Last week we ended by noting heat build up is minimal as we use nearly all of our input horsepower to perform a work function. Using power to perform work does not appreciably add to system heat. Hydraulic oil flow under pressure consumed as a leak through a worn pump or motor, passing over a relief valve, pressure drop through hoses and fittings, or through a compensator valve will add heat directly in proportion to the pressure drop and flow loss inherent in the complete system.
In addition to the efficient use of pressurized oil, a large hydraulic oil sump is included in our systems. This allows for additional dwell time in the sump which enhances natural cooling and dissipation of any air entrained within the oil.
These and other design criteria allow us to eliminate the need for an oil cooler, including its direct and installation cost thereby reducing the price of the machine to our customers.
Perhaps the most important reason is eliminating the need for a machine owner to clean out a chaff/dirt filled oil cooler to keep the oil cool. If the system stays cool naturally, you will not experience a “cooked” hydraulic system that needs high cost replacement parts.
How do you know if a hydraulic system is over heated. I have observed operators say it is so hot I can’t touch it, and it may be hot, but is it too hot. An old rule of thumb says that up to 15 Degrees F. over ambient is acceptable. This equates to about 225 Degrees in most climes.
When you consider that 140/145 Degrees F. is scalding, and will blister your skin, touching is probably not an accurate test or a safe practice.
Continued next week.