Hydraulic motor case temperature
At the latest my project I used hydraulic motor Rexroth A2FLM710 (710cc). The motor works at 1400 rpm and provides 590 HP to the consumer. For safe motor work, I always try to keep the case temperature below 80*C. The easiest way to do this is a flushing flow adjustment.
In addition to the flow, you need to keep your eyes on the motor case pressure and try balancing to prevent overpressure in the motor case (check in the motor manufacturer’s catalog the max available case pressure to make longer life of motor shaft seals).
The values I have gotten: 21 GPM at 30 psi case pressure and in the worst-case scenario (max motor load, warm hydraulic oil) max case temperature was around 80*C
Hydraulic motor case flushing flow and case pressure
There are no prescriptions or recommendations for valve or orifice size in motor catalogs for flushing flow, so the selection of flushing valves is a challenge.
Of course, you can find orifices (with different diameters) provided by the manufacturer with the motor in the motor’s catalog. But the flow and result case temperature will be different from application to application and the selection of the correct orifice is an engineering responsibility without any help or advice from the motor manufacturer.
Moreover, the manufacturer can’t provide all range of orifice diameters so the selection in the catalog is usually limited. And as you can see, sometimes values of flushing flow can be really huge and the only experience helps me to select the right flushing valve size at the beginning of the project.
I still believe, manufacturers can provide some diagrams/charts with correlation “power -> flushing flow” for approximate/preliminary estimation of the flushing valve size. Because I do not think everyone has a chance to make long tests during production and play with valves sizes…
What do you think?