The correct choice of valve method
Gate valve is used as a cut-off medium, the entire circulation through the fully open, this time the pressure loss of medium operation minimum. Gate valve is usually applied to do not often need to open and close, and keep the gate fully open or fully closed conditions. Not suitable for use as a regulator or throttling. For high-speed flow media, the gate may cause gate vibration when the gate is open partially, and the vibration may damage the sealing surface of the gate and valve seat, which can cause the gate to suffer erosion of the medium. The main difference from the structural form is the form of the sealing element used. According to the form of the sealing element, the gate valve is often divided into several different types, such as wedge gate valve, parallel gate valve, parallel double gate gate valve, wedge double gate gate and the like. The most common forms are wedge gate valves and parallel gate valves. Globe valve stem valve stem valve seat sealing surface perpendicular to. Stem opening or closing stroke is relatively short, and has a very reliable cut off action, making this valve is very suitable as a medium cut off or adjust and throttle. Once the valve flap of the globe valve is open, its contact between the valve seat and the flap sealing surface no longer contacts and has a very reliable cut-off action, making this valve ideal as a medium to cut or adjust Flow use. Once the stop valve is open, its valve seat and disc seal surface no longer have contact between, and therefore its sealing surface mechanical wear and tear less, as most of the valve seat and the disc valve is relatively easy to repair or replacement Sealing components without having to remove the entire valve from the pipeline, which for the valve and pipe welding is integrated into the case is very applicable. The flow direction of the medium as it passes through such a valve changes, so the shut-off valve has a higher flow resistance than the other valves. There are several commonly used stop valves: 1) Angular stop valves; in angle stop valves, the fluid only needs to be changed in one direction so that the pressure drop across this valve is less than that of conventional stop valves. 2) DC shut-off valve; In the DC or Y-type shut-off valve, the valve body flow path and the main flow channel into a slash, so that the flow of state damage than the conventional valve is smaller, so the pressure loss through the valve accordingly Small 3) Plunger globe valve: This type of globe valve is a variation of a conventional globe valve. In this valve, the disc and seat are usually designed based on the plunger principle. Polished valve plunger into a plunger connected with the stem, the seal is set by the plunger in the two elastic ring to achieve. The two elastomeric seals are separated by a collar, and the seal around the plunger is pressed firmly by the load exerted by the bonnet nut on the bonnet. Elastomeric seals are interchangeable and can be made in a wide variety of materials. The valves are mainly used to "open" or "close", but with a special form of plunger or special collar that can also be used to regulate flow . Butterfly butterfly valve disc installed in the pipe diameter direction. In the butterfly valve body cylindrical channel, the disc-shaped disc rotates about the axis, the rotation angle is between 0 ° ~ 90 °, when rotated to 90 °, the valve is fully open state card. Butterfly valve structure is simple, small size, light weight, only a few components. And just turn 90 ° to quickly open and close, easy to operate, while the valve has good fluid control features. When the butterfly valve is fully open, the thickness of the disc is the only resistance to the flow of the medium through the valve body, so the pressure drop across the valve is small and therefore has good flow control characteristics. Butterfly valve seal and metal seal two types of seal. Flexible sealing valves, seals can be embedded in the body or attached to the butterfly plate around. Valves with metal seals generally have a longer life than elastomeric valves, but are harder to seal completely. Metal seals can adapt to higher operating temperatures, while flexible seals have temperature-limited defects. If the butterfly valve is required to be used as a flow control, the main choice is the correct size and type of valve. The structural principle of the butterfly valve is especially suitable for making large diameter valves. Butterfly valve not only in the oil, gas, chemicals, water treatment and other general industry has been widely used, but also used in thermal power station cooling water system. Commonly used butterfly valve clamp butterfly valve and flange two. The butterfly valve on the folder is to use double-headed bolts to connect the valve between the two pipe flanges, flanged butterfly valve is equipped with a flange on the valve, with bolts on both sides of the valve flange connected to the pipe flange. Ball valve ball valve is evolved from the plug. It has the same 90 degree rotation action, except that the plug body is a sphere with a circular through hole or passage through its axis. The ratio of the sphere to the channel should be such that when the sphere is rotated 90 degrees, the sphere should be fully spherical at the inlet and outlet to cut off the flow. Ball valve only need to rotate 90 degrees of operation and a small turning moment can be closed tight. The completely equal body cavity provides a medium-sized, straight-through runner with low resistance. Ball valves are generally considered to be the most suitable for direct opening and closing, but recent developments have designed the ball valve to be throttling and controlling flow. The main features of the ball valve is its compact structure, easy operation and maintenance, suitable for general working media such as water, solvents, acids and natural gas, but also for media with bad working conditions such as oxygen, hydrogen peroxide, methane and ethylene. Ball valve body can be a whole, it can be combined. By preventing the media back to select the valve The role of this type of valve is to allow only medium to flow in one direction, but also to prevent the flow direction. Usually this kind of valve is automatic working, the valve flap opens under the pressure of the fluid flowing in one direction; when the fluid flows in the opposite direction, the valve flap is acted upon by the fluid pressure and the self-weight of the valve flap to cut off the flow. Which check valve belongs to this type of valve, which includes the swing check valve and lift check valve. Swing check valves have a hinged hinge mechanism and a flap-like flap freely rests against the slanted seat surface. To ensure that the valve flap reaches the proper seating surface every time, the valve flap is designed on the hinge mechanism so that the valve flap has enough swivel-open space for true and complete valve flap contact. The valve flap can be made entirely of metal, or it can be fitted with a leather, rubber or synthetic cover over the metal, depending on the performance requirements. Swing check valve in the fully open condition, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. Lift check valve seat is located on the valve seat sealing surface. In addition to the valve flap valve can be free to rise and fall, the rest of the same as the cut-off valve, the fluid pressure so that the valve flap from the valve seat lifting surface, the media back to cause the valve flap down to the seat, and cut off the flow. Depending on the conditions of use, the valve disc can be of all-metal construction or it can be in the form of a rubber gasket or rubber ring inlaid on the valve disc holder. Like the stop valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than the swing check valve and the flow through the swing check valve is limited Few. Press the media parameters to adjust the selection of valves In the production process, in order to make the media pressure, flow and other parameters in line with the requirements of the process, the need to install the adjustment mechanism to adjust the above parameters. The main working principle of the adjusting mechanism is to change the valve disc and the flow area between the valve disc and valve seat to achieve the purpose of adjusting the above parameters. Belong to this type of valve collectively referred to as the control valve, which is divided into rely on the media itself driven by self-driven control valves such as pressure relief valves, pressure regulators, etc., where the leading power-driven (such as electricity, compressed air and liquid Power) called his drive control valves, such as electric control valve, pneumatic control valve and hydraulic control valve.
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