原文：
　　  通常PN≥16MPa的阀被称为高压阀。高压阀使用中的主要问题是寿命问题(大压差下出现的汽蚀、闪蒸、冲蚀等物理现象对阀内件的破坏)。一般结构的阀在高压差条件下仅可使用1～2个月，为了解决高压阀寿命短的问题，国内外的厂家均作了很大的努力，分别在材质和结构上做了大量的探索，形成了形形色色的产品，主要有多级式高压阀、迷宫式高压阀和单座套筒负荷式高压阀等。其目的只有一个，通过减轻汽蚀、冲蚀、闪蒸等物理现象对阀的破坏，来提高高压阀的使用寿命。在众多结构中，呼吸阀华林公司按照“简单就是美”的原则设计反汽蚀高压阀，不仅结构简单，维护方便，更主要是解决了高压阀寿命短这一难题，在国内享有名气。

 　　一、阀寿命短的原因致使高压阀的使用寿命短的原因主要有两个：汽蚀、冲蚀。闪蒸、汽蚀如果阀门上的压差(P1-P2)大于了介质的最大饱和压差(△Pmax)，那么就会产生闪蒸，由此再产生汽蚀，并对阀门内部及相邻近的管道结构造成破坏。介质通过截面最小的节流口时流速是最大的。流速(或动能)的增加伴随着压力(或势能)的大大降低。当压力低于介质饱和蒸汽压时，气泡就会在介质中形成。随着节流口处压力的进一步下降，气泡会大量地形成。在此阶段闪蒸和汽蚀之间没有本质的差别，但是对阀门的结构破坏的可能性却是肯定存在的。

 　　闪蒸、冲蚀：如果介质通过节流口后，减压阀压力仍低于介质饱和蒸汽压力。气泡将保留在节流口后的流束中，我们称之为闪蒸。闪蒸对阀门的阀芯会产生严重的冲刷破坏，其特点是受冲刷的表面有平滑抛光的外形，如图9-3所示。冲刷破坏最严重的地方一般是流速最高的地方，通常位于阀芯和阀座的接触线上或附近。尤其是在小开度，节流间隙小，流速高的环境下，冲蚀破坏也最严重。因此，高压阀应尽量避免小开度工作。再好的阀门，若长期处于小开度工作，其寿命将成倍减小。要避免小开度工作，关键在计算、选型，这是设计院和用户要倍加注意的。 　　闪蒸破坏的典型外形汽蚀：另一方面，如果介质流经节流口后介质压力恢复到介质饱和蒸汽压力以上时，气泡会破裂或向内爆炸，从而产生汽蚀。蒸汽气泡破裂释放出能量，并产生一种类似于砂石流过阀门的噪音。如果气泡在接近阀门内的固体表面破裂，释放出的能量会慢慢撕裂材料，留下蜂窝状的小孔。汽蚀的破坏作用可能会延伸到邻近的下游管道。显而易见，从压力恢复系数来看，高恢复阀门比较容易发生汽蚀，因为它的节流口后的压力更有可能升至介质饱和蒸汽压之上。针型阀 气蚀破坏的典型外形闪蒸与汽蚀、冲蚀之间的关系：小开度工作时，节流口流速更快，压力更低，介质中气泡含量更多，因此，此时闪蒸破坏更严重，冲刷破坏是主要矛盾。在大开度工作时，主要矛盾是系统压力恢复到饱和压力以上时造成的汽蚀破坏。所以，用户在使用高压差阀时应尽量避免小开度工作，生产厂家制造的高压阀必须有较好的反汽蚀措施，否则，阀很快会因汽蚀、冲蚀作用而破坏。

 　　二一种成熟的反汽蚀高压阀现在使用最多的高压阀从结构上划分主要为多级式高压阀、迷宫式高压阀和单座套筒负荷式高压阀等几类。从使用情况看，它们各有优势，但多级式和迷宫式高压内部结构比较复杂，备品备件准备及更换较难，使用上很不方便。针对这些情况，华林公司开发了单座负荷式精小型反汽蚀高压阀。该产品备品备件简单，更换维修方便，很好地解决了上述难题。1992年该产品获得了国家专利(专利号：ZL 92 2 20633.3)。(该反汽蚀高压阀结构示意如图9-8。

     它采用的是“孔板+单座阀+套筒阀”三级节流结构：

　　●一次节流--接管缩径(①处)相当于孔板节流，约占总压降的10%。

　　●二次节流--单座节流(主节流、②处)单座阀的结构，约占总压降的30%。

 　　●三次节流--套筒节流(③处)套筒结构，调节阀约占总压降的60%。 气动薄膜反汽蚀高压阀“孔板+单座阀+套筒阀”三级节流结构，将通过阀门的压降分成数个较小的压降，每个较小压降都确保其节流面最小处的压力大于饱和蒸汽压力，避免或减轻闪蒸效应对阀的破坏作用。同时用小孔喷射型结构的套筒节流件取代常规的“导向衬套＋阀座”方式，可以彻底根治导向衬套易松落的问题，同时小孔喷射节流结构可以减少抗流对阀芯座的单边局部破坏作用，降低节流喑音。因为小孔喷射方式承受了阀节流压降的大部分(约60%)，可以将汽蚀破坏作用由阀座迁至小孔，保护了密封面，提高了阀使用寿命，可达普通高压差阀的2～3倍。

　　三、反汽蚀措施 (1)过去采用硬质合金的方式不可取，应采用硬度与韧性综合性能更好的耐汽蚀、抗冲刷的材料。─?㈥┰??? ? (2)70年代常采用阀后设置孔板工艺技术来降低阀上压降，借用此思路可在阀内设阻力，达到较好的降压效果。(3)防止小开度工作，降低冲刷流体的速度。(4)选择流体方式改变尽可能小锻钢阀门的阀门如直行程角形阀来减小颗粒冲击作用。(5)挠流会造成局部严重冲蚀，应采用分散扰流的方法来克服。 (6)采用多级节流结构，将通过阀门的压降分成数个较小的压降来提高阀使用寿命。(7)增大阀杆直径，提高阀杆刚度，防止断裂。(8)大口径、大压差时，应配强力活塞式执行机构。 　　四、使用注意事项(1)防止小开度工作是关键，小开度工作会成倍缩短寿命。选型遇到这类情况时，应缩小DN或dg；(2)对大口径阀，必须仔细计算不平衡力，选好执行机构和弹簧范围，防止阀关不到位；(3)对口径小、压差又特别大的阀，备好节流件，以便需要时及时换上；(4)95年化工部通报了某化工厂因阀芯断裂，流闭型高压阀(侧进底出)阀芯头自动关闭，压力升高，导致设备爆炸，造成了严重的伤亡事故。因此，从安全第一的角度考虑，应选用流开型(底进侧出)。

“ Anti-cavitation pressure control valve selection tips ”是由中国调节阀网提供的国际阀门新闻，译文仅供参考。另外，中国调节阀网还提供相关产品搜索： CV3000调节阀、 电动调节阀、 气动调节阀 水力调节阀、 执行器和附件等。

译文：
             Usually PN ≥ 16MPa high-pressure valves known as the valve. High-pressure valves used in the main problem is life problems (arising under great pressure cavitation, flashing, erosion and other physical phenomena on the trim of the damage). General structure of the valve in the pressure differential can be used only under the condition of 1 ~ 2 months, in order to solve the problem, short-lived high-pressure valve, both domestic and foreign manufacturers made great efforts in the material and structure were a lot of exploration to form all sorts of products, mainly high-pressure valve more level, maze-pressure valve seat sleeve and single-load-type high-pressure valve. The purpose is only one, by reducing cavitation, erosion, flash, and other physical phenomena on the valve damage, to improve the life of high-pressure valve. Among the many structures, Hualin Company in accordance with "less is more" principle, designing anti cavitation pressure valve, simple structure, easy maintenance, more high-pressure valve is solved this problem Shouming short, enjoy the fame at home. 1, valve short life to the causes of short life of high-pressure valve for two main reasons: cavitation, erosion. Flash, cavitation if the pressure valve (P1-P2) is greater than the maximum saturation pressure of the medium (△ Pmax), it will produce flash, resulting again in cavitation, and the internal valve and the proximity of the pipeline structure damage. Medium through the smallest orifice cross-section when the flow rate is the greatest. Velocity (or kinetic energy) increases with the pressure (or potential) is greatly reduced. When the pressure below the saturatedCast Gate, Globe, Check Valves vapor pressure, the bubbles can form in the medium. With the throttle orifice pressure drop further, the bubble will be formed in large numbers. At this stage there is no flash and cavitation essential difference between, but the possibility of damage to the valve structure is definitely there. Flash, erosion: If media through the orifice, the pressure is still lower than the saturated steam pressure. Bubble will remain in the flow after the orifice beam, which we call flash. Flash on the valve spool will produce serious erosion damage, characterized by the erosion of the surface of smooth polished appearance, as shown in Figure 9-3. Scour the most severely damaged areas is generally where the highest velocity, usually located in the valve core and valve seat or near the contact line. Especially in the small opening, saving space is small, high velocity environment, the erosion damage is grave. Therefore, the high-pressure valve to avoid the work of a small opening. Even the best valve, if the long-term work in a small opening, its life will decrease exponentially. To avoid the small opening work, the key in the calculation, selection, design institutes and the user is to be more attention. The typical form of flash cavitation damage: On the other hand, if the medium flows through the throttle back to the media after the media pressure over saturated steam pressure, the bubble will burst or explode inward, resulting in cavitation. Steam bubble burst release energy and produce a similar sand flow through the valve noise. If the bubble near the solid surface within the valve rupture, the released energy will slowly tear material, leaving a honeycomb of holes. The destructive effects of cavitation may be extended to the neighboring downstream channels. Clearly, from the pressure recovery coefficient shows high recovery valve cavitation more likely to occur, because it's the pressure after the orifice is more likely to rise above the saturated vapor pressure. The typical appearance of cavitation damage and cavitation flash, the relationship between erosion: small opening work, the throttle flow faster, lower-pressure, medium bubble content more, so at this time flash damage more serious erosion damage is the principal contradiction. Large opening in the work, the main contradiction is the system pressure back to the saturation pressure above the cavitation damage caused. Therefore, users using Gao Ya Cha valve is necessary to prevent Xiao Kaidugongzuo, Sheng forged Gate, Globe, Check ValvesChan's high-pressure valve factory Zhizao Must have good understanding anti-steam erosion measures, otherwise, due to cavitation valve Henkuai Hui, the role of Er erosion damage. 21 kinds of sophisticated anti-cavitation valve is most commonly used high-pressure high-pressure valve structure is divided from the main multi-stage high-pressure valve, high pressure valve and maze single-seat high-pressure valve sleeve load types. From the use of situation, they have their own advantages, but the multi-stage high-pressure internal structure and the maze more complicated to prepare and replacement of spare parts more difficult, inconvenient to use. For these conditions, Waring has developed a single-seat load-type precision high-pressure small-scale anti-cavitation valve. The product is simple and spare parts, replacement and easy maintenance, a good solution to these problems. The product won the 1992 national patent (Patent No.: ZL 92 2 20633.3). (The anti-cavitation pressure valve structure indicated in Figure 9-8. It uses the "single-seat valve orifice + + sleeve valve" 3 throttle structure: ● time saving - over reduced diameter (① Department) is equivalent to plate cutting, representing about 10% of the total pressure drop. ● secondary throttle - single-seat throttle (main throttle, ② Department) single seat valve structure, accounting for about 30% of the total pressure drop. ● Three throttle - throttle sleeve (③ Office) sleeve structure, accounting for about 60% of the total pressure drop. High-pressure pneumatic membrane anti-cavitation valve "single-seat valve orifice + + sleeve valve" three cutting structure, the pressure drop through the valve into a number of smaller pressure drop, pressure drop is to ensure Ball Valvesthat every young cutting surface pressure is more than the minimum Department of saturated vapor pressure, flash to avoid or mitigate the damaging effect on the valve. At the same time with the jet structure of the sleeve hole cutting parts to replace conventional "guided bush + seat" mode, which can completely cure-oriented trade loosening bushing problem, while hole injection structure can reduce the resistance to flow throttle on Block spool unilateral partial damage effect, reduce the throttle sound dumb. Because the hole injection means to bear the throttle valve pressure drop of the majority (60%), the role of cavitation damage can be moved from the seat hole, to protectResilient Seated Gate Valves the sealing surface, increase valve life, up to ordinary high-pressure poor valve 2 to 3 times. Third, anti-cavitation measures (1) in the past by way of undesirable carbide, hardness and toughness should be better integrated performance of cavitation-resistant, anti-erosion materials. ─? Vi ┰???? (2) 70 years after the setting orifice valve is often used technology to reduce the valve pressure drop, to borrow this idea can be internal resistance in the valve to achieve a better antihypertensive effect. (3) to prevent small opening work, reduces the speed of fluid erosion. (4) the fluid way to change the valves as small as possible such as the direct journey to reduce the particle impact angular valve function. (5) radial flow could result in serious erosion, should be decentralized approach to overcome the spoiler. (6) multi-level cutting structure, the pressure drop through the valve into a number of smaller pressure drop to increase valve life. (7) increased stem diameter, increased stem stiffness, to prevent breakage. (8) large diameter, large pressure difference should be equipped with powerful piston actuator. 4, using the Notes (1) to prevent the small opening is critical, small opening work will shorten the life multiplied. Selection of these circumstances, should narrow the DN or dg; (2) of the large diameter valve, unbalanced force must be carefully calculated, selecting theAutomatic Control Valves scope of the implementing agencies and the spring, not in place to prevent the valve off; (3) small-caliber , pressure has been particularly large valves, cutting pieces ready to put on when they need it; (4) 95 years, informed the Ministry of Chemical Industry in a chemical plant due to valve fracture, closed-type high-pressure flow valve (the side into the bottom out) the first self-closing valve, the pressure increased, resulting in plant explosion, causing serious casualties. Therefore, the first from the security point of view, should be used away and type (bottom into the side).

原文来源：http://www.1tiaojiefa.com/

2010-08-16 07:26

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