Catching the Drift

Calibration Software Beats Spreadsheets for Managing Complexity, Reducing “Field Trips” Without Risk and Even Predicting the Next Time an Instrument Will Drift Out of Spec

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This article was printed in CONTROL's March 2009 edition.

By Bob Sperber is a contributing editor to Control.

How much time do your technicians waste testing instruments in-situ that don’t need recalibration? On one hand, it’s a sign of a healthy asset when a test reveals identical as-left and as-found conditions. On the other, it’s a waste to send technicians to the field too frequently.

Calibration management software (CMS) is the toolbox that makes it possible to turn that theoretical waste into real savings without risk to reliability, safety or compliance. CMS systems provide one environment for managing instrument data, test protocols, work processes and documentation. The software downloads documenting calibrators to eliminate manual typing before the test, and when a bi-directional HART or fieldbus data flow is present, it’s uploaded to make automated data entry more thorough and accurate than manual operations allow. (See “Features of Calibration Management Software.”)

Even without such automation, the management functions alone bear examination. General benefits include:

  • More efficient calibration maintenance scheduling
  • Reduction/elimination of error-prone manual typing of test and recordkeeping data
  • The ability to track and trend data for quality and cost reductions when calibration frequency can be reduced
  • Better meeting of benchmarks and slimming of ongoing instrument maintenance backlogs
  • Improved regulatory compliance

Reducing Frequency

A 2007 survey by calibrator-and-software seller Beamex found that 50% of respondents across the process industries calibrate their instruments no more than once a year. In the  pharmaceutical industry, 42% said they calibrate once a year, and another 42% calibrated twice a year. Some plants do pH calibrations 365 days a year to comply with wastewater rules.

Reducing the frequency is an oft-cited benefit that comes from trending years of calibration test results. One engineer at a U.K. pharmaceutical plant, who oversees more than 8,000 instrument calibrations, told Control that he reduced his calibration labor 20% overall and 80% in a grinding and milling area, doubling intervals from three to six months; six to 12 months; and 12 months to two or more years.

It’s hard to achieve these gains without a good CMS.

Do You Need It?

Temperature control is critical for Ed Jett, plant engineer at Berry Plastics, Homer, La., which has up to 30 control zones per extruder. Calibration is a “big deal” for ISO 9001 and overall quality requirements, he says.

In all respects, this is a typical plant—all analog and management of calibrations done using time-honored spreadsheet and paper methods. Considering the potential of CMS, he says, “We see plenty of gains out there for us to go get. We’re beginning to move in that direction.”

Vendors estimate that 20-25% of process plants mate their smart calibrators to accompanying software. The rest use various databases, spreadsheet variants and file cabinets to track calibrations.

Should you be part of that 25%? A plant with a few hundred instruments to maintain may not need a calibration management solution, while one with 1,000+ instruments won’t be able to maintain all the information or work flows without one. That threshold can move, depending on each plant’s assessment of current pain and potential benefits.

An all-analog plant obviously won’t need and can’t use a CMS that supports a digital data flow, unless it’s part of a long-term changeover plan. But even used as a transactional information storehouse, “most users report improvement to their calibration efforts simply because the CMS standardizes the calibration process, which reduces variability from one calibration to the next,” says Eric Olson, instrumentation device management product manager, ABB Process Automation. He adds that without linking the software to a documenting calibrator, “updating calibration procedures and analyzing the results is very difficult. The CMS provides a user interface that simplifies all of this, making it easier to achieve results, such as reducing how often a device is scheduled to be calibrated based on past results, or in replacing a device because its zero drift is getting much worse over time.”

Smart Calibrators Maturing

HART protocol-compliant documenting calibrators tethered to CMS software reduced the amount of equipment and paperwork that has to be taken out in the field, according to Jeff Cason senior instruments and controls technician at Georgia Power’s Plant Yates, Newnan, Ga. His favorite features include “easy upload of calibrations to a PC and easy-to-read calibration certificates,” as well as “the ability to search for instruments that are due for calibration.”  Plant Yates uses Beamex MC5 multifunction calibrators, vacuum calibration pumps, both high- and low-pressure calibration pumps and Beamex’s calibration software.

In any given plant, smart calibrator know-how “depends on the size of the user’s instrument department,” says integrator Kristin Scharf, a consultant with New England Controls (NEC), who works with users of Emerson Process Management’s PlantWeb distributed control system (DCS). “Of the plants we work with, I’d say probably 30% have their own people who know how to use smart calibrators,” Scharf says. The other 70% have contractors such as NEC do their calibration and reporting chores.

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