Fluid contamination can bring a hydraulic system to its knees which is why aggressive contaminant monitoring is important. Ensure the long life of your hydraulic system by following the right regimen.
Here is a scary statistic: 55% of hydraulic systems fail due to contaminants in their fluid. How can this outcome be prevented? By regularly monitoring the hydraulic system's contamination level and guarding it against the most obvious contamination sources.
To monitor contaminants, you must first understand how they get into the system. The first of four contaminant sources is in the original fabrication process. Even the best-made systems can have some degree of residue in the form of dust, grit, paint chips, or other debris that remains from fabrication. For new or rebuilt systems, a "running-in" period is suggested to completely flush out the contaminants.
A second source of contamination is from air that gets into the system. Typically, hydraulic systems allow a certain amount of air to enter and circulate to compensate for fluctuation in the fluid level due to thermal contraction and expansion. Though necessary, this air can contain microscopic bits of dirt that contaminate the system. Whenever portals are opened for maintenance, special care should be taken to ensure that they are immediately resealed afterwards. Additionally, a close eye should be kept on the wiper seals that are intended to remove the thin layer of oil that clings to the pistons. If the seals are not totally effective, fine grain contaminants can stick to this film and be drawn into the fluid supply. If this is the case, install rod boots or bellows with vents to limit the amount of contaminants that get inside.
Thirdly, contaminants can also be generated through the wear and tear that naturally occurs in the system. Even a system running on clean fluid is subject to the natural erosion of its components, and although commonplace, this source of contamination is the most harmful. If the contaminated particles are not quickly collected and removed, they create even more particles at an accelerated rate, exponentially increasing the likelihood of a breakdown.
Finally, a hydraulic system's fluid can be contaminated when new oil is added. Although hydraulic fluids are blended under clean conditions, by the time they reach the system, they would have passed through so many pipes, hoses, and pumps, that it is almost certain that contaminants would have been brought along with them.
With particle contamination in the hydraulic fluid accounting for 70% to 80% of component wear; it is extremely important to continually monitor the system's contamination level. Visually inspecting a sample of the hydraulic fluid is not enough, as much of the contaminants in the fluid are too small to be seen by the naked eye. Instead, fluid should be collected in a certified "superclean" container, and then sent to be analyzed. The analysis can reveal much about the fluid and the nature of its contaminants, including the size and composition of the particles, the viscosity of the fluid in relation to time and temperature, and its Total Acid Number (TAN). The TAN method measures the fluid's acidic level, and predicts the remaining usefulness of the hydraulic fluid. Proper analysis can also be done in the field by using particle counters and moisture detectors.
In addition to monitoring, prevention is a key factor in avoiding hydraulic system failure. Filtering systems are among the most effective measures in this regard. For the best results, filters should be positioned at strategic points in the system. These positions are: immediately downstream of any pump, in return lines, and in a re-circulating loop. Each filter should be equipped with a sensor to indicate clogging so that they can be immediately changed.
Another worthwhile method of prevention is to first run any new fluid to be added to the system, through a portable transfer cart pump fitted with a high-particulate and water removal filter. This ensures that the hydraulic fluid is of the highest quality. In the case of water that has already found its way into the system, a dewatering unit can be employed. These self-operating portable units withdraw the fluid, remove any water that is present, and returns the distilled fluid to the system.
A third, newly available preventive measure is Fourier transformed infrared spectroscopy. This technique gives maintenance engineers the advantage of analyzing oil samples in real-time. By regularly monitoring the oil, longevity is increased as the volume of waste oil for disposal is lessened, by the addition of preset quantities of anti-wear and antioxidant additives. Whoever handles the procedure needs to pay careful attention that the additives do not bring about an adverse reaction in the fluid.
In many ways, the hydraulic system is similar to the body. If cared properly, it can be expected to last a long time. If, however, it is neglected, it will fail its owner sooner than later. By following the above monitoring and preventive measures, maintenance professionals can keep their hydraulic system running smoothly for years to come.
