PTB Ex PT Scheme. Procedure Instruction of program Explosion Pressure - Test Round 2017

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1 Procedure Instruction of program Explosion Pressure - Test Round 2017 Content 1 General Performance Measurand / Characteristic of interest Test Item and Configurations Components Blind flanges prepared in advance Homogeneity and Stability Homogeneity test Stability Configurations of Test Sample EP and measurements Configuration a) Configuration b) Identification Procedure Flowchart for determination of explosion pressure at normal ambient temperature Flowchart for determination of explosion pressure at ambient temperature of - 40 C Boundary / Environmental Conditions Data acquisition and Transmission Records and additional Documentation Additional Instructions Uncertainty of measurement (optional) Data Analysis and Evaluation Reporting Annex Example of filled in templates PTB Working Group Page 1 of 26

2 1 General Performance In the program Explosion Pressure, the quantity selected which is to be compared (measurand of interest), is the explosion pressure (reference pressure). As has already been mentioned in the "Roll Out Paper", the general routine procedure is described by the standard Explosive atmospheres - Part 1: Equipment protection by flameproof enclosures d - IEC , Edition 7.0. The general routine procedure to determine the explosion pressure is described in clause of IEC The measurand of interest is to determine with the Test Sample EP for two different configurations (single chamber and combination of both chambers with orifice), two different ambient temperatures (normal temperature and ambient temperature of - 40 C) and two different explosive mixtures (ethylene & hydrogen) selected according to IEC On the basis of two configurations of the Test Sample EP, two explosive mixtures, two ambient temperatures and five ignitions each, a total of 40 explosion tests must be performed by each participant for the program Explosion Pressure. The workload to perform this program is approximately three working days. 2 Measurand / Characteristic of interest The measurand of interest is the explosion pressure (reference pressure). This is the quantity selected which is to be compared in the program. 3 Test Item and Configurations To ensure comparability and homogeneity, all Test Samples EP are completely developed and prepared by the coordinator. Every participating laboratory of the program Explosion Pressure will receive all components of the Test Sample EP directly from the coordinator which are needed to perform the program. Please notice that the Test Sample EP which is used in this Test Round 2017 is identical to the test sample which was used in the previous Test Round 2010 of program Explosion Pressure and is almost identical to the test sample which was used in the previous program Flame Transmission - Test Round Participating laboratories which already possess the Test Sample EP or FT shall use it again for this Test Round The required orifice and new gaskets to perform this test round are provided by the coordinator. PTB Working Group Page 2 of 26

3 3.1 Components The Test Sample EP (see Figure 1) consists of two cylindrical compartments of different lengths as well as an orifice. Additionally, two blank flanges are included, each equipped with five test holes of different thread forms. The test sample is composed of 75 single components. Table 1: List of components of Test Sample EP No. Component description Quantity 1 Pipe A (1 x pipe section including 2 x connecting flanges with a total length of mm) (Material: F304L; stainless steel) 2 Pipe B (1 x pipe section including 2 x connecting flanges with a total length of mm) (Material: F304L; stainless steel) 3 Blind flanges with connection holes (Material: F304L; stainless steel) x connecting screws + 24 x nuts (hexagon screws M20, length 80 mm) 48 (Material: A2; steel) 5 Flange gasket (Material: aramid fiber with nitrile rubber) x locking screws + 8 x sealing rings 16 (2 x M 10 x 1; 2 x M 14x 1.25; 2 x G 1/2" A; 2 x G 3/8" A) (Material screws: A2; steel; Material sealing rings: copper) 7 Orifice (ø = 220 mm, material thickness: 6 mm) (Material: duraluminium) 1 Total 75 Figure 1: Exploded view of Test Sample EP PTB Working Group Page 3 of 26

4 3.1.1 Blind flanges prepared in advance The blind flanges located at the pipe ends are equipped with five connection holes of different thread forms. The respective installation holes are used depending on the installation technology. The hole for the pressure sensor is located in the center position. The other installation holes can be used for the gas supply and the ignition source respective individual installation technology adaptors. In addition to the specified installation holes, the participant can locate a threaded hole on his own at the predefined position (if necessary). Figure 2: Position of installation holes on the blind flanges (located at the pipe ends) (1) Predefined position for an installation hole to be placed by the participant on his own if required (2) Installation hole M 10 x 1 (3) Installation hole G 1/2" A (4) Installation hole G 3/8" A (5) Installation hole M 14 x 1.25 (6) Hole (M 10 x 1) for installation of the pressure sensor PTB Working Group Page 4 of 26

5 3.2 Homogeneity and Stability To ensure homogeneity and stability in accordance with ISO/IEC 17043, homogeneity tests are carried out for each test sample before sending it to the participants Homogeneity test The homogeneity test consists of a visual check to control the processing of the sample and a linear measurement to control the geometry and dimensions of the respective components. The following parameters have been checked to assure homogeneity: - Visual check - Length of Pipe A (250 ± 2) mm - Length of Pipe B (500 ± 2) mm - Internal diameter of the pipes (161.5 ± 2) mm The tolerances of the parameters have been determined related to preliminary tests performed at PTB. Scattering within the range of tolerance has no measurable influence on the explosion pressure Stability Due to the massive construction of the test sample and the used high-quality materials, long-term stability can be assumed. Furthermore, preliminary investigations and extensive measurement series on the test sample have not caused any changes in the geometry. Therefore, no further special stability test has been performed. 3.3 Configurations of Test Sample EP and measurements The configurations of the Test Sample EP to perform the tests are as follows: Configuration a) Pipe A Five ignition tests with explosive mixture (1) (ethylene 8 % ± 0.5 %) at normal ambient temperature (ignition side 1) Five ignition tests with explosive mixture (2) (hydrogen 31 % ± 1 %) at normal ambient temperature (ignition side 1) Five ignition tests with explosive mixture (1) (ethylene 8 % ± 0.5 %) for use at an ambient temperature of - 40 C (ignition side 1) Five ignition tests with explosive mixture (2) (hydrogen 31 % ± 1 %) for use at an ambient temperature of - 40 C (ignition side 1) Figure 3: Configuration a) PTB Working Group Page 5 of 26

6 3.3.2 Configuration b) Pipe A combined with Pipe B and orifice Five ignition tests with explosive mixture (1) (ethylene 8 % ± 0.5 %) at normal ambient temperature (ignition side 2) Five ignition tests with explosive mixture (2) (hydrogen 31 % ± 1 %) at normal ambient temperature (ignition side 2) Five ignition tests with explosive mixture (1) (ethylene 8 % ± 0.5 %) for use at an ambient temperature of - 40 C (ignition side 2) Five ignition tests with explosive mixture (2) (hydrogen 31 % ± 1 %) for use at an ambient temperature of - 40 C (ignition side 2) 3.4 Identification Figure 4: Configuration b) The two Pipes A and B, the flanges and the orifice of the Test Samples EP are marked with a unique identification number. The identification number is structured depending on the version - as follows: Figure 5: Structure of identification number of Test Sample EP Version Test Round 2010 Figure 6: Structure of identification number of Test Sample EP Version Test Round 2013, Test Sample FT PTB Working Group Page 6 of 26

7 Figure 7: Structure of identification number of Test Sample EP Version Test Round Procedure The program Explosion Pressure - Test Round 2017 is performed on two configurations of the Test Sample EP, two explosive mixtures and two ambient temperatures. To perform the program, the individual routine procedure of each test laboratory needs to be applied (used every day for achieving the test results for real projects). Additionally, detailed guidance how to perform the tests together with the test samples provided in this paper is to be applied. The following program flowcharts show the single steps for the performance of the tests for program Explosion Pressure - Test Round PTB Working Group Page 7 of 26

8 4.1 Flowchart for determination of explosion pressure at normal ambient temperature Start 1. Setting up the configuration (selection a) or b)) 2. Recording the ambient pressure and temperature 13. Rinse test sample with sufficient air 3. Selection and setting up the concentration of the explosive mixture 13. Rinse test sample with sufficient air 4. Filling up the test sample with the explosive mixture 5. Recording the concentration of the explosive mixture No 6. Relief or adjust the explosive mixture to atmospheric pressure 7. Recording the pressure, temperature and humidity of the explosive mixture (if available 8.Ignition No 9. Recording the measurement result (explosion pressure) 10. Have the five measurements been performed with the explosive mixture? Yes 11. Have the ten measurements for the configuration been performed? Yes 12. Photo documentation of the configuration End Figure 8: Flowchart for normal ambient temperature PTB Working Group Page 8 of 26

9 Table 2: Explanations of the flowchart for determination of explosion pressure at normal ambient temperature Step Explanation Note 1 Setting up the selected configuration a) or b). One cycle in the program flowchart always relates to one configuration. 2 The recording of the ambient pressure and temperature of the test facility can be helpful for further analysis of the test results. 3 Selection and setting the concentration of the gas-air mixture in accordance with IEC , section : Explosive mixture: (1) ethylene (8 ± 0.5) % or Explosive mixture: (2) hydrogen (31 ± 1) % 4 Filling up the test sample with the explosive mixture until the specified concentration has been reached. 5 Recording the concentration of the explosive mixture in the test sample. 6 Relief of the explosive mixture overpressure in the test sample and adjust to atmospheric pressure. 7 If available, the recording of the pressure, temperature and humidity of the explosive mixture can be helpful for further analysis of the test results. 8 Trigger ignition device: Ignition on Side 1 for configuration a) or Ignition on Side 2 for configuration b) 9 Recording of the measurement results for the respective configuration (a) or b)) with accompanied uncertainty (if available). In addition, the selected pressure curves shall be recorded. 10 After five measurements for one explosive mixture in the selected configuration have been completed, measurements for the second explosive mixture can be carried out. 11 After the ten measurements (five measurements per explosive mixture) for the selected configuration have been performed, measurements for the next configuration can be carried out. 12 For a complete documentation of the test set-up, photos showing the total set-up as well as the connections used should be taken. 13 To eliminate possible combustion and remaining humidity from previous ignitions, the test sample should be sufficiently purged with air after each ignition. See section 3.3; See Table 1 See section 5.1; Template: Test Record EP See section 3.3; See section 5.1; Template: Test Record EP See section 5.1; Template: Test Record EP See section 3.3; See section 5.1; See Section 9; Template: Test Record EP Start again with step 1 of the program flowchart See section 5.1; Template: Test Setup EP PTB Working Group Page 9 of 26

10 4.2 Flowchart for determination of explosion pressure at ambient temperature of - 40 C Start 1. Setting up the configuration (selection a) or b)) 14. Rinse test sample with sufficient air 2. Selection and setting up the concentration of the explosive mixture 14. Rinse test sample with sufficient air 3. Filling up the test sample with the explosive mixture No Test at 40 C 5a. Cooling down the temperature of the explosive mixture to -40 C 4. Choosing a method for an ambient temperature of -40 C in accordance to Test with increased pressure 5b. Increasing the pressure of the explosive mixture using the formula of Recording the concentration of the explosive mixture 7. Relief or adjust the explosive mixture to atmospheric pressure (only for testing at -40 C) 8. Recording the pressure, temperature and humidity of the explosive mixture (if available No 9.Ignition 10. Recording the measurement results (explosion pressure) 11. Have the five measurements been performed with the explosive mixture? Yes 12. Have the ten measurements for the configuration been performed? Yes 13. Photo documentation of the configuration End Figure 9 Flowchart for ambient temperature of 40 C PTB Working Group Page 10 of 26

11 Table 3 Explanations of the flowchart for determination of explosion pressure at ambient temperature of 40 C Step Explanation Note 1 Setting up the selected configuration a) or b). One cycle in the program flowchart always relates to one configuration. 2 Selection and setting the concentration of the gas-air mixture in accordance with IEC , section : Explosive mixture: (1) ethylene (8 ± 0.5) % or Explosive mixture: (2) hydrogen (31 ± 1) % 3 Filling up the test sample with the explosive mixture until the specified concentration has been reached. 4 The reference pressure for use at ambient pressure of 40 C shall be determined by one of the following methods in accordance to IEC , section : (a) The reference pressure shall be determined at a temperature not higher than the minimum ambient temperature, or (b) the reference pressure shall be determined at normal ambient temperature using the defined test mixture(s), but at increased pressure. 5a Cooling down the temperature of the explosive mixture to 40 C 5b The absolute pressure of the explosive mixture (P), in kpa, shall be calculated by the following formula, using T a, min in C: P = 100[293 / (T a, min + 273)] kpa 6 Recording the concentration of the explosive mixture in the test sample. 7 Relief of the explosive mixture overpressure in the test sample and adjust to atmospheric pressure. (This only applies using the method to determine the reference pressure at an ambient temperature of 40 C.) 8 If available, the recording of the pressure, temperature and humidity of the explosive mixture can be helpful for further analysis of the test results. 9 Trigger ignition device: Ignition on Side 1 for configuration a) or Ignition on Side 2 for configuration b) 10 Recording of the measurement results for the respective configuration (a) or b)) with accompanied uncertainty (if available). In addition, the selected pressure curves shall be recorded. 11 After five measurements for one explosive mixture in the selected configuration have been completed, measurements for the second explosive mixture can be carried out. 12 After the ten measurements (five measurements per explosive mixture) for the selected configuration have been performed, measurements for the next configuration can be carried out. 13 For a complete documentation of the test set-up, photos showing the total set-up as well as the connections used should be taken. 14 To eliminate possible combustion and remaining humidity from previous ignitions, the test sample should be sufficiently purged with air after each ignition. See section 3.3; See Table 1 See section 3.3; See IEC , section ; See section 5.1; Template: Test Record EP See section 5.1; Template: Test Record EP See section 3.3; See section 5.1; See section 9; Template: Test Record EP Start again with step 1 of the program flowchart See section 5.1; Template: Test Setup EP PTB Working Group Page 11 of 26

12 4.3 Boundary / Environmental Conditions The tests shall be performed with the ambience conditions which are to be applied for the individual routine procedure of each laboratory (in accordance with the requirements of IEC ). Due to the relationship between explosion pressure and specific conditions it could be helpful for the analysis of the results to get as much detailed information about the boundary / environmental conditions during the tests as possible. The environmental parameters of interest are ambient pressure and ambient temperature. Further interesting parameters are pressure, temperature and humidity of the explosive mixture inside the sample respectively inside the system. The Test Record EP provides the opportunity to record the mentioned parameters. 5 Data acquisition and Transmission The templates for all data, information and documentation to be recorded are made available in an electronic form on the PTB Ex PTS website. Web address: Menu items: Programs -> Program "Explosion Pressure" (Test Round 2017) -> Download 5.1 Records and additional Documentation There are two documents which are to be completed during the tests, Test Record EP and Test Setup EP. Furthermore, pressure curves shall be recorded. In the document Test Record EP the following values / parameters shall be determined: Ambient temperature Ambient pressure The explosive mixture to be used, in volumetric ratio with air Pressure of explosive mixture Temperature of explosive mixture Humidity of explosive mixture Explosion pressure P 1 (Side 1) with accompanied uncertainty (if available) Explosion pressure P 2 (Side 2) with accompanied uncertainty (if available) In the document Test Setup EP the following information shall be provided: Photos showing the total setup as well as the connections used Photos showing the used measuring system to measure the explosion pressure (pressure transducers, amplifiers, data acquisition device / system, etc.) Photos showing the used system to produce and analyze the explosive mixture Photos showing the method of cooling down the temperature of the explosive mixture to 40 C (if this method has been chosen) PTB Working Group Page 12 of 26

13 As the explosion pressure to be measured shows a dynamic behaviour, it is important to record also pressure curves. It is not necessary to record all pressure curves for each one of the ten ignitions per configuration, but the selection shown in the following should be made at least: For configurations a) and b) at normal ambient temperature, the pressure curve with the highest explosion pressure per explosive mixture must be recorded: 1. Configuration a) -> ethylene -> maximum explosion pressure 2. Configuration a) -> hydrogen -> maximum explosion pressure 3. Configuration b) -> ethylene -> maximum explosion pressure 4. Configuration b) -> hydrogen -> maximum explosion pressure For configurations a) and b) at ambient temperature of - 40 C, the pressure curve with the highest explosion pressure per explosive mixture must be recorded: 5. Configuration a) -> ethylene -> maximum explosion pressure 6. Configuration a) -> hydrogen -> maximum explosion pressure 7. Configuration b) -> ethylene -> maximum explosion pressure 8. Configuration b) -> hydrogen -> maximum explosion pressure The completed templates Test Record EP, Test Setup EP and the pressure curves are to be uploaded on the PTB Ex PTS website ( in the upload area. By this, the documents are forwarded to the coordinator. Menu items: Programs -> "Explosion Pressure" (Test Round 2017) -> Upload 6 Additional Instructions It is very welcomed that a participating laboratory, which has the technical possibilities to perform the tests for an ambient temperature of 40 C with the method of increasing pressure as well as cooling down the temperature of the explosive mixture, perform the tests with both methods. Should that be the case, the results which shall be used for the evaluation in the reports (as the official participants results) must be noted in the comments section of Test Record EP. The transmitted data must be the original data. To get a better understanding for completing the documentation, a model documentation (Test Record EP Example, Test Setup EP Example) with fictional values is enclosed in Annex You can also find them in an electronic form on the website in the download section. (Menu items: Programs -> Program "Explosion Pressure" (Test Round 2017) -> Download) To facilitate the data analysis please upload your Test Record EP in the given *.xls(x) format. The Test Samples EP are provided for the use within the PTB Ex PT Program Explosion Pressure - Test Round It is not intended to use the test samples for other purposes. PTB Working Group Page 13 of 26

14 The Test Sample EP should be kept by the participant after the performance of the tests for future programs. To assure homogeneity, the positions of the two pressure sensors on the flanges are predetermined. The position for pressure sensors S1 and S2 is in the center of the prepared flanges. Participants shall always perform the tests according to the applying standard and the Procedure Instruction for EP. In addition, participants shall perform as they would do in their daily in-house routine. Please take notice of the Best Practice Paper Explosion Pressure 2010 available on the PTB Ex PTS website under: Menu items: Best Practice Papers / QM -> Best Practice Papers -> Best Practice Paper Explosion Pressure Uncertainty of measurement (optional) In accordance to OD 012 of IECEx the measurement of explosion pressure is a test where test method and handling of the results has already taken into account measurement uncertainties by testing under worst case conditions and by application of safety factors. Therefore, it is not necessary to calculate the uncertainty associated with the measurement result. Nevertheless, for the calculation of performance statistics and the evaluation of the performance of a participating laboratory within a proficiency testing scheme, it is forward-looking and fruitful to have a statement about the accompanied uncertainty of the result of a measurement. A first step to get in touch with the topic is to get an overview about the significance and the handling of uncertainty of measurement in the participating laboratories. Therefore, we would like the participants to make uncertainty of measurement calculations for the measured explosion pressures in program Explosion Pressure Test Round As a guide for application of uncertainty of measurement IECEx OD 012 can be used. The Test Record EP provides fields for the values of uncertainty as well as space for a description of the used calculation method and the uncertainty budget. 8 Data Analysis and Evaluation The statistical methods used to analyze and evaluate the participants results are developed and documented in accordance to ISO/IEC and ISO It is documented in the reports and describes in detail the use of descriptive statistics, methods used to determine the assigned value, interpretation of the statistical analysis and criteria for performance evaluation. 9 Reporting Reports are made available electronically in compliance with the requirements of standard ISO/IEC 17043, clause 4.8. Reports include a summary of the results for all participants of the PTB Ex Proficiency Testing Program Explosion Pressure - Test Round 2017 in form of tabular and graphical presentations. Furthermore, the reports include detailed information like a description of the test samples used, a description of the test samples preparation and homogeneity and stability assessment, procedures used to establish the assigned values and information about procedures used to statistically analyze the data. The reporting structure is organized in two parts, an interim report and a final report. After performance of the tests the participating laboratories receive an interim report. They can analyze PTB Working Group Page 14 of 26

15 their results compared with the other laboratories and are invited to repeat the tests in a second phase after improvement of their procedures and instrumentation, if they are not happy with their position regarding the difference with the assigned value. After this second phase with the new uploaded results a final report will be issued. If a participant does not want to take part in the phase II session, the participants data of phase I will be used for the final report of the program. All participants are requested to handle all information and data of the reports confidentially. PTB Working Group Page 15 of 26

16 10 Annex 10.1 Example of filled in templates PTB Working Group Page 16 of 26

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