Beat The Heat: 3 Reasons You Might Experience High Fluid Temperature

When hydraulic fluids and lubricants are exposed to high temperatures for extended periods of time, the fluids will begin to experience permanent deterioration and a major reduction in viscosity.

The reduced viscosity can render lubricants and hydraulic oil useless when it comes to protecting components through reducing friction, preventing abrasive damage, and minimizing the speed of wear. Depending on pressure and temperature, some fluids may eventually reach a vapor state, leading to damaged systems and components.

Since heat can be so damaging to a hydraulic system, it is important to track down the cause of high fluid temperature.

High friction

Heat generation commonly results from fluid flowing from an area of high pressure to an area of low pressure without any output of mechanical work. High friction in the system will generate heat, and sources can include:

• Fluid passing through a constricting orifice or restriction at high speed
• Fluid flowing through a restricted passage
• Components that have been improperly lubricated
• Use of a fluid with too high or too low viscosity for the system
• Pressure activated piston seals

Obstructions

Other sources of heat can include the compression of aerated fluids, which occurs when the hydraulic fluid is contaminated with air. The compression of aerated fluid within a pump can quickly lead to temperatures of over 1000c.

High fluid temperature can also 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, 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 needs to be monitored. It’s also important to check for obstructions to airflow around the reservoir, such as a build up of dirt or debris (keeping the reservoir clean is crucial for proper heat dissipation).

The heat exchanger requires regular inspection to ensure the core is not blocked. It’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. 

Leaks

High fluid temperature can also result when any component has abnormal internal leakage that increases the heat load on the system, for example when a cylinder leaks high-pressure fluid past its piston seal. Another common source of excessive heat due to internal leakage is an undersized or overused pressure relief valve.

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.

How hot is too hot?

Hydraulic fluid temperatures above 82°C (180°F) can damage most seal compounds and accelerate degradation of the oil. While the operation of any hydraulic system at temperatures above 82°C should be avoided, fluid temperature is too high when viscosity falls below the optimum value for the hydraulic system’s components. This can occur well below 82°C, depending on the fluid’s viscosity grade.

Beat the Heat

There are typically two ways to solve overheating problems in hydraulic systems: decrease heat load or increase heat dissipation. This can be accomplished by following some essential troubleshooting of the hydraulic system:

• Check that there are no obstructions to airflow around the reservoir, such as a build up of dirt or debris.
• Inspect the heat exchanger and ensure that the core is not blocked (the ability of the heat exchanger to dissipate heat is dependent on the flow-rate and temperature of both the hydraulic fluid and the cooling air or water circulating through the exchanger).
• Check the performance of all cooling circuit components, and replace as necessary.
• Hydraulic systems dissipate heat through the reservoir, therefore it is important to monitor the reservoir fluid level and if low, fill to the correct level.
• Install a fluid temperature alarm in your hydraulic system to provide alerts for potential problems.

At Hydraulic Distributors our engineers are highly experienced in troubleshooting hydraulic equipment across numerous industries, including marine hydraulics, earthmoving equipment, transport hydraulics, mining hydraulics and more. Please contact us today to arrange a consulation on-site or at our workshop in Riverstone, NSW.