A reliable, reproducible and accurate particle count measurement is a critical requirement in any predictive maintenance (PdM) program. The primary function of an effective PdM is to perform value added maintenance and/or service when necessary rather than performing scheduled service that can either be too early or even worse, too late. A particle count sample that has been compromised by the residue of a previous sample is therefore an unreliable measurement and failure for obvious reasons.
Several factors can contribute to the severity of the “sample to sample carryover” phenomenon. These factors include but are not limited to previous sample contamination level, viscosity, fluid miscibility, and flow rate, however, the particle counter fluid delivery system is considered to play a highly significant role and frequently is the primary factor. The new HIAC 8011+ particle counting system design provides a distinct advantage on this issue due to its minimal dead volume (~1.8ml) and high pressure to facilitate delivery of the sample through the system. The flow path of the new HIAC 8011+ has been designed to minimize the amount of sample to sample carryover by introducing a new feature of small volume requirement of residual fluid to be purged before an accurate measurement of the new sample can begin.
Proper sample preparation is another significant factor which can help to minimize the carryover phenomenon. Excessive wait times between sample runs, using a blank or clean fluid between the sample runs, and a sample probe wipe down with a lint free cloth are helpful, but can be both time consuming and cost prohibitive.
In this application note, we describe a simple experimental protocol to validate the minimal sample to sample carryover when the new HIAC 8011+ is used to measure the particle count level.