Symptom: unstable pressure fluctuations Failure Analysis: 1, oil mixed with air. 2, damping holes are sometimes blocked. 3, slide valve and valve body hole roundness exceeds the provisions of the valve stuck. 4, the spring deformation or stuck in the spool valve, the spool valve movement difficult or too soft. 5, the ball is not round, ball and valve seat is not good or cone valve is not installed correctly. Remedy: 1, remove the oil in the air. 2, clean the orifice. 3, repair valve hole and slide valve. 4, replace the spring. 5, replace the ball or open the cone valve adjustment. Pressure reducing valve Symptom: Secondary pressure rise is not high Failure Analysis: 1, external leakage. 2, cone valve seat and poor contact. Remedy: 1, replace the seals, tighten the screws, and to ensure that the torque evenly. 2, repair or replacement. Pressure reducing valve failure phenomenon: can not afford the role of decompression Failure Analysis: 1, the drain is blocked; drain pipe connected to the return pipe, and back to the oil pressure. 2, the main spool in the fully open position card. Remedy: 1, the drain pipe must be separate from the oil return pipe, separate back into the tank. 2, repair, replacement parts, check the oil.