In your last hydraulics bulletin, we discussed what causes a hydraulic system to overheat. Today I want to explain a technique that is very useful when you’re troubleshooting a system that’s overheating. This technique involves using an infrared thermometer – sometimes called a heat gun, to measure the oil’s temperature drop across the heat exchanger. The heat rejection of the exchanger can then be calculated and when this is expressed as a percentage of input power, it will reveal whether the problem is in the cooling circuit or elsewhere in the system. The exact procedure for doing this is explained in detail on pages 103 – 104 of The Hydraulic Troubleshooting Handbook

Installed cooling capacity typically ranges between 25 and 40 percent of input power. So if a system has a continuous input power of 100 kilowatts and the exchanger is dissipating 26 kilowatts of heat, this means the efficiency of the system has fallen below 74 percent. If the system is overheating, this is a good indication that there is abnormal heat load somewhere in the system. On the other hand, if a system has a continuous input power of 100 kilowatts and the exchanger is dissipating 10 kilowatts of heat and the system is overheating, this means that there’s a problem somewhere in the cooling circuit or the system does not have enough installed cooling capacity. In your next hydraulics bulletin in a few days time, I’ll explain how to locate this abnormal heat load.

Yours for better hydraulics knowledge,
Brendan Casey