Hydraulic control valves are generally divided into diaphragm type and piston type. Both of them work in the same principle. Hydraulic control valves are driven by the pressure difference between upstream and downstream (P). The hydraulic differential operation of diaphragm (piston) is controlled by a guide valve, which can be automatically adjusted by hydraulic force, so that the main valve disc is fully opened or closed, or in a state of regulation. It is composed of a main valve (shown in Fig. 1 and 2) and its external needle valve, guide valve, conduit and pressure gauge. It evolves into a remote control floating ball valve, pressure reducing valve, slow-closing check valve, flow control valve, pressure relief/pressure holding valve, hydraulic electric control valve, water level control valve, pump control valve/emergency shut-off valve, etc. in accordance with different purposes, functions and places of use.