Cryogenic valve is a important indispensable equipment
in section of petrochemical industry, coal chemical industry,
air classification, natural gas, Tobacco. Its Performance and
reliability can effect safe and economical operation of these
complete plant directly .except liquid nitrogen and liquid inert
gases, most of medium through Cryogenic valve are flammable ,
explosive and have strong permeability.
The lowest using temperature of cryogenic valve is -269 Celsius
and the maximum safe working pressure is 10Mpa.such extreme operating
conditions presents new challenges to cryogenic valve .the standard
of design , manufacture and test are different from common valve.
there are three risk factors cryogenic valve have to overcome
:
1.when open or close valve , exceptional pressure boost caused
by Vaporization of medium which remain in the valve body is a
risk factor.
2.packing fail because of low temperature ,which can cause valve
leak in the packing case.
3.pressure-load part have less unti-low-temperature impact .scope
of cryogenic system become larger and larger and demand of cryogenic
valve is bigger and bigger.
We choose long-neck bonnet because these reasons:
1. long-neck bonnet can protect packing case which is most important
part. If a part of packing case leak ,the heat insulation performance
can reduce, which can made liquefying gas gasification .general
speaking ,the scope of temperature-controlling in packing case
should exceed 8Celsius.
2. long-neck bonnet structure can winding heat insulation material
conveniently,protecting cold energy out
3. if long-neck bonnet structure is chosen,main port of valve
can be replaced or ,maintained conveniently. long-neck bonnet
structure can let body and each pipe become a unity.Which can
reduce leak in cold box. making sure of good leak tightness.
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