Common wedge gate valve types and application characteristics
The common types of wedge gate valves are: rising stem wedge single gate valve, Non rising stem wedge single gate valve, rising stem wedge double gate valve, Non rising stem wedge double gate valve and purging gate valve.
Rising stem wedge single gate valve:
The gate of rising stem wedge single gate valve is wedge-shaped single gate, one end of the valve rod is provided with trapezoidal transmission thread, and the valve rod and gate are connected together through T-shaped groove. A valve stem nut is fixed on the upper part of the valve cover, and a hand wheel is arranged outside the valve stem nut. When the hand wheel is rotated anticlockwise, the valve rod drives the gate to rise and the valve opens. When the hand wheel is rotated clockwise, the valve rod descends, and then the gate is wedged and the valve is closed.
Non rising stem wedge single gate valve:
Non rising stem wedge single gate valve. There is a through-hole in the middle of the wedge-shaped gate. The guide device is composed of guide grooves on both sides of the non sealing surface and the guide rib on the valve body. A valve rod nut with trapezoidal thread is installed in the groove on the upper part of the gate, which forms a driving pair with the trapezoidal thread at the lower end of the valve rod. The hand wheel is operated by the hand wheel installed at the top of the valve rod. When the hand wheel is rotated clockwise, the valve rod rotates, the wedge gate descends and wedges tightly, and the valve is closed. When the hand wheel is rotated anticlockwise, the gate rises and the valve opens. When the valve is opened or closed, the stem of the Non rising wedge gate valve only rotates, but does not rise or fall. Therefore, the height of the valve stem is not large, which is also conducive to the sealing of the stem packing. In order to determine the opening and closing position of the gate, special indicator can be used.
Rising stem wedge double gate valve:
The rising stem wedge double gate valve is equipped with two disc gates in the valve body, which are combined by the hemispherical core in the middle. The angle between the two sealing surfaces can float and wedge according to the angle between the two valve seats, so as to eliminate the adverse factors caused by processing error and valve body deformation between the two sealing surfaces, so as to achieve better sealing. The double gate valve is only allowed to be installed on the horizontal pipeline, and the valve stem is installed vertically. However, in many pipelines, the valve stem of double gate valve is installed horizontally, which causes the hemispherical core not to fall to the bottom of the valve but to the valve body, which not only causes the hemispherical core not to function normally, but also causes the valve not to close tightly and opens and closes difficultly.
Non rising stem wedge double gate valve:
Compared with the single gate valve, the advantages of the wedge double gate valve are that the wedge sealing surface of the gate and the valve seat are better, more tight and more convenient to process. In addition, when the valve is affected by high temperature and high pressure and the valve body is deformed, the two sealing surfaces of the double gate can change with the valve body under the action of the wedge force of the valve rod, so as to ensure the tightness of the sealing, and the probability of the gate sticking is relatively low.
Purge gate valve:
Rising stem wedge single gate high temperature purge gate valve. Based on the common wedge single gate valve, the valve is equipped with purging device on the valve body and valve cover. By injecting high-pressure water or steam into the purging device, the pipeline and valve with easy coking and granular medium can be cleaned and flushed, and the impurities in the pipeline and valve can be removed online. It has the advantages of convenience and time saving, and effectively improves the service life of the system. It is suitable for the pipeline of water, steam, flue gas, oil or mist, powder, granular medium, etc. it is used as the opening and closing device, especially for the oil transportation and catalytic cracking unit in the petrochemical industry, playing the role of opening and closing, cleaning and flushing the pipeline.