Why pumps fail
Using the wrong type of fluid in a system certainly can cause premature pump failure, but keep in mind that most pump failures don't occur because the wrong fluid was specified. More than 90% of hydraulic pump failures can be attributed to one or more of these causes:
Contamination — any foreign material in the fluid that affects its performance — dirt, metal particles, water, air, etc. Contamination can cause abrasive scratching, corrosion, wear, buildup of deposits, or any combination of these.
Aeration — the presence of dispersed air bubbles in the system's hydraulic fluid. Aeration can result in severe erosion of pump components when the bubbles collapse as they suddenly encounter high pressure when entering the discharge area of the pump.
Cavitation — occurs when the pump is starved of hydraulic fluid. When this happens, air enters the pump and causes damage similar to that of aeration. Cavitation usually can be distinguished from aeration by the sound. Aeration produces an intermittent sound, whereas the sound of cavitation is more constant.
Excessive heat — temperature above a specified limit that reduces fluid viscosity. It causes fluid degradation, resulting in acid, sludge, gum, resin, and varnish formation.
Over pressurization — subjecting the pump to higher pressures than it is designed to accommodate can result in catastrophic failure.
Improper fluid viscosity — fluid with too high a viscosity can cause premature wear and excessive heat. Too low a viscosity can have the same detrimental effects but lead to pump cavitation as well.
Partner with your fluid supplier
The most important practice you can do to maintain the integrity of a hydraulic system and save money is to consult closely with your fluid supplier. Discuss each specific application and the environment in which your equipment is operating.
Does your equipment run in wet conditions? If so, your fluid probably needs an additive package that provides corrosion protection and contains a demulsifier to separate water from the fluid. Are high temperatures an issue? If so, you'll need an additive package that provides good thermal and oxidation stability. Various environments and applications call for a different mix of additive components.
In addition to the smaller systems and longer drain intervals previously mentioned, several other hydraulic equipment trends impact the demand on fluids and additives. Higher pressures and temperatures increase the chance of varnish deposits and sludge. Higher power density and shorter cycle times also push the limits of additives. However, a greater focus on the cleanliness and filterability of the fluid helps reduce the detrimental effects of contamination.
Other trends have evolved from such environmental sensitivities as biodegradability, recycling, reclaiming, and reconditioning the fluid, and fluid disposal concerns.