Evolution sorbent Products (UK) Limited. Report No. R1609/GLH dated 31 st August G L Hearn B.Sc C.Eng M.I.E.T

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1 Wolfson Electrostatics Limited 32 Church Lane, Highfield Southampton SO17 1BJ England Tel: +44 (0) Fax: +44 (0) TEST REPORT FOR Evolution sorbent Products (UK) Limited ELECTROSTATIC CHARGE DECAY MEASUREMENTS ON SPILL CONTROL PADS TO STANDARDS BS 7506 AND IEC G L Hearn B.Sc C.Eng M.I.E.T

2 OVERVIEW This report gives the test method and results for electrostatic charge decay tests performed on non-woven polypropylene pads used in spill control. The pads are typically 15 x18 by about 1/8 thick provided by ESP Limited. The pre-conditioning and testing were performed at the Wolfson Electrostatics Laboratory at Southampton University over the period August 2016 and were undertaken in accordance with Section 7 of Standard BS 5706 Part 2 (1996) and Parts 2-1 and Annex A.1 of Standard IEC Samples were pre-conditioned and tested at 23±2C/50±5%RH and 23±2C/15±2%RH as stipulated in the Standards. TEST METHOD Two test methods were employed which are described fully in the Standards. It should be noted that due to the rapid charge dissipation exhibited by the test samples, the methods used deviated slightly from the Standards. The first method is fully described in the Section 7 of BS 7506 Part 2. The electrode arrangement used was equivalent to that described in Section of the Standard and used an applied voltage of ±400 DC with the sample placed on a groundable metal plane. The method of measurement used a digital storage oscilloscope to capture the charge decay curve from the sample which was monitored using a JCI 140/148 electric field meter/electrostatic voltmeter combination (John Chubb Instruments). As prescribed in the Standard, the charge decay time was taken as 1/e (36.8%) of the initial applied voltage and the charge decay time readings given in this report refer to these times. Three measurements at both positive and negative voltages were undertaken for each sample under test at each condition of temperature and relative humidity. In each case the test was performed on a new sample area of the material supplied. The second test method is described in Section 4.3 of Standard IEC This method differs from BS 7506 in the way the sample is charged (corona versus charged plate) and in the electrode configuration. An applied corona voltage of ±14,00 DC on a small brush electrode was used applied directly to the surface of the sample. As before, the sample placed on a groundable metal plane. Again, three measurements at both positive and negative voltages were undertaken for each sample under test at each condition of temperature and relative humidity. SAMPLE CONDITIONING All samples were pre-conditioned at 23±2C/50±5%RH and 23±2C/15±2%RH for a minimum of 20 hours immediately prior to testing. The tests were also performed under these conditions. It was noted that the higher humidity conditioning and testing requirement is not included in Standard IEC However, this was also undertaken as part of this testing since the samples were available due to the BS 7506 requirement (see below). Page 2

3 TEST RESULTS The test results obtained at 23±2C/50±5%RH and 23±2C/15±2%RH are given in Table 1. In all cases, the times given are for the initial voltage to decay to 1/e of the initial applied voltage. There was very little variation in the results obtained for each sample over the repeat runs and very little difference between the two humidity levels. BS 7506 polarity 23±2C/50±5%RH 23±2C/15±2%RH sample sample sample sample sample sample seconds seconds IEC polarity 23±2C/50±5%RH 23±2C/15±2%RH sample sample sample sample sample sample seconds seconds Table 1: Charge decay times measured according to Standards BS 5706 Part 2 and IEC measured with both polarities of charge at low and moderate humidity. Examples of the actual charge decay curves (at each test condition) are given in Appendix A of this report. Note that elapsed time runs from left to right and the horizontal scale (time base) is 200 milliseconds per division. SUMMARY AND INTERPRETATION OF RESULTS Under all test conditions, the material under test exhibited excellent charge dissipation properties with charge decay times of 30 milliseconds or faster. This material is suitable for use in sensitive flammable atmospheres (zones 0, 1, 20 and 21). End of main text. Page 3

4 APPENDIX A. CHARGE DECAY CURVES +400 BS 7506 method positive polarity charge at 23±2C/50±5%RH -400 BS 7506 method negative polarity charge at 23±2C/50±5%RH Page 4

5 IEC method positive polarity corona charging at 23±2C/50±5%RH IEC method negative polarity corona charging at 23±2C/50±5%RH Page 5

6 BS 7506 method positive polarity charge at 23±2C/15±2%RH BS 7506 method negative polarity charge at 23±2C/15±2%RH Page 6

7 IEC method positive polarity corona charging at 23±2C/12±3%RH IEC method negative polarity corona charging at 23±2C/12±3%RH Page 7