Is it true the cleanliness code for particle count has been wrong and it is not 2-5-15 but that it is 4-6-16 or something close to that. I heard this and was wanting to know for sure.
Posted by maintenance-tips at April 6, 2004 08:37 PMThe ISO 4406 cleanliness code upon which Pall base their cleanliness code was revised from the original code of 1987 to a new format in 1999. The reasoning behind this change was the result of research by NIST into the true size of the test dust. The former test dust that had been used (Air Cleaner Fine Test Dust - ACFTD) was no longer available so ISO recommended the adoption of ISO Medium Test Dust (ISOMTD) which was assumed to have a similar distribution to ACFTD. But the findings of NIST concluded that the distribution was somewhat different. hence, for all Automatic Particle Counters now calibrated in accordance with ISO standards, the size categories for the cleanliness code are now >4µm/>6µm/>14µm (please note 14, not 16). It should also be noted that ISO 4406 (1987) (2/5/15) still applies if the cleanliness is measured by the use of an optical microscope. In fact the 'error' of the distribution affected more than just the cleanliness code, the rating of filters was also changed. Any use of the new test dust and standards is normally denoted by the use of the letter 'C') in brackets after a filter size rating or in the quotation of a particle count, for example a 5(c)µm filter is tested as per the new ISOMTD and standards. I trust that this helps, please feel free to ask any further questions relating to this matter, and try a search of the Practicing Oil Analysis magazine archives on the internet as Dr Leonard Bensch and Mike Day (both of Pall) have authored articles on the matter. Regards, Martin. Martin Williamson BSc Noria UK Ltd. PO Box 3156 Chester CH4 7WE Telephone: +44 (0)1244 659381 Facsimile: +44 (0)1244 679482 Mobile/Cell: +44 (0)7798 638994 Email: mwilliamson@noria.co.uk Web Site: www.noria.co.uk Noria Corporation