It is important to understand that a single VOC analyzer (e.g., phx42/TVA2020) can only store one active calibration at a time. Any subsequent calibration overwrites the previous one.
If an analyzer is calibrated with both a standard probe and an extension probe in the morning (referred to going forward as a “dual calibration”), any drift assessment performed later in the day will only reflect the second calibration (the one which overwrote the first).
For example, a calibration is performed with a standard probe at 8:00am. Then, at 8:05am, a calibration with an extension probe is performed. In this scenario, the 8:05am extension probe calibration overwrote the 8:00am standard probe calibration.
Because of this, LDARtools has adopted a Best Practice for managing Standard and Extension Probe calibrations and drift assessments. However, it is understood that some users, based on their independent assessment of the regulations and the capability of their VOC analyzers, have decided dual calibration and subsequent dual drifts are allowed. While this is not advised, nor supported in Chateau, a workaround may be used.
Best Practice
To ensure accurate drift assessments when using both the standard probe and extension probe, you must calibrate and drift sequentially:
- Calibrate with the standard probe.
- Perform all standard probe inspections.
- Do the drift assessment with the standard probe.
- Then, calibrate with the extension probe.
- Perform your extension probe monitoring.
- Do the drift assessment with the extension probe.
This method has been used for more than 20 years by Cal5.0 and SpanBox users, and is considered best practice for LDAR calibration recordkeeping.
Workaround (Dual Calibration)
This workaround is recognized and can only be used under the following conditions:
- Calibration records must be recorded in Chateau Mobile.
- Note: This workaround is not compatible with SpanBox or Cal5.0.
- Only End of Day (EOD) Drift Assessments are performed
- Note: If mid-day drift assessments are required, this method will not work.
- Calibrate the analyzer with the standard probe.
- Calibrate the analyzer with the extension probe.
- Perform inspections, exchanging the standard and extension probes as necessary.
- At the end of the day, perform a drift assessment with the standard probe and document it in Chateau Mobile as the Mid-Day Drift Assessment.
- Then, perform a drift assessment with the extension probe and document it in Chateau Mobile as the End-of-Day Drift Assessment.
- Document, in writing and in a suitable place, that you are “using the Mid-Day Drift Assessment field to document the actual End-of-Day Drift Assessment for the [probe type] as demonstrated by the accurate time stamp on the record.”
Response Times with Extension Probes
Most extension probes use an increased tubing length which likely increases the analyzer’s response time. This new response time is measured and stored in Chateau during the quarterly Precision Calibration done with the extension probe.
It is crucial that technicians are aware of this additional response time as it impacts the monitoring technique for Method 21. Method 21 requires the probe be positioned at the site of the highest reading for a duration of twice the analyzer’s response time.
Please understand the Inspection Sample Time feature in Chateau Mobile does not automatically adjust for the use of an extension probe. Technicians must know to adjust the sample time when a deflection is found while using an extension probe.
Our research consistently indicates each foot of additional tubing can add as much as 1 second to the response time. However, the actual response time results for each analyzer and probe type as determined during the Precision Calibration process each quarter should be used.
Note: If you would like to create a Component Prompt to notify your technicians of this additional time when they are inspecting extension probe components, please submit a support ticket.