How to choose the valve according to the characteristics of the medium

The gate valve is used as a cut-off medium. When it is fully open, the whole flow is straight through. At this time, the pressure loss of the medium operation is small. Gate valves are generally suitable for applications that do not require frequent opening and closing, but also keep the shutter fully open or fully closed. Not suitable for use as an adjustment or throttling. For high-speed flowing media, the gate can cause vibration of the gate under partial opening conditions, and the vibration may damage the sealing surface of the gate and the valve seat, and the throttling will cause the ram to be eroded by the medium. The main difference in terms of structural form is the form of the sealing element used. Depending on the form of the sealing element, the gate valves are often divided into several different types, such as wedge gate valves, parallel gate valves, parallel double gate gate valves, wedge double gate gates, and the like. Commonly used forms of zui are wedge gate valves and parallel gate valves.

Shut-off valve

The stem axis of the shutoff valve is perpendicular to the seat sealing surface. The valve stem has a relatively short opening or closing stroke and a very reliable shut-off action, making this valve ideal for use as a medium for cutting or regulating and throttling.

Once the valve flap of the shut-off valve is in the open state, its valve seat and the valve sealing surface are no longer in contact with each other, and it has a very reliable cutting action. This valve is very suitable as the cutting or adjusting and section of the medium. Stream usage.

Once the shut-off valve is open, there is no contact between its seat and the disc sealing surface, so its sealing surface is less mechanically worn, because the valve seat and disc of most shut-off valves are easier to repair or replace. It is not necessary to remove the entire valve from the pipeline when sealing the components, which is very suitable for the case where the valve and the pipeline are welded together. The flow direction of the medium as it passes through such a valve changes, so the flow resistance of the shut-off valve is higher than other valves.

Commonly used shut-off valves are as follows: 1) An angle-type shut-off valve; in a corner-type shut-off valve, the fluid only needs to change in one direction, so that the pressure drop through the valve is smaller than that of a conventional structure. 2) DC type stop valve; in the DC or Y-shaped stop valve, the flow path of the valve body is inclined with the main flow path, so that the degree of damage of the flow state is smaller than that of the conventional stop valve, and thus the pressure loss through the valve is correspondingly Small. 3) Plunger shut-off valve: This type of shut-off valve is a variant of a conventional shut-off valve. In this valve, the flap and seat are usually designed based on the principle of the plunger. The valve flap is polished into a plunger that is coupled to the valve stem, and the seal is achieved by two elastomeric sealing rings that are placed over the plunger. The two elastomeric seals are separated by a collar and the seal around the plunger is pressed by the load exerted by the bonnet nut on the bonnet. The elastomeric seal can be replaced and can be made from a wide variety of materials. The valve is mainly used for "opening" or "off", but with a special form of plunger or special collar, it can also be used to regulate flow. .

Butterfly valve

The butterfly valve's disc is mounted in the diameter direction of the pipe. In the cylindrical passage of the butterfly valve body, the disc-shaped disc rotates around the axis, and the rotation angle is between 0° and 90°. When the rotation is 90°, the valve is fully open.

The butterfly valve is simple in structure, small in size and light in weight, and consists of only a few parts. Moreover, it can be quickly opened and closed by rotating 90°, and the operation is simple, and the valve has good fluid control characteristics. When the butterfly valve is in the fully open position, the thickness of the disc is the only resistance when the medium flows through the valve body, so the pressure drop generated by the valve is small, so it has better flow control characteristics. The butterfly valve has two sealing types: a spring seal and a metal seal. Elastomeric sealing valve, the sealing ring can be mounted on the valve body or attached to the periphery of the disc.

Valves with metal seals generally have a longer life than elastomeric seals, but are difficult to seal completely. Metal seals can accommodate higher operating temperatures, while elastomeric seals have temperature-limited defects.

    If a butterfly valve is required for 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 valves are widely used not only in general industries such as petroleum, gas, chemical, and water treatment, but also in cooling water systems for thermal power plants. Common butterfly valves are clip-on butterfly valves and flanged butterfly valves. The wafer type butterfly valve uses a stud bolt to connect the valve between the two pipe flanges. The flange type butterfly valve has a flange on the valve, and the flanges on both ends of the valve are connected to the pipe flange by bolts.

Ball valve

Ball valves are evolved from plug valves. It has the same 90 degree lift action, except that the plug body is a sphere with a circular through hole or passage through its axis. The ratio of the spherical surface to the passage opening should be such that when the ball is rotated 90 degrees, the spherical surface should be entirely present at the inlet and outlet to intercept the flow.

The ball valve only needs to be rotated 90 degrees and a small turning torque to close tightly. The fully equal valve body cavity provides a small, straight-through flow path for the medium. It is generally considered that the ball valve Zui is suitable for direct opening and closing, but recent developments have designed the ball valve to have throttling and control flow. The main features of the ball valve are its compact structure, easy operation and maintenance, suitable for general working media such as water, solvent, acid and natural gas, and also suitable for medium with harsh working conditions such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body may be integral or combined.

Press the valve to prevent backflow of the medium

The function of this type of valve is to only allow the medium to flow in one direction and prevent the direction from flowing. Usually, the valve is automatically operated, and the valve flap is opened by the fluid pressure flowing in one direction; when the fluid flows in the opposite direction, the fluid pressure and the self-reclosing valve flap of the valve disc act on the valve seat to cut off the flow. Among them, the check valve belongs to this type of valve, which includes a swing check valve and a lift check valve. The swing check valve has a hinge mechanism and a door-like flap that rests freely against the inclined seat surface. In order to ensure that the valve flap can reach the proper position of the valve seat surface each time, the valve flap is designed in the hinge mechanism, so that the valve flap has enough swinging space and the valve flap is truly and comprehensively in contact with the valve seat. The discs can all be made of metal, or they can be inlaid with leather, rubber, or synthetic coverings depending on the performance requirements. In the fully open condition of the swing check valve, the fluid pressure is almost unimpeded, so the pressure drop across the valve is relatively small. The valve flap of the lift check valve is located on the valve seat sealing surface of the valve body. In addition to the valve flap being free to lift and lower, the valve is like a shut-off valve. The fluid pressure causes the valve flap to lift from the valve seat sealing surface. The return of the medium causes the valve flap to fall back to the valve seat and shut off the flow. Depending on the conditions of use, the flap may be of an all-metal construction or may be in the form of a rubber or rubber ring on the valve disc holder. Like the shut-off 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 that of the swing check valve, and the flow rate of the swing check valve is limited. Very few.

Select valve according to adjusting medium parameters

In the production process, in order to make the pressure, flow and other parameters of the medium meet the requirements of the process flow, it is necessary to install an adjustment mechanism to adjust the above parameters. The main working principle of the adjustment mechanism is to adjust the flow area between the valve flap and the valve flap and the valve seat to achieve the purpose of adjusting the above parameters. These valves are collectively referred to as control valves, which are divided into self-driven control valves such as pressure reducing valves and pressure regulators that are driven by the medium itself. Where ling is first driven by power (such as electricity, compressed air and Hydraulic power is called his drive control valve, such as electric control valve, pneumatic control valve and hydraulic control valve.