Prevention of premature hydraulic component failure
Premature failure of hydraulic components decreases the productivity and increases the operating cost of a hydraulic system. This failure may simply be defined as the failure of a component prior to it achieving its expected service life. The expected life of individual components within the hydraulic system varies and is influenced by a number factors such as:
• Type of component
• Circuit design
• Operating load
• Duty cycle
• Operating conditions.
From an operation and maintenance perspective, the factor that has the most impact on component service life is the condition under which the hydraulic components operate. The following conditions will have a negative impact on hydraulic component service life and in extreme cases will lead to a premature failure.
High fluid temperature
A fluid temperature above 82 °C (180 °F) damages seals and reduces the life of the fluid. At higher temperatures, inadequate lubrication due to lower fluid viscosity causes damage to the system components. To avoid system damage due to overheating, it is important that a temperature alarm is fitted in the system.
Incorrect fluid viscosity
Generally, optimum operating efficiency is achieved with a fluid viscosity in the range of 16-36 est. Maximum bearing life is achieved with a minimum viscosity of 25 est. A very high fluid viscosity may damage the system components through cavitation, while low fluid viscosity may result in damage through inadequate lubrication.
Contamination of the hydraulic fluid may occur on account of the influence of air, water, solid particles or any other matter that impairs the function of a fluid.
Air contamination can result in damage to the system components through loss of lubrication, overheating and oxidation of seals. Common entry points for air contamination include the vortex effect at the pump suction (due to low reservoir oil level) or faulty seals. To avoid this, the reservoir oil level should always be maintained at the desired level.
Water contamination can result in damage to the system components through corrosion,cavitation and altered fluid viscosity. In order to avoid this, ensure that all possible points of penetration into the reservoir oil space are sealed. Also ensure that the maximum oil level is maintained, to minimize condensation within the reservoir.
Contamination from solid particles can result in damage to the system components through abrasive wear or can be generated internally. Common entry points of particle contamination are through the reservoir air space and on the surface of the cylinder rods.
To avoid this and to reduce the contamination load on the system’s filters, the following
measures should be undertaken:
• All penetration points into the reservoir airspace must be sealed and an air filter of 5 !linstalled in the breather.
• The chrome surfaces of the cylinder rods must be made free from pitting, dents and scoring.
• The filters should be replaced regularly and fluid contamination levels monitored through regular sampling.
Incorrect commissioning or adjustment
Incorrect commissioning of hydraulic components can result in damage to the system components through inadequate lubrication, cavitation and aeration. Additionally, incorrect settings of the hydraulic system adjustments can result in component damage through over-pressurization, cavitation and aeration.
After the event
When premature failure does occur, a thorough investigation should be conducted, to understand the root cause of the failure. Consult a hydraulic specialist if necessary. Although, the failure analysis is not conclusive in all cases, it can provide valuable clues at identifying the cause of failure. This is essential in order to effect remedial action aimed at preventing a re-occurrence of the same.