24 Air Monitoring
stated in the various CEN and ISO standards. The variability of the measured values obtained with the AMS is then evaluated against the required uncertainty.
The QAL 2 procedures are repeated either: periodically; after a major change of plant operation; after a failure of the AMS or as required by legislation.
The AST is a procedure designed to evaluate whether the measured values obtained from the AMS still meet the required uncertainty criteria – as demonstrated in the previous QAL 2 test. It also determines whether the calibration function obtained during the previous QAL 2 test is still valid. The validity of the measured values obtained with the AMS is checked by means of a series of functional tests as well as by the performance of a limited number of parallel measurements using an appropriate SRM. Refer Figure 1.
Figure 1 Quality Assurance Flowchart Frequency of tests
A full QAL 2 procedure shall be performed at least every 5 years for every AMS and more frequently if so required by legislation (Incineration of Waste specifies parallel measurements every 3 years). In addition, after each major change in plant operation (e.g. change in flue gas abatement system or change of fuel) or major changes in the set-up of the AMS, a full QAL 2 for the components influenced by the change shall be performed and reported within 6 months after the changes. During the period before a new calibration function has been established the previous calibration function (where necessary with extrapolation) shall be used.
A Standard Reference Method (SRM) is used to sample the emissions at a point in the duct that is as close as possible to the AMS, without interfering with its operation, having demonstrated that the sampling location is representative by means of duct surveys performed according to EN 15259. The duration of the SRM sampling shall be identical to the duration of measurement made by the AMS.
The AST is carried out on the anniversary of the first QAL2 tests and subsequently every year up until a new QAL2 is required.
Functional tests of the AMS required by QAL2 and AST
One of the major challenges in carrying out successful QAL2 and AST is the organising of the functional tests, usually carried out by the AMS supplier.
Table 3 shows the function tests that must be carried out for QAL2 and AST.
Activity
Service of the analyser/system Alignment and cleanliness Sampling system
Documentation and records Serviceability Leak test
Figure 1: Quality Assurance Flowchart
Tests required by QAL 2 & AST Testing shall cover the following items: • Installation of the AMS;
• Calibration of the AMS by means of parallel measurements with a SRM;
• Determination of the variability of the AMS, and the check of compliance with the required uncertainty.
The sequence of the combined tests is shown in figure 2. Figure 2 Sequence of testing for QAL2 & AST
Zero and span check Linearity
Interferences
Zero & span drift (QAL3 audit) Response time Report
Table 3: Function tests for QAL2 and AST tests The details of the tests are as follows.
Alignment and cleanliness A visual inspection, with reference to the AMS manuals, shall be carried out on the following when applicable:
• internal control of analyser • cleanliness of the optical components
Extractive AMS
X
X X X X X X X X X X
In-situ AMS
X X
X X
X X X X X X
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• flushing-air supply • obstructions in the optical path
After re-assembly at the measurement location at least the following shall be checked:
• alignment of the measuring instrument • contamination control (internal control of optical surfaces) • flushing air supply
Sampling system
A visual inspection of the sampling system shall be performed, noting the condition of the following components, when fitted:
• sampling probe
• gas conditioning systems • pumps
• all connections • sample lines • power supplies • filters
The sampling system shall be in good condition and free of any visible faults, which would decrease the quality of data.
Documentation and records
The following documentation shall be controlled, readily accessible and up do date:
• General arrangement and schematic of the AMS • All manuals (maintenance, users, etc.) • Log books
• Possible malfunctions and action taken • Service reports
• QAL 3 documentation • Actions taken as a result of out of control situations
• Management system procedures for maintenance, calibration and training
• Training records
• Maintenance schedules • Auditing plans and records
Serviceability
There shall be provisions for the effective management and maintenance of the AMS, in order to ensure the maintenance of the quality of data. Such provisions include at least the following:
• Safe and clean working environment with sufficient space and weather protections
• Easy and safe access to the AMS itself
• Adequate supplies of calibration materials, tools and spare parts
Leak test
Leak testing shall be performed according to the AMS manuals. The test shall cover the entire sampling system.
Zero and span check
Reference zero and span materials shall be used to verify the corresponding readings of the AMS.
In case of non-extractive AMS zero and span checks shall be performed on a waste gas free reference path before and after the readjustment and after re-assembly of the AMS at the measurement location.
Figure 2: Sequence of testing for QAL2 & AST IET March / April 2014
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