HH49 micro-retardant closed butterfly check valve is suitable for clean water, sewage, seawater and other media pipelines with a nominal pressure of 1 MPa and a medium temperature of ≤ 80%, as well as water supply and drainage pressurized pump sets. Through the unique micro-retardant closing device of this butterfly check valve, it can effectively prevent the occurrence of water hammer and ensure the safe operation of the pipeline system.