The relief valve protects pump, motor and machine structure: never set it above the value specified for the circuit and the pump. Too high a setting can burst hoses, fittings or cylinders. Setting changes must be made by qualified personnel, with a gauge connected to the circuit.
From force to pressure, from speed to flow
The force the cylinder must exert, divided by the piston area, gives the working pressure: it is the first number of the configuration and sets the relief valve. The speed of the movement, multiplied by the piston area, gives the flow: it is the second number and sets the pump displacement. Everything else follows from these two.
| Input | What it sets |
|---|---|
| Required force | Working pressure and relief valve setting |
| Movement speed | Flow, hence pump displacement |
| Duty cycle | Motor type: AC S1 duty or DC S3 duty |
| Available voltage | AC 230/400V or DC 12/24V motor |
| Cylinder oil volume | Reservoir capacity |
| Control functions | Solenoid valves and modular elements on the manifold |
From duty cycle to motor
Required power is estimated as P(kW) ≈ pressure(bar) × flow(l/min) / 600 / efficiency. But power alone is not enough: continuous operation calls for an AC motor in S1 duty; short bursts (a liftgate, a dump body) only need a DC motor in intermittent S3 duty, smaller and cheaper. Getting the duty wrong is worse than getting the power wrong.
Reservoir and controls
The reservoir must hold the oil displaced by the cylinders plus a reserve (see the dedicated sizing guide). Control functions (single or double acting, controlled lowering, pressure holding) translate into the choice of solenoid valves and modular elements on the manifold. This is where a custom configuration beats a catalogue product.
What are the most common mistakes?
The three mistakes we see most often in the configurations we have prepared since 1998: oversizing the motor "to be safe" (costs more and runs hotter), undersizing the reservoir (overheating and foaming), and forgetting protections (relief valve not set for the real application). Our online configurator avoids all three; for non-standard cases, a technical quote is free.
Up to 230 bar continuous, peaks above 250 bar
More displacement means more flow but a lower maximum pressure: high pressures come from small displacements.
| Pump | Displacement (cm³/rev) | Max continuous pressure |
|---|---|---|
| Group 1, single pump PA | 0.9 to 2.6 | 210 bar |
| Group 1, single pump PA | 3.2 to 4.2 | 190 bar |
| Group 1, single pump PA | 4.8 to 5.8 | 170 bar |
| Group 1, single pump PA | 8.0 | 160 bar |
| Group 1, single pump PA | 9.8 | 130 bar |
| Group 1, reversible pump PR | 1.1 to 2.7 | 230 bar |
| Group 1, reversible pump PR | 3.2 to 4.2 | 210 bar |
| Group 1, reversible pump PR | 4.8 to 5.8 | 190 bar |
| Group 1, reversible pump PR | 8.0 | 160 bar |
| Group 0.5 | 0.88 and 1 | 230 bar |
What the customer needs is force, not pressure. A Ø50 cylinder at 210 bar pushes about 41 kN (just over 4 tonnes); a Ø63 cylinder gives the same force at 130 bar, about 40 kN. When you need both force and speed, the cylinder bore is the lever.