EDGE-SEGMENT 1957192 - Caterpillar

Relief Valve (Line )
Closed
Illustration 1 g01293683
Closed position of the relief valve (1) Locknut (2) Adjustment screw (3) Passage to the tank (4) Port to the rod end of the cylinder (5) Passage (6) ValveThe line relief valve is a pilot type valve.The function of the line relief valve protects the cylinders and the lines from high pressures.The line relief valve for the head end and the line relief valve for the rod end are direct operating valves. Both valves operate in the same manner.This oil acts against valve (6). If the oil pressure for the circuit is less than the setting for the line relief valve, the force of spring will hold valve (6) in the closed position.When the force from the pressure in passages (4) and (5) is more than the force of spring, valve (6) moves into the open operation.Open
Illustration 2 g01293683
Closed position of the relief valve (1) Locknut (2) Adjustment screw (3) Passage to the tank (4) Port to the rod end of the cylinder (5) Passage (6) ValveIn the open position, valve (6) moves upward. This opens a path to tank passage (3). Oil flows past valve (6) as the valve opens. The oil flows through passage (3) to the hydraulic tank.Valve (6) remains open, if the pressure of the oil that is in port (4) is above the setting for the line relief valve. In the open position, the line relief valve prevents a rise in pressure that is above the setting of the line relief valve.Makeup Valve Operation
Illustration 3 g01293683
Closed position of the relief valve (1) Locknut (2) Adjustment screw (3) Passage to the tank (4) Port to the rod end of the cylinder (5) Passage (6) ValveThe function of the makeup valve of the line relief valve helps prevent cavitation of the cylinder.Cavitation of the cylinder can occur, when the oil pressure of the pump that flows to the cylinder through port (4) is lower than return oil pressure. If pump oil pressure is lower than return oil pressure, the pump oil that flows through passage (5) is a lower pressure than the pressure of the return oil.The return oil causes valve (6) to move upward because return oil pressure is higher than pump oil pressure. Pressure is maintained in the tank line at 690 kPa (100 psi). The pressure is maintained because of a back pressure check valve in the tank line.When valve (6) moves upward, the valve opens. The return oil pressure that is higher can flow past valve (6) into work port (4). This return oil mixes with pump oil in order to help prevent cavitation of the cylinder.