Hydraulic Power Unit Components

A complete HPU includes: pump, electric motor, reservoir, relief valve, filter, cooler, and accessories. Each must be sized to match system requirements.

Pump Sizing

Displacement = (Q x 1000) / (RPM x Efficiency)

Select pump type based on pressure and performance needs: gear (simple), vane (quiet), piston (high pressure).

Motor Sizing

Power (kW) = (Q x P) / (600 x Eff_pump x Eff_motor)

Add 10-15% margin for starting and peak loads.

Reservoir Sizing Rules

• Continuous duty: 3-4 x pump flow (GPM) in gallons
• Intermittent: 2-3 x pump flow
• High heat: 4-5 x pump flow

Cooler Sizing

Required when heat generation exceeds natural dissipation:

Cooler capacity = Heat load - Natural cooling

Natural cooling ~ 6-8 W per m2 reservoir surface per C above ambient.

Filter Sizing

Size return filter for 2x pump flow. Pressure filter sized for system flow.