves operating between -46°C and 345°C.

6. Low-Alloy Steel (WC6, WC9)

Valves made of low-alloy steel (such as carbon-molybdenum and chrome-molybdenum steels) can handle a wide range of media, including saturated and superheated steam, cold and hot oil, natural gas, and air. Carbon steel valves can operate up to 500°C, while low-alloy steel valves can operate above 600°C. At high temperatures, low-alloy steel exhibits superior mechanical properties compared to carbon steel.

C5 and C12 are suitable for high-temperature, high-pressure valves operating in non-corrosive media between -29°C and 595°C; C5 and C12 are suitable for high-temperature, high-pressure valves operating in corrosive media between -29°C and 650°C.

7. Austenitic Stainless Steel

Austenitic stainless steel contains approximately 18% chromium and 8% nickel. 18-8 austenitic stainless steel is often used as a valve body and bonnet material in both high and low temperature environments and under highly corrosive conditions. Adding molybdenum to the 18-8 stainless steel base and slightly increasing the nickel content substantially enhances its corrosion resistance. Valves made of this steel can be widely used in the chemical industry, such as conveying acetic acid, nitric acid, alkali, bleaching liquid, food, fruit juice, carbonic acid, leather making liquid and many other chemical products.

In order to be suitable for high temperature range, the material composition is further changed and niobium is added to this stainless steel, which is what we know as 18-10-Nb, and the temperature can be used up to 800℃.

Austenitic stainless steel is usually used at very low temperatures without becoming brittle, so valves made of this material (such as 18-8 and 18-10-3Mo) are very suitable for working at low temperatures. For example, it can convey liquid gases such as natural gas, biogas, oxygen and nitrogen. It is suitable for valves with corrosive media with an operating temperature between -196-600℃. Austenitic stainless steel is also an ideal low-temperature valve material.

8. Hastelloy Alloy

Mainly suitable for valves with highly corrosive media such as dilute sulfuric acid.

(1) Hastelloy B

This alloy contains 60% nickel, 30% molybdenum and 5% iron. It is particularly resistant to strong corrosion from inorganic acids. Hastelloy B can be used up to the boiling point of hydrochloric acid at all concentrations, and up to 70°C at the most corrosive concentration for sulfuric acid. It can be used under all conditions for phosphoric acid, and Hastelloy B is also suitable for ammonium chloride, zinc chloride, aluminum sulfate and ammonium sulfate.

In oxidizing atmospheres, Hastelloy B can be used up to about 800°C, and in reducing atmospheres, the operating temperature can be higher.

(2) Hastelloy C

This alloy is a nickel-based alloy containing 15% chromium and 17% molybdenum. It can be used up to 1100°C in both oxidizing and reducing atmospheres. It has good corrosion resistance to hydrochloric acid, sulfuric acid and phosphoric acid. In many cases, it can also be used for nitric acid.

Hastelloy C has strong corrosion resistance to chlorides, hydrochlorides, sulfides, oxidizing salt solutions and many other corrosive media. It is also particularly suitable for hydrohalic acid media, such as hydrofluoric acid.