Hydraulic cylinders use hydraulic oils, a fluid that has changed in composition with changing technology and regulations. As today’s zinc-free ashless oils age, fine solids are formed that do not dissolve in the oil. This product of oil aging is referred to as varnish. It settles on oily surfaces and can interfere with the function of the mechanism. Varnish build up may result in seizing valve spools, overheated solenoids, and short filter duration.
Was a time, hydraulic and lubrication fluid contained additives that included heavy metals and other potentially toxic substances. Modern compositions contain no toxins, carcinogens, or heavy metals. They are also considered ashless, which means that they do not produce any residue, or ash, as a byproduct of combustion. Due to the absence of heavy metals, the fluid is low in electrical conductivity. The oil that flows through the filters of a hydraulic system generates electrostatic charges, which build up and can lead to sparking. Sparking breaks the bonds in the fluid, which then forms free radicals that polymerize into long chains, resulting in oil-aging and the production of varnish.
Varnish is a byproduct of a chemical reaction that leads to compromised oil quality. The generation of electrostatic discharges that can cause sparking may lead to hot spots in the system, another symptom that varnish may be building. Deposits in the reservoir may not be a big issue per se, but they may cause problems down the line for other components.
Varnish build up adversely affects valves, causes spool to stick, and can lead to a host of operational malfunctions. It can cause components to fail before their time. As an insoluble soft material, varnish accumulation can quickly clog hydraulic filters.
Specialized filters are available that are designed to remove varnish, but these types of filters do nothing to prevent it from forming. There are filter elements available that may actually help to stem rapid oil aging. These electrostatically optimized elements work to prevent discharges in the oil, halting or slowing the formation of oil aging products such as varnish. Heat can be a major culprit in oil aging. Depending on the system, lowering the temperature of the hydraulic oil may help extend its integrity. Another way to keep on top of varnish accumulation is by monitoring. Taking a regular oil sample and doing analysis can offer useful information for heading off trouble. Your business equipment is a tremendous investment, and an efficient hydraulics system is the power that makes it go. Whether it is a custom platform, components, filters, or fluids, Bernell Hydraulics has the products and the expertise to keep your operation humming.