The ease of maintenance and extended service intervals are major selling points for filtration systems. The challenge in achieving these marks of quality lies in developing solutions that will be easy to implement, low-cost and efficient enough to support any proactive maintenance approach.

Contamination of hydraulic fluid by insoluble particles is one of the factors that can reduce the service life of hydraulic components. The rate at which damage occurs depends on the quantity and size of particles present in the fluid. The most dangerous particles, highly abrasive ones, are the ones smaller than five microns.

The most damaging particles are the ones that are relatively close in size to the operating tolerances within the machine. This can range in a hydraulic system anywhere from zero to 100 microns and above. In certain instances where the operating tolerances are greater than five microns, all particles smaller will cause absolutely no damage. They will cause rapid wear of hydraulic components if present in sufficient quantities.

That is why an appropriate fluid cleanliness level must be defined and maintained on a continuous basis. Hydraulic experts recommend good maintenance practices on an ongoing basis in order to save costs and increase a system's life expectancy.

New Filtration Units
Internormen Technology adds to its product spectrum of off-line filter units. New models include the UMFC and UMCC, the additions to UM/US and USP/UST models, which have proved successful for a number of years.

The main aim of the mobile oil service unit, UMFC, is to simplify off-line filtration and filling of reservoirs, and to monitor the ISO cleanliness levels at the same time. Instead of having to replace oil prematurely, the oil can be filtered and used again, saving the costs of oil disposal or buying new oil. This is also friendly to the environment.

The area of application of the UMFC unit implies secondary flow filtration in addition to the existing operating filter, secondary flow filtration without the action of the operating filter, and filtration during filling of the oil reservoir.



Figure 4. Changing the Element

Easy Access
The filter unit must not be used to pump contaminated hydraulic fluids, and is therefore designed without a switchover fitting to bypass the filter. The compact structural design, on a baseplate without pipe, makes the unit small and reliable.

The mobile cart makes it easy to move the unit close to hard-to-reach and confined locations, and to fix the accessories (such as hoses or the connection cable) in a safe and reliable manner.

The device is equipped with a gear pump driven by an E-motor. The flow conveyed by the gear pump is fed over a filter element. To meet different requirements, the UMFC unit is equipped with either Interporvlies (fiberglass) filter elements, from 1 to 20 µm, or with Watersorp filter elements. At a pressure difference greater than 2.5 bar, the element is fully contaminated and must be removed and replaced with a new element.

This can be done with no tools and requires minimal training. After removing the straining screw and the housing cover, the filter element can be exchanged easily. The filter elements are supplied with seals. Because it is not possible to clean the element, the user should keep an adequate supply of spare elements in stock, a good practice in any preventive maintenance program. A safety valve on the filter unit protects from overpressure.

The E-motor is made safe with a motor-protection switch to prevent overloading. At a working pressure greater than 6 or 10 bar (depending on whether it is the UMFC 41 or 81), the motor-protection switch stops the E-motor. The line, venting and draining connections are identified according to their function. Drainage is necessary when the filter unit is being cleaned in connection with changing the filter element and the fluid medium.

The UMFC units are designed to accommodate various oil viscosities and flows. Knowing the consequences of particle contamination, it is essential to define a target cleanliness level, to test the fluid cleanliness and to maintain it at a certain level.

Fluid Control
The mobile off-line filter unit UMFC includes a fluid-control function, performed by the particle counter set CCT 01 and the water sensor WSPS 03. To determine the fluid's condition, the contamination classes and the water saturation of the oil between the pump and the filter unit are measured.

To accomplish this, the system is provided with the contamination class transmitter CCT 01, with integrated three-channel particle counter, in combination with the particle flow sensor PFS 01 and the water sensor WSPS 03 for reliable online measurement of temperature and water saturation. The WSPS 03 sensor determines the water saturation and warns of dangerous levels of free water present in the fluid.

The measurement signals received from the laser sensor are displayed in contamination classes according to ISO 4406:99 (> 4 µm(c), > 6 µm(c), > 14 µm(c)) and in percent of water saturation of oil, and passed on as analog output (4 to 20 mA).

Data can be transferred to a standard PC via USB-interface on one line for further processing. Up to 1,000 measurements can be saved.

Operating Modes
The UMFC unit is equipped with four separate operating modes:

  • Mode 1: manual stop

  • Mode 2: auto-stop contamination classes

  • Mode 3: auto-stop water saturation

  • Mode 4: auto-stop contamination classes and water saturation

The UMFC automatically shuts down when the threshold values for contamination classes and/or water saturation are reached. In case of drawn-off oil, the contamination classes can be determined in front of the filter by the contamination control sensor PFS01.

By choosing one of the operating modes, the running filter unit can be switched off manually or automatically after reaching the given limits for the contamination classes and/or through saturation of the water. Mode 1 allows the user to manually stop the process. Because of the various modes of operation, the UMFC unit requires no extra supervision and allows the operator to perform other tasks.

By changing over the pole, the motor of the unit can be run at half- or full-speed (UMFC 81), making the unit more versatile in different applications.

For the protection of the pump, there is a cleanable metal strainer with a mesh size of 250 µm in the suction line. To protect the sensors, the unit is automatically stopped when the oil reaches 70°C. The PFS01 measures oil contamination at temperatures up to 50°C only. Otherwise, the sensor will overheat.

Temperature Control
The UMFC unit is fitted with a temperature control that protects the particle sensors from overheating. To avoid damage, the sensor of the particle counter set CCT 01 switches off if the oil temperature exceeds 50°C.

The maximum tolerable oil temperature is 70°C, and exceeding this value causes an automatic shutdown. All conditions are displayed by pilot lamps on the LCD monitor.

The UMFC filtration unit provides high separation rates. Its dirt-holding capacity ensures advantageous service intervals and accurately defines contamination classes.

About the Author

Suzana Vidakovic is marketing director for Internormen Technology. The company manufactures hydraulic and lubricating fluid filters. For more information, visit or e-mail