Material selection of ultra-low temperature valve: valve body: ferritic stainless steel can be selected when the temperature is higher than - 100 ℃, austenitic stainless steel can be selected when the temperature is lower than - 100 ℃, and copper alloy or aluminum alloy can be selected for low pressure and small caliber valves. Valve rod: It is made of austenitic stainless acid resistant steel, and needs to be properly heat treated to improve the tensile strength. At the same time, it must be plated with hard chromium (coating thickness 0.04~0.06mm), or nitrided to improve the surface hardness. Gasket: when the service temperature is higher than - 196 ℃ and the maximum service pressure at low temperature is 3MPa, the asbestos rubber plate made of long fiber from asbestos can be used; When the service temperature is higher than - 196 ℃ and the maximum service pressure at low temperature is 5MPa, stainless steel with asbestos spiral wound gasket, stainless steel with PTFE spiral wound gasket or stainless steel with expanded graphite spiral wound gasket can be used. Fastener: when the temperature is higher than - 100 ℃, the bolt material shall be alloy steel such as Ni, Cr Mo, etc., which shall be subject to appropriate heat treatment to prevent thread bite; When the temperature is lower than - 100 ℃, the bolt material can be austenitic stainless steel. The nut is generally made of Mo steel or Ni steel, and the thread gauge is coated with a disulfide key.

Second, from the perspective of environmental application capability, the water resistance of pneumatic ball valve is excellent. Although the use of the device will be harmed in a humid or even waterlogged environment, it will not cause more serious harm due to electric sparks like hardware and electric tools. The pneumatic ball valve can operate in various adverse or even harsh working environments with the help of an internal combustion engine air pump.