We all know that if the gate valve is classified according to the structure of the valve stem, it can be divided into two categories: dark stem gate valve and rising stem gate valve.
Dark stem gate valve: The stem nut is in the valve body and is in direct contact with the medium. When opening and closing the gate, it is realized by rotating the valve stem. The advantage of this structure is that the height of the gate valve remains the same, so the installation space is small, and it is suitable for gate valves with large diameters or limited installation space. This structure should be equipped with an opening and closing indicator to indicate the degree of opening and closing. The disadvantage of this structure is that the valve stem thread is not only unable to lubricate, but also directly eroded by the medium and easily damaged.
Rising stem gate valve: The stem nut is on the bonnet or bracket. When opening and closing the gate, the stem nut is rotated to realize the lifting and lowering of the valve stem. This structure is beneficial to the lubrication of the valve stem, and the degree of opening and closing is obvious, so it is widely used.
The difference between the dark stem gate valve and the rising stem gate valve is roughly divided into three points:
1. The dark rod valve cannot see the lead screw, and the open rod valve can see the lead screw.
two,When the dark stem valve is switched on and off, the steering wheel and the valve stem are connected together and relatively stationary. It is opened and closed by rotating the valve stem at a fixed point to drive the valve disc to lift up and lower the gate. The rising stem valve lifts or lowers the valve disc through the threaded transmission of the valve stem and the steering wheel.
3. The lifting screw of the flanged gate valve only rotates and does not move up and down. Only a rod is exposed, and its nut is fixed on the gate. The gate is lifted by the rotation of the screw, and there is no visible gantry. ;The lifting screw of the rising stem flange gate valve is exposed, and the nut is close to the handwheel and is fixed (not rotating or moving axially). The gate is lifted by rotating the screw. There is no relative axial displacement, and the appearance is a portal bracket.
The above three points are the difference between the dark stem gate valve and the open stem gate valve, it will definitely help you, collect it and forward it~