The sleeve also rises up the shaft, and when it rises beyond a certain point, it operates a throttle valve lever, and so reduces the flow of steam.

• 套筒也随之顺轴上升。而当套筒升过一定的点时，套筒就会带动一个节流阀的阀杆进入工作，这样就能减少蒸汽的流量。