Contamination is the cause of 80% of all oil-related faults and failures and can cost hundreds of thousands of SEK, up to millions, in downtime costs, spare parts, and production stoppages. Metal particles, water, and dust, along with temperature fluctuations, are just some of the circumstances that cause poor oil quality and failures.
When it comes to protecting oil and lubricants, filtration is the second and most powerful line of defense, the first being a breather filter.
There are a number of types of oil filtration; the two most typical are "full-flow filtration" and "bypass filtration". Full-flow filters are oil filters commonly placed as return filters in or near the hydraulic tank, or as pressure filters, usually directly after the hydraulic pump.
The size of a full-flow filter must be adapted, partly for the total oil flow and partly for the cleanliness requirement. This means that greater cleanliness requirements necessitate denser filters and thus a larger filter mass. This is to avoid causing too high pressure in the system, which would bypass the oil through the filter's safety valve.
A typical full-flow filter, often pre-installed by the manufacturer, has an approx. 2 mm thick fiberglass filter that can capture larger particles, around 5-20μ (micron), but cannot filter out sludge, oxides, and water, which are the direct cause of the oil's degradation process.
(see also preventive breather filtration).
The advantage of a depth-filtering bypass filter is that it consists of a strong cellulose filter element. The filter unit is usually connected to the pressure side of the hydraulic system as a separate small system, which continuously allows a smaller amount of oil to be filtered and cleaned when the hydraulic system is activated. This means that "denser" and more efficient filters can be used without the risk of hindering the system's oil flow. The filter unit is adapted to the system's oil volume, cleanliness requirements, and contamination level (the system's own generation of contaminants)
Unlike a full-flow filter's approx. 2mm thin filter mass, ROVAB's depth-filtering bypass filter has an approx. 114 mm thick filter mass with a filtration degree of <2 μ (micron), providing absolutely clean oil. It works by allowing the oil to flow naturally down through the filter via the axial flow principle and does not require its own pump when installed in an existing hydraulic system.
The most common filter elements (the material through which the oil is filtered) – are fiberglass and cellulose. Fiberglass can have good filtration capacity when they are of really good quality and have a purification degree of approx. 2-5 μ. In some cases, they can compare to cellulose filters. Fiberglass also does not saturate as quickly. The disadvantage of fiberglass filters is that they cannot absorb moisture, sludge, and oxides in the same way as a cellulose filter – as long as water enters or is not removed from the system, the risk of oil degradation increases, and bacterial growth can also become a problem if the situation is prolonged.
Cellulose filters are filters made of cellulose, i.e., paper, and these are most common in depth filtration via bypass systems. Despite their simple construction, they are some of the best filters for oil purification. ROVAB's cellulose filters remove particles down to < 2 μ, and also absorb moisture, oxides, sludge, and resin products down to bacterial levels.
Absolutely clean oil, free from water, sludge, resin, and oxides, minimizes the risk of oil leakage, as hoses and seals maintain their original elasticity. Clean oil also means reduced wear, which results in minimized costs for expensive component failures and unplanned downtime.
If one of ROVAB's depth-filtering bypass filters is installed together with ROVAB's particle and water-absorbing breather filter, particle and water ingress and all associated problems can be virtually eliminated, ultimately saving significant costs that would otherwise be spent on unplanned downtime, failures, and spare parts.
ROVAB's depth-filtering bypass systems are equipped with pressure and flow control and can therefore be connected to pressure systems up to 300 bar.
A gauge indicates when the filter element should be replaced. If a filter element saturates abnormally quickly and therefore needs to be replaced more often than usual, it is a clear indication that there are deficiencies in the system where particles are entering or being generated.
A bypass filter can, in this way, also act as a diagnostic tool or warning indicator.
