The check valve is one of the valve components for air compressors. Its function is to prevent lubricating oil from being injected into the oil‑gas separator through the oil‑return pipe during system‑pressure release after the air compressor stops running, which would otherwise increase the oil content in output air upon compressor restart.

The check valve prevents gas backflow into the air compressor and the resulting series of equipment problems, as detailed below:

Ⅰ. Gas backflow will cause loaded‑start fault. Excessive internal machine pressure during start‑up leads to heavy‑duty motor starting with extremely high starting current, and imposes severe impact on transmission components. Quality‑grade machines are generally equipped with this type of protective function.

Ⅱ. In multi‑compressor systems, water may fill the oil‑gas separator tank and render the unit unable to start normally.

Ⅲ. Since the unloading valve of most air compressors stays open under shutdown conditions, gas backflow will also result in energy loss.

Check‑valve maintenance includes cleaning the valve core, gaskets and other parts, and replacing damaged components.