Gate valve types and characteristics

Posted by uuuseff on November 18th, 2019

Gate valve is the closing member (gate) along the centerline of the vertical movement of the valve. Gate valve in the pipeline can only be fully open and all off with off, not for regulation and throttling. Gate valve is the use of a wide range of valves, the general diameter DN ≥ 50mm cutting devices are used it, and sometimes a small caliber shut-off device is also used gate valve. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used gate valves form a wedge. The wedge angle varies from valve to valve, typically 50, with a 2 ° 52 'medium temperature. Wedge gate valve gate can be made as a whole, called the rigid gate; can also be made to produce a slight deformation of the gate, to improve its technology to make up for sealing surface angle in the process of deviation, this gate The board is called a flexible gate. When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, self-sealing by relying on the medium pressure to press the sealing surface of the gate valve to the valve seat on the other side to ensure the sealing surface. Most of the gate valve is forced seal, that is, when the valve is closed, it must rely on external force to force the gate to the valve seat to ensure the sealing surface of the seal. Gate valve gate with the stem for linear motion, called lifting rod gate valve (also known as rod gate valve). Trapezoidal thread is usually on the lifting rod, through the valve at the top of the nut and the guide groove on the valve body, the rotary motion into a linear motion, that is, the operating torque into the thrust. When the valve is opened, the fluid passage is completely clear when the lift of the valve is equal to 1: 1 of the valve diameter, but this position can not be monitored during operation. The actual use is based on the top of the valve stem as a sign, that is, an open position, as its fully open position. To consider the temperature change lock phenomenon, usually in the open to the top position, and then back 1 / 2-1 lap, as a fully open valve position. Therefore, the valve fully open position, according to the gate position (ie stroke> to determine. Gate valve type 1, according to the structure of the gate can be divided 1) parallel gate valve: sealing surface and vertical centerline parallel, that is, two seals Gate valves parallel to each other. In parallel gate valves, the structure with thrust wedges is the most common, with double-sided thrust wedges in the middle of the two gate plates. This type of gate valve is suitable for low pressure medium and small bore (DN40-300mm) gate valves. There is also a spring between the two rams, the spring can produce preload, is conducive to the gate seal. 2) wedge gate valve: sealing surface and the vertical center line into a certain angle, that is, two sealing surface into a wedge-shaped gate valve. The sealing surface of the tilt angle is generally 2 ° 52 ', 3 ° 30', 5 °, 8 °, 10 °, the size of the angle depends on the medium temperature level. The higher the general operating temperature, the angle taken should be greater in order to reduce the possibility of wedging occurs when the temperature changes. In the wedge gate valve, there is a single gate, double gate and elastic gate of the points. Single gate wedge gate valve, simple structure, reliable, but the sealing surface angle of the higher precision, processing and maintenance more difficult, wedges the possibility of temperature changes is great. Double gate wedge gate valve in the water and steam medium pipe used more. Its advantages are: low precision of the sealing surface angle, the temperature change is not easy to cause wedging phenomenon, the sealing surface wear, you can add gasket compensation. However, this structure more parts in the viscous medium easy to bond, affecting the seal. More importantly, the long-term use of the lower bezel easy to produce corrosion, easy to fall off the gate. Flexible gate wedge gate valve, it has a single gate wedge gate valve structure is simple, the use of * can have the advantage of producing a small amount of elastic deformation make up the sealing surface angle of the process of deviation, improve the process, has been a large number use. 2, according to the structure of the valve stem can be divided into 1) Ming rod valve: stem nut in the valve cover or bracket, open the gate, the use of rotating stem nut to achieve stem lifting. This structure is beneficial to the lubrication of the valve stem, opening and closing a clear degree, it is widely used. 2) dark bar gate valve: stem nut in the valve body, and the media in direct contact. Open and close the gate, the rotary valve stem to achieve. The advantage of this structure is that the height of the gate valve always remains unchanged, so the installation space is small, suitable for large-caliber or gate valves with 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 not only is the stem thread unlubricated, but it is also subject to direct media erosion and damage. Advantages and disadvantages of gate valve gate valve advantages: (1) small fluid resistance gate valve body because the media channel is straight through, the medium flow through the gate valve does not change its flow direction, so the fluid resistance is small. (2) opening and closing torque, opening and closing more effort because the gate valve opening and closing direction of flow and medium flow perpendicular to the vertical, compared with the cut-off valve, gate valve opening and closing more effort. (3) The flow direction of the medium is not restricted, the flow is not disturbed, and the pressure medium can flow in any direction from both sides of the gate valve, so as to achieve the purpose of use. More suitable for medium flow direction may change in the pipeline. (4) the structure of a shorter length because the gate valve gate is placed vertically in the valve body, and the valve is placed horizontally in the valve body, and therefore the structure of the length of the valve short. (5) good sealing performance when fully open seal surface erosion by smaller. (6) fully open, the sealing surface by the erosion of the working medium smaller than the shut-off valve. (7) shape is relatively simple, good casting process, a wide range of applications. Disadvantages of the gate valve: (1) easy to seal the sealing surface When opening and closing the gate and the valve seat contact between the two seals and the relative friction between, easy to damage, affecting the seal with the service life, maintenance more difficult. (2) Opening and closing a long time, the height of the gate valve opening and closing to be fully open or closed, the gate stroke, open with a certain space, high dimensions, installation space required.

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