Practical Guide to QAL3: CMM AutoQAL Makes QAL3 Easier and More Cost-Efficient

QAL3 is the on-going quality assurance process of a continuous emissions monitoring system. According to the EN 14181, the aim of QAL3 is to maintain and demonstrate the quality of a CEMs, so that the requirements for the stated zero and span repeatability and drift values are met during ongoing operation and the CEMS is maintained in the same operational condition as when installed and calibrated in QAL2.

In practice, QAL3 procedures mean CEMs zero and span gas drift check and control. Process operators and CEM owners are responsible for carrying out the QAL3 procedures

Usually, QAL3 is carried out by feeding the zero gas (typically Nitrogen) and span gas through entire emissions monitoring system and monitoring the measuring results of zero and the span gas. This gives us valid and reliable information on the drift and precision and confirms proper operation of the CEMs.

In Gasmet’s new device CMM AutoQAL for continuous Mercury monitoring, the fully integrated, EN 15267 certified QAL3 validation tool enables automatic span/zero gas input and all QAL3 measurements and control according to EN 14181. Previously, external tools and equipment were needed for the test gas input, but with CMM AutoQAL external measuring instruments are no longer required.

The results of QAL3 measurements are monitored and examined against approval limits. The approval limits can be set according to the EN 15267 QAL1 certification test results, or the maximum permissible uncertainty limits, which are defined in the IED, Industrial Emissions Directive. If the QAL3 inspection exceeds these limits, the emissions monitoring system needs to be maintained or repaired.

The minimum timespan for the frequency of QAL3 measurements is predetermined by the EN 15267 certifications tests, i.e. in QAL1. A field test is included in the QAL1, and the length of a successful field test dictates the length of the maintenance interval. The longer the field testing lasts, the longer the maintenance interval of a CEMs is. A QAL3 check of a CEMs needs to be performed at least once per maintenance interval.

In terms of examining the results of QAL3, the results are inspected by using so-called control charts. Examples given in the EN 14181 are Shewhart, CUSUM (cumulative sum), EWMA (exponentially weighted moving-average) but there are other applicable ones as well.

Integrated QAL3 in CMM AutoQAL Offers Cost-Efficiency and Ease of Operation in Hg Monitoring

Generally, in continuous mercury emissions monitoring systems, conducting QAL3 measurements has required an external and fully manual set of equipment for the gas input. This can result QAL3 to be a costly and time-consuming procedure.

Gasmet’s new CMM AutoQAL and its EN 15267 QAL1 tests point out that with a fully integrated QAL3 validation tool the whole QAL3 process can be carried out automatically and reliably with no extra costs. This way the plant or system operator does not have to acquire any extra equipment or instruments for the QAL3, nor outsource the service.