Flow Test / 10 LPM Test

The filter (candle or disc) is placed in a sealed chamber. Air is injected into the chamber at a predetermined rate as to surround the filter and permeate through the filters structure into the core. The process of flowing air through the filter in this way generates a pressure drop, ΔP (Delta P), across the filter medium. In the case of the B&M Longworth flow test; this reading is used to test the cleanliness of the filter.

If the filter design allows, it is beneficial to carry out the test with the pressure flow in the same direction as production flow. This affords some degree of on-line simulation.

In recent years adaptations have been made to the flow test to meet changing needs within industry. One notable adaptation to the flow test is the 10 Litre Per Minute (LPM) Test.

The 10 LPM test been proven to give important information regarding medium degradation over time. The type of degradation highlighted by this type of test is usually a sign of the imminent failure of that filter element.

The uncertainty towards wider adoption of the test centres on the claim that a flow rate of 10 LPM fails to physically challenge the media of some filter elements.