Q: How do I prevent or fix high fluid temperature?
A: High fluid temperature can be caused by anything that either reduces the system’s capacity to dissipate heat or increases its heat load. This includes an excessive workload, a high duty cycle and/or a failed or worn component with internal leakage.
Hydraulic systems dissipate heat through the reservoir and heat exchanger if equipped, so the reservoir fluid level should be monitored. Also check for obstructions to airflow around the reservoir, such as a buildup of dirt or debris. Keep the reservoir clean for proper heat dissipation.
Inspect the heat exchanger to ensure the core is not blocked. The heat exchanger’s ability to dissipate heat is dependent on the flow rate of the hydraulic fluid and the cooling air passing through the exchanger. All cooling circuit components and heat-generating components should be checked and replaced as necessary.
Installing a fluid temperature alarm in your hydraulic system can alert you to problems.
High fluid temperature can result when any component has abnormal internal leakage that increases the heat load on the system, such as when a cylinder leaks high-pressure fluid past its piston seal. A hand-held infrared thermometer or thermal camera can be used to identify components that have internal leakage. While in operation, failed or worn components will show higher temperatures than other components in the system. A common source of excessive heat due to internal leakage is an undersized or overused pressure relief valve.
Q: What causes slow operation?
A: In a hydraulic system, fluid flow determines actuator speed and response. A loss of speed indicates a loss of flow at the point of use.
Loss of flow in a hydraulic circuit can be caused by an external or internal leak. External leaks are typically easy to find, such as a burst hose. Internal leaks are more difficult to pinpoint, since they can occur in the pump, valves or actuators.
For slow operation when a load is applied, it’s always good to verify adjustable settings in the hydraulic system. For systems with variable displacement pumps, it is common for a pump-mounted pressure compensator to reduce flow at a set pressure. Since the pressure compensator reduces flow at the set pressure, the set pressure should be verified. Pressure relief valves are another common component that can cause reduced flow. When relief valve set pressures are too close to system operating pressures, it can cause internal leakage and slow operation. For systems with both variable displacement pressure compensating pumps and pressure relief valves, the pressure relief valve should be set a few hundred psi higher than the pump pressure compensator to prevent excessive operation of the relief valve.
Because internal leakage influences heat load, the issues of high fluid temperature and slow operation often occur together. Fluid temperature increases result in a decrease in viscosity, which in turn causes internal leakage to increase. That causes the heat load — and fluid temperatures — to increase even more.
Maintaining the correct fluid level, using proper filtration and repairing any leaks are the first line of defense against excessive heat and contamination. Using the correct, high-quality fluid is also important.
Troubleshooting hydraulic system problems
Keeping your machine maintained and running smoothly helps you avoid component failure — and ensure you have the hydraulic power you need for critical jobs. Following these best practices can help keep your hydraulic system operating reliably and in top performance.
Now that you’ve gotten some hydraulic system tips, read this article to learn more about troubleshooting common performance and maintenance issues with pneumatic tools.