The difference between rising gate valve and no-rising stem gate valve

The gate valve is a gate for opening and closing. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled.

Rising stem valve

By turning the hand wheel, the thread of the hand wheel and the valve stem advances or retreats, and the valve plate connected with the valve stem is raised or lowered to achieve the function of opening and closing.

Advantages of rising stem gate valve:

The fluid resistance is small, and the sealing surface is less eroded and corroded by the medium.

It saves effort to open and close.

The flow direction of the medium is not restricted, does not disturb the flow, and does not reduce the pressure.

The shape is simple, the length of the structure is short, the manufacturing process is good, and the scope of application is wide.

Disadvantages of rising stem gate valve:

It is easy to cause erosion and scratches between the sealing surfaces, and it is difficult to maintain.

The overall size is large, it needs a certain amount of space to open, and the opening and closing time is long.

The structure is more complicated.

Dark stem valve

  Dark stem gate valve is also called rotating stem gate valve (also called dark stem wedge gate valve). The valve stem nut is set on the gate. The rotation of the handwheel drives the rotation of the valve stem to lift the gate. There is usually a trapezoidal thread at the bottom end of the valve stem. The thread on the bottom end of the valve and the guide groove on the disc will rotate the valve. It becomes linear motion, that is, the operating torque is changed to operating thrust.

  When the valve is opened, when the lift height of the gate is equal to 1:1 times the valve diameter, the fluid passage is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as the mark, that is, the unmovable position, as its fully open position. In order to take into account the locking phenomenon caused by temperature changes, it is usually opened to the top position, and then rewind 1/2 to 1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (that is, the stroke).

   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 must 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.

rising gate VS no-rising gate

1. The screw can not be seen in the valve with dark rod, while the screw can be seen in the valve with open rod.

2. 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 lifting screw of the rising rod 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, and the screw and the gate only have relative rotational movement. There is no relative axial displacement, and the appearance is a gate-shaped bracket.

3. 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.