To control the hydraulic system of the hydraulic support of the coal mine, control the opening and locking of the upper and lower cavities of the hydraulic support dome. Generally, the safety valve installed or no safety valve installed, according to the requirements of the dry jacket working resistance management, two safety valves can also be installed. Mainly used to control premature stratospheric delamination of the coal wall, at the same time to achieve the connection of the first and second protective panels, avoiding from behind the hook of the second protection caused by the tear of the roof pipe. Specifications Rated flow rate: 125 L/min Rated pressure: 50 MPa Material: medium carbon/stainless steel/1 Cr18Ni9