Heat is an inevitable byproduct of hydraulic operation. When power is converted into force through any means, some of that energy is always lost as heat. You see this everywhere. From the smartphone in your pocket, to your refrigerator, which generates heat as a byproduct while keeping the interior cool.
A hydraulic system also converts energy into heat during operation and the heating of hydraulic fluid is increased by inefficiencies. Inefficiencies can arise when a cylinder is not fit for the application - such as a slow jacking cylinder used in a high repetition, high duty cycle application. Normal wear also leads to increased friction and poor operation, which decreases efficiency. That's why well-designed and well-maintained hydraulic systems don't generally get too hot. But the less efficient and the worse their condition, the more heat is generated.
High heat has several detrimental effects on a hydraulic system that is not designed to cope with it, but in this article we'll focus on one of the most important aspects. The detrimental effects of heat on hydraulic oil.
Higher heat equals lower oil viscosity.
You may assume that oil is oil and can withstand extreme temperatures. After all, oil is present in internal combustion engines and survives at high temperature for thousands of running hours. However, this is not the case for all oils for a simple reason. Oil viscosity changes with temperature. At high temperates, oil becomes thinner. This is important because hydraulic oil is also responsible for lubrication within a hydraulic system. Oil with lower viscosity has poor lubricating properties and after a certain point it is no longer capable of protecting reciprocating parts. So, the hotter the oil, the more chance you have of experiencing accelerated mechanical wear. Which means you'll be replacing pumps and cylinders more often.
Increased heat leads to increased oxidation.
Oxidation is a chemical reaction that occurs when air is present in a hydraulic system. Oxidation is one of the primary causes for decreasing the stability of hydraulic fluid and causes oil to turn dark and become contaminated. The chemical reaction results in the formation of acids that can increase the fluid viscosity, and cause corrosion, lead to gumming, varnish and lead to sluggish operation. The worst part is that for every 10 degrees increase in temperature, the rate of this chemical reaction doubles. So the hotter the oil, the faster the rate of oxidation.
Protect your equipment. Prolong your hydraulic oil life.
The bottom line is that too much heat has a dramatic effect on the lifespan of your hydraulic oil and poor maintenance, which leads to inefficiencies, leads to heat. This has a cascading effect on your entire system. In other words, if you fail to fix a component when it starts to get abnormally hot, you will likely increase the wear on other parts of your hydraulic system and you'll be replacing more components in short order.