Span Found - Tec Trek Web Site

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A recent call from a government inspector has prompted me to provide the following information to you related to required data on your ASH Calibration Sheets.

The question posed was, "Is it required to document the span found setting on the quarterly calibration report?"

Before I commented, I gave a brief explanation of what that data represents and why it is should be included.

The span found reading is what is given when span gas has been applied to an ASH Detector, specifically a Catalytic Bead, detector.  The purpose is to see how much the beads have degraded over time or to determine if they may have come into contact with a contaminate, that would cause the bead to loose sensitivity.

In a perfect world, once the span gas has been applied, the detector should read 50% LEL/LFL, however that is not always the case. Which is the reason of why calibrations are required on these type sensors every 90 days.

To the trained eye, it also provides us with data to potentially determine if a sensor has been contaminated, or is approaching its end of service. It can also verify that calibrations are actually being conducted.

So back to the original question, is this data required on the calibration sheets?

The above represents calibration procedure for a manufacturers gas detector. Line item 9, states to record this reading on the calibration form in column labeled " Reading Before Adjustment" , which in our case is the span found.

Also the above is referenced in API RP 14C Section D.4

I have found the same type data across several manufacturers equipment, but considering how many manufacturers there are it would be very impractical and time consuming for me to post them all.

For Technicians/Inspectors:
Some smart detectors do not allow you to view the span found reading, in this case we have no choice but to label the span found column as Auto Span or prior to calibration, place all potential isolation devices in bypass and test the sensor with span gas to observe the maximum reading.

Also for systems that require the use of your Digital Multi-Meter for calibration purpose, get out your pencil and utilize the mathematical equation to convert from DMM to % LEL/LFL.

If you should have a system that does not allow you to view the span found setting then shoot me an email of the make and model, so that I can forward this information to the manufacture for possible changes to their systems OS.

If you require more information regarding the terms and explanations above, contact me by email or phone for assistance.

The above information is covered in the following Tec Trek class segments: Awareness Training (FG-01A), Basic Technical Training (FG-01)

For more information regarding training schedules and course curriculum, please visit our Web Site at www.tectrek.org

or Contact Todd Olivier at (337) 298-7959.

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Email: todd@tectrek.org