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  多回转阀门结构特点 (2)
Multi-Turn Valve Design Detail (2)

美国尼必可有限公司

   3) 明杆-外螺纹和支架结构是铸铁多回转阀门的首选结构。由于螺纹位于阀门外部,有利于防止被流体介质腐蚀,有利于润滑油的加注。当阀杆上升时,要留心阀杆的上方有足够的空间,防止螺纹受到损坏。阀杆的高低能够指示阀门处于开启或关闭状态。
   3) Rising stem-outside screw and yoke is preferred in iron multi-turn valves. threads are external to the valve, protecting them from flow media and enabling lubrication. Care should be taken for clearance as the stem rises so that threads are not damaged. The stem position provides indication that valve is opened or closed.

   阀体-阀盖连接方式
   Body-Bonnet Connection
   1)管接头式阀盖: 对于建筑物管道系统中的青铜多回转阀门,管接头式阀盖是值得推荐的结构形式,但是,并不是所有类型的阀门都需要这种结构。管接头式阀盖具有一定的强度,易于安装和拆卸。
   1) Union bonnet is recommended as the best choice for building services piping for bronze multi-turn valves, although not all styles offer this design. The union bonnet offers strength and ease of assembly-disassembly.   
   2) 螺纹旋进式阀盖:通常用于轻型管道系统和小尺寸青铜多回转阀门中。
   2) Threaded-in bonnet is common in lighter-duty services and smaller sizes of bronze multi-turn valves.
   3) 螺栓阀体式阀盖:铸铁多回转阀门的主要结构形式。这种带衬垫连接方式坚固耐用,并且易于安装和拆卸。
   3) Bolted body-bonnet connection is the principal design used in iron multi-turn valves. This gasketed joint is strong and easy to assemble/disassemble.

  b) 截止阀/角式截止阀
  b) Globe/Angle-Globe Valves

   优点-推荐
   Positive Features - Recommendations
   1) 推荐作为节流阀使用
   1) Recommended for throttling applications
   2) 如果配置的是弹性阀座,就能够具备真正的无气泡关闭功能。
   2) Positive bubble-tight shutoff when equipped with resilient seating
   3) 适用于频繁操作
   3) Good for frequent operation

   缺点
   Disadvantages
   1) 流程中具有明显的压降
   1) Significant pressure drop due to flow path
   2) 成本比其它种类阀门高
   2) More costly than alternate valves

   阀瓣和阀座结构
   Disc and Seat Designs
   1) 弹性(软)阀座阀瓣是首选结构。但是对于高温管道系统,高精密度节流,或流体介质具有研磨性等应用环境,则合金金属就是更好的选择。对于大多数管道系统而言,聚四氟乙烯是最好的弹性阀瓣材料,但是在冷水环境中,橡胶具有更好的柔软性。
   1) Resilient (soft) seat discs are preferred over metalto-metal except where temperatures, very close throttling or abrasive flow make metal alloy seating a better choice. TFE is the best resilient disc material for most services, although rubber’s softness gives good performance in cold water.
   2) 插入式阀瓣/阀座:通常采用硬度较大的金属合金,特别适用于需要精确节流,且流体介质温度超过聚四氟乙烯的温度上限(260oC),或者流体包括研磨剂。铸铁截止阀通常采用半插入式青铜阀瓣/阀座结构。
   2) Plug-type disc/seat, often with harder metal alloys, is best for very close throttling, when media temperature is beyond the range of TFE (500°F) or when abrasive flow is involved. Iron globe valves most commonly use semi-plug bronze disc/seat design.
   3) 自动蒸汽截止止回阀和角式截止阀适用于中压蒸汽管道系统,此时半插入式阀瓣的滑动作用使得阀门能够起到关闭阀、节流阀和止回阀的作用。
   3) Automatic steam stop-check angle-globe valves are best on medium-pressure steam service where the sliding action of the semi-plug disc assembly permits the valve to serve as a shut-off valve, a throttling valve and a check valve.

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