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The Difference Between Open Stem Gate Valve and Dark Stem Gate Valve

Blog,Industry News | Sep.22.2020

The gate valve can be divided into:

1. Rising stem gate valve: The stem nut is on the valve cover or bracket. When opening and closing the gate, the stem nut is rotated to achieve the lifting of the 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.

2. 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 always remains the same, so the installation space is small, and it is suitable for gate valves with large diameters or restricted 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 not only cannot be lubricated, but it is directly corroded by the medium and is easily damaged.

The main difference between the exposed stem gate valve and the dark stem gate valve:

  • The lifting screw of the concealed rod flange gate valve only rotates and does not move up or down. Only a rod is exposed. The nut is fixed on the gate. The gate is lifted by the rotation of the screw, and there is no visible door frame.
  • The gate is lifted by rotating the screw. The screw and the gate only have relative rotational movement without relative movement. The axial displacement, the appearance is gate-shaped bracket.
  • The screw rod can not be seen in the valve with dark rod, while the screw rod can be seen in the valve with open rod.
  • The steering wheel and the valve stem of the dark stem valve are connected together and relatively immovable when the valve is opened and closed. The valve stem is rotated at a fixed point to drive the valve disc to lift up and down to complete the opening and closing.
  • The rising stem valve raises or lowers the disc through the threaded drive of the valve stem and the steering wheel. To put it simply, the rising stem valve is that the disc is connected with the stem to move up and down, and the steering wheel is always at a fixed point.

As a valve manufacturer for gate valve, check valve, globe valve, butterfly valve, ball valve with electric actuator or pneumatic actuator, COVNA will help you to choose the right valve for your project and help your business grows!


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