Feature: The importance of preventive maintenance and calibration

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One of the main goals in every industry, whether in manufacturing or  in service, is to have a smooth and reliable operation of every piece  of equipment or instrument used. One way to achieve this goal is to implement a quality control procedure with a preventive maintenance  schedule and calibration for the instrument in situ. In this article, Torsten  Ruppert, ATLAS International Service Manager, explains the importance of preventive maintenance and calibration for weathering instruments. 

Preventive maintenance and calibration are the  first step in performance control and the baseline  for reproducible sample test results. Without a  reliable preventative maintenance and calibration  process, the risk of misinterpretation of the test  result increases. This might cause product failure, customer claims and, in the end, higher costs in  production and product replacement. 

WHAT IS PREVENTIVE MAINTENANCE?

Preventive maintenance (or PM) is a familiar  term mostly related to equipment maintenance, and has the following definitions:- The work carried out on equipment  in order to avoid its breakdown or  malfunction. It is a regular and routine  action taken on equipment in order to  prevent its breakdown. Usually, it includes a  systematic component test, measurements,  adjustments, calibrations, parts replacement  and cleaning. Again, all this in order  to prevent faults or malfunctions from  occurring. 

WHY IS PREVENTIVE MAINTENANCE REQUIRED?

To improve repeatability and reproducibility  of the test results. To reduce or eliminate unplanned instrument down time. To increase customer satisfaction. Having a preventive maintenance process in place helps to keep the instrument at its best performance, and to extend its lifetime! Thus, it optimises the efficiency of the capital investment. 

Here are some typical examples that show  a direct influence on the operation of the instrument, or an indirect one on the sample  test performance:

1. Dust on optical components blocks  irradiation and is an indicator of insufficient air quality.

2. Contamination on optical components  blocks irradiation and is an indicator of  insufficient water quality.

3. Corrosion on electronic boards leads to  electrical malfunctioning and is an indicator  of insufficient ambient conditions.

The situations shown above drive instruments  out of performance and result in operation  failure and costly repair. Also, instrument downtime increases, and expected test results  may be delayed.  With good PM in place, and  taking good care of the instrument from its  first moment of use, ensures the high quality of  operation which is required for reliable sample  testing results. 

WHAT IS A GOOD PREVENTIVE MAINTENANCE?

A manufacturer needs to identify the key issues  for the individual instrument and has to setup a  PM programme for the customer. The following  key items are examples for a good PM indicated by the manufacturer.  

Availability of a detailed PM guideline for the work to be performed.

PM parts with information on the parts replacement schedule.

Consumable parts tailored to the customer’s requirements and application.

Highly trained and skilled service engineers

Providing a checklist with all details of  inspected components and their status. In other words, regular maintenance helps to  optimise instrument performance and maximise  instrument uptime. 

CALIBRATION IMPORTANT

Besides PM, the calibration of the instrument’s  measurement and control parameters, such as  irradiance, temperature and relative humidity, is another important requirement. While the  instrument is in operation, providing stressful  ambient conditions to the tested samples, it is also causing stress to its indicating sensors. While they are designed to operate as stably  as possible under the harsh conditions inside  a weathering instrument, based on the time of use and the local instrument conditions, an  aging drift might influence the sensors. This  may cause wrong setpoints and a change of the test conditions.  With calibration, this drift  or deviation can be detected and corrected, which is the second important factor for quality control procedures needed to ensure  reproducible test results. 

WHAT IS CALIBRATION?

Comparison between CURRENT-VALUE  (instrument displayed value) and REFERENCE- VALUE (reading from master tool) usually made in three steps:- •  Step one: Measure the “As Found” value. This records the current status and allows the review of past conditions. Step two: Comparison between current and reference value and adjustment (correction) of the instrument indicator, if values are out of the given tolerance. Step three: Measure the “As Left” value after the entire PM and adjustment. The deviation between “As Found” and “As Left” is a good indicator of the drift of a parameter and a key indicator of the overall instrument performance.

WHY IS CALIBRATION NEEDED?

  To preserve the quality of the products

Product failure prevention, saving of cost, traceability of measurement.

Due to standards requirements

Accreditation according to ISO 9000 is only possible with calibration.

Traceability of instrument parameter by calibration with traceable tools.

Product liability

Valid documentation of instrument maintenance and calibration process.

WHAT IS A GOOD CALIBRATION?

A good calibration is when a manufacturer has a calibration system process in place and maintains it. Below are some key items that are  needed for a good calibration service.  

The calibration service has an accreditation following the ISO 17025 standard.

A qualified calibration guideline is in place for the individual instruments.

The instrument supports the calibration philosophy eg assigned calibration position, calibration adapter etc.

Qualified and trained service engineers.

A calibration certificate which includes all relevant calibration data.

Whenever possible, instrument independent calibration tools should be used.

Calibration tools have to be in traceable to a national standard organisation.

Calibration tolerances, intervention limits and adjustment ranges are specified.

CONCLUSIONS

In conclusion, preventive maintenance and calibration are required aspects of any weathering instrument in order to get the best  weathering testing results! It is the baseline for  a quality control procedure, and reproducible  and reliable testing. Common industrial  standards consider this and request periodical  PM and calibration servicing. Preventive maintenance helps to improve the  lifetime of the instruments, reduce downtime  and save cost.  Keep your instrument in a good shape!

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