Such as asbestos packing of ptfe impregnated or molding molecular compound plastic packing, and glass fiber reinforced plastic for heat conduction coefficient little, most used as a thermal bridge components. ( 2) Processing period after the investigation, not the pin groove on the valve cover processing (according to the drawing FIG. 1) 。 。 3, the default 3. 1, material selection, air thunder big cryogenic propellant rocket ordinary liquid hydrogen and liquid oxygen and fluorine gas, because this valve material ability to low temperature, corrosion resistance and low temperature medium compatibility and low thermal conductivity. Because gravity utility stem buckling under the boot, shall have the stem and bonnet flange hole axiality deviation. group thought and the heat insulation outside using right way to use polyurethane foam heat preservation, protection layer thickness of 200 mm. ( 1) Shelf-life storage period level setting and was laid in an open valve, the valve stem and disc form cantilever beam structure, the cantilever length 147 mm, the cantilever weighs 418 kg. The original alignment in the preset maximum deviation is 0. 1 mm, tear down after the measured axiality deviation is about 0. 4mm。 Cryogenic valves with gasket must be under normal temperature, low temperature and temperature change have reliable tightly closed and recover, because the ordinary pick the gasket material performance changes little. Office medium low temperature gas hydrogen, liquid hydrogen supreme apply pressure to 25 mpa nominal diameter 65 mm minimum temperature using liquid hydrogen temperature driving type pneumatic ( Cylinder two-way ventilation) Operating air nitrogen, 5 & amp; plusmn; 012 mpa petition form flange type 2. 2, the structure of low temperature by the Industrial Valves consists of body, disc, stem and cylinder, etc. Because both parts material for OCr18Ni9 stainless steel, low temperature there is no way to lubricating oil, and moves because the axiality deviation of big initiation phenomenon. Emerged against the use of the Marine valve stem and valve body between occlusion and the problem of have no way of action implementation of all aspects of analysis, and put forward solutions. Not for himself what the dialysising, comprised of two aspects of the boot failure. In found that after the collapse of the valve, the Industrial Valves stem and valve cover revealed occlusion, stem line looks at the heart of the symmetry location two deep scratches, matching under the bonnet flange on the corresponding position also has two scratches. 3. 3 better success, adiabatic structure so as to realize the low temperature by the valve of the adiabatic, will cover the preset into fiber structure, extended thermal bridge, avoid the stuffing box local undercooling and make the stuffing box in parts of the upper part of the valve stem and valve cover parts frost, affect the use. See fit and use insulating pad ( Material for epoxy phenolic laminated glass fiber cloth) The valve stem is divided into upper and lower two local, reduce the current, successful implementation adiabatic. Square groove machining in the drawing into circular arc wall, influence the normal right pin and pin groove, the valve stem to lateral force, thus causing the valve stem and valve cover initiation relate. 1, the general narration of low temperature by the valve is a kind of office in the medium of cryogenic hydrogen gas or liquid hydrogen, used to connect or truncation pipeline media device. 2 2, structure the unique place. 1, the technology of low temperature parameter of valve technical parameter as described below. This paper introduce a kind of used for hydrogen gas engine to try on low temperature by the end of Industrial Valves, there is no way to emerge in the process of using valve action, a failure analysis, the improved structure, make the normal operation of the valve to try in the system. 4, failure analysis after low temperature by the valve applied to try system, revealed the fault have no way of action. Q: liquid hydrogen as of valve failure analysis and improvement a: introduce the rocket engine try system structure of high pressure liquid hydrogen as the unique place, and the material selection, tightly closed and the disposal measures to technical problems such as thermal insulation structure. Upper and lower section of the stem middle plate with gas epoxy phenolic laminated glass fiber reinforced plastic cloth to achieve adiabatic, flange sealing surface closely sees fit and use aluminum sheet, packing using ptfe, cylinder using double tightly closed, to reduce the friction, valve group sees fit and use of polyurethane foam to keep warm. 3. 2 when closing a preset, tightly closed structure, the seat right and use a hard material - — — Stainless steel disc saw fit, and the use of soft materials - — — Copper, austenitic phase transformation occurs when the low temperature, tightly closed face unfair, soft materials in the operating force under the effect of deformation and flush with the valve seat joint emergency initiation, repay for thermal stress and stress of the actuating materials variant team, solves the tightly closed questions with high pressure, low temperature conditions. So far, the use of more metal material with austenitic steel, copper or aluminum, non-metallic materials such as glass reinforced plastics, teflon. From metallographic thinking problem, metal materials possess face-centered cubic lattice of austenitic steel, copper and aluminium in the low temperature will not appear under the condition of low temperature brittleness, but because of the hardness of aluminium and aluminium alloy is not high, aluminum tightly closed surface wear and abrasion resistance is poor, so in the application of cryogenic valves have certain limit, only used in low pressure and small diameter valves. Body, bonnet and stem see fit and use stainless steel, such as using copper disc saw fit.
cast iron gate valve wedge valve processes have been widely used to produce os&y valve such as resilient seal gate valve, resilient valve, and resilient gate valve etc.
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