Understanding Flowmeter Recalibration Traceability…

Customers often ask if they need to have their flow meter instrumentation calibrated annually. Along with calibration-related questions, traceability is another area that garners its fair share of inquiries.

In this week’s post, I’ll share the answers to these commons questions you may have been wondering about.

Do I need to have my mass flow meter recalibrated annually?

No, annual calibration isn’t necessary. However, industry standards like ISO 9001 and quality assurance procedures may still necessitate sending in your meter for periodic recalibration, typically once a year. For example, we sell mass flow controllers and meters to the pharmaceutical industry, which has strict protocols in place to ensure consistency in flow meter measurement. Natural gas is another example of an industry with stringent guidelines, in this case for bulk gas custody transfer applications.

What is traceability?

Traceability can be defined as an unbroken chain of measurements and associated uncertainties. As used here, the word “traceability” always means “metrological traceability.” To establish and maintain traceability, the readings of a mass flow meter must be compared to a primary standard. In the United States, that standard is set by the National Institute of Standards and Technology.

Here at Sierra Instruments, we use a primary calibration device called a CalBench (piston prover) to calibrate flow meters. The CalBench consists of a number of calibrating gas tubes and sensors that are individually calibrated by the NIST or NMI, the Dutch equivalent. These calibrations in combination with the error analysis of the system, guarantee a maximum uncertainty of rate (mass flow) of 0.2% up to 50 slpm. This is one of the highest obtainable uncertainties in gas mass calibrations.  As a result, calibration of equipment by Sierra is fully traceable to a national standard.

Do Your Own Flow Calibrations

Companies with a large installed base of mass flow controllers or meters all needing annual calibration are opting to do their own.  The rule of thumb is that you need to have at least 25 flow instruments for this to make financial sense.   Typical payback on the up front capital investment in a flow calibration system, if you own 25 flow meters, is 24 months assuming calibration once per year.  Many pharmaceuticals must calibrate their flow meters twice per year, so their payback is much faster.

Sierra has a comprehensive line of primary standard piston provers called CalTrak that are manufactured to ISO 17025 standards at a NVLAP accredited lab using assets that are directly traceable to NIST.  These allow the end-user to do their own on site calibration and are an ideal solution for owners and users of many flow instruments.  Watch video about our CalTrak calibration products.

Have a mass flow meter that requires regular recalibration? Sierra can help. Contact us today for more information.