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| Illustration 1 | g00577810 |
Main relief valve in the inlet manifold | |
The main relief valve is located in the inlet manifold. The inlet manifold is attached to the bottom of the control valve stack.
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| Illustration 2 | g00512611 |
Main relief valve (1) Nut (2) Spring (3) Valve (4) Inlet passage (5) Drain passages (6) Setscrew | |
The main relief valve is a directly operated valve. Since the setting of the main relief valve is above all of the operating pressures, the valve serves as a backup valve. The main relief valve limits the increases (spikes) in pump pressure.
Note: The main relief valve is not capable of handling full pump flow.
Pump oil flows through passage (4) to valve (3). Spring (2) keeps valve (3) closed when the oil pressure is less than the setting of the relief valve.
When the oil pressure increases to the setting of the relief valve, valve (3) opens. The oil in passage (4) flows around valve (3). The oil flows through drain passages (5) to the tank. The pump pressure can not exceed the setting of the main relief valve.
The compressed length of spring (2) determines the force that is applied by spring (2) to valve (3). An increase or a decrease in the force that is applied by spring (2) changes the pressure setting of the relief valve.
Loosen nut (1) and turn setscrew (6) clockwise in order to increase the pressure setting. Loosen nut (1) and turn setscrew (6) counterclockwise in order to decrease the pressure setting.
The pressure setting is specified in the following table. The test was completed at a temperature of 49° ± 3°C (120° ± 5°F).
| Pressure and Flow | ||
| Pressure | Flow | |
| Inlet | Outlet | Inlet |
42000 ± 400 kPa (6090 ± 60 psi) |
70 ± 7 kPa (10 ± 1 psi) |
5 ± 1 L/min (1.3 ± 0.3 US gpm) |