Practical guide to QAL3: CMM AutoQAL makes QAL3 easier and more cost-efficient

The complexities of QAL (Quality Assurance Level) procedures for continuous emissions monitoring equipment and the EU Directives behind them can be cumbersome to grasp for any emissions monitoring operator. Quality assurance is closely connected to the EU Standards EN 14181 and EN 15267 (QAL1), and in this article, we will look into the details of QAL3, which can now be done a lot easier, thanks to our new continuous mercury monitoring system CMM AutoQAL with an EN 15267 certified, integrated and automatic QAL3 Validation Tool. Read on to find out more about the new device, and QAL3 in general.

What does QAL3 mean?

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 operating 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.

How is QAL3 typically carried out?

Usually, QAL3 is carried out by feeding the zero gas (typically Nitrogen) and span gas through the 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 the proper operation of the CEMs.

QAL3 measurement in emissions monitoring systems can mostly be done automatically, which saves time and reduces costs for the plant operators. It is also important to carry out the QAL3 measurements as time-efficiently as possible in order to minimize any downtime of the emissions monitoring system.

No external measuring equipment needed with CMM AutoQAL

In our 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.

QAL3 measurements and approval limits

In short, 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.

QAL3 inspections are done according to the EN 14181 and they need to be documented. QAL3 results and information about any possible repair work done in the case of exceeding the approval limits need to be available for the QAL2 and AST measurements.

The minimum time span 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.

According to EN 15267-3:

Table 8 – Maximum allowable maintenance intervals

Field test duration  Maximum allowable maintenance interval
3 months 1 month
6 months 3 months
12 months 6 months
24 months 12 months

A QAL3 check of 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.

Gasmet solutions’ maintenance intervals are:

  • CEMS II e : 6 months
  • CEMS II ef : 4 weeks. As a system can have only one maintenance interval and CEMS II ef has an integrated FID analyzer with a 4-week maintenance interval. For FTIR and O2 analyzers in CEMS II ef, however, the QAL3 inspection needs to be done only every 6 months at a minimum.
  • CMM: 3 months
  • CMM AutoQAL: 4 weeks. As the CMM AutoQAL is preceded by the widely tested and certified Gasmet CMM, a longer maintenance period is not needed.

QAL3 can be carried out more frequently than defined in the device’s maintenance interval guidelines. From zero drift and span drift checks’ point of view, this is advisable in the beginning when a new technology has been implemented – for example on a monthly basis or more often. For example, in Gasmet CMM AutoQAL automatic QAL3 measurement and internal pass/fail to examine of the QAL3 results is done typically once per week.

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 in QAL3 being a costly and time-consuming procedure.

Gasmet’s 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.

With automated QAL3 tests in CMM AutoQAL you can enjoy the benefits of:

  • Minimal operation costs
  • Savings in time and other resources
  • Easy and quick inspection of the results (software gives Pass/Fail results immediately)
  • No external instruments and measuring equipment need

Read more about how CMM AutoQAL offers unparalleled efficiency for continuous mercury monitoring.


Mercury Emission Monitoring – CMM & CMM AutoQAL

Continuous Mercury Monitoring systems CMM AutoQAL and CMM are the perfect solutions for monitoring mercury continuously from hot, wet and corrosive gas streams. These future-proof systems have the lowest certified range in the world (0-5 µg/m3) and CMM AutoQAL has an automatic and integrated QAL3 validation tool.

Learn more here

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