闸阀
GATE VALVES

　　流体可以从闸阀的任一个端口流入。但是也有例外，比如有旁通管焊接在阀体上或在阀门的一端钻有一个减压孔。检查管道分布图，找对位置和流体流向。闸阀应该在楔板或阀板处于完全关闭位置时才能安装或焊接到管道中。如果阀门处于开启或部分开启状态，可能会造成变形并在使用过程中产生泄漏。保持阀门处于完全关闭状态，有助于防止焊花飞溅直接落到阀座连接面上。
　　The flow through gate valves can be from either end. There may be exceptions to this if bypass piping is welded to the valve body or if a pressure relief hole is drilled in one side of the valve. Check your piping layout drawing to ensure correct position and direction of flow. Gate valves should be installed and welded into the pipline with the wedge or disc in the fully closed position. If the valve is left open or partially open, it could distort and leak during operation. Leaving the valve in a fully closed position helps prevent weld spatter from falling directly onto the mating faces of the seats.

　　闸阀最好垂直安装。闸阀可能安装在其它方向，但是任何偏离垂直方向都可能带来危险。不推荐垂直向下安装，因为这种安装可能导致污垢淤积在阀帽里。如果阀门超过DN300，与垂直方向倾斜角度超过45^o时，可能需要配置导管表面硬化。
　　The preferred orientation of a gate valve is upright. The valve may be installed in other orientations, but any deviation from vertical is a compromise. Installation upside down is not recommended because of possible dirt build-up in the bonnet. Consult the Velan Engineering Department during the quotation review process. Hardfacing of guides maybe required when valves over 12" are tilted beyond 45^o from the vertical position.

　　对于完全后座支撑和完全关闭位置，建议阀杆后退¹/₈"到¹/₄"转，以防止阀杆”生长“，弯曲或产生热弯曲。这样做并不会影响阀门关闭。
　　For both the fully back seated and fully closed position, it is recommended that the stem be backed off ¹/₈" to ¹/₄" turn to prevent the stem from "growing", bending or causing thermal binding. Taking this action will not affect valve shut off.

截止阀
GLOBE VALVES

　　安装截止阀时，通常把进口安装在阀座下方。必须仔细检查，避免安装错误。如果节流环境特别严酷，Velan建议安装截止阀时应该让流体从阀座上方流进，向下流经截止阀。这样能够保持阀门处于更加稳定的状态，磨损降到最小，外部噪音也比较小。由于关闭阀门所需的扭矩较小，操作阀门也比较容易。但是，应该注意到填料处于恒负载状态。一般的截止阀适合用于适度的节流应用。一般而言，通径足够大的截止阀（例如管道内水流速度在15至25英尺/秒之间，蒸汽流速在200至300英尺/秒之间），节流后的流量不应该小于完全开启状态流量（流量系数大约为全冲程的20%）的35%以下。如果节流条件比较严酷，小于完全流量的35%，就应该由应用部门分析并决定在可能的空洞、冲刷、噪音和振动现象下的适用性。
　　Globe valves are usually installed with the inlet below the valve seat. This must be checked carefully to prevent incorrect installation. If throttling service is particularly severe, Velan recommends that the valve be installed so that the flow enters over the top of the seat and goes down through it. This maintains the valve in a more stable condition, the amount of wear is minimized and there is less external noise. Valve operation also becomes easier because less torque is required to close the valve. However, it should be noted that the packing is under constant load. Regular style globe valves are suitable for moderate throttling applications. As a general rule, an adequately sized globe valve (i.e. with pipe velocity between 15 to 25 ft/sec for water and 200 to 300 ft/sec for steam) should not be throttled down below 35% of its maximum full open C_V capacity (approximately 20% of full stroke). Harsh throttling, below 35% of full C_V capacity , will require analysis by applications department to determine suitability under possible cavitation, flashing, noise and vibration.

　　应该在截止阀阀瓣处于完全关闭状态下进行安装和焊接，以避免在安装过程中队阀门造成损坏。保持阀瓣处于完全关闭位置也能够避免焊花直接掉在阀座和阀瓣的连接面上。
　　Globe valves should be installed and welded with the disc in a fully closed position to prevent damage to the valve during installation. Leaving the disc in a fully closed position firmly closed also prevents weld spatter from falling directly onto the mating faces of the seat and disc.

止回阀
CHECK VALVES

　　必须按照箭头所指方向安装止回阀的进口。安装阀门之前必须细心检查。如果止回阀安装方向错误，阀瓣就无法正常旋启，阀门的作用也无法正常发挥。
　　Check valves must be installed with the inlet in the direction of arrow. This must be checked carefully before installing the valve. Placing a check valve in the opposite direction to the flow will prevent the disc from swinging free and will therefore prevent normal operation of the valve.

　　阀座孔和最小流量对于止回阀的选型至关重要。没有适当的通径，可能会造成止回阀内部严重损坏。脉冲式倒流也可能导致损坏。
　　Seat bores and minimum flows are crucial in check valve selection. Without proper sizing, extreme damage can occur in check valve internals. Pulsed flow reversals can also cause damage.

　　如果旋启式或翻转式止回阀被安装在距离弯头或泵十倍管道直径内的位置，则必须采用其他方法转移或减小流量。噪音太大是发生空洞现象的一个征兆。
　　If Swing or Tilting Disc Check Valves are located within 10 pipe diameters from elbows or pumps, other means to divert/minimize flows are necessary. Excessive noise is an indication that cavitation is occurring.

压力密封垫圈扭矩
PRESSURE SEAL GASKET TORQUES

• 没有动负载阀帽的压力密封结构（没有弹簧垫圈）：在工作试验压力和温度达到限制值时，必须重新检查垫圈螺栓的紧固性。没有动负载，当系统失去压力时，螺栓紧固性就会丧失。
  Pressure seal design without live load bonnet (no spring washers): The gasket bolt tightness must be rechecked after operating test pressure and temperature has been achieved. Without live-loading, bolt tightness will be lost, when the system loses pressure.
• 带有动负载的压力密封结构：由于振动转移或螺栓蠕变，动负载阀帽螺栓也可能会丧失一些螺栓负载。可以在工作压力下检查动负载阀帽的螺栓扭矩，除非阀门被拆卸，否则不需要对垫圈螺栓进行紧固。在这种情况下，垫圈螺栓扭矩必须保持适当，在达到工作试验压力和温度后，应该重新检查螺栓的紧固性。
  Pressure seal design with live load bonnet:
  A live-loaded bonnet bolt may also lose some bolt load, due to vibration in transit or bolt creep. It is advisable that live-loaded bonnets be checked for bolt torque at operating pressure, no future tightening of gasket bolting will be necessary, unless the valve has been dismantled, in which case, the gasket bolts must be torqued to appropriate values and bolt tightness rechecked after operating test pressure and temperature has been achieved.