1, overview of cryogenic globe valve is a kind of work in the low temperature hydrogen gas or liquid hydrogen medium, device used to put through or cut off the line media. This paper introduces a low temperature cut-off valve for hydrogen engine test bench, for valve cannot action problems in use process, has carried on the fault analysis, by improving the structure, make the normal operation of the valve in the test system. 2, structure features. 1, the technical parameters of low temperature cut-off valve technical parameters are as follows. Working medium low temperature gas hydrogen, liquid hydrogen nominal diameter 65 mm high working pressure, 25 mpa minimum temperature liquid hydrogen temperature pneumatic drive way, Cylinder two-way ventilation) Operating air nitrogen, 5 + 012 mpa connection flange type 2. 2, the structure of low temperature cut-off valve by valve body, disc, stem and cylinder, etc. body, valve stem and valve cover adopt stainless steel, the disc with copper. Two middle section of the stem with epoxy phenolic laminated glass fiber cloth plate achieve adiabatic, flange sealing surface aluminum gaskets, packing with ptfe, cylinder using double seal, to reduce the friction, polyurethane (pu) foam insulation valve as a whole. 3, design 3. 1, material selection, space rocket with cryogenic propellant generally have a liquid hydrogen and liquid oxygen and fluorine, therefore requires the valve material ability at low temperature, corrosion resistance and low temperature medium consistency and have low thermal conductivity. At present, use more metal materials with austenitic steel, copper or aluminum, non-metallic materials such as glass reinforced plastics, teflon. From metallographic, metal material in a face-centered cubic lattice austenitic steel, copper and aluminium under low temperature condition will not be low temperature brittleness, but because of the hardness of aluminium and aluminium alloy is not high, aluminum sealing surface wear resistance, abrasion resistance is poor, so in the use of cryogenic valves have certain limitations, only used in low pressure and small diameter valves. Cryogenic valves with gasket must be reliably under normal temperature, low temperature and temperature change of sealing and recovery, so generally choose small gasket material performance changes. Such as asbestos packing of ptfe impregnated or molding plastic packing, and glass fiber reinforced plastic due to thermal conductivity is very small, mostly used for thermal bridge components. 3. 2, sealing structure in closed design, seat is a hard material - — — Stainless steel, the disc with softer materials - — — Copper, austenitic phase transformation occurs, when low temperature sealing surface is rugged, soft materials in the operating force produced under the action of deformation and make it fit tightly with the valve seat, compensation caused by thermal stress and organization stress material deformation, solves the sealing problem under the high pressure working condition of low temperature. 3. 3, adiabatic structure to realize low temperature cut-off valve well thermal insulation, design will cover into slender structure, extended thermal bridge, prevent for stuffing box part is too cold and bringing in stuffing box parts of the upper part of the valve stem and valve cover parts frost, affect the use. Using insulation pad ( Material for epoxy phenolic laminated glass fiber cloth) The valve stem is divided into upper and lower two parts, reduce heat, achieve adiabatic. Integral form, the heat insulation outside using valve using polyurethane foam insulation, protection layer of 200 mm thick. 4, failure analysis after low temperature cut-off valve is applied to test system, the action of fault. In found that after the break-up of the Industrial Valves, the valve stem and valve cover the bite, the stem axis symmetry location on the surface of the two deep scratches, matching under the bonnet flange on the corresponding position also has two scratches. After analysis, there are two aspects to the causes of failure. ( 1) During the storage period of valve store in horizontal and in an open position, the valve stem and disc form cantilever beam structure, the cantilever length 147 mm, the cantilever weighs 418 kg. Stem bending under likely caused by gravity, so that the stem and bonnet flange hole axiality deviation. The original design of coaxial degree maximum deviation of 0. 1 mm, after dismantling the measured axiality deviation is about 0. 4mm。 Because both parts material for OCr18Ni9 stainless steel, low temperature to lubrication, activity produce bite because of the large axiality deviation phenomenon. ( 2) Processing period through inspection, not the pin groove on the valve cover processing (according to the drawing FIG. 1) 。 Square groove machining in the drawing into circular arc wall, affected the normal pin and pin groove, the stem under lateral force, leading to the valve stem and valve cover produce interference. 5, the improvement aiming at the problems in the analysis, the cut-off valve structure made improvement in low temperature. ( 1) The valve stem and valve cover with part of the stem & lt; 51 mm place into a H62 brass ( FIG. 2) , OCr18Ni9 hardness hb 160 stainless steel, brass H62 56 hb hardness, in this way can avoid direct contact with the same material and produce scuffing. Will be under the bonnet flange hole & lt; Processing to 51 mm & lt; 57 mm, accordingly with the valve stem in clearance fit ( H8/f7) , not only ensure the cooperate with smaller dynamic friction force, and has played a guiding role. ( 2) Stem anti-rotating device pin and pin groove cooperates is to avoid the effect of rotate the valve stem. Because of the valve disc, valve stem, cylinder and piston of rotors, such as whether the stem rotation won't impact on its sealing and opening and closing performance. In order to avoid because of improper pin and pin groove cooperates and make the stem under lateral force under, cancelled the pin. 6, conclusion the improved cut-off valve action good performance in actual use. In general, cryogenic valves in clearance when appropriate, can adopt stainless steel, but the long-term use of the lateral force or shaft deformation conditions are prone to bite, so not as much as possible. In addition, the valve should be upright and use, not for a long time, should make the valve closed.
We are a performance driven culture that uses resilient wedge gate valve to ensure continuous improvement.
Shenzhen Mech Valve Trading Co., Ltd. offers the best products, high-quality services and innovative technology.
The more people who do a certain thing, the more likely others are to do it as well. When Mech can demonstrate their popularity or satisfaction across a wide customer base, other consumers are more likely to buy in as well.