Siristar News

What is a plug valve?

The plug valve is a valve whose opening and closing member (plug) is driven by the valve stem and rotates around the axis of the valve stem.

The plug valve is the first type of valve used by people to shut off flow. The opening and closing of the valve are completed by rotating 90 ° to connect or disconnect the passage port on the plug and the passage port on the valve body.

The plug valve is most suitable for shutting off the medium and dividing the flow. However, according to the nature of use and the erosion resistance of the sealing surface, it can be used in throttling conditions through special structural design and changing the shape of the channel of the plug. Because the movement between the sealing surfaces of the plug valve has a wiping effect, and can completely prevent contact with the flowing medium at the full start, it can usually also be used for medium with suspended particles.

The characteristics and structure of the plug valve

One: the advantages and disadvantages of the plug valve

(1) Advantages of plug valve

①Simple structure, few parts, small size and light weight.

②The fluid resistance is small. When the medium flows through the plug valve, the fluid channel can not be reduced or changed, so the fluid resistance is small.

③ It opens and closes quickly, and the flow direction of the medium is not restricted. It is very convenient to open and close by simply rotating the plug by 90°.

(2) Disadvantages of plug valve

①The opening and closing torque is large. Between the plug valve body and the plug, the contact sealing surface is large, so the opening and closing torque is large. If a lubricated structure is used, or the plug can be lifted first when opening and closing, the opening and closing torque can be greatly reduced.

②The sealing surface is a conical surface, which is large and easy to wear; It is easy to deform and get stuck at high temperature.

③Conical surface processing (grinding) is difficult, it is difficult to ensure sealing, and it is not easy to maintain. However, if the oil seal structure is adopted, the sealing performance can be improved.

Two: the structure of the plug valve

The structure of the plug valve is simple, mainly composed of the valve body, the plug and the packing gland and other components. A simple plug valve does not even have a packing gland and packing, only a valve body and a plug.

(1) Valve body

The valve body of the plug valve has the form of straight-through, three-way and four-way. The straight-through plug valve is used to cut off the medium, and the valve body has a straight line inlet and outlet channels. Three-way and four-way plug valves are used to change the direction of media flow or for media distribution. The valve body of the plug valve is all cast . The plug channel of the three-way plug valve is L-shaped or T-shaped, and the L-shaped channel has three distribution forms. There are four distribution forms for the T-channel. There are four channels on the valve body of the four-way plug valve, and there are three distribution forms.

(2) Plug

The plug is the opening and closing part of the plug valve, which is cylindrical or conical. Cylindrical plug have a rectangular or circular channel section, and conical plug have a rectangular, trapezoidal or circular channel section. These shapes make the structure of the plug valve compact and lightweight, but cause a certain pressure drop. If the shape of the channel of the plug is appropriately changed, the plug valve can be used as a flow control valve, and a good adjustment accuracy can be obtained.

The plug of the plug valve can be integrated with the valve stem, the top of the plug is machined with a square head, and the wrench can be put on to open and close.

The sealing surface of the plug and the valve body must be in close contact to achieve the purpose of sealing. Therefore, the machining accuracy of the geometric dimensions of the valve body and the sealing surface of the plug is very high, and the surface roughness level is also very high, so that they can cooperate well.

For the conical plug valve, in order to ensure the sealing, the force must be applied along the axis of the plug to press the plug on the valve body, so as to form a certain sealing pressure between the sealing surfaces of the mesh body to achieve sealing.