Gate Valves

What is a gate valve?

The gate valve is a gate with opening and closing parts. The movement direction of the gate valve is perpendicular to the fluid direction. The gate valve can only be fully opened and fully closed, not adjusted and throttled. The gate valve is sealed by the contact between the valve seat and the gate. Usually, the sealing surface will be overlaid with metal materials to increase the wear resistance, such as overlaying 1Cr13. Stl6. Stainless steel, etc. The gate valve has rigid gate valve and elastic gate valve. According to different gate valves, the gate valve is divided into rigid gate valve and elastic gate valve.


Working principle of gate valve

The opening and closing part of the gate valve is the gate, and the movement direction of the gate is perpendicular to the fluid direction. The gate valve can only be fully opened and closed, not adjusted and throttled. The ram has two sealing surfaces. The most commonly used mode is that the two sealing surfaces of the ram valve form a wedge. The wedge angle varies with the valve parameters, usually 5°, and 2° 52′ when the medium temperature is not high. The gate of wedge gate valve can be made into a whole, which is called rigid gate valve; It can also be made into a ram that can produce slight deformation to improve its manufacturability and make up for the deviation of the angle of the sealing surface in the processing process. This kind of ram is called elastic ram. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate valve can be pressed to the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self sealing. Most gate valves are forced sealed, that is, when the valve is closed, the gate shall be forced to the valve seat by external force to ensure the tightness of the sealing surface. The gate of the gate valve moves in a straight line with the valve stem, which is also called rising stem gate valve. Generally, there are trapezoidal threads on the lifting rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, when the lifting height of the ram is equal to 1:1 times the valve diameter, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the vertex of the valve stem is used as the mark, that is, the position that cannot be opened is used as its fully open position. In order to consider the locking phenomenon caused by temperature change, it is usually opened to the peak position and then turned back 1/2-1 turn as the position of fully open valve. Therefore, the fully open position of the valve is determined according to the position of the ram, that is, the travel. For some gate valves, the valve stem nut is set on the ram, and the rotation of the hand wheel drives the valve stem to rotate and lift the ram. This kind of valve is called rotary rod gate valve or Non rising rod gate valve.

Movement mode of gate valve

When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate valve can be pressed to the valve seat on the other side only by the medium pressure to ensure the sealing of the sealing surface, which is self sealing. Most gate valves are forced sealed, that is, when the valve is closed, the gate shall be forced to the valve seat by external force to ensure the tightness of the sealing surface.
Movement mode: the gate of the gate valve moves in a straight line with the valve stem, also known as rising stem gate valve. Generally, there are trapezoidal threads on the lifting rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, when the lifting height of the ram is equal to 1:1 times the valve diameter, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the vertex of the valve stem is used as the mark, that is, the position that cannot be opened is used as its fully open position. In order to consider the locking phenomenon caused by temperature change, it is usually opened to the peak position and then turned back 1 / 2-1 turn as the position of fully open valve. Therefore, the fully open position of the valve is determined according to the position of the RAM (i.e. stroke). Some gate valve stem nuts are set on the gate, and the rotation of the hand wheel drives the valve stem to rotate and lift the gate. This kind of valve is called rotary rod gate valve or Non rising rod gate valve.

Types of gate valves

Gate valves are divided into wedge type and parallel type according to the structure of the gate. Wedge ram has three structures: single ram, double ram and elastic ram.
Gate valves are divided into flat gate valves and knife gate valves according to different structural types.
Working principle of manual gate valve: turn the hand wheel to open and close the valve plate connected with the valve stem through the advance and retreat of the thread between the hand wheel and the valve stem.
According to the classification of shell / main body materials, gate valves can be divided into:
Metal valves: such as carbon steel valves, alloy steel valves, stainless steel valves, cast iron valves, titanium alloy valves, Monel valves, copper alloy valves, lead alloy valves, etc.
Metal body lined valves: such as rubber lined valves, fluorine lined valves, lead lined valves, plastic lined valves and enamel lined valves.
Non metallic valves: such as ceramic valves, glass valves and plastic valves.

Characteristics of gate valve

Light weight

The body is made of high-grade nodular cast iron, which reduces the weight by about 20% ~ 30% compared with the traditional gate valve, and is convenient for installation and maintenance.

Flat bottom gate seat

After the traditional gate valve is washed with water, foreign objects such as stones, wood blocks, cement, iron filings and sundries are deposited in the groove at the valve bottom, which is easy to cause water leakage. The bottom of the elastic seat sealed gate valve adopts the same flat bottom design as the water pipe machine, which is not easy to cause sundries to deposit and make the fluid unobstructed.

Integral coating

The ram adopts high-quality rubber for internal and external rubber. The European rubber vulcanization technology enables the vulcanized ram to ensure accurate geometric dimensions, and the rubber and nodular cast RAM are firm, not easy to fall off and have good elastic memory.

Precision casting valve body

The valve body adopts precision casting, and the precise geometric size makes the valve body without any finishing processing to ensure the sealing of the valve.

Installation points of gate valve

  • 1) The installation position, height, inlet and outlet direction must meet the design requirements, and the connection shall be firm and tight.
  • 2) The handle of various manual valves installed on the insulation pipeline shall not be downward.
  • 3) Visual inspection must be carried out before valve installation, and the valve nameplate shall comply with the provisions of the current national standard general valve mark gb12220. For valves whose working pressure is greater than 1.0MPa and which cut off the main pipe, strength and tightness tests shall be carried out before installation, and they can be used only after they are qualified. During the strength test, the test pressure shall be 1.5 times of the nominal pressure and the duration shall not be less than 5min. The valve shell and packing shall be qualified if there is no leakage. During the tightness test, the test pressure shall be 1.1 times of the nominal pressure; The test pressure shall meet the requirements of GB50243 standard during the test duration, and it is qualified if there is no leakage on the sealing surface of the valve disc.
  • 4) Hand wheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited.
  • 5) . the gate valve with transmission mechanism shall be installed according to the provisions of the product operation manual.

China gate valves manufacturer www.sfutube.com supplies Industrial gate valve for industrial use, in kinds of materials such as carbon steel, stainless steel, alloy steel, etc.

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