Valve purchase knowledge Daquan
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I. 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 the self-driven control valves such as pressure reducing valves, pressure regulating valves, where the leading power-driven (such as electricity, compressed air and hydraulic power ) He called him driving control valve, such as electric control valve, pneumatic control valve and hydraulic control valve. Second, 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 fluid pressure 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 in 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 freely up and down, the rest of the same as the cut-off valve, the fluid pressure from the valve seat sealing surface lift up, the media back to the valve seat caused by the valve back down and cut off the flow. According to the conditions of use, the solenoid valve disc can be all-metal structure, it can be in the valve frame inlaid rubber pad or rubber ring form. 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. Third, according to the nature of the media off valve selection: 1. Gate valve: gate valve is used as a cut-off medium, the entire circulation straight through, 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. Valve production Shanghai Star Ou valve is 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. 2. Stop valve stem axis and valve seat sealing surface perpendicular. Diaphragm valve stem open or close the 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 use. When the valve is open, its valve seat and disc seal surface no longer contact between, and has a very reliable cut off action, combined with this valve is very suitable as a medium cut off or adjust and throttle . 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. Trap medium flow through this type of valve has changed, so the flow resistance of the shut-off valve is higher than the other valves. There are several commonly used stop valves: 1) Angle stop valve: In the angle stop valve, the fluid only needs to change direction once, so that the pressure through this valve is smaller than that of the conventional stop valve. 2) DC-type globe valve: In the DC or Y-type valve, the body of the flow channel and the main flow into a slash, so that the flow of damage than the normal cut-off 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. Stopcock The two elastomeric seals are separated by a collar and pressed against the seal around the plunger by the load applied to the bonnet by the bonnet nut. Elastomeric seals are interchangeable and can be made from a wide variety of materials. The valve is mainly used for on or off but with a special form of plunger or special collar, it can also be used to regulate flow. 3. Butterfly valve: butterfly valve butterfly installed in the pipe diameter direction. In the butterfly valve body cylindrical channel, disc disc rotates around the axis, the rotation angle is between 0 ° ~ 90 °, when rotated to 90 °, the valve is in the fully open state. 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. 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, it is mainly the correct choice of valve size and type. The structural principle of the butterfly valve is especially suitable for making large diameter valves. Butterfly valve not only in the oil, gas, chemical, 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 plunger valve is a valve with flanges, bolts on both ends of the valve flange on the pipe flange . 4. Ball Valve: Ball valve is evolved from the plug valve. 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. That is, when the ball is rotated 90 degrees, the entrance and exit should be fully spherical, thus cutting 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. Shanghai Xingou valve professionals think the most suitable ball valve to do the opening and closing the use of direct, but the recent development of the ball valve has been designed so that it has throttling and flow control purposes. 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.