The check valve, also known as non-return valve, is generally used between several or dozens of drill pipes. Its function is to ensure that the flushing fluid can be smoothly transferred to the bottom of the hole through the inner hole of the drill pipe in the process of drilling, but cannot be returned to the hole through the inner hole of the drill pipe, that is, to ensure the one-way flow of the flushing medium and prevent the reverse flow.

Check valves include ordinary check valve and wireline check valve. The ordinary check valve is used for ordinary rotary drilling, and it can ensure the one-way flow of washing medium to the hole bottom. The wireline check valve is used in directional drilling construction, and the internal cable device is set up. It not only ensures the one-way flow of washing medium, but also transmits the hole bottom signal through the wireline device inside the check valve.