Selection and application of common valves I. Gate VALVE SELECTION Application gate valve is used as a cut-off medium, the entire flow through the full open, at this time the pressure loss of medium operation is minimal. Gate valves are generally applicable to work conditions that do not require frequent opening and closing, and which keep the gate fully open or closed. Not suitable for use as an adjustment or throttling. For the high-speed flow of the medium, the gate in the local opening conditions can cause the vibration of the gate, and vibration may damage the gate and the seat of the sealing surface, and throttling will make the gate under the media erosion. From the structural form, the main difference is the form of the sealing element used. According to the form of sealing elements, the gate valve is often divided into several different types, such as: wedge-type gate valve, parallel gate valve, parallel double gate gate valve, wedge-type double gate gate and so on.

The most commonly used forms are wedge-type gate valves and parallel gate valves.

Ii. selection and application of cut-off valve The stem axis of the globe valve is perpendicular to the seat sealing surface.

The valve stem opening or closing stroke is relatively short, and has a very reliable cut-off action, the valve is very suitable as a medium for cutting off or adjustment and throttling use.

Once the valve flap of the globe valve is in the open condition, the valve seat and the disc sealing face are no longer contacted, the valve is very suitable for cutting or regulating and throttling use as medium. Once the globe valve is in the open state, there is no contact between the seat and the disc seal surface. Therefore, its sealing surface is less mechanical wear, because most of the valve seat and disc valve is easier to repair or replace the sealing elements without the entire valve from the pipeline removed, the door and pipeline welding into one of the occasions is very applicable.

The flow direction of the medium through this type of valve changed, the force is higher than other valves.

The common cut-off valves are as follows:

1 angle stop valve; In the angle-type globe valve, the fluid only needs to be changed in one direction so that the pressure drop through the valve is smaller than the conventional cut-off valve.

2 DC type globe valve; In the DC-type or Y-shaped globe valve, the valve body of the flow channel and the main line into a diagonal, so that the flow of the state of damage than the conventional cut-off valve to smaller, and thus through the valve pressure loss is correspondingly small. 3 Plunger type globe valve: This form of cut-off valve is a conventional cut-off valve variant. In this valve, the disc and seat are usually designed based on the plunger principle.

The disc-polished plunger is connected with the stem, and the seal is realized by two elastic seals that are set in the plunger.

A ring is separated and the sealing ring around the plunger is pressed through the load exerted on the bonnet by the bonnet nut.

Made of various materials, the valve is mainly used for "open" or "off", but it is provided with a specially formed plunger or special sleeve ring, which can also be used to regulate the flow rate.

Iii. selection and application of ball valve The ball valve is evolved from a plug valve. It has the same rotational 90-degree lifting motion, and the difference is that the plug body is a sphere with a circular through hole or passage through its axis.

The ratio of spherical and channel ports should be the same, that is, when the ball rotates 90 degrees, at the inlet and outlet should all render the spherical surface, thus truncating the flow. The ball valve can be closed strictly with a rotating 90-degree operation and a small rotational torque. The fully equal valve body cavity provides a small, straight flow channel for the medium. Ball valves are generally considered to be the most suitable for open and closed use, but the recent development of the ball valve has been designed so that it has throttling and control flow. Ball valve is characterized by its compact structure, easy operation and maintenance, applicable to water, solvents, so that the valve cut-off valve for the flow resistance of two elastic seals with acid and natural gas and other general work and has a very reliable cut dynamic elastic seal ring can be replaced.