球体和阀座密封圈都采用金属材料制造，密封比压很大，依靠介质本身的压力已达不到密封的要求，必须施加外力。
Ball and valve seat rings are metal materials, sealing pressure than the large, rely on the media itself can not seal the pressure has reached the requirements to be imposed by external forces.
因此，在调节管接螺母的紧固度时，阀座对球体的压力就一直存在着。
Thus, by adjusting the tightness of the union nut, the squeeze of the seats against the ball would be maintained.
当关闭通道时，用阀杆的楔形头使球体涨开与阀座压紧达到密封。
When the closed channel, the wedge-shaped head with a stem to open up the ball and pressed to seal the valve seat.
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