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By Dan Hebert, Senior Technical Editor
The challenges of moving from paper-based procedures to an automated electronic calibration system are significant, but not insurmountable. The question is, are the gains of the switch worth the effort? Any calibration program contains five steps: planning, organization, execution, documentation and analysis. Planning consists of listing all instruments, deciding on calibration ranges and intervals, and developing standard operating procedures.
During organization, resources are marshaled and trained to carry out the scheduled calibration tasks. The execution stage is where the actual instrument calibration takes place.
Documentation and storage of calibration results typically involve signing and approving calibration records. Based on calibration results, companies then have to analyze the data and optimize calibration intervals.
An automated calibration system will affect each of these stages differently—some more than others.
Planning is much the same whether calibration is manual or automated.
An automated calibration system actually makes organization more difficult, as the tools needed are much harder to use. An automated calibration software system has two main components: the calibration software and the handheld electronic documenting calibrator. Learning how the software works is not trivial, as these programs are powerful and necessarily contain a degree of complexity. Implementation can be eased for smaller systems by using scaled-down software, such as Beamex’s CMX Light.
The software must be installed on at least one PC and often on a network. For maximum effectiveness, it is often linked to other plant computing systems, such as ERP or computerized maintenance management, and it should also be linked to the handheld calibrators.
A handheld electronic documenting calibrator that can download data from calibration management software, walk an instrument tech through a calibration sequence, record the calibration data and upload the data back to the calibration management software is a complicated piece of equipment. A few days of training is typically required to get plant personnel up to speed on the calibrator.
Since an automated calibration system has little effect on planning and makes organization more difficult, why bother? The payoff comes during the next three steps.
Execution with a manual system requires generation of a calibration sheet for each instrument. The instrument tech then takes the cal sheet to each instrument and calibrates it based on the sheet instructions. With an automated system, a single handheld calibrator holds instructions for hundreds of instruments. The tech can then take the calibrator to the field and calibrate each instrument based upon on-screen instructions and prompts.
Documentation and storage of results is a nightmare with a paper-based system. Calibration data must be recorded manually by instrument techs in the field, usually on cal sheets. Filing these thousands of sheets each year in a manner designed to allow easy retrieval is a complex task that can quickly overwhelm.
To avoid these issues, many plants transfer data from cal sheets to spreadsheets, databases or other software programs, which takes a lot of time and leads to errors. An automated calibration system automatically transfers data from the handheld calibrators to the calibration management software.
Finally, analysis is virtually impossible with a paper-based system, but quite viable with an automated system. The chief advantage of analysis is that it allows calibration of each instrument to be performed only as needed. Reducing the calibration frequency for non-critical instruments that tend to stay within parameters saves money. Increasing calibration frequency for critical instruments that often drift can help process plants avoid off-spec products, downtime and accidents.
ControlGlobal.com is exclusively dedicated to the global process automation market. We report on developing industry trends, illustrate successful industry applications, and update the basic skills and knowledge base that provide the profession's foundation.