The difference between rising stem gate valves and non-rising stem gate valves

Gate valve can be divided into:

1, rising stem gate valve: stem nut in the valve cover or bracket, open and close the gate, with rotary stem nut to achieve the rise and fall of the stem. This structure is advantageous to the lubrication of the stem, and the degree of opening and closing is obvious, so it is widely used.

2, dark stem gate valve: stem nut in the valve body, direct contact with the medium. Open and close the gate by rotating the stem. The advantages of this structure are: the height of the gate valve always remains the same, so the installation space is small, suitable for large diameter or limited to the installation space of the gate valve. The structure shall be equipped with an opening and closing indicator to indicate the opening and closing degree. The disadvantage of this structure is that the stem thread can not only be lubricated, but also directly accept medium erosion, easy to damage.

Main differences between rising stem gate valves and non-rising stem gate valves:

1. The lifting screw of the dark stem flange gate valve only rotates and moves down, and the exposed is only a rod. The nut is fixed on the gate plate, and the screw is rotated to lift the gate plate, without visible frame; The lifting screw of the rising stem flange gate valve is exposed, the nut is close to the handwheel and is fixed (neither rotating nor axial movement), by rotating the screw to lift the gate, the screw and the gate only have relative rotational movement without relative axial displacement, the appearance is a portal bracket.

2, dark rod valve can not see the lead screw, and the rising rod can see the lead screw.

3. The steering wheel and the valve stem are connected relatively stationary when the valve is switched on and off. It is opened and closed by rotating the valve stem at a fixed point to drive the disc upward and down the brake. Rising stem valves are threaded between the stem and the steering wheel to raise or lower the disc. To put it simply, a rising stem valve is a disc moving up and down with the stem, with the steering wheel in place at all times.