PC200-6 Main Relief Valve Safety Relief Valve

The core function of the main safety valve of the Komatsu PC200 - 6 excavator is to limit the system pressure and prevent abnormal pressure increase. When the excavator encounters sudden situations during operation, such as a sudden increase in digging resistance, causing the hydraulic system pressure to exceed the normal range, the main safety valve acts quickly. It can prevent damage to expensive and precise hydraulic components such as the hydraulic pump, hydraulic cylinder, and distribution valve due to excessive pressure, thereby ensuring the stable and reliable operation of the entire hydraulic system, extending the service life of the equipment, and reducing maintenance costs and downtime.

Working Principle
The main safety valve of the PC200 - 6 is generally of a pilot-operated structure. During normal operation, when the system pressure is lower than the set value of the main safety valve, the main valve core remains closed under the force of the spring, and the hydraulic oil flows normally through the various working components of the system. When the system pressure rises and reaches the opening pressure of the pilot valve, the pilot valve opens first, and a small amount of hydraulic oil enters the control chamber of the main valve core through the pilot valve, generating a pressure sufficient to overcome the spring force of the main valve core and push it open. A large amount of hydraulic oil then flows back to the tank through the main valve's overflow port, rapidly reducing the system pressure. When the system pressure drops below the closing pressure of the pilot valve, the pilot valve closes, and the oil pressure in the control chamber of the main valve core decreases. The main valve core returns to the closed position under the force of the spring, and the hydraulic system resumes normal working pressure.

Common Faults and Solutions

Insufficient pressure: This may be due to severe wear of the main safety valve core, resulting in a decline in sealing performance and causing hydraulic oil leakage and overflow at a relatively low pressure. The wear of the valve core should be checked. If the wear is minor, it can be repaired by grinding; if the wear is severe, a new valve core should be replaced. Additionally, if the spring is fatigued or broken, preventing it from maintaining the normal opening pressure, it will also cause insufficient pressure. In this case, a high-quality spring of the same specification should be replaced.

Excessive pressure: The common cause is that the main valve core is stuck by foreign objects and cannot open for overflow normally. The safety valve should be disassembled, and the valve core and valve seat should be carefully cleaned to remove the foreign objects. Another possible reason is that the adjusting screw of the pilot valve is loose, causing the opening pressure of the pilot valve to increase and subsequently leading to an excessively high opening pressure of the main safety valve. The adjusting screw of the pilot valve should be readjusted to set the opening pressure to the specified value and then tightened.

Large pressure fluctuations: If the damping hole of the pilot valve is blocked, the control pressure of the pilot valve will be unstable, causing the main safety valve to open and close frequently and resulting in pressure fluctuations in the system. The damping hole should be cleaned to ensure it is unobstructed. Additionally, if air is mixed into the system, it can also cause pressure fluctuations. This can be resolved by setting an exhaust valve at the high point of the system and performing an exhaust operation.