Hydraulic oil that is too thick at start-up can restrict the pump inlet; oil that becomes too thin during hot operation may reduce lubrication and increase internal leakage. The correct grade is therefore chosen from the component makers’ viscosity limits across the machine’s real temperature range.
Use operating viscosity, not only the ISO VG label
An ISO viscosity grade describes a reference-temperature property, not the viscosity at every working point. Plot the fluid supplier’s viscosity-temperature data against the pump, valve and motor requirements. Parker’s pump catalog specifically warns against selecting oil so heavy at start-up that it promotes cavitation. Its recommended values apply to the named pump family; a different component can have a different optimum range.
Technische Prüfungen
- Record minimum ambient and oil temperature before starting.
- Measure steady-state tank and component case temperatures at heavy duty.
- Check pump inlet pressure with cold oil and the selected suction arrangement.
- Confirm seal and hose compatibility with the chosen fluid.
- Account for future fluid changes and mixing controls.
Häufiger Fehler, den es zu vermeiden gilt
Selecting a thicker oil solely to reduce hot leakage can create a cold-start problem. Conversely, choosing a thin oil for easy starting may leave hot components outside their lubrication range.
Angaben, die einer Anfrage beizufügen sind
- All component viscosity limits and fluid approvals.
- Temperature history for start-up and peak-duty periods.
- Desired warm-up procedure.
- Sampling and oil-condition monitoring plan.
Use measured temperatures and the fluid maker’s viscosity curve to confirm that one grade works across the full duty cycle. For related selection guidance, see our hydraulic pump cavitation guide.
Technische Hinweise: Parker PGP/PGM pump fluid recommendations; Parker hydraulic fluids and viscosity data. Titelbild: ursprüngliche Konzeptskizze, kein Produktfoto.