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Monday, November 10, 2014

A Story from the Test Lab: Calibration & Maintenance Frequency

Let's say a mill has 2 paper machines that use the same test lab. Each machine has a turn up every 30 minutes.  Each turn up requires that a given property be measured manually at 2 locations across the machine. At each location only 1 measurement is made due to time constraints. If the value is very far off specification it will be retested. All of this occurs every day, month and year.  The instrument normally only goes through a complete primary calibration procedure once a month.  Therefore, there are 4,320 manual tests performed per month (between primary calibrations). If Preventative Maintenance service personnel visits one time per year, there are 51,840 manual tests between routine maintenance visits.

If automated testing equipment is being used, the system is programmed to make 10 measurements across the test strip.  This means 21,600 automated tests are performed per month (between primary calibrations).  That means if service personnel visits only one time per year, there are 259,200 automated tests between routine maintenance visits.

In this example, there are 5 times more tests between primary calibrations and between Preventative Maintenance visitsIt is unrealistic to think that even equipment designed for MORE usage is going to require 5 times LESS routine maintenance.  Even if Preventative Maintenance were increased to four times per year, we would be expecting the equipment to perform for a longer period of time between tune-ups based on the number of measurements.

If you increase the volume of testing with automated testing (or through some other means) consider increasing the frequency of checking calibration and scheduled routing Preventative Maintenance.

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