According to the structure of the valve stem knife gate valve can be divided into:
1 .Rising stem knife gate valve: Stem nut in the valve cover or bracket, when open or close the gate, use the rotary valve stem nut to achieve the valve stem up and down. This kind of structure is beneficial to the lubrication of the valve stem, and its opening and closing is obvious, so it is widely used.
2 Non-rising stem knife gate valve: The stem nut is in the valve body and is in direct contact with the medium. When opening or closing the gate, use a rotary valve stem. The advantage of this structure is that the height of the gate valve always remains the same, so the installation space is small and it is suitable for large diameter or gate valves with limited installation space. This structure should be equipped with open and close indicators to indicate the degree of opening and closing. The disadvantage of this structure is that the stem thread cannot be lubricated, but also directly contact the media erosion and is easily damaged.
The main difference:
1. The screw stem of the non-rising flanged knife gate valve is only rotated without moving up and down. The exposed rod is just a rod. The nut is fixed on the gate plate. The gate is lifted by the rotation of the screw. There is no visible door. The screw stem of the rising stem gate valve is exposed. The nut is close to the hand wheel and is fixed (no rotation or axial movement). The rotation of the screw is used to lift the gate, and the screw and the gate only have relative rotational motion but not relative axial displacement, the appearance of the valve with a gate bracket.
2. The non-rising stem knife gate valve cannot see the screw, but the rising stem type can see the screw stem.
3. Non-rising stem knife gate valve ---When the lever valve is on and off, the steering wheel and the valve rod are connected and relatively inoperable. It is through the valve stem rotating at a fixed point to drive the valve flap to lift upwards and close the gate to complete the opening and closing.
Rising stem knife gate valve--The lever valve is used to raise or lower the valve plate through the thread of the valve stem and the steering wheel.Simple say is that the valve is connected to the valve stem with the valve stem up and down movement, the steering wheel is always at a fixed point.