Five Common Valve Types

1. Gate valve

The gate valve is used as a cut-off medium. When it is fully opened, the whole flow is straight through. At this time, the pressure of the medium is small and the loss is small. Gate valves are usually suitable for conditions that do not require frequent opening and closing, and that keep the gate fully open or fully closed. Not suitable for use as a regulator, throttling. For high-speed flow of the medium, the gate in the local open condition, can cause the vibration of the valve, and vibration, and may damage the sealing surface of the gate and valve seat, and throttling, will make the gate subjected to media erosion. From the structural form, the main difference is the form of the sealing element. According to the form of sealing components, often the gate valve is divided into several different types, such as: wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate gate, etc. Commonly used in the form of wedge gate valve and parallel gate valve.

2. Stop valve

The stem axis of the globe valve is perpendicular to the sealing surface of the valve seat. The opening or closing stroke of the valve stem is relatively short. Once the valve flap of the globe valve is in an open state, its valve seat and valve flap sealing surface are no longer in contact, so its sealing surface is less mechanically worn. As most of the valve seat and valve flap of the globe valve are relatively easy to repair, when replacing the sealing element, there is no need to remove the entire valve from the pipeline, which is very suitable for occasions where the valve and pipeline are welded into one. The above features make the cut-off valve very suitable for use as a medium to cut off or adjust and throttle. When the medium passes through such valves, the flow direction changes. Therefore, the flow resistance of the shut-off valve is higher than that of other valves.

Commonly used globe valve, there are the following:

Angle cut-off valve: In the angle cut-off valve, the fluid only needs to change the direction once, so that the pressure through the secondary valve is smaller than that of the regular structure.

Direct-flow cut-off valve: In the direct-flow, or Y-shaped cut-off valve, the circulation of the valve body and the main flow into a diagonal line, so the degree of damage to the flow state is smaller than that of the regular cut-off valve. Therefore, the pressure loss through the valve is correspondingly small.

Plunger type globe valve: this form of globe valve is, regular the deformation of the globe valve. In this valve, the valve flap and the valve seat are usually designed based on the plunger principle. The valve clack is polished to connect the plunger with the valve stem, and the seal is made up of two elastic sealing rings on the plunger. The two elastic sealing rings are separated by a collar, and the sealing ring around the plunger is pressed firmly by the load applied to the bonnet by the bonnet nut. Elastic sealing ring can be replaced, can be made of a variety of materials, the valve is mainly used for "open" or "off", but each has a special form of plunger or special collar, can also be used to adjust the flow.

3. Butterfly valve

The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0 and 90 degrees. When the valve is rotated to 90 degrees, the butterfly valve is fully open. The structure is simple, small in size and light in weight. A few parts. And only need to rotate 90 degrees, you can quickly open and close, simple operation, at the same time the valve, has good fluid control characteristics. When the butterfly valve is in the fully open position, the thickness of the butterfly valve is the only resistance when the medium flows through the valve body. Therefore, the pressure drop generated by the valve is very small. Butterfly valve has elastic seal and metal seal two kinds of sealing form. Elastic sealing valve, sealing ring can be embedded in the valve body, or near the butterfly plate periphery. Metal-sealed valves generally have a longer life than elastic-sealed valves, but it is difficult to seal completely. Metal seals can adapt to higher operating temperatures, while elastic seals have defects that are limited by temperature. If the butterfly valve is required to be used as a flow control, the main thing is to correctly select the size and type of the valve. Butterfly valve structure principle, especially suitable for making large diameter valve. Butterfly valve is not only widely used in oil, gas, chemical industry, water treatment and other general industries, but also used in the cooling water system of thermal power station. Commonly used butterfly valve has wafer type butterfly valve or flange type butterfly valve two kinds: wafer type butterfly valve is, with a stud bolt to connect the valve between the two pipe flanges. Flange butterfly valve is, with a flange on the valve, with bolts on both ends of the valve flange connected to the pipe flange.

4. Ball valve

Ball valve is evolved from the rotary valve. It has the same rotation 90 degrees action, except that the cock body is a sphere, consisting of a circular through hole, or a passage through its axis. The ratio of the spherical surface and the channel opening should be such that when the ball rotates 90 degrees, the spherical surface should be fully present at the inlet and outlet, thus intercepting the flow. The ball valve can be closed tightly with only 90 degrees of operation and a small turning force. Safety and equality of the valve cavity, for the medium to provide a small resistance, straight-through flow. It is generally believed that the ball valve is suitable for direct opening and closing, but recent developments have designed the ball valve to enable him to throttle and control flow. The main feature of the ball valve is that it is compact, easy to operate and maintain, suitable for water, solvents, acids and natural gas and other general working media, but also suitable for harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body can be integral or combined.

5. Check valve

The check valve only allows the medium to flow in one direction and prevents the flow in the opposite direction. Check valve is usually automatic work, flow in one direction under the action of fluid pressure, the valve open; fluid flow in the opposite direction, by the fluid pressure and valve flap weight and valve acting on the valve seat, thereby cutting off the flow. Check valves include swing check valves and lift check valves. Swing check valves have a dielectric hinge mechanism and a door-like disc that rests freely on the inclined seat surface. In order to ensure that the valve flap can reach the appropriate position of the valve seat surface every time, the valve flap is arranged in the hinge mechanism so that the valve flap has enough space to swing and make the valve flap truly and comprehensively contact the valve seat. The disc can be made entirely of metal, or it can be inlaid with leather, rubber, or a synthetic cover, depending on the applicable performance requirements. Swing check valve in the fully open condition, the fluid pressure is almost unimpeded, so the pressure drop through the valve will be small. Lift check valve disc seat, located on the valve seat on the sealing surface. This valve in addition to the valve can be free to lift, the rest of the same as the cut-off valve, fluid pressure so that the valve, from the valve seat sealing surface lift, medium back to cause the valve back down the valve seat, and cut off the flow. According to the applicable conditions, the valve can make the all-metal body, can also make the valve holder inlaid with rubber pad, or rubber ring form. Like the valve, the fluid through the lift check valve channel is narrow, so the pressure drop through the lift check valve, larger than the swing check valve, and swing check valve flow, subject to very few restrictions. Select the valve according to the adjustment medium parameters. In the production process, in order to make the medium pressure, flow and other parameters meet the requirements of the process, it is necessary to install an adjustment mechanism to adjust the above parameters. The main working principle of the regulating mechanism is to adjust the above parameters by changing the flow area of the valve disc and the valve disc and the valve seat. Belong to this kind of valve is collectively referred to as the control valve, which is divided into relying on the medium itself power-driven called self-drive control valve, such as: pressure reducing valve, regulator valve, etc., where the leading up the power-driven (such as electricity, compressed air and hydraulic power) called he drive control valve, such as electric control valve, pneumatic control valve and hydraulic control valve.