A check valve, also known as a check valve, one-way valve, reflux valve, or isolation valve, is a type of valve that automatically opens and closes the valve disc based on the flow of the medium itself to prevent the medium from flowing back. The working principle of a check valve is that when the medium flows in from the inlet end, the valve disc is pushed open by the pressure of the medium, allowing the medium to flow; When the medium flows back, the valve disc closes under the dual action of its own weight and the pressure of the backflow medium, preventing the medium from flowing back.

Check valves can be classified into various types based on their structure and working principle, mainly including:
Lift check valve: The valve disc slides along the vertical centerline of the valve body, suitable for scenarios with smaller diameters and lower pressures.
Swing check valve: The valve disc rotates around the shaft and is suitable for large diameters and low flow rates. It has good sealing performance and low fluid resistance.
Butterfly check valve: The valve disc is disc-shaped and rotates around the central axis of the valve seat, with a simple structure and low flow resistance.
Diaphragm check valve: Especially suitable for pipelines that are prone to water hammer, its diaphragm can effectively eliminate water hammer caused by medium backflow.
Spherical check valve: suitable for medium and low pressure pipelines, and can be made into large diameters. The shell material can be stainless steel, and the sealing element is polytetrafluoroethylene engineering plastic.

Preventing medium backflow: The main function of a check valve is to prevent medium backflow in pipelines or equipment, protecting the system from the influence of reverse pressure.
Quick opening and closing: The valve disc of the check valve can quickly open and close, ensuring the normal flow direction of the fluid.
Good sealing performance: The sealing components of check valves are usually made of materials such as rubber and polytetrafluoroethylene, which have good sealing performance.
Wide applicability: Check valves can be used for various fluid media and temperature ranges, meeting the needs of different working conditions.

Check valves are widely used in various industrial and daily life scenarios, and are key components to ensure the safe operation of systems. For example:
Oil and gas pipeline systems: prevent the backflow of liquids or gases, protect pipeline systems, and prevent explosion risks.
Chemical production process: effectively prevent the reflux of media and prevent corrosive substances from damaging equipment.
Urban water supply and drainage systems: prevent backflow of tap water and sewage, ensure clean water quality and stable operation of drainage systems.
Seasonal drainage: prevent floods from flowing into the urban drainage system and reduce the risk of urban waterlogging.

Installation precautions:
Ensure that the direction of medium flow is consistent with the direction indicated by the arrow on the valve body.
Large check valves should be independently supported to avoid bearing pressure from the pipeline system.
Lift type vertical flap check valves should be installed on vertical pipelines, and horizontal flap check valves should be installed on horizontal pipelines.
Avoid direct connection with other valves to reduce potential damage to check valves.
Maintenance and upkeep:
Regularly check the working condition of the check valve, including the wear of components such as the valve seat, disc, and stem.
Regularly clean the surface and internal components of the check valve to remove dust, dirt, and other impurities.
Regularly replace the seals to ensure the sealing performance of the valve.
Regularly apply rust proof oil or grease in damp environments to prevent valve rusting.