通用闸阀用途 Purpose of general gate valve

【上海精工阀门厂 技术资讯】
    闸阀的启闭件是闸板，闸板的运动方向与流体方向垂直。闸阀只能作全开和全关，不能作调节的节流。闸板有两个密封面，最 常用的楔式闸板阀的两个密封面形成楔形，楔形角随阀门参数而异，通常为5°，介质温度不高时为2°52‘。楔式闸阀的闸板可以做成 一个整体，叫做刚性闸板；也可以做成能产生微虽变形的闸板，以改善其工艺性，弥补密封面角度在加工过程中产生的偏差，这种 闸板叫做弹性闸板。

    闸阀关闭时，密封面可以只依靠介质压力来密封，即依靠介质压力将闸板的密封面压向另一侧的阀座来保证密封面的密封，这 就是自密封。大部分闸阀是采用强制密封的，即阀门关闭时，要依靠外力强行将闸板压向阀座，以保证密封面的密封性。

    闸阀的阀板随阀杆一起作直线运动的，叫升降杆闸阀（亦叫明杆闸阀）。通常在升降杆上有梯形螺纹，通过阀门顶端的螺母以 及阀体上的导槽，将旋转运动转变为直线运动，也就是将操作转矩变为操作推力。

    开启阀门时，当闸板提升高度等于阀门通径1: 1倍时，流体的通道完全畅通，但在运行时此位置是无法监视的。实际使用时， 是以阀杆的顶点作为标志，即开不动的位置，作为它的全开位置。为考虑温度变化出现锁死现象，通常在开到顶点位黄上，再倒回 1/2-1圈，作为全开阀门的位置。因此，阀门的全开位置，按闸板的位置（即行程）来确定。

    The opening&closing part of gate valve is gate disc,its movement direction is vertical to that of liquid,and the gate vale is only used to openand close fully,but not to adjust the flux.The disc has two seal surfaces,for the most general wedge gate valve,its two seal surfaces form thewedge each other,and the wedge angle is different for different valve parameters,it is 50 generally,and 20 52'when the medium temperature is nothigh.The disc of wedge gate valve may be made into a whole，i.e.the rigid gate disc,or may be made into a kind of little distortion disc,which isavailable to improve its craftwork and makes up the deviation of seal surface angle caused in the processing course,i.e the flexible gate disc.

    when the gate valve is closed.the seal surface is available to seal by the pressure of medium,i.e.relies on the medium pressure to push theseal surface of gate disc down to the seat on the other side,which is just called self-sealing.Most of gate valves adopt the compulsive seal.i.e.when the valve is closed.it relies on external force to compulsively push gate disc down to valve seat to ensure the seal of seal surface.

    Which its gate plate moves in straight line together with valve stem,is called rising stem type gate valve（also outside screw rising stem gatevalve）。Generally,the 丨adder-shape screw on rising stem changes the rotary movement into a straight-line movement through the nut on top ofvalve and the guidance on valve body.i.e.changes the operation torsion into operation thrust.

    When open the valve,and the gate disc rises to the height as much as the valve diameter,the liquid passage is through fully,but it can't bemonitored on this position.In the practical operation,it uses the peak of valve stem as the mark,i.e. the non-lifted position as its fuf卜open positionConside门ng that the change of temperature probably results in locked status,the stem is usually returned I/2?1 round when the gate disc risesto the top position,i.e.as the fuH-open position.Therefore,the fu丨卜open position is decided by the position of gate disc（i.e_the stroke of gate disc）。