Standard proportional relief valves RPEC-8DN with pilot stage RBAP have a limited pressure range. Gravity also affects the setting of standard proportional relief valves. The two circuits show a proportional reducing valve to pilot operate a CBV. The combination provides an alternative pressure relief function.
- Vented counterbalance: CW**
- Proportional pressure-reducing/relieving: PR*L
Benefits of this circuit arrangement
- Fig.1 shows a proportional pressure-reducing valve controlling the pressure in the vent port of a counterbalance valve. The pressure in the vent port is additive to the setting by a factor of the pilot ratio plus one. A controlled pressure of 1000 psi will increase the setting of a 5:1 counterbalance valve by 6 times 1000 psi. The solenoid tube of the pressure control valve sees max 1000 psi, not the resulting 6000 psi setting, therefore a safety margin is maintained.
- Fig.2 shows a shows a proportional pressure-reducing valve controlling the pressure on the pilot line of the counterbalance valve. The control pressure reduces the setting by a factor based on the pilot ratio. The setting of a CW*G-LGN set at 6000 psi with a pilot ratio of 5:1 can be reduced to a minimum pressure by a pilot pressure of 1200 psi. So the CW*G is fully open. The circuit requires a separate source of 1200 psi.
- Both circuit incorporate a reverse free-flow check.
