Working principle and characteristics of check valve

A check valve is a valve that automatically opens and closes the valve disc by the flow of the medium itself to prevent the medium from flowing back. It is also called a check valve, a one-way valve, a reverse flow valve or a back pressure valve. The following is a detailed introduction:

一、Working principle

The check valve relies on the weight of the opening and closing parts (valve disc) and the medium pressure to achieve automatic opening and closing. When the medium flows in from the inlet end and flows out from the outlet end, the valve disc opens under the action of the medium pressure; when the inlet pressure is less than the sum of the weight of the valve disc and its flow resistance, the valve closes to prevent the medium from flowing back.

二、Types and structural characteristics

1. Lifting check valve:

Structure: The valve disc slides along the vertical center line of the valve body, which is similar to the stop valve structure, but lacks the valve stem that drives the valve disc.

Features: Simple structure, large fluid resistance coefficient, suitable for horizontal pipeline installation. The valve disc can be a full metal structure or in the form of a rubber pad or rubber ring embedded in the valve disc frame.

Application: Suitable for small-diameter, high-pressure pipeline systems, such as steam pipelines, hydraulic systems, and high-purity fluid pipelines in the chemical and pharmaceutical industries.

2. Swing check valve:

Structure: The valve disc rotates around the pin outside the valve seat.

Features: Low fluid resistance and low pressure loss; flexible installation, can be installed horizontally, vertically or tilted.

Application: Suitable for large-diameter pipelines, such as water treatment systems, oil and gas industries, and boiler water supply systems in the power industry.

3. Butterfly check valve:

Structure: The butterfly structure is adopted, and the valve disc controls the closing speed through a spring or buffer mechanism.

Features: Compact structure, small fluid resistance, and slow closing design can effectively reduce water hammer impact.

Application: Suitable for large flow, low pressure, and large-diameter systems, such as water supply networks, fire protection systems, and industrial circulating water systems.

4. Double-plate check valve:

Structure: It consists of two symmetrical semicircular discs, and the valve disc opens to both sides under the action of fluid pressure.

Features: Compact structure, light weight, small fluid resistance, and spring-assisted closing can reduce water hammer effect.

Application: Suitable for large-caliber, high-flow occasions, such as municipal water supply systems, seawater desalination equipment, chemical and metallurgical industries.

5. Ball check valve:

Structure: The valve disc is spherical, and the one-way flow of the fluid is controlled by the movement of the ball.

Features: Simple structure, good sealing performance, suitable for small and medium-caliber pipes.

Application: Commonly used in pipes with liquid media such as water and oil.

三、 Application scenarios

1. Industrial field:

Chemical industry: Prevent corrosive or high-viscosity fluids from flowing back and protect equipment safety.

Oil and gas industry: Transport high-temperature and high-pressure media to prevent fluid backflow in the pipeline system.

Power industry: Boiler water supply system, prevent water hammer phenomenon, and ensure stable operation of the system.

2. Water treatment system:

Water supply system: Prevent water hammer phenomenon and protect water pumps and pipes.

Sewage treatment plant: Prevent sewage backflow and avoid pollution spread.

3. Civil field:

Household water system: Prevent water backflow and protect household water safety.

4. Special uses:

Desalination equipment: prevent seawater backflow and protect equipment from corrosion.

Air compressor: prevent gas backflow and improve system efficiency.