What is a check valve?

Check valve, also known as check valve, check valve, counterflow valve, back pressure valve and isolation valve, is an automatic valve, its main function is to prevent media backflow, protect the pump and drive motor from reverse damage, and prevent the leakage of container media. The working principle of the check valve is mainly based on the automatic opening and closing of the valve disc. When the fluid flows in the predetermined direction, the valve disc is opened by the fluid pressure to allow the fluid to pass through; When the fluid flows in the opposite direction, the valve disc will close under the action of the fluid pressure and its own gravity, preventing the fluid from flowing back.

First, the classification of check valves

Check valves can be divided into the following types according to their structure and mode of movement:

1. Swing check valve: the disc is connected with the valve body through the hinge mechanism and can rotate freely. When the fluid is flowing forward, the valve disc rotates around the hinge mechanism under the action of fluid pressure; When the fluid flows in the opposite direction, the valve disc will rotate around the hinge mechanism under the action of fluid pressure and its own gravity. Swing check valve according to the number of valves can also be divided into single valve, double valve and multi-valve, suitable for different caliber pipelines.

2. Lift check valve: the disc moves up and down along the axis. When the fluid is flowing forward, the valve disc is lifted by the fluid pressure to open the channel; When the fluid flows in reverse, the valve disc is lowered under the action of the fluid pressure and its own gravity, closing the channel. Lift check valves are usually installed on horizontal pipes, but there are also special designs for vertical installation.

3. Butterfly check valve: the disc rotates around the pin in the seat. The butterfly check valve has a simple structure, but the tightness is relatively poor, and is usually installed on the horizontal pipe.

4. Pipe check valve: the disc slides along the center line of the valve body. This valve is small in size, light in weight and good in processing technology, and is one of the development directions of check valves. However, the fluid resistance coefficient is slightly larger than that of the swing check valve.

Second, the application field of check valve

The application field of check valves is very wide, covering almost all the areas that need to prevent media backflow. Here are some of the main application scenarios:

1. Family life: prevent sewage or hot water backflow in the water supply and drainage system to protect equipment from damage; Make sure water flows in one direction in household appliances such as dishwashers and washing machines.

2. Industrial production: in chemical, petroleum, metallurgy and other industries to prevent corrosive, flammable and explosive characteristics of the media backflow, protect equipment safety, to ensure the smooth progress of the production process.

3. Hvac system: Ensure that hot water and heating can only flow in one direction to avoid energy waste and equipment damage caused by reverse flow of cooling water.

4. Gas system: prevent gas backflow to ensure user safety.

5. In the field of new energy: in the use of renewable energy such as solar energy and wind energy, to prevent the backflow of the medium and protect the safety of the equipment.

6. Environmental protection: Prevent the backflow of harmful substances in environmental protection projects such as sewage treatment and waste incineration to protect the environment and human health.

Third, check valve selection and installation precautions

When choosing a check valve, you need to consider the nature of the fluid, working pressure, temperature, flow control needs, and installation environment. At the same time, the following matters should also be noted during installation and use:

1. Pay attention to the direction of the medium flow: ensure that the direction of the medium flow is consistent with the direction of the arrow marked on the valve body.

2. Correct installation position: the lifting vertical flap check valve should be installed on the vertical pipe, and the lifting horizontal flap check valve should be installed on the horizontal pipe.

3. Avoid bearing weight: Do not let the check valve bear weight in the pipeline system, and the large check valve should be independently supported.

4. Regular maintenance inspection: Check the working status of the check valve regularly to ensure that the valve disc can be freely opened and closed to prevent valve failure due to impurities blockage or wear and other reasons.

To sum up, the check valve is an important fluid control device that plays an indispensable role in a variety of industrial and life scenarios. Through reasonable selection and correct installation of the check valve, the safe operation of the pipeline system and the smooth flow of the medium can be ensured.