Certification of AMS acc. EN 15267, Part 3 - Overview and First Experience - Dr. Wolfgang Jockel, Martin Schneider, TÜV Rheinland Group, D-51105 Cologne / Germany 1. Introduction A new basis for the certification of automated emission measurement systems (AMS) has been set up when the European standard series EN 15267 entered into force. Standard EN 15267-3 implements a standard schedule for approval tests of emission measurement systems. Standard EN 15267-1 describes the basic principles of the certification process and Standard EN 15267-2 defines the requirements on the quality management system of the manufacturer and the periodic inspection audit of the manufacturing process as well as the management of modifications of tested and certified measurement systems. From now on the approval testing procedure for an emission monitoring system always requires the consideration of the new European standard series EN 15267. In Germany the system is managed by the responsible test laboratory (TÜV). The responsible statecommittee for the approval of emission measurement systems in Germany, BLAI, now supports the new system as responsible body. The approval process will be completed with the certificate provided by UBA (Federal Environmental Agency) and TÜV and will be finished with the publication of the measurement system in the German Federal Gazette. A flow chart of the new certification procedure is attached in chapter 4. EN 15267-1 General principles This standard defines common procedures and requirements for the certification of AMS to facilitate mutual recognition by the relevant bodies and thereby minimise administrative and cost burdens on AMS manufacturers seeking certification in multiple member states. It also describes the roles and responsibilities of manufacturers, test laboratories, certification bodies and relevant bodies under these procedures. EN 15267-2 Initial assessment of the AMS manufacturer s quality management system and post certification surveillance for the manufacturing process This standard specifies the requirements for the manufacturer s quality management system, the initial assessment of the manufacturer s production control and the continuing surveillance of the effect of subsequent design changes on the performance of certified automated measuring systems. EN 15267-3 Certification of automated measuring system EN 15267 Part 3 defines the performance criteria and procedures for performance testing of automated measuring systems (AMS) which measure gases and particulate matter and flow of the waste gas from stationary sources. In Germany this European Standard will replace the VDI 4203 Part 2 from 2004 and the Uniform Practice in Monitoring Emissions from 2005. The new standard provides detailed procedures covering the QAL1 requirements of EN 14181 and, where required, input data used in QAL3. The total uncertainty of the AMS determined from the tests according this standard should be at least 25 % below the maximum permissible uncertainty specified e g. in applicable regulations. A sufficient margin for the uncertainty contribution from the individual installation of the AMS is necessary to pass QAL2 and QAL3 of EN 14181 successfully.
The testing consists of two parts: the laboratory test as well as the field test. Laboratory testing is designed to assess whether an AMS can meet under controlled conditions, the technical requirements of the relevant performance criteria. Field testing over a minimum 3 month period is designed to assess whether an AMS can continue to work and meet the relevant performance criteria in a real application. Field testing is carried out on an industrial process representative of the intended application for the AMS for which the manufacturer seeks certification. Both parts can also be divided into two sections: covering general test requirements for all AMS followed by component specific test requirements. Test laboratories for the certification of AMS shall be accredited to EN ISO/IEC 17025 and the appropriate test standards for carrying out the tests defined in this standard. Test laboratories have to give evidence in knowledge on the uncertainties attributed to the individual test procedures applied during performance testing. 2. Performance Criteria s The main parameters of testing procedures are as follows: lack of fit (linearity) under laboratory and field conditions cross-sensitivity to likely interferents contained in waste gas other than measured component influence of variations in flow rate on extractive AMS influence of variations of the waste gas pressure response time under laboratory and field conditions influence of ambient conditions on zero and span readings performance and accuracy of the AMS against a standard reference method (SRM) in field reproducibility from two AMS under identical field conditions availability and maintenance interval under field conditions time-dependent zero and span drift under field conditions repeatability standard deviation at zero and span points Influence on vibrations for stack mounted AMS Excursion of the measurement beam of in-situ AMS Converter efficiency for AMS measuring NO x Performance Criteria Definitions A performance criterion is a value that corresponds to the largest permitted deviation allowed for each test, regardless of the sign of the deviation determined in the test. These criteria are specified for gas and particulate monitoring AMS in each for case laboratory and field test. The maximum allowable deviations of the measured signals are given as volume concentrations (volume fraction) for oxygen measuring AMS and as relative percentage of the upper limit of the certification range for other gases and particulates (see Table 1 and 2).
Performance characteristic Performance criteria Tested in Gases L = Laboratory O except O 2 2 F = Field Table 1: Response time 200 s (400 s for NH3, HCl and HF) 200 s L + F Repeatability standard deviation at zero point 2,0 % A 0,2 % B L Repeatability standard deviation at span point 2,0 % A 0,2 % B L Lack of fit (linearity) 2,0 % A 0,2 % B L + F Influence of ambient temperature change from 20 C within specified range at zero point 5,0 % A 0,5 % B L Influence of ambient temperature change from 20 C within specified range at span point 5,0 % A 0,5 % B L Influence of sample gas pressure at span point, for a pressure change p of 2kPa 2,0 % A 0,2 % B L Influence of sample gas flow on extractive AMS for a given specification by the manufacturer 2,0 % A 0,2 % B L Influence of voltage, at -15% and at + 10% from nominal supply voltage 2,0 % A 0,2 % B L Influence of vibration 2,0 % A 0,2 % B L Cross sensitivity 4,0 % A 0,4 % B L Excursion of the measurement beam of cross-stack in situ AMS 2,0 % A --- L Converter efficiency for AMS measuring NO x 95,0% --- L Determination coefficient of calibration function R 2 0,95% 0,95% F Minimum maintenance interval 8 days 8 days F Zero drift, within maintenance interval 3,0 % A 0,2 % B F Span drift, within maintenance interval 3,0 % A 0,2 % B F Availability 95,0% 95,0% F Reproducibility 3,3 % A 0,2 % B F A Percentage value as percentage of the upper limit of the certification range. B Percentage value as oxygen volume concentration (volume fraction) Performance criteria for gas monitoring AMS in laboratory and field test Table 2: Performance characteristic Performance criteria Tested in L = Laboratory F = Field Response time 200 s L + F Repeatability standard deviation at zero point 2,0 % A L Repeatability standard deviation at span point 5,0 % B L Lack of fit (linearity) 3,0 % A L + F Influence of ambient temperature change from 20 C within specified range at zero point 5,0 % A L Influence of ambient temperature change from 20 C within specified range at span point 5,0 % A L Influence of voltage, at -15% and at + 10% from nominal supply voltage 2,0 % A L Determination coefficient of calibration function R 2 0,90 F Minimum maintenance interval 8 days F Zero drift, within maintenance interval 3,0 % A F Span drift, within maintenance interval 3,0 % A F Availability 95,0% F Reproducibility 3,3 % A a) for concentrations > 20 mg/m³ 2,0 % A F b) for concentrations 20 mg/m³ 3,3 % A A Percentage value as percentage of the upper limit of the certification range. B Percentage value as percentage of the emission limit value Performance criteria for particulate monitoring AMS in laboratory and field test
3. First Experience with Selected Test Points Response time Commonly the certification work in laboratory starts with the evaluation of the response time. The response time of the instrument has an important influence on the duration of the complete laboratory test work. After each change in the concentration the measured signals of the AMS shall be determined by waiting the time equivalent to one independent reading and then recording three consecutive individual readings. An independent reading is defined as four times the response time; an individual reading is defined as an reading averaged over a time period equal to the response time. This has influence to each single test gas step during the certification. Duration of a test gas procedure for a fast AMS with a response time of 30 sec equals 210 sec (3.5 minutes)! Duration of a test gas procedure for a slow AMS with a response time of 150 sec equals 1050 sec (17.5 minutes)! Influence of ambient temperature The influence of ambient temperature changes is determined in a climate chamber which can control the ambient temperature within limits of +/- 1.0 K. In case of AMS installed outside, the following temperatures are to be set in the climate chamber in the given order or sequence: 20 C 0 C -20 C 20 C 50 C 20 C In case of AMS installed at temperature-controlled locations, the following temperatures are set in the climate chamber in the given order or sequence: 20 C 5 C 20 C 40 C 20 C The equilibration time between two temperature steps has to be at minimum 6 hours. Lack of fit The Lack of fit is performed with 7 different test gas concentrations. To avoid hysteresis effects the test gas concentrations have to be achieved in a fixed sequence: of the certification range. 0% 70% 40% 0% 60% 10% 30% 90% 0% Were no other method is practicable, the linearity test can also be performed with the aid of reference materials such as grating filters or gas filters. To calculate the lack of fit a regression line is established between the instrument readings of the AMS and the reference materials (Figure 1). In the next step the averages of AMS readings at each level has to be calculated. Then the deviation (residual) of this average to the regression line is calculated. These residuals have to meet the performance criteria of EN 15267.
250 4,0 Target value [mg/m³] 200 150 100 50 > 2% failed! 0 0 50 100 150 200 250 Reading AMS [mg/m³] Readings max allow ed deviation Residues Figure 1: Linearity check (e.g. AMS for SO 2 ) 3,0 2,0 1,0 0,0-1,0-2,0-3,0-4,0 Residues [%] Analytical function under field conditions (acc. QAL2 of EN 14181) The calibration curve of an AMS is defined as results of performance and accuracy against a standard reference method (SRM). The results for the individual measured component will be determined during the field test by performing parallel measurements with SRM. To fulfill the minimum requirements it is necessary to obtain a calibration function with a R 2 of minimum 0.90. In case of low or very constant gas/dust concentrations on the field test site, it is not possible to fulfill this requirement, even if the testes AMS works very precise. The requirement of R 2 is a problem especially for dust monitoring systems. In Figure 2 and Figure 3 a typical calibration function of a gaseous and a dust measuring AMS is shown.
Component NO Range of calibration 0-101.1 mg/m³ Certification range 0-100 mg/m³ Case *) (A) Regression analysis Gradient b 6,382 mg/m³/ma Axis intercept a -25.29 mg/m³ Standard deviation s D 7.73 mg/m³ Correlation coefficientt R² 0.9513 Certification range (E) 200 mg/m³, ntr Confidence interval 20 % of limit value Confidence interval 40 mg/m³ 15 % of limit value 30 mg/m³ Difference y smax - y smin 32.9 mg/m³ 120 Comparison measurements at the end of field test NO, Device 1 100 SRM [mg/m³] 80 60 40 20 0 Passed Comparison measurement Calibration function 0 2 4 6 8 10 12 14 16 18 20 AMS [ma] Figure 2: Analytical Function, gaseous component
Component dust gas condition of device Operating conditions Certification range 0 to 11 mg/m³ Case (A) Regression analysis Slope b 0.686 mg/m³/ma Axis intercept a -2.689 mg/m³ Standard deviation s D 0.89 mg/m³ Correlation coefficient R² 0.8094 Measuring range (E) 10 mg/m³, standard dry Confidence interval 30 % of limit value Confidence interval 3 mg/m³ 15 % of limit value 1.5 mg/m³ Difference y smax - y smin 6.3 mg/m³ Parallel measurements for Dust, beginning of field test, device 3 SRM [mg/m³] 12 10 8 6 4 2 0 Parallel measurements Calibration function (AMS operation conditions) Not Passed! R 2 > 0,90 meaningful? 0 2 4 6 8 10 12 14 16 18 20 AMS [ma] Figure 3: Analytical Function, component dust
Determination of total Uncertainty Finally the total uncertainty will be calculated with results of laboratory and field test. The allowed total uncertainties are listed in the EU Directives (2000/76/EG, 2001/80/EG). To fulfill the requirements of EN 15267-3 the tested AMS have to reach a total uncertainty of 75 % of the allowed value. Not for each component total uncertainties are given. An AMS that fulfills all the individual performance criteria will pass the overall uncertainty criteria not generally. In Table 3 and Table 4 examples for uncertainty calculations are given. Table 3: Uncertainty calculation acc. EN ISO 14956 (e.g. AMS for dust)
Table 4: Uncertainty calculation acc. EN ISO 14956 (e.g. AMS for SO 2 )
4. Process of Certification in Germany Manufacturer applies for approval test at TÜV. TÜV announces the test at the BLAI. TÜV conducts approval test according to EN 15267-3. TÜV assesses the QM-System of the manufacturer according to EN 15267-2 / ISO 9001. TÜV submits the documentations (test report and QMS assessment) to BLAI TÜV conducts further evaluations. Assessment of BLAI: Do the submitted documents fulfil the requirements? No, revision is required. Yes TÜV creates a certificate for the tested AMS. UBA initialises the publication in the German Federal Gazette. UBA and TÜV Rheinland sign and issue the certificate. Start of ongoing surveillance according to EN 15267-2.
References: EN 14181 (2004). Stationary source emissions. Quality assurance of automated measuring systems. CEN, Brussels, Belgium. EN 15267-1 (2007). Air Quality Certification of Automated Measuring Systems (AMS) Part 1: General aspects. EN 15267-2 (2009). Air Quality Certification of Automated Measuring Systems (AMS) Part 2: Minimum requirements for product quality assurance, initial assessment and on-going surveillance. EN 15267-3 (2009). Air Quality Certification of Automated Measuring Systems (AMS) Part 3: Performance standards and procedures for testing the performance of AMS of stationary source emissions.