Gate valves are classified according to the type of stem, which can be divided into two types: Non-rising stem gate valve and Rising stem gate valve.
Non-rising stem gate valve
♦ Non-rising stems are threaded into the gate, and rotate with the wedge rising and lowering inside the valve. They take up less vertical space since the stem is kept within the valve body. Generally, an open-close indicator should be installed to indicate the degree of open-close.
Advantage: The height of the Non-rising stem gate valve is small, and it will not take up too much space during installation.
Disadvantage: Failure to lubricate stem threads will result in medium erosion and easy damage.
Rising stem gate valve
♦ Stem nut for rising stem gate valve is on its cover. Rotation of stem nut drives stems up and down when opening or closing gate valve. It opens and closes the disc connected to the stem by lifting or lowering the thread between the handwheel and the stem and fully open position does not disrupt the flow. This design is favorable to the lubrication of the valve stem.
Advantage: 1.Easy to open and close.
Disadvantages: 1.The sealing surface is easy to be eroded and scraped, difficult for maintenance.
2.Larger structure requires more space and long-time opening.
The difference between non-rising stem gate valve and rising stem gate valve:
1.The rising stem gate valve can be seen from the appearance whether the valve is closed or open. The lead screw can be seen while the non-rising stem gate valve cannot.
2. The lifting screw of rising stem gate valve is exposed outside, the nut cling to the handwheel is fixed (not rotating axial movement), the rotation of the screw and gate only relative motion without relative axial displacement of the disc and stem up and down together. The lifting screw of the non-rising stem gate valve only rotates and does not move up and down.
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