NF ISO 3968

Une des caractéristiques des filtres est la perte de charge qu'ils créent dans le circuit où ils sont installés; cette perte de charge varie en fonction du débit. Cette norme décrit la façon de mesurer non seulement la perte de charge d'un filtre complet mais aussi celle de ses divers éléments.

ISO 3668:2017 specifies a procedure for evaluating differential pressure versus flow characteristics of hydraulic filters and constitutes a basis for agreement between the filter manufacturer and user. It also specifies a method for measurement of the differential pressure generated at different flow rates and viscosities by the relevant parts of a filter assembly, spin-on and any valves contained within the filter which are in the flow stream. The typical types of filter to be tested are as follows: Type 1: which are spin-on filters in which the replaceable unit does not include a filter head (it might or might not include the element by-pass valve); Type 2: which are spin-on filters in which the replaceable element is tested together with a filter head (it might or might not include the element by-pass valve); Type 3: which are filter assembly, usually of the replacement element type, that is the housing (head and bowl) and element.