Mobile Systems Create Unique Reservoir Design Challenges
Due to space and weight constraints in most mobile systems, traditional reservoir design “rules of thumb” – such as sizing reservoir volume at 3x pump flow – are simply impractical. Small reservoirs are the standard, and that can cause headaches.
One big issue with smaller, low volume-to-flow ratios in mobile reservoirs is that the dwell time of the hydraulic fluid in the reservoir is so short. Less time in the reservoir translates to less time for entrained air to naturally dissipate…and entrained air in hydraulic fluid can cause a whole host of problems.
- Reduced Stiffness – Because of the compressibility of entrained air, the system is not as stiff. I have personally witnessed a loss of hydraulic steering due to this phenomenon.
- Cavitation – Once the free air bubbles reach the pressure side of the pump, they collapse. This can damage the local componentry and destroy hydraulic fluid because it generates high temperatures.
- Reduced Lubrication – The presence of air can reduce the lubrication properties of hydraulic fluids.
- Power Loss – It takes power to compress air bubbles during cavitation.
As I discuss in my video, Eaton’s “cyclone” reservoir deals very well with the problem of aeration in mobile systems. The reservoir is best suited to systems that do not have large differential volume cylinders; some examples would be steering circuits and fan drive circuits. Eaton’s current design works with flows of up to 18 GPM.
The reservoir works by introducing return flow tangentially back into the cylindrical reservoir so that as the fluid is accelerated around the interior of the reservoir, air bubbles are forced to the center and are dissipated. The unit has the additional advantage of forcing high velocity flow toward the suction port of the reservoir, reducing the likelihood of cavitation in the system.
Thanks for taking the time to watch my video and if you have any questions, please don’t hesitate to contact me.