Plug valve is a type of quick opening and closing straight through valve. Due to the wiping effect of the movement between the sealing surfaces, it can completely prevent contact with the flowing medium when fully opened. Therefore, it is usually used for media with suspended particles. Another important feature of a plug valve is its ease of adapting to multi-channel structures, allowing one valve to obtain two, three, or even four different flow channels. This can simplify the design of pipeline systems, reduce the number of valves used, and minimize the need for some connecting accessories in equipment.

2working principle

A valve with a plug body with a through-hole as the opening and closing component. The plug body rotates with the valve stem to achieve opening and closing actions. Small unfilled plug valves, also known as“Cork”The plug body of a plug valve is mostly conical (or cylindrical), which cooperates with the conical hole surface of the valve body to form a sealing pair. Plug valve is the earliest type of valve used, with a simple structure, quick opening and closing, and low fluid resistance. Ordinary plug valves rely on direct contact between the precision machined metal plug body and the valve body for sealing, so the sealing performance is poor, the opening and closing force is large, and it is easy to wear. It is usually only used for low pressure (not higher than)1Megapascals) and small-diameter (less than)100In the case of millimeters.

3purpose

Plug valves are widely used in oil field extraction, transportation, and refining equipment, as well as in the petrochemical, chemical, coal gas, natural gas, liquefied petroleum gas, HVAC industries, and general industries.

4classification

Plug valves are classified according to their uses, including soft sealed plug valves, oil lubricated hard sealed plug valves, lift plug valves, three-way and four-way plug valves.

Soft seal

Soft sealed plug valves are commonly used in harsh environments such as corrosive, highly toxic, and hazardous media, where leakage is strictly prohibited, and where valve materials do not contaminate the media. The valve body can be made of carbon steel, alloy steel, and stainless steel materials according to the working medium.

A.It can be used according to the operating temperature and working mediumF4、F46、PVDF、PP、PO、PEWhen the self-lubricating material lining is well lubricated, the friction coefficient of the sealing pair is small throughout the entire working process, the plug body operates flexibly, and the service life is long.

B.The design of the inlet and outlet windows of the valve body and the double groove sealing ring structure. During the rotation of the plug, the sealing pressure between the sealing pairs gradually changes until it reaches the fully open or fully closed position, generating sufficient sealing pressure and achieving zero leakage of the sealing pairs.

C.The double groove sealing ring can not only stabilize the liner inside the valve body without displacement, but also absorb the slight deformation of the liner caused by temperature differences. At the same time, there is strong friction between the liner and the plug, which has an automatic cleaning effect and improves the service life of the sealing surface.

D.The unique anti lip sealing design at the top of the plunger uses a combination of soft sealing material diaphragm and metal diaphragm with adjusting gasket to adjust the sealing pressure between the sealing surfaces, making the plug rotate flexibly and ensuring the sealing of the inlet and outlet ends and the middle flange connection end.

E.Suitable for high erosion gas-solid. Liquid solid phase medium. asPVCIn production facilities for urea, acetic anhydride, and caustic soda, or with high medium requirements for external leakage, such asHF,Phosgene, etc.

F.The medium can flow in both directions, and the installation direction is not restricted, enabling online maintenance and making it more convenient to use

G.The unique design can prevent static electricity, ensure fire safety, and ensure safe use.

Oil lubricated hard seal

Oil lubricated hard seal plug valves can be divided into conventional oil lubricated plug valves and pressure balanced plug valves. Specially made lubricating grease is injected from the top of the plug body into the space between the valve body taper hole and the plug body, forming an oil film to reduce the valve opening and closing torque, improve sealing performance and service life. Its work pressure can reach64MPaThe maximum working temperature can reach325Degree, the maximum caliber can reach600mm.

1Conventional oil lubrication plug valve

A.The installation method of the plug cone for conventional hard sealed plug valves is formal installation. In order to reduce the friction between the valve body and the sealing surface of the plug, valves generally use a sealing structure with a grease lubricated valve seat. The high-pressure sealing oil injected from the high-pressure oil nozzle forms a high-pressure sealing ring around the plug, that is, there is a layer of oil film between the valve body and the cone sealing surface of the plug, which can be both sealed and lubricated, making it easy to open and close.

B.In order to further reduce the opening and closing force of the plug valve, the method of reducing the plug diameter is usually adopted. Therefore, the plug valve usually adopts a rectangular flow channel. This method not only reduces the opening and closing torque of the plug valve, but also increases the fluid resistance of the plug valve

C.Welding of sealing part of plug coneSTLAlloy materials or surface hardening technology are used to enhance the wear resistance and corrosion resistance of the sealing surface, resulting in a long service life

D.The surface of the plug cone is finely ground to a mirror finish, and the sealing surface of the valve body is ground to have a lower opening and closing torque.

2Pressure balanced plug valve

In order to reduce the torque of conventional hard sealed plug valves, pressure balanced plug valves are often used. In addition to the characteristics of conventional oil lubricated plug valves, pressure balanced plug valves also have the following features:

A.The installation method of the plug cone of the pressure balanced plug valve is inverted. There is a check valve on the upper part of the plug cone.

When the valve is closed, due to the difference in cross-sectional area between the upper and lower parts of the plug cone, the injected high-pressure sealing oil exerts an upward lifting force on the plug body, enabling better sealing between the plug body and the valve sealing surface.

B.At the moment of valve opening, the pressure in the lower chamber of the valve body is balanced with the medium pressure in the pipeline. The high-pressure sealing oil in the upper chamber exerts a downward thrust on the plug body, causing a small gap between the plug cone and the sealing surface of the valve body. The torque when rotating the plug body will be effectively reduced. It can also protect the sealing pair.

C.Under high temperature conditions, the thermal expansion of the plug can be absorbed by its lifting and lowering, avoiding the sealing pair from wedging.

Oil lubricated hard sealed plug valves, although using oil lubrication can reduce the opening and closing torque appropriately, may also contaminate the medium. Therefore, choose sealing lubricating oil for actual working conditions.