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| Illustration 1 | g01042405 |
(1) Inlet passage (2) Valve (3) Passage to tank (4) Spring (5) Locknut (6) Adjusting screw (7) Port (8) Passage to tank (9) Valve | |
The main relief valve is located in the inlet section of the bank valve. Refer to Specifications, "Relief Valve (Main)" for the pressure settings of the main relief valve.
The relief valve is a direct acting valve. Pressure oil flows into passage (1). The oil acts against the right side of valve (2) which is held closed by the force of spring (4) .
When an outside force causes pressure in any of the cylinders to rise, that increase in pressure is also felt in passage (1). As the pressure rises above the valve setting, the oil overcomes the force of spring (4) and the oil causes valve (2) to move left. Oil flows through port (7) through passage (8) to the tank. The oil flow through port (7) causes a pressure drop to the left of valve (2). This pressure drop causes valve (9) to shift to the left because system pressure is acting against valve (9) .
Hydraulic oil in the inlet manifold flows past valve (9) and through passages (3) back to the hydraulic tank.
Since the relief valve is allowing oil to travel to the tank, the oil pressure in the cylinders cannot increase. When the oil pressure goes below the setting of the relief valve, spring (4) moves valve (2) back to the left onto the valve seat. Valve (9) shifts to the right.
The relief valve pressure setting is adjusted by removing the cap, loosening locknut (5) and turning adjusting screw (6). Adjusting screw (6) can be turned clockwise in order to increase the pressure setting of the relief valve. Adjusting screw (6) can be turned counterclockwise in order to decrease the pressure setting of the relief valve.