多晶硅装置用阀门，2Cr13和304材质作阀芯，哪个更好? 对多晶硅工艺中使用的材质，容器，管道和泵都提出了相应的设计要求。 materials of construction in the absence of water, carbon steel is satisfactory for piping and other equipment used to contain chlorosilanes. non-ferrous metals and alloys such as aluminium, bronze, copper, zinc or magnesium should never be used. they are more readily corroded and many, in case of fire, have low melting points. cast iron, due to its brittleness, must not be used to contain chlorosilanes; cast steel and forged steel can be used. plastics should not be used in chlorosilane service due to incompatibility and reactivity of this material. vessels storage vessels should be designed and fabricated in accordance with local regulations. generally storage tanks should be completely vacuum resistant or should be equipped with automatic pressure controled nitrogen supply and shut down systems which avoid dangerous underpressure. design pressure is dependent on the properties of the chlorosilanes stored. generally vessels should have emergency vents. they should satisfy the requirements stated in the local regulations. as an alternative to emergency vents, the storage vessels may be equipped with safety devices which will stop all pressure producing units immediately as soon as a predetermined pressure is reached. vessels being equipped with pressure-relief valves to relieve excess internal pressure due to fire or other pressurising causes should have for preference a non-fragmenting-type rupture disk ahead of or after the relief valve on chlorosilane storage vessels; otherwise, it must be avoided that the valve can be clogged with hydrolysis products from chlorosilane contact with moisture in air. "rain hats" should be used over the ends of t he vent pipe outlets. a preventive maintenance schedule programme should be established to inspect pressure relief systems. vessel supports should be made of reinforced concrete or structural steel. fire-protective coatings shall be used if the stored chlorosilane is flammable. piping carbon steel piping is recommended. welded and flanged piping connections are preferred in order to maintain a leak-tight system. the class of flange is to be based on the pressure- temperature rating of the process. only flange gaskets which are stable to chlorosilanes (non-asbestos compressed materials, teflon, graphite) must be used to provide a leak-tight joint. chlorosilane producers should be contacted for advice on appropriate materials. spiral-wound metallic gaskets or metal/graphite gaskets are preferred when maximum fire resistance is desired. prior to use all piping has to be checked by pressurising with nitrogen for tightness. all piping should be checked regularly for leakage. valves of all sizes can be ductile iron, forged steel, or cast steel valves with stainless steel or steel trim. 18 remotely controlled valves are recommended for bottom connections on vessels for quick shut-off in case of fire exposure or other emergency cases. the interconnection of road / rail tank cars or portable tanks to permanent piping can be made with swing arm rotary joints (best solution) or seamless, braided flexible metal hose. use flanged or union connections. do not use quick disconnect couplings. pumps pump selection should be based on the one that provides the best features against leakage to the atmosphere. in general, canned pumps are recommended.查看更多
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