How many temperature and pressure valves can choose which material
1. The operating temperature of the valve
The operating temperature of the valve is determined by the material of the valve. The service temperature of commonly used materials for valves is as follows:
The service temperature of gray cast iron valve is -15~250℃;
The service temperature of malleable cast iron valve is -15~250℃;
The service temperature of ductile iron valve is -30~350℃;
The highest operating temperature of high nickel cast iron valve is 400℃;
The operating temperature of carbon steel valve is 29~450℃, and the recommended operating temperature is t<425℃ in the JB/T3595-93 standard;
The maximum operating temperature of 1Cr5Mo and alloy steel valves is 550℃;
The maximum operating temperature of 12Cr1MoVA and alloy steel valves is 570℃;
The operating temperature of 1Cr18Ni9Ti and 1Cr18Ni12Mo2Ti stainless steel valves is 196~600℃;
The service temperature of copper alloy valve is 273~250℃;
Maximum operating temperature of plastic valve:
Nylon is 100°C;
Polychlorinated polyether is 100°C;
Polyvinyl chloride is 60°C;
Polytrifluoroethylene-60~120℃;
PTFE-180~150℃.
Rubber diaphragm valves have different operating temperatures due to different types of rubber:
Natural rubber is 60°C;
Nitrile rubber and chloroprene rubber are 80°C;
Fluorine rubber is 200℃;
When rubber or plastic is used for valve lining, the temperature resistance of rubber and plastic shall prevail.
Ceramic valves, because of their poor temperature resistance, are generally used in working conditions below 150°C. Recently, a super-performance ceramic valve appeared, which can withstand high temperatures below 1000°C.
Glass valves have poor temperature resistance and are generally used in working conditions below 90°C.
The temperature resistance of the enamel valve is limited by the material of the sealing ring, and the maximum operating temperature does not exceed 150°C.
2. The pressure used by the valve
The use pressure of the valve is determined by the material of which the valve is made.
The maximum allowed value for gray cast iron valves is 1MPa;
The maximum nominal pressure allowed for malleable cast iron valves is 2.5MPa;
The maximum nominal pressure allowed for the ductile iron valve is 4.0MPa;
The maximum nominal pressure allowed for copper alloy valves is 2.5MPa;
The maximum nominal pressure allowed for titanium alloy valves is 2.5MPa;
The maximum nominal pressure allowed for the carbon steel valve is 32MPa;
The maximum nominal pressure allowed for alloy steel valves is 300MPa;
The maximum nominal pressure allowed for stainless steel valves is 32MPa;
The maximum nominal pressure allowed for plastic valves is 0.6MPa;
The maximum nominal pressure allowed for ceramic, glass and enamel valves is 0.6MPa;
The maximum nominal pressure allowed for FRP valves is 1.6MPa.
3. The relationship between valve temperature and pressure
The valve operating temperature and pressure have a certain internal connection and influence each other. Among them, temperature is the dominant factor affecting the valve. A valve with a certain pressure can only be adapted to a certain temperature range, and changes in valve temperature can affect the valve's operating pressure.
For example: the nominal pressure of a carbon steel valve is 10MPa, when the working temperature of the medium is 20℃, its maximum working pressure P20 is 10MPa; when the working temperature of the medium is 400℃, its maximum working pressure P40 is 5.4MPa; When the working temperature is 450℃, its maximum working pressure is 4.5MPa for P54.