Hydraulic Oil Filtration Terms

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-Filtration ratio,   βx   ( filtration efficiency )

This means the ratio between particles counted up stream and down stream, detected according to the multi – pass test method ( ISO 16889 ). For comprehensive evidence of the filtration range the ratio βx (c) is shown as a time related average value in the following rates

βx = 2                      βx = 10
βx = 75                   βx = 100
βx = 200                βx = 1000

– Dirt – holding  capacity

Gravimeter determination of the mass particles in grams according to ISO 4572 is the mass which could be absorbed by the filter element until a point where one of the test limits ( time or pressure ) is reached.

– Burst pressur.

According to ISO 2941 the burst pressure is the maximum allowed pressure when filter material still has complete operatability.

– Breaking strength.

The breaking strength of INTERNORMEN – filter elements is the maximum allowed pressure difference. However, high rate of security is given before the component are destroyed.

– Bubble – point test:
*Determination of the production quality according to ISO 2942
Function of the standard:
Examination or confirmation of the perfect production of filter element. The examination according to this standard is for:

– The release of further tests

– The release of an element after production (final control)
– The release for operational use ( Vendor inspection ).

-Maximum allowed pressure loss at the filter ( ∆p max )

During the normal volume flow in flow direction the maximum allowed pressure loss grows without negative impact of the filter function.

– Effective filtration area:

The total filtration surface of the porous material or of the wire mesh of the filter element which is penetrated by the flow rate.

– Filter efficiency:

Nominal filter efficiency:
Arbitrary statement of the filter fineness in micron, to be considered as a rough statement only.

Absolute filter efficiency:
Biggest diameter in micron through which particles could flow under specific test condition.

– Filter Service life
Is the operating time in practical operation until the contamination level of the filter is so high that the allowed flow resistance is exceeded.
– Contamination class

The transmission of the power hydraulic – and lubrication systems is effected through fluids under pressure.
These fluids have a natural contamination (primary and secondary contamination)
The level of this contamination (number of particles in a defined fluid volume) is defined in standards ISO 4406 and NAS 1638.They are divided into contamination classes.

Flow-fatigue test

The filter element is tested to ISO 3724 to examine the ability of the element to withstand alternating flows.

(A) Test filter

(B) Dirt addition (ACFTD) until the final pressure difference is reached.

A specified number of pressure shock cycles are sent to the filter element. The pressure characteristic must be sinusoidal and have a frequency of ≤ 1 Hz. The filter element has passed the test if there is no visible sign of damage on the complete element, seals or filter material after the pre-determined (or customer specified) number of pressure shock cycles have been endured.