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One Page Tip #5
Planning for Linearities, Actual Linearity Activities, and Wrapping it Up

Regulatory references:
P75 Appendix A, § 3.2 and 6.2, Appendix B 2.2.1, P75 Policy Manual Section # 9 (Span, Calibration and Linearity) and StackVision User Guide.
Planning for Linearities:
  1. Generate and review the “QA Test Deadlines Report” found in StackVision (from the Home Page, click on “New Client →QA Test Deadlines”). Also review the features of this report and of the Linearity Editor in the “Help” section of StackVision. From the StackVision Home Page, “StackVision Help” can be reached by clicking on the “Help” option (the right most option at the top of the page).
  1. Review your in-house procedure for performing these activities. Preparing and following a site specific procedure helps lead to consistent and successful results.
  1. Linearities need to be separated by at least 30 calendar days, if possible.
  1. Linearities are required for a unit after it has operated in at least 168 clock hours in a calendar quarter.
  1. If you did not perform a linearity in a quarter, you will have 168 operating hour grace period available in the next calendar quarter.
  1. Verify that you have the correct blend of gas cylinders needed to perform a linearity check.
  1. Verify that you have enough gas in each cylinder to allow you to perform 6-7 runs (several runs for troubleshooting and then three good runs for the actual linearity).
  1. Prepare for the linearity check itself by selecting the date for performing it and schedule it for that date with the various parties involved (your boss, the operating staff, etc.). Remember, the unit or emission source which the CEM systems are monitoring must be in service (combusting a fuel and making steam or electricity) during the entire time the linearity check is being performed.
  1. Assemble whatever other supplies you need to perform the linearity check.  This might include, but it is not limited to:
    1. Linearity check list or an in-house procedure. 
    2. Whatever notes you need to use to perform a linearity.  
Actual Linearity Activities:
  1. Review your in-house linearity procedure making sure you understand it and can answer questions from those whom you will work or interface with.
  1. Confirm with the other parties involved that the linearity can proceed today, and that the unit is scheduled to operate long enough to complete the linearity.
  1. The linearity should only be performed after successfully completing the daily calibration check. Adjustments are allowed to improve the response or to reduce the calibration error %.
  1. When you are ready to begin, contact the control room operator and tell them you are beginning and ask if you can have steady operating conditions until you are done. Make them aware that they may see the CEMs reading jumping around as you perform the linearity.
  1. A successful linearity is completed by running three different sets of blended gases through the system three separate times.  Each set of gases will have a low, mid and high concentration gas to it, and the average linearity error calculated at each level is ≤ 5.0% (or is within the difference allowed for the alternate specification) to be a successful linearity audit. Typically, the gases are cycled through the system in a “low, mid, high, low, mid, high, low, mid and high” pattern.
  1. Once you begin, and until the ninth run is recorded, no adjustments can be made to the monitors.  If any adjustment is necessary, then the linearity for that monitor is now aborted and the EPA considers an aborted linearity to be a failed linearity.  You must start over and begin a new linearity.
  1. Start each run of the three gases after the data system has recorded minute data in the first two clock quadrants.  A properly executed linearity can be successfully completed in three hours, and still have valid hourly averages based on collecting two data points per hour during a QA check.
  1. When the linearity is over, review the system while you are still in the shelter and make sure it has been restored to normal operating status. Make sure the gas cylinders are set up and valved in for a successful calibration check the next morning.
  1. Using your in-house procedure, use the linearity editor to create the linearity record. Be sure to link the certification information for the three gas cylinders to the linearity records.
  1. Remember, CO monitors are not found under Part 75. If a linearity was performed on the CO monitoring system, do not click the box for including the linearity record “in the EDR file”.
Wrapping It Up:
  1. Take your notes from the linearity and setup your linearity records in the linearity editor of StackVision.
    1. Make sure the editor says that you have “Passed”.
    2. Save the linearity records.
  1. Make a note of how much pressure remains in the cylinders for the next round of linearities.  If any cylinder has less than 500 psi, it’s time to verify that you have a replacement cylinder in hand.  If none are available, then order at least two more sets of cylinders.  Remember, it takes at least 28 days at the factory to blend a Protocol I gas, as required by USEPA.
  1. Certain types of maintenance work can require a single run or full three run linearity check. These quality assurance checks (a single set or all three run sets) can happen at any time and therefore, be sure you have at least enough gas in all three of the cylinders to perform a full linearity check. If you are unsure if you have enough gas on hand, order additional cylinders as needed immediately.
  1. Remember to associate or link the relevant gas cylinder certificates used in the linearities for the Part 75 gas monitors.  Linking these certificates for a CGA under P60 is not necessary.
  1. When you think the linearity records are completed, generate a QA file for the date that the linearity was performed on.  Import that EDR file into ECMPS and evaluate it.  The evaluation report should report “No Errors”.  If it reports any errors, follow up appropriately in StackVision (SV) as needed.
  1. Remember that linearity records for SO2, NOx, CO2, or O2 are only to be included in QA EDR files.  Do not check the box to “Include in the EDR file” for CO or any other type of systems.
  1. QA records for linearities can be submitted at any time, once they are deemed clean and ready. Submissions of QA records through ECMPS should only be made through the prior approval of the Designated Representative (DR) according to your plant’s submission procedures.
  1. A CGA (Cylinder Gas Audit) is not the same as a linearity. A CGA is performed with only two gas cylinders of different concentrations while a linearity requires three cylinders with concentrations within a specific range of the span of the system.  For more details regarding CGAs, see the One Page Tips for P60.
  1. Do you need to update your linearity procedure?  Are there any lessons learned or better steps to follow that you uncovered during this round of testing? Update them now to improve your chances for success.
  1. Consider locking down your linearity data base so that it does not get accidentally changed or altered. Use the “Data Locking Wizard” found under “Tools” under the Main Menu page of SV.
For questions, suggestions, or for a general chat, please do not hesitate to contact me.

Download the PDF document here.

Jon Konings, Senior Regulatory and Reporting Engineer, ESC

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