It is mounted on the pressure line of the hydraulic system and is used to remove or stop the mechanical impurities mixed into the hydraulic oil and the Gum, pitch, carbon residue, etc. produced by the hydraulic chemical reaction itself, prevent the valve core jam, throttle hole, gap and damping hole plug and hydraulic components too fast wear, and other failures. The dropper is equipped with a pressure difference transmitter. When the temperature core is blocked by pollution to the pressure difference of the oil inlet and outlet is 0.35 MPA, the switch signal is sent out. The leakage core should be cleaned or replaced to ensure the safety of the system.