scope:

This Standard specifies procedures for assessing the number of particles present on a membrane filter using a back projection microscope. The procedures relate to a membrane filter, as specified in DEF STAN 05-43, which has been contaminated with particles from a quantity of hydraulic fluid by one of the sample methods specified in DEF STAN 05-43. The procedures are not considered suitable for sizing particles smaller than 5 micrometres (μm).

The basic assessment procedure is as follows:

Preparation of a microscope slide by mounting the contaminated membrane filter using:

A fixative and mountant fluid or

A mountant fluid only

Particle sizing and counting, using transmitted light.

The procedure is not suitable for determination of the nature of the contaminant.