In various industrial pipeline systems such as water supply and drainage, petrochemical, electric power and fire fighting, medium backflow will cause pump damage, equipment shutdown, medium pollution and even safety accidents. As an automatic check valve, swing check valve is the key equipment for pipeline backflow prevention, and is often called flap check valve and check valve in the industry.

The swing check valve is mainly composed of the valve body, bonnet, rocker, pin roll and disc valve disc. The valve disc is suspended in the valve body by the hinge rocker, which can rotate and swing around the pin roll. There is no need for electric and pneumatic actuators, and the automatic opening and closing can be realized completely by the medium pressure. It is a self-operated valve. When the medium flows forward, the fluid pressure pushes the valve clack to rotate outward, the channel opens and the medium passes through smoothly; Once the pipeline stops pumping or the pressure reverses, the valve clack will quickly fall back under the combined action of its own gravity and the return medium pressure, compress the valve seat, block the reverse flow of the medium and realize one-way flow protection.

Swing check valves can be divided into single-flap, double-flap and multi-flap types according to the structure of valve clack. Single-disk swing check valve is the mainstream valve in the market, with large diameter and smooth flow passage, which is suitable for DN50 and above large-diameter pipelines; Two-flap, multi-flap construction for medium calibre, fast shutoff response and reduced water hammer impact. The sealing form is divided into metal hard seal and rubber soft seal: the hard seal is resistant to high temperature and high pressure and is suitable for steam, oil and high temperature process medium; Soft seal has good sealing performance and is mostly used for clean water and sewage medium at normal temperature.

Compared with lift check valve, swing check valve has the following advantages: full bore, small fluid resistance and low pressure loss, so it is very suitable for large-diameter trunk pipeline. Flexible installation mode, priority shall be given to horizontal pipes, and vertical pipes can also be fitted. However, the product also has inherent limitations: closing relying on its own weight, closing speed is slow, and frequent start and stop of pipeline media is easy to produce water hammer impact; The inner hinge pin shaft is worn, which is not suitable for containing a large amount of solid particles and high-viscosity media, which easily causes the hinge to be clamped and affects the sealing and action reliability.

Therefore, it is necessary to regularly maintain the pin roll and the valve clack sealing surface, check the wear condition, and timely clean the impurities deposited in the valve body to extend the service life of the valve.

In international trade engineering projects, swing check valves have become one of the preferred valves for one-way protection of overseas fluid projects due to their stability, reliability, outstanding cost performance, and support of multi-standard customization.