What Is a Stopcock?

A plug valve is a closing piece or a plunger-shaped rotary valve. By rotating 90 degrees, the passage opening on the valve plug is communicated with or separated from the passage opening on the valve body to realize opening or closing.

The plug valve is ^[1]

Use the plug with through hole as the valve of the opening and closing member. Plug body with ^[2]

According to the structure, it can be divided into four types: tight stopcock, self-sealing stopcock, stopcock and oil injection stopcock. According to the channel form, it can be divided into three types: straight plug valve, three plug valve and four plug valve. There are also card-type plug valves.

Plug valves are classified according to use: soft-sealed plug valves, oil-lubricated hard-sealed plug valves, poppet plug valves, three-way and four-way plug valves.

1. The plug valve is used for frequent operations, and can be opened and closed quickly and easily.

2. Small fluid resistance of the plug valve.

3. The plug valve has a simple structure, relatively small volume, light weight and easy maintenance.

4. Good sealing performance.

5. It is not restricted by the installation direction, and the flow direction of the medium can be arbitrary.

6. No vibration and low noise.

There are many forms. Common straight-through is mainly used to cut off fluid. ^[5]

When installing the plug valve, in order to prevent damage to the plug valve and ensure the full performance of the plug valve, the following four points should be noted:

1. Make sure the valve is open. Heat the pipes first. Transfer as much heat as possible from the pipe to the plug valve. Avoid prolonging the heating time of the plug valve itself.

2. Use gauze or wire brush to remove pipes and cutting parts, and make their metal surfaces glow. It is not recommended to use steel wool.

3. First cut the pipe along the vertical direction, trim and remove the burr, and measure the pipe diameter.

4. Apply flux to the outside of the pipe and the inside of the welding cover. The flux must completely cover the welding surface. Use flux sparingly.

According to the structural characteristics of the plug valve and the functions that can be achieved in design, it can be selected according to the following principles.

It is used to distribute the medium and change the flow direction of the medium. Its working temperature is not higher than 300 , the nominal pressure is PN1.6MPa, and the nominal diameter is not greater than 300mm. It is recommended to use a multi-channel plug valve.

On the equipment and pipes of food enterprises such as milk, juice, beer, and pharmaceutical factories, it is recommended to use austenitic stainless steel, tight-type conical plug valves.

In oil field exploitation, natural gas field exploitation, pipeline conveying branch pipe, refining and cleaning equipment, the nominal pressure level is not greater than Class300 and the nominal diameter is not greater than 300mm. It is recommended to use oil-sealed conical plug valve.

In oil field extraction, natural gas extraction, pipeline branching, refining and cleaning equipment, the nominal pressure level is not greater than Class7500, the nominal diameter is not greater than 900mm, and the operating temperature is not higher than 340 ° C. It is recommended to use oil-sealed conical plug valves.

In the large-scale chemical industry, where pipes and equipment containing corrosive media are required to be opened or closed quickly, polytetrafluoroethylene sleeve-sealed conical plug valves can be used for nitric acid-based media; For acetic acid-based medium, Crl8Nil 2M02Ti stainless steel inlaid with Teflon sleeve can be used to seal the conical plug valve.

On the pipeline neutralization equipment of gas, natural gas, and HVAC systems, the nominal diameter is not greater than 200nm, and a packing-type conical plug valve should be used.