How hot is “HOT OIL”?

The question that I have been asked over and over again by participants in training session & customers is – How hot is “HOT OIL”, in a hydraulic system?

The heat production is due to inefficiencies in system. Though most of the energy consumed by a machine is used to do useful work, a part of the energy gets converted into heat. If the rate of heat buildup is larger than the heat dissipation capacity to the ambient air by natural radiation, the oil will start heating up. If this heat is not managed properly, the temperature of the oil & the equipment keeps increasing till it overheats, causing irreparable damage, which in turn reduces the efficiency further. The end result is increased power consumption, reduced equipment life, break downs & increased maintenance cost.

This brings us to the question of the right oil temperature. For this we should refer to specifications of hydraulic components installed in the hydraulic power unit. For reference a page from the Yuken elements catalogue is attached below:

It may be noted that all components are tolerant of Hydraulic fluid temperatures of 60C. Temperatures above this will result in accelerated damage to internal parts. Increase in temperatures beyond 80C will also result in irreversible damage to seals. At such high temperatures the viscosity of the oil also reduces drastically resulting in increased internal & external leakages, which in turn result in rapid heat production & further drop in efficiencies.

To achieve a stable oil temperature, a well-designed hydraulic system must have the capability to dissipate heat in access of the heat buildup. As a rule of thumb 70% of the installed motor capacity.Not treated properly this has a cascading affect as the machines over heat, causing increased wear & tear, which in turn leads to higher energy consumption, increased maintenance & reduced equipment life.

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