Significantly better results in the 2nd round robin test for determining the recovery rate of test particles according to VDA 19 Part 1

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As part of the second round-robin test to determine the recovery rate of test particles, numerous companies took the opportunity this year again to qualify their process procedures for cleanliness testing. Some were able to significantly improve their results compared to the previous year.

Among the participants were again renowned OEMs, Tier 1 and Tier 2 suppliers, as well as many laboratories offering cleanliness investigations as a service. Especially the latter used the opportunity to convince potential customers of the quality of their laboratory by publishing their company logo in connection with a positive result. This is possible, among other things, on the internet presence of the provider Marhan Normpartikel. In this way, a "living" database is created here, where companies whose order volume of parts with cleanliness specifications does not justify their own laboratory can inform themselves about the quality of their potential service providers. The publication of a result in connection with the company logo, however, only occurs at the explicit request of the participants. Great importance is attached to discretion during the round-robin test. Even the employees of Marhan Normpartikel are not able to link a test result to the associated company. Well-designed evaluation regulations ensure that only the respective participant can combine their result with their own company.

The specially developed standard for cleanliness investigations, "ParticleMaster," used by Marhan for the determination of the recovery rate of test particles, was also extremely successful in the second round-robin test. The standard involves a glass microscope slide that is deliberately contaminated with test particles. The test particles are fixed on the slide in such a way that they detach during the extraction of a cleanliness test and thereby enter the process flow of the cleanliness investigation—extraction, drying, filter handling, microscopy. The number and size distribution of the standard particles on the slide are microscopically determined, and the result protocol, called the specification protocol, is attached to the contaminated slide. It provides information about the exact particle count and size distribution of the test particles on the slide. This creates an object with a known level of contamination. During the round-robin test, however, the specification protocol is initially kept confidential so that participants do not know how many particles of which size distribution are on the slide. This allows for an objective evaluation. At the end of the test, each participant receives their personal recovery rate along with a participation certificate.

The average recovery rate in the second round-robin test was significantly higher than in the first. While the average recovery rate of all participants last year was 89%, this year an average of 93% was achieved. Furthermore, some participants were able to significantly improve their results compared to the previous year. Considering that extraction, as the most important component of cleanliness testing, can be excellently qualified through the determination of the recovery rate, it becomes clear how important this qualification opportunity is. Even the best microscopic evaluation system can hardly salvage a poorly performed extraction. Incorrect handling or faulty extraction equipment can often cause many particles relevant to the result to be lost unnoticed during cleanliness testing. The blind value determination provides information on the extent to which the result of a cleanliness test is distorted by irrelevant and externally introduced particles. By determining the recovery rate of test particles, it can be ensured that no particles originating from the component under test and relevant to the result are lost. Therefore, regular application of this method is recommended. This way, it can be ensured that all process procedures meet the target specifications and that the testing equipment operates in perfect condition.

Among others, the following companies / cleanliness laboratories achieved a 100% recovery rate in the 2017 round-robin test:

- DHD Technology GmbH & Co. KG, Address: Rother Str. 1, D-91174 Spalt
- DHD Clean Parts GmbH & Co. KG, Address: Gewerbepark Hügelmühle 43, D-91174 Spalt
- Inspekt e.G., Address: Südbeckenstraße 20A, D-76189 Karlsruhe
- parts and particles GbR, Address: Vogelsbergstraße 3, D-63674 Altenstadt

- SAS hagmann GmbH, Address: Weberstraße 3, D-72160 Horb a.N.
- Techsa-Cleancheck Kft., Address: Árpád utca 17, H-9321 Farád