Circulating lubrication: design & calculation (flow, cooling, filter)

At the Circulating lubrication The correct design determines stability and service life: flow for the desired Cooling performance, matching Filter fineness and reliable Sensors.

1) Derive flow from cooling capacity

Rule of thumb: Thermal output P → mass flow ṁ = P / (c · ΔT). The oil density ρ results in volume flow Q = ṁ / ρ.

Example: P = 6 kW, ΔT = 10 K, oil c ≈ 1.9 kJ/kgK, ρ ≈ 850 kg/m³ → Q ≈ 22.3 L/min.

2) Filtration & Cleanliness

• Select the filter fineness to match the bearing/gap size (e.g. 10–25 µm)
• Pressure maintaining valve/bypass prevents cavitation risks
• Plan for a clogging indicator and differential pressure sensor

3) Sensors & monitoring

• Pressure (flow/return), temperature (tank/flow), flow per circuit
• Messages/alarms in PLC/HMI with trends

4) Medium & Viscosity

• viscosity according to operating temperature; sufficient film & pump window
• Monitor oil condition (aging/particles/water)

Checklist

1. Define heat output ΔT → calculate Q
2. Set filter fineness & bypass
3. Select sensors/signals (OK/Warning/Alarm)
4. Determine oil choice & service plan (filter change/oil change).

Components: Pumps & aggregates · filter · Advice