Media use as a cut-off valve in the flow through the fully open, then the pressure medium run minimal loss. Valve is usually applied to less frequent opening and closing, and keeping the shutter fully open or fully closed condition. Not suitable for use as a regulating or throttling. For the high-speed flow of the medium, the gate in local conditions can cause vibration of the gate, and vibration and possible damage to the gate and seat sealing surface, while the throttle damper will suffer erosion of the medium. From a structural form, the main difference is that the sealing element is used. According to the form of the sealing element, often divided into several different valve types, such as: wedge gate valves, parallel gate valve, parallel Gate Valve, double plate wedge gate and so on. The most common form of wedge gate and parallel gate valve. Cut-off valve
As of the stem axis perpendicular to the valve seat sealing surface. Stem to open or close the relatively short trip, and has a very reliable cutting action, making this valve is suitable for medium off or adjusted and throttling. Once the cut-off contact with the valve in the valve open position, between its valve seat and valve sealing surface is no longer, and has a very reliable cutting action, and combine this valve is suitable for medium cut or regulation and section stream uses.
Once the valve is turned on, its valve seat and valve sealing surface is no longer in contact, so it's less mechanical wear of the seal faces, most due to valve seat and valve shut-off valve is relatively easy to repair or replace when the sealing element without removing the entire valve from the pipeline to which the valve is welded into one pipe and the case is applicable. The medium flow direction through the valve when such a change occurs, and therefore a higher cut-off valve in the flow resistance of the other valves.
Commonly used cut-off valve are the following: a) angle type valve; in angle type valve, the fluid simply by changing a direction, so that the pressure drop through the valve shut-off valve small than conventional structure. 2) DC-type valve; at once-or Y-shaped valve, the valve of the flow channel and the main channel into a slash, the extent of damage this flow state is smaller than the conventional cut-off valve, and thus the pressure loss through the valve accordingly the small. 3) plunger-type valve: This form of cut-off valve is a variant of the conventional cut-off valve. In the valve, the valve and the valve seat is usually based on the principle of the plunger. Polished into the plunger and valve stem is connected seal is set on two elastic plunger seals to achieve. Two elastomeric seals separated by a collar, and through the valve cover nut load exerted on the valve cover seals around the plunger pressed firmly. Elastic ring can be replaced, you can use a variety of materials, the valve is mainly used in the "on" or "off", but with a special form of a plunger or special rings can also be used to adjust the flow .
Butterfly
Butterfly butterfly plate installed on the pipe diameter direction. Cylindrical passage in the valve body, disc-shaped disc around the axis of rotation, rotation angle of between 0 ° ~ 90 °, rotation to 90 °, the valve is fully open state licensing.
Butterfly simple structure, small size, light weight, only by a few parts. And just rotate 90 ° to quickly open and close, easy to operate, while the fluid control valve has a good feature. Butterfly valve in the fully open position, the disc thickness is only when the medium flows through the body resistance, produced by the valve pressure drop is small, it has a better flow control characteristics. Butterfly shells sealed and two metal seal type. Resilient seal valves, seals can be mounted on the body or attached to the disc periphery.
Using a long metal seal valve life in general than the elastic sealing valve, but it is difficult to completely seal. Metal seals can adapt to higher operating temperature, flexible seal is affected by temperature limit of the defect.
If you require the use of flow control valve as the main choice is the right size and type of valve. Butterfly structure principle is particularly suitable for the production of large diameter valves. Butterfly valves are widely used not only in the oil, gas, chemical, water treatment and other general industrial, but also used in thermal power plant cooling water system.
Butterfly valves are commonly used in wafer type butterfly valve and flange type butterfly two kinds. Wafer type butterfly valve with stud connection between two pipe flanges, flanged butterfly valve is a valve with a flange with bolt flanged ends of the valve on the pipe flange.
Ball
Ball is a plug evolved. It has the same movement rotated 90 degrees to mention, is the cock body is different sphere, there are circular holes or channels through its axis. Sphere and the ratio of openings should be such that when the ball is rotated 90 degrees, in the import and export of office should be fully rendered sphere, thus cutting off the flow.
Just use the rotary ball valve operation and a small 90-degree rotational torque can be closed tightly. Full equality body cavity for the media provided little resistance, through the flow channel. Generally considered the most suitable valve opening and closing done directly used, but recent development has been designed so that it has a throttle ball and control the flow purposes. Main features of valve itself is compact structure, easy operation and maintenance for water, solvents, acids and gas work in general media, but also for the poor working conditions of media, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve may be integral, or may be modular.
Backflow valve to prevent the media chosen by
The role of this type of valve is only allowed media to flow in one direction, and stop the flow direction. Usually the valve is automatically work under the direction of flow of the fluid pressure of a role, the valve opens; opposite direction of fluid flow from the fluid pressure and valve from the coincidence of acting on the valve seat, thereby cutting off the flow. Check them belong to this type of valve, which includes swing check valves and lift check valves. Swing check valves have ordinary hinge, there is a door on the same freedom leaning tilt valve seat surface. To ensure that every time the valve seat face to reach a suitable position, the valve design in the hinge mechanism, so that the valve has sufficient swing space, and the valve real, comprehensive engagement with the valve seat. Valve can all be made of metal can also be embedded in the leather, rubber on metal, or synthetic coverage, depending on performance requirements. Swing check valve in the fully open position, the fluid pressure is almost unimpeded, so the valve by the pressure drop is relatively small. Lift check valve is located at the sealing surface of the valve seat on the valve body. Addition to this valve disc is free to lift, the other part of the same as the cut-off valve, the fluid pressure valve lift from the valve seat sealing surface, medium return valve flap down to the seat, and cut off the flow. Depending on conditions, the valve can be all metal construction, can also be embedded in the form of rubber or rubber ring in the valve holder. Like cutoff valves, fluid passage through the lift valve is narrow, so through the lift valve pressure drop than the bigger swing check valve, swing check valves and flow restrictions rarely.
Medium parameters by adjusting the valve selection
In the production process, in order to make the medium pressure, flow and other parameters meet the requirements of the process, you need to install the adjusting mechanism to adjust these parameters. The main working principle of regulating bodies, is by changing the flow area of the valve and the valve between the valve and valve seat, to adjust these parameters purposes. Such valves are referred to as control valves, which is divided into relying on the media itself is called a self-powered drive control valve such as valve, regulator valve, all leading up power-driven (such as electricity, compressed air and liquid power) as he was driving the control valve, such as the electric control valve, pneumatic control valves and hydraulic control valve.
