The industrial hydraulic power units comes from the manufurer with three main filter types: The succion filter ( often a strainer ), a return filter ( most often a spin-on ) and also a high pressure filter. These filters are part of a first category called on-line filtration.

The filters are installed on the hydraulic circuit's lines ( pipes ). Sadly, from the hydraulic system's conceptualisation stage, the designers and manufacturers are too often making conventinal choices when it comes to selecting the filters that will be installed.

Starting form the basic recognized principle that says 80% of the troubleshooting on hydraulics systems comes from a high level of contamination, we have to make a special attention on the importance of analyzing the basic concepts in filtration. So, it's becoming more and more important to look at the off-line filtration ( out of the circuit filtration ). In this second category, we talking about a filtration kidney, and by-pass filtration. In fact these two concept are part of a lesser known category.

Because they are directly placed on the hydraulic circuit, the on-line filters selection must be wisely chosen. There are many parameters that must be taken in account when doing this. A fine filtration type and adequate media are important to protect the delicate and critical components. The viscosity and operating temperature should have a big impact on the size of the the housing and filtration element. We should also adapt the filter's retension to the anticipated level of oil contamination. It's also important to have a Delta-P gauge installed on the housings, for this is an essential mean of filtration elements saturation level monitoring. Too often, hydraulics systems are working with clogged filters thus bringing oil to go to the by-pass valve and so the oil get no more filtration. This type of filtration, very often seen in the industries, is producing a very rapid increase of dirt in systems. So, in the case of an on-line, inadequate or insufficient filtration, we can consider using the off-line filtration solution.

While searching for an efficient complement to off-line filters, the Harvard corporation discovered a very performing media that raised the effiency of this type of filtration. The key this principle is to make a constant re-circulation of the oil from the tank thru a filter. We should not forget that contamination refers to water in the oil as well as solid particles. The two existing off-line filtration techniques are: The mobile filtration kidney (« purification unit » ) and the derivation filter on the system ( « By-pass filter » ) or « kidney loop » These two filtration type have serious advantages, mostly when used with the Harvard element because it also gets water off of the oil.

The Harvard patent ( see diagram ) is consisting of an élément for « off-line » filtration. While offering a very high retention capacity, in fact, 10 to 20 time the capacity of a standard filter made out of pleated média, that also has the advantage of being able to filter down to 1 micron. Its in depth filtering media give's you the opportunity to purify oil up to êxtrême levels. This special element made out of multi-coat compressed cellulose can be used in a mobile filtration unit ( mobile kidney ). or in a permanent installation housing, connected in a derivation mode on the hydraulic power unit. The mobile filtration unit would be desirable only for a plant with many hydraulic systems or one that would like to recycle his used oil.

The Harvard principle for off-line filtration The filter makes the différence

The filter is made just like a housing with multiple filtering elements, however here, its all about only one element consisting of two, four or or six sections. On the diagram however this is a four section element. A special patented sealing joint is placed between each section to make them independant. The oil flow carries the contaminated particules in an axial way thru the the media bed of each section. The thicker the media bed, the more solid particules are cached: If we compare 2 element of same lenght, one with two section and one with four section, the one with two section will have a better effiency. The hydraulic pressure surrounding the element, compresses the media and makes it catch fine particules particules down to 1 miron (1µm).

There is no restriction created by surface loading. Each 1000 serie element being 7.5’’ in diameter, by 20’’long, can get rid of up to 10 kilos of dirt and up to 4 litre of water under well controlled conditions. Now were talking about high-end technical economy and effiency.

In reality, users of hydraulic systems and the machinery service technicians are more often than not face to face with the consequences of a lack of filtration. Most of the time they just did not had the chance to participate to the on-line filter selection stage, the filter bein already installed. Even the installation of high pressure filters will not protect anything but the machine's most critical components, and it will not decontaminate the power unit either. In fact, the most valuable solution to counter-act the the rise of contamination is in most cases, the off-line filtration. There is some rules of the thumb to install this type of filter that an industrial filtration proffessional will be pleased to show you. You can join Benoît pageau at the following numer: 1-888-FILTRES