16 Nov

This article focuses on the common problems associated with hydraulic systems and how these issues can affect individual components as well as the systems themselves. It gives an in-depth insight into how problems initially develop, any knock on effects and how failures can happen if the issue isn’t diagnosed correctly.

Abnormally high fluid temperatures

High fluid temperatures are usually caused when the system struggles to correctly dissipate heat and can lead to increased heat load. When fluid temperatures exceed 180°F (82°C), this can lead to damage to the seals and in turn start to degrade the fluid itself.

When viscosity levels drop below optimal values for the system components, the fluid temperature is judged to be too high and the reservoir should be checked for any obstructions or blockages.

The heat exchanger is another component that should be checked making sure the core is not blocked. In order for the heat exchanger to successfully dissipate heat, the flow rate of both the hydraulic fluid and cooling air/water should be at the correct levels.

When fluid circulates to areas of differing pressures without correct pressure correction, excess heat can be generated and any areas that show signs of internal leakage can increase the heat load on the system. This includes anything from a leaking cylinder to an incorrectly adjusted relief valve.

High fluid temperatures can also have an effect of components as they go through a thinning process which affects the oil film, otherwise known as a low viscosity which leads to inadequate lubrication. This issue can be tackled by setting up a fluid temperature alarm to warn of dangerously high temperatures.

Poor operation

When a machine starts to show signs of reduced performance and functionality this points to a problem with the hydraulic system. A loss of speed in the system is usually caused by a poor flow rate and can be noted when the system takes longer to cycle or is slow in its general operation.

Leakage is a common cause of slow operating speeds as flow can escape from hydraulic circuits. This leakage can be either internal or external with typical candidates being burst or degraded hoses or leakage from pumps, valves and actuators.

A useful tool to measure leakages and pressure drops is an infrared thermometer which can identify components with internal leakage. So going by the manufacturers limits for correct temperatures, the thermometer can pinpoint potential problems. Incorrect hydraulic oil out of manufacturer specification can also lead to pressure changes and a decrease in system performance. A successful infrared test will also pick this issue up.

System over-operation

Sometimes, under extreme operation, overworked machines start to overheat. Using the correct oil viscosity will help to alleviate this issue from occurring in the first place and avoid costly failures by lubricating the system effectively. It is also important to let the system prime itself before use thus ensuring all important components are lubricated correctly and to manufacturer standards.

Abnormal and irregular operative noise

Abnormal or irregular sounds while the system is operating are good warning signs of a potential problem either currently occurring or about to occur.

There are two main candidates that attribute to this problem – aeration and cavitation. Aeration is a condition where too much air enters the system and contaminates the hydraulic fluid within. This commonly leads to a loud banging or knocking noise from the system when it compresses and decompresses whilst the fluid circulates through the system. Actuator movement can also become erratic and the fluid degradation can eventually lead to damage to seals through overheating.

Cavitation commonly occurs when a hydraulic circuit demands too high a level of fluid than is being supplied at any given time. This in turn causes circuit pressure to fall below the level of vapour in the hydraulic fluid. The knocking sound that comes from this is caused as the vapour cavities implode during compression.

Both these issues can cause component or system damage with extreme cases of cavitation being known to cause metal erosion and failure of system components.