Introduce the pressure rating and temperature rating of American standard gate valves

2025-04-18 09:35:22

The pressure rating and temperature rating of American standard gate valves are mainly determined based on standards such as ASME B16.34 "Valve Flange Connections, Threaded Connections, and Welded Ends", and their design needs to meet the requirements of pressure and temperature coordination working conditions simultaneously. Here is a specific analysis:

1、 Pressure Classes

The American standard pressure rating is represented by "Class", which reflects the maximum working pressure (MWP) of the valve at a specific temperature

2. Key characteristics

The effect of temperature on pressure:

As the temperature increases, the material strength decreases, and the maximum working pressure of the valve will decrease. For example:

At 650 ° F (343 ° C), the maximum working pressure of Class 300 carbon steel valves drops to 545 psi (3.76 MPa);

Stainless steel valves (such as 316) maintain better strength at high temperatures, and Class 300 can still reach 460 psi (3.17 MPa) at 1000 ° F (538 ℃).

Standard reference: The allowable pressure should be checked based on the material and temperature, in conjunction with ASME B16.34 Tables A-1 to A-20 or the pressure temperature gauge provided by the manufacturer.

2、 Temperature Ratings

The temperature level depends on the temperature resistance of the valve material and is divided into three levels: low temperature, normal temperature, and high temperature. The temperature range corresponding to common materials is as follows:

1. Low temperature conditions (≤ -29 ℃/-20 ° F)

Material requirements: Must meet low-temperature toughness (such as passing Charpy impact test), commonly used materials:

LF2 (Low Temperature Carbon Steel):- 46℃/-50°F ~ 343℃/650°F

304/316 stainless steel:- 196 ℃/-321 ° F~650 ℃/1200 ° F (excellent low-temperature performance, used in ultra-low temperature scenarios such as LNG)

Nickel based alloys (such as Inconel):- 253 ℃/-423 ° F~1093 ℃/2000 ° F (extreme low or high temperature)

Sealing design: Low temperature resistant packing (such as polytetrafluoroethylene) and anti freezing structure should be used.

2. Normal temperature conditions (-29 ℃~343 ℃/-20 ° F~650 ° F)

General materials:

WCB Carbon Steel:- 29 ℃~427 ℃ (800 ° F), most commonly used, suitable for water, steam, and oil products;

WC6/WC9 chromium molybdenum steel:- 29 ℃~593 ℃ (1100 ° F), used for medium and high temperature steam (such as power plant boilers);

CF8/CF8M stainless steel:- 29 ℃~650 ℃ (1200 ° F), corrosion-resistant, suitable for chemical media.

3. High temperature conditions (>343 ℃/650 ° F)

High temperature resistant material:

F91/F92 alloy steel: up to 650 ℃ (1200 ° F), used in supercritical power plants;

Hastelloy alloy: up to 1200 ℃ (2192 ° F), suitable for strong acids and high-temperature gases;

Design points: Consider thermal expansion compensation (such as flexible valve stem, extended valve cover) and sealing surface hardening (such as welding Stellite alloy).

4. Special temperature conditions

Ultra low temperature (such as -196 ℃/-321 ° F, LNG pipeline): Austenitic stainless steel or aluminum alloy must be used to avoid low-temperature brittle fracture of carbon steel;

High temperature and high pressure: It must comply with ASME BPVC Section VIII and other specifications, and the material must pass the high-temperature endurance strength test.

3、 Collaborative design of pressure and temperature

Application of pressure temperature gauge:

When selecting valves, it is necessary to search for the maximum allowable working pressure of the corresponding class from the standard table based on the medium temperature and material. For example:

Class 300、 The maximum working pressure of WCB (carbon steel) at 400 ℃ (752 ° F) is 620 psi (4.27 MPa), which is lower than 875 psi at room temperature.

Material compatibility:

At high temperatures, it is necessary to prevent material oxidation (such as using aluminum infiltrated steel), and at low temperatures, hydrogen embrittlement should be avoided (such as controlling the hydrogen content of the material).

Sealing structure adaptation:

Metal hard seals (such as conical seals) are used at high temperatures, and elastic soft seals (such as reinforced polytetrafluoroethylene) are used at low temperatures to ensure sealing reliability under temperature changes.

4、 Standards and Identification

Pressure rating identification: Valves are usually labeled with a Class rating (such as "CL300") and indicate compliance with ASME B16.34;

Temperature grade identification: Some valves will be labeled with material codes (such as "WCB" corresponding to room temperature carbon steel), or directly labeled with applicable temperature ranges (such as"-20°F~800°F").

summarize

The pressure rating of American standard Gate valves is based on Class pounds, and the actual working pressure is determined by combining temperature and material; The temperature level depends on the temperature resistance of the material and needs to be matched with specific working conditions through a pressure temperature gauge. When selecting, it is necessary to simultaneously meet the four elements of medium characteristics, pressure, temperature, and material standards to ensure the safe and reliable operation of the valve within the design range.