Types, Characteristics and Selection Principles of Plug Valves

Ⅰ. Plug valves types

1. Fastening plug valves

The fastening set plug valves are usually used for low-pressure straight pipe. The sealing performance completely depends on the fit between the plug and the plug body. The compression of its sealing surface depends on tightening the nut at the lower part. Generally used for PN ≤ 0.6Mpa.

2. Packing plug valves

The packing plug valves provided by many valve suppliers realize the sealing of the plug and the plug body by compressing the packing. Due to the packing, the sealing performance is good. Usually, this plug valve has a packing gland, and the plug does not extend out of the valve body, thus reducing the leakage path of a working medium. This plug valve is widely used for the pressure of PN ≤ 1Mpa.

3. Self-sealing plug valves

As one of plug valves types, the self-sealing plug valves realize the compression seal between the plug and the plug body through the pressure of the medium itself. The small end of the plug extends upward out of the body, and the medium enters the big end of the plug through the small hole at the inlet to compress the plug upward. This structure is generally used for air medium.

4. Oil seal plug valves

In recent years, the application scope of plug valves have been expanding, and oil seal plug valves with forced lubrication have appeared. Due to forced lubrication, an oil film is formed between the sealing surface of the plug and the plug body. In this way, the sealing performance is better, the opening and closing is labor-saving, and the sealing surface is prevented from being damaged.

Ⅱ. The structural characteristics of plug valves

1. The plug valves have the advantages of direct flow, small resistance, convenient and rapid opening and closing.

2. Plug valves are mainly used to cut off, upgrade and change the medium flow direction in the pipeline. The plug valves are easy to adapt to the multi-channel structure, so that one valve can obtain two, three or even four different flow channels, which can simplify the design of the pipeline system and reduce the consumption of valves and some connecting accessories required in the equipment.

3. Plug valve is the earliest valve used by people in history. Due to its simple structure, rapid opening and closing, the opening and closing action can be completed by rotating the plug 1/4 circle, convenient operation and low fluid resistance, it is still widely used today. Plug valves are mainly used under low pressure, small diameter and low medium temperature.

Ⅲ. The selection principles of plug valves

1. It is used to distribute medium and change medium flow direction. Its working temperature is not higher than 300℃, nominal pressure PN≤1.6MPa and nominal diameter is not greater than 300mm. It is recommended to select multi-channel plug valves.

2. On the equipment and pipelines of food enterprises such as milk, fruit juice and beer and pharmaceutical factories, it is recommended to select fastening conical plug valves made of austenitic stainless steel.

3. In oil field production, natural gas field production, branch pipe of pipeline transportation, refining and cleaning equipment, the nominal pressure level shall not be greater than class300 and the nominal diameter shall not be greater than 300mm. It is recommended to select oil sealed conical plug valves.

4. In oil field production, natural gas field production, branch pipe of pipeline transportation, refining and cleaning equipment, the nominal pressure level shall not be greater than class7500, the nominal diameter shall not be greater than 900mm, and the working temperature shall not be higher than 340℃. It is recommended to select oil sealed conical plug valves.

5. In the large-scale chemical industry, in the pipeline and equipment containing corrosive medium, where the opening or closing speed is required to be fast, the PTFE sleeve sealed conical plug valves can be selected for the medium based on nitric acid; For the medium based on acetic acid, Crl8Nil 2M02Ti stainless steel with PTFE sleeve can be selected to seal the conical plug valves.

6. In the pipeline and equipment of gas, natural gas and HVAC system, the nominal diameter shall not be greater than 200nm, and the packing conical plug valves shall be selected.

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