On the list of the most common causes of hydraulic equipment failure, overheating ranks at number two. Unfortunately, the general understanding about how to identify and address overheating issues is all too often misunderstood.
Overheating’s main cause is the general inefficiency of the system. Any inefficiency will cause input power to be lost. These losses undergo a conversion to heat, which is important, as the total power lost is equal to a system’s heat load. If heat dissipates at a rate that’s less than the total input power lost, overheating will eventually occur.
Target Temperature for Seal Damage
The compounds that hydraulic seals and o-rings are made of become damaged when the temperature of hydraulic fluid rises above 82°C. Hydraulic oil also begins to degrade at this point. However, it’s important to concentrate on the viscosity of fluid, as this will tell you when fluid temperature is too high. When fluid viscosity is below its optimum for the components it’s being used for, this is when failure occurs, and it can happen at temperatures far below the 82°C mark. This makes it crucial to ensure temperature stable temperature.
Achieving a Stable Temperature
The way to achieve stability with hydraulic fluid temperature is to ensure that the rate at which the system dissipates heat is higher than its heat load. To do this effectively, one must look at the cooling capacity of the system, and then ensure measures are taken to exceed that capacity.
How to Solve Overheating
The increase in dissipation of heat or the decrease in heat load are the only two ways to solve the problem of overheating in hydraulic systems.
Concentrate on the Reservoir
The reservoir is where systems dissipate heat. Checking this location’s level of fluid and then filling it to the proper level can solve overheating. Another thing to check is that airflow around the reservoir is able to occur unobstructed by debris or dirt.
Look at the Core
Core blocking in the heat exchanger can be another problem area. The heat exchanger should be inspected for blockages in the core. As well, the temperature and flow rate of both the hydraulic fluid and the water or air used to cool it should be checked, as should all components in the circuit used for cooling. If deficiencies are found, replacing these components can address overheating issues.
The performance of heat exchangers can be checked using an infrared thermometer, as long as the flow rate of the hydraulic fluid passing through it is a known value.
Heat Increases due to Drop in Pressure
Heat is the result when pressure drops. Drops in pressure occur when system components are leaking internally or abnormally. And these leaks will increase system heat load. Heat generation can occur as the result of a relief valve that hasn’t been properly adjusted, or a piston seal which is allowing high-pressure fluid from the cylinder. Items like this need to be monitored, identified and then adjusted or replaced.
Checking Relief Valve Settings
Inside closed centre circuits, heat can be generated when the relief valve has been set too close to or below the setting of the pressure compensator on the variable-displacement pump. When this is the case, system pressure cannot reach the pressure compensator’s settings, which causes the pump to continue to produce flow. Flow generates heat when it passes over the relief valve.
This problem can be prevented by ensuring the relief valve is set at 250 PSI above the pressure compensator setting.
Any overheating detected in a hydraulic system should be addressed by first shutting it down, and then finding the cause and addressing it. Not doing so will only guarantee that damage will be done.