Ex PROFICIENCY TESTING PROGRAM

Transcription

1 Procedure Instruction i (1) Contents 1. General performance Procedure Functional test of Test Box "i" Calibration Contact resistance according to IEC : Data acquisition and data transmission Recording of the Test Results Documentation of the test setup PTB Working Group 3.54 Ex Proficiency Testing Team Version 1

2 1. General performance In this test round, the ignition probabilities are determined for each of the 12 circuits of Test Box "i" by means of a spark test apparatus in accordance with IEC :2007 Annex B. For this purpose, an explosive test mixture of group IIC, Table 7 (IEC :2007), consisting of 21% ± 2 % hydrogen mixed in air with the safety factor 1.0, has to be used for all tests/calibrations. The circuits of Test Box "i" are be connected to the spark test apparatus one after the other (Figure 1). Figure 1: Diagrammatic sketch of the test setup PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 1 of 10

3 2. Procedure The complete test procedure and the individual test steps are shown in the program flowchart and described in the associated table (Figure 2). Before the test to determine the ignition probability for the 12 circuits the number of revolutions and the contact resistance (see section 2.3) of used STA should be determined and entered into the template Test setup i (see section 3.2). Note: The ignition probability is understood as the ratio between the number of ignitons and the whole number of contacts. To determine the ignition probability for each of the 12 circuits 20 ignitions have to be realised. Thereby, the number of contacts (alternatively: the time or the revolutions) until ignition takes place must be recorded for each circuit. Note: The number of contacts means the number of wire movements across the cadmium disk or the number of revolutions of the wire holder multiplied by 4. The parameters and the dimensioning to be used to determine the ignition probabilities are predetermined in Test Box "i" as described in the "Roll-out" of the Proficiency Testing Program. After the circuit has been selected by rotary switch, the functional test is to be carried out in accordance with the Procedure Instruction, Section 2.1. Each time before and after the selected circuit is tested, the spark test apparatus has to be calibrated in accordance with IEC :2007 (Procedure Instruction, Section 2.2). For calibration, the number of contacts (alternatively: the time or the revolutions) until ignition takes place is recorded and entered into the template Test record i. The calibration circuit is installed in Test Box "i" too. The calibration currents are set with the potentiometer (see: Description of Test Sample i, Figure 7). After the calibration has been completed successfully, the ignition tests to determine the ignition probability of the selected circuit are carried out. The ignition probability is obtained from the average of the number of contacts (the time or the revolutions) until ignition takes place, whereby a total of 20 ignitions has to be achieved with the selected circuit. Additional Instructions: 1. After a total of 4000 contacts (1000 revolutions or 12.5 min at 80 min -1 ) in the calibration or in the ignition tests, the wires have to be replaced. PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 2 of 10

4 2. If during the ignition tests for one circuit (1000 revolutions or 12.5 min (at 80 min -1 )) no ignition has taken place after 4000 contacts, the tungsten wires have to be replaced and the above-mentioned calibration has to be carried out once again. After this new calibration, the ignition test has to be repeated with this circuit. After a total of 8000 contacts (2000 revolutions or 25 min (at 80 min -1 )) has taken place without any ignition occuring, the testing of this circuit has to be stopped. The break-off has to be recorded in the template Test record i. Figure 2: Flowchart of the test for each single circuit PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 3 of 10

5 Table 1: Explanations to the program flowchart Step Measure Remark 1 Selection of the circuit to be tested with the rotary switch 2 Functional test of Test Box "i" to check whether the selected circuit is damaged. 3 For every selected circuit, new tungsten wires have to be used for the test. 4 The calibration of the spark test apparatus must always be carried out before the selected circuit is tested(see Description of Test Sample i, section 2.2.2). The number of contacts until ignition takes place is to be entered in the template Test record i, Table 2. 5 Realisation of the ignition tests with the selected circuit(see Description of Test Sample i, section 2.2.1); Flush the spark test apparatus; Start the ignition test; Determination of the ignition probability (i.e. the average of 20 ignitions). 6 Maximum: 4000 contacts (1000 revolutions/12.5 min.) If within 4000 contacts, no ignition occurs, then: replace the wires, repeat the calibration and the ignition test. 7 The number of contacts (alternatively: the time/revolutions) until ignition takes place is to be entered in the template Test record i, Table 1. 8 After 20 ignitions the ignition test with the selected circuit ist finished 9 Calibration after testing(see Description of Test Sample i, section 2.2.2). The successful calibration after testing is also, at the same time, the calibration before testing of the next circuit (if there is no longer break between the tests i.e. less than 1 hour). The number of contacts is to be recorded in the Test record i, Table 2. see: Procedure Instruction, Section 2.1 see: Procedure Instruction, Section 2.2 See: Additional Instructions, No. 1 See: Additional Instructions, No. 2 see: Section 2.2 PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 4 of 10

6 2.1 Functional test of Test Box "i" The functional test has to be carried out by the participant for each circuit under test. The electrical values have to be in compliance with Table 2. All values have to meet the listed specifications. In the functional test, the installed voltage and the current of the respective circuit are to be measured and entered into the template Test record i. After both values in Table 2 have been achieved, the circuit may be applied in further measurements. Table 2: Measured voltages and currents for the circuits in Test Box "i" Circuits Installed Installed nominal voltage/v nominal current/ma Circuit 1 24 ± ± 5% Circuit 2 48 ± ± 5% Circuit 3 24 ± ± 5% Circuit 4 24 ± ± 5% Circuit 5 24 ± ± 5 % Circuit 6 24 ± ± 5% Circuit 7 24 ± ± 5% Circuit 8 22 ± ± 5% Circuit 9 22 ± ± 5 % Circuit ± ± 5% Circuit ± ± 5% Circuit ± ± 5% PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 5 of 10

7 2.2 Calibration The sensitivity of the spark test apparatus has to be checked before and after the testing with the calibration circuit. The calibration is carried out with the calibration circuit installed in Test Box "i". By means of potentiometer setting the current shall be reduced step by step. The sensitivity can be regarded as sufficient if an ignition occurs within 1760 contacts of the wire holder (alternatively: 440 revolutions or 5.5 min. (at 80 min -1 )) and with positive polarity. Regarding the flowchart of the calibration before and after the testing, see the diagram below and the associated table. The calibration starts at 35 ma. Then, the current is to reduce step by step by 1 ma down to a value of 30 ma. Entern the calibration results into the template Test record i, Table 2. The sensitivity of the spark test apparatus is sufficient if an ignition occurs within the above-mentioned contacts/revolutions of at least 30 ma. Additional instruction for the calibration: Step 1: If the sensitivity does not comply with the determined sensitivity, the following measures have to be taken: a) the composition of the explosive test mixture has to be checked; b) insertion of new tungsten wires; c) the spark test apparatus(sta) must be connected with a circuit of 95 mh/24 V/100 ma, and run the STA with the contacts in air for a duration of at least revolutions (about 250 min) of the electrode holder Step 2: After this, the calibration has to be repeated in accordance with the flowchart. The calibration has to be recorded in the template Test record i Step 3: If the current limit is measured only at 31 ma - 33 ma, the number of the contacts be recorded in the template Test record i. If the sensitivity of the spark test apparatus is not yet sufficient at 33 ma, please contact PTB. PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 6 of 10

8 Figure 3: Flowchart of the calibration Table 3: Explanations to the calibration flowchart Step Measure Remark 1 The calibration starts at 35 ma by potentiometer setting. see: Test Sample i, Section Maximum: 1760 contacts (440 revolutions/5.5 min.) If within 1760 contacts no ignition takes place, see: Additional Instruction for the Calibration then the measures listed under "Step 1" of the Additional Instruction for the Calibration have to be taken. 3 The number of contacts until ignition takes place is to be entered into the template Test record i, Table 2. 4 The sensitivity is sufficient if an ignition occurs at at least 30 ma. 5 The current is reduced step by step by 1 ma down to 30 ma. PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 7 of 10

9 2.3 Contact resistance according to IEC :2007 Because of reliability the contact resistance of the spark test apparatus is measured at 4 different contact positions, with the contacts closed, at a direct current of 1A, by using the following measurement setup: Figure 4: Measurement setup for the determination of the contact resistance The detected contact resistances should be recorded in the document Test setup i, Table 1. PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 8 of 10

10 3. Data acquisition and data transmission The templates for all the data, information and documentation to be collected are made available electronically via the Internet platform. Web address: Menu items: Participants area Test Round i Procedure Additional Instructions: 1. The transmitted data must be original data. 2. The information documentation Test setup i and the template Test record i should be filled in completely and uploaded to PTB Ex PTP Homepage in the section Participants area Result upload. No further action is required. 3. To understand easier which way the documentation should be drawn up, a sample documentation is included in "Procedure Instruction", with fictitious values. 3.1 Recording of the Test Results The test results of each circuit in Test Box "i" have to be entered into the template Test record i. For each circuit, the following data have to be entered into the template Test record i: Number of contacts until ignition occurred (for each ignition) Number of contacts until ignition occurred during the calibration; Voltage and current values of the circuit during the functional test. At the end of the test round, the template Test record i has to be uploaded at least 12 times for 12 circuits which should be transmitted to PTB. PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 9 of 10

11 3.2 Documentation of the test setup For a better understanding and for an analysis of the measurement results, additional information on the test setup should be provided. For the documentation of the test setup, the document Test setup i should be downloaded from the PTB Ex PTP Homepage. The following data should be entered into the documentation: a verbal description of the explosive test mixture preparation; one or two photos, showing the condition of the cadmium disk used (1 photo showing the whole disk and 1 close-up view); one photo of the spark test apparatus; one photo of the device for the explosive test mixture preparation; Protocol for the determination of the contact resistance. Please ensure that the whole setup is visible at the photo. The completed documents can be uploaded on the PTB Ex PTP Homepage and are transmitted to PTB. PTB Working Group 3.54 Ex Proficiency Testing Team Version 1 Page 10 of 10