控制流量用的阀门
Valve for flow control
通常选择易于调节流量的阀门作为控制流量用。向下闭合式阀门（如截止阀）适于这一用途，因为它的阀座尺寸与关闭件的行程之间成正比关系。旋转式阀门（旋塞阀、蝶阀、球阀）和挠曲阀体式阀门（夹紧阀、隔膜阀）也可用于节流控制，但通常只能在有限的阀门口径范围内适用。闸阀是以圆盘形闸板对圆形阀座口做横切运动，它只有在接近关闭位置时，才能较好地控制流量，故通常不用于流量控制。
Usually choose the valve which is easy to adjust the flow rate as the control flow. Downward closing valves, such as globe valves, are suitable for this purpose because their seat size is proportional to the stroke of the closing member. Rotary valves (plug valves, butterfly valves, ball valves) and flexure body valves (clamp valves, diaphragm valves) can also be used for throttling control, but they are usually only suitable for a limited valve diameter range. Gate valve is a disc-shaped gate to make a cross cutting movement to the circular valve seat. It can control the flow well only when it is close to the closed position, so it is not usually used for flow control.