What are your options when faced with a hydraulic system that is overheating? Assuming the system's cooling circuit is working as it should, i.e. no faults, then my standard answer, and the only correct one, is there are only two possible options:
- reduce heat load on the system; or
- increase heat dissipation from the system.
Anything you can do to alleviate the problem will fall into one of the above two categories. For example, you can reduce the load (power draw) on the system. This should reduce internal leakage and therefore reduce the heat load on the system. You can set up an electric fan to circulate air around the reservoir - to increase heat dissipation. You can change out any components with abnormal internal leakage - to reduce heat load. You can bite the bullet and install a bigger heat exchanger - to increase heat dissipation... or you can get yourself a tin of spray paint. Eh? Yup, a tin a spray paint. Let me explain.
Painting bare metal surfaces can reduce the reflectance and increase the emissivity of an object, enabling better heat rejection. And in some situations, this may just be enough to tip the balance in order to maintain hydraulic system operating temperature within acceptable limits. Consider this case-study which was published in H&P magazine:
An industrial hydraulic installation was originally designed to operate at 1200 PSI and at a maximum operating temperature of 120°F (49°C). Zinc-coated steel tube distributes fluid from the 600 liter reservoir to the various stations around the plant. Over the years the system had been added to (without any increase in installed cooling capacity) to the point were it was now overheating in the summer months.
Because the system operated satisfactorily for 10 months of the year, management did not want to spend the money necessary to upgrade the cooling system. So one of the maintenance guys on staff, who was familiar with the theory of thermal radiation, suggested painting the hydraulic system's extensive network of tubing.
Before proceeding, the maintenance team did a test. They applied electrical tape to two of the hydraulic lines, and using an infrared camera, they measured the difference in temperature between the taped and un-taped areas. They found the taped areas on the tubes were 7°F (4°C) cooler than the un-taped areas.
This gave the maintenance team the confidence to proceed with the idea. Because the rest of the hydraulic system was painted flat white, the tubing was painted the same color. And the result? A week and 12 cans of spray paint later the system was running 10°F (5.5°C) cooler. This might not sound like much, but the end result meant that the hydraulic system could now operate through the two hottest months of the year without overheating. It also meant the need to increase installed cooling capacity was at least deferred, if not eliminated.
This was a good result for the maintenance department. Because allowing a hydraulic system to operate while overheated is a costly mistake. And to discover six other mistakes you want to be sure to avoid with your hydraulic equipment, get "Six Costly Mistakes Most Hydraulics Users Make... And How You Can Avoid Them!" available for FREE download here.