1. 随着压力增加，阀盖密封性能也随之增强
   Bonnet seal increases with pressure
2. 随着压力减小，阀盖密封性能也随之减小
   Bonnet seal decreases with less of pressure
3. 系统压力
   System pressure
4. 压力带来的密封力
   Sealing forces due to pressure.
   

1. 无论压力-温度如何波动，动负载始终维持阀帽密封。
   Live-loading maintains bonnet seal regardless of pressure-temperature fluctuations

　　内部压力越大，密封力就越大。将阀帽总装拆离阀腔，采用推针取出四个部分的推力环，拆卸变得简便易行。
　　The higher the internal pressure, the greater the sealing force. Easy dismantling is made possible by dropping the bonnet assembly into the body cavity and driving out the four-segmental thrust rings by means of a push pin.

　　18-8嵌体上方的1^o 阀体锥度，保证即使使用多年后，垫圈仍然容易滑入安装。
　　A 1^o body taper above the 18-8 inlay ensures easy sliding of the gasket even after years of service.

• 双头螺栓的内部排列组成压力密封连接的初始密封。
  Inner row of studs establishes the initial seal of the pressure seal joint.
• 弧形止推环吸收内部压力施加的全部推力。
  Segmental thrust ring absorbs all the thrust applied by internal pressure.
• 使用推针，从钻孔上取出止推环。
  Drilled knock-out holes for driving out thrust rings, using pins.
• 双头螺栓的外部排列将阀架固定在阀体上。
  Outer row of studs secures the yoke to the body.
• 隔离环提供支撑面，防止垫圈的变形。
  Spacer ring provides bearing surface and prevents deformation of the gasket.
• 100 Brinnel的软碳钢密封垫圈，镀银的软防腐外层，使得大面积密封更加完美。我们也可提供石墨垫圈作为用户的选择（参见下面）。
  Soft carbon steel sealing gasket of 100 Brinnel, silver-plated for soft corrosion-resistant coating, provides large contact area for perfect sealing. Graphite gaskets are offered as an option (see below).
• 18-8嵌体保证主要阀体密封区域的坚固性和防腐性，适用于碳钢和合金钢阀门。对于石墨垫圈来说，并不需要18-8嵌体。
  18-8 inlay ensures soundness and corrosion-resistance in the vital body sealing zone for carbon and alloy steel valves. The 18-8 inlay is not required for graphite gaskets.

1. 当压力改变时，阀帽容易上下移动。
   Bonnet tendency to move up or down as pressure changes.
2. 一般情况下，螺栓负载产生初始密封。
   Bolt load nominal to create initial seal.
3. 在水力测试时，垫圈会变形，螺栓松动，因此在水力测试后必须加以紧固。（压力/温度转换或周期循环在阀门上产生相似的机械作用。）
   Gasket deforms during hydrotest, bolts lose torque and must be retightened after hydrotest. (Pressure/temperature transient or frequent cycling produces similar mechanical action in valve.)

　　由于不断改进设计，Velan的“take-up”螺栓阀帽动负载成为标准的压力密封阀门的特点。现在，动负载已经应用在DN150至DN600，1500磅级和DN200至DN600，2500磅级的阀门上。
　　As a result of continuous design improvements, Velan is offering live-loading of bonnet "take-up" bolting as a standard pressure seal valve feature. At the present time, live-loading is available in 6-24" (150-600 mm) Class 1500 and 8-24" (200-600 mm) Class 2500.

　　这种新型设计已经成功地通过严酷的电力应用，如联合发电厂或DSS, WSS厂的峰值现场测试，在测试过程中，阀们频繁的进行开启和关闭。
　　This new design has been successfully field tested in tough power applications such as in "peaking type cogeneration plants or DSS, WSS plants where valves are subject to frequent start-ups and shut-downs.

储存的螺栓能量（磅英寸）
普通设计
动负载设计
补偿阀帽运动（英寸）
Stored Bolt Energy (lbf)
Standard design
With live-loading
Compensation for bonnet movement (in)

　　Velan建议在高温和频繁温度循环变化的应用场合，采用石墨压力密封垫圈来取代普通的软铁垫圈。日常的开启和关闭（DSS）和周末的开启和关闭（WSS）操作需要石墨垫圈。在这种情况下，用户最好告诉我们。
　　Velan recommends the use of graphite pressure seal gaskets, in lieu of standard soft iron gaskets, in high temperature and frequently temperature-cycled applications. Daily Start and Stop (DSS) and Week-end Start and Stop (WSS) operations require graphite gaskets. Customer must inform Velan of such applications.

• 在1,000 psi工作压力下，建议采用石墨垫圈。
  Below 1,000 psi operating pressure graphite gaskets are recommended.
• 在500至700 psi工作压力下，必须采用石墨垫圈。
  Between 500 and 700 psi graphite gaskets are a must.
• 500 psi工作压力下，建议采用螺栓阀帽阀门。
  Below 500 psi bolted bonnet valves are recommended.