Function and principle of plug valve

Function and principle of plug valve:

Plugvalve: the plug body with a through hole is used as the valve for opening and closing parts. The plug body rotates with the stem to realize the opening and closing action. Small packless plug valves are also known as "cocks". Plug valve plug body for the cone (also have cylinder), and the body of the cone hole surface to form a sealing pair. The plug valve, the structure is simple, the switch is quick, the fluid resistance is small. Ordinary plug valve depends on the metal plug body and the body of the direct contact to seal, so poor sealing, opening and closing force, easy to wear, usually can only be used for low (no more than 1 mpa) and small diameter (less than 100 mm) occasions. In order to enlarge the application range of the plug valve, many new structures have been developed. Oil lubricated two - way all - copper plug valve is an important type of z. Special grease is injected from the top of the plug body into the body between the cone and the plug body to form an oil film to reduce the opening and closing torque and improve the sealing performance and service life. Its working pressure can reach 64 mpa,z high working temperature can reach 325℃,z large diameter can reach 600 mm. Access to plug valves comes in many forms. The common straight-through form is mainly used to cut off the fluid. Three-way and four-way plug valves are suitable for the fluid reversing plug valve opening and closing parts are a cylindrical body with holes, around the axis perpendicular to the channel, so as to achieve the purpose of opening and closing the channel. The plug valve is mainly used for opening and closing pipelines and equipment media.

The main advantages of the plug valve are as follows:

1. It is suitable for frequent operation, quick opening and closing, and portable. 2. Low fluid resistance. 3, simple structure, relatively small volume, light weight, easy maintenance. 4, good sealing performance 5, not limited by the installation direction, the flow of media can be arbitrary. 6. No vibration, low noise.

According to its structure, the plug valve can be divided into four types: compact type plug valve, self-sealing type plug valve, packing type plug valve and oil injection type plug valve. According to the channel form, it can be divided into three types: straight-through, three-way and four-way. Cock valve - valve type and purpose a cock valve is a valve in which the closing member (plug) rotates around the centerline of the body to open and close. The plug valve is mainly used for cutting off, distributing and changing the flow direction of the medium in the pipeline.

Due to the simple structure of the plug valve, open and close quickly (the plug can be completed by rotating a quarter of a circle), easy to operate, small fluid resistance, is still widely used. At present, it is mainly used for low pressure, small diameter and medium temperature. Plug valve plug and plug body is a well - matched cone, its taper is generally 1:6 and 1:7.

One, two through the copper core plug valve two through the copper core plug valve is usually used for low-pressure straight pipe, sealing performance depends entirely on the plug and plug body of the good or bad fit, its sealing surface pressure is achieved by tightening the nut at the bottom. Generally used for PN≤ 0.6mpa.

Two, two - way cast iron plug valve two - way cast iron plug valve is through compression packing to achieve the sealing of the plug and plug body. As a result of the packing, so the sealing performance is better. Usually they have a packing gland and the plug does not extend out of the body, thus reducing the leakage path of a working medium. This plug valve is widely used for PN≤1Mpa pressure.

Three, two - way all copper plug valve two - way all copper plug valve is through the pressure of the medium itself to achieve the pressure between the plug and plug body tightly sealed. The small head of the plug is extended upward out of the body, and the medium enters the big head of the plug through a small hole at the entrance, and the plug is pressed upward. This structure is generally used for air medium.

Four, three - way all copper plug valve in recent years, the application of the expanding scope of the plug valve, the emergence of three - way all copper plug valve with forced lubrication. A film of oil is formed between the plug and the sealing surface of the plug body due to forced lubrication. In this way, the sealing performance is better, opening and closing labor saving, to prevent damage to the sealing surface.