ISO-13319-2000.pdf

Reference number ISO 13319:2000(E) ©ISO 2000 INTERNATIONAL STANDARD ISO 13319 First edition 2000-04-01 Determination of particle size distributions Electrical sensing zone method Détermination des répartitions granulométriques Méthodes de la zone de détection électrique Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 13319:2000(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ©ISO 2000 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 ? CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 734 10 79 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland ii© ISO 2000 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 13319:2000(E) © ISO 2000 All rights reservediii ContentsPage Foreword.iv 1Scope 1 2Terms and definitions .1 3Symbols1 4Principle2 5General operation3 6Operational procedures 4 7Calculation of results 10 8Analysis11 9Validation11 Annex A (informative) Table of materials and electrolyte solutions12 Annex B (informative) Technique using two (or more) sensors 23 Annex C (informative) Example of calibration by mass integration 25 Annex D (informative) Calibration and control of frequently used orifices 27 Annex E (informative) Data sheet28 Bibliography30 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 13319:2000(E) iv© ISO 2000 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 13319 was prepared by Technical Committee ISO/TC 24,Sieves, sieving, and other sizing methods, Subcommittee SC 4,Sizing by methods other than sieving. Annexes A to E of this International Standard are for information only. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARDISO 13319:2000(E) © ISO 2000 All rights reserved1 Determination of particle size distributions Electrical sensing zone method 1Scope This International Standard gives guidance on the measurement of the size distributions of particles dispersed in an electrolyte solution using the electrical sensing zone method. It does not address the specific requirements of the particle size measurement of specific materials. The method described in this International Standard measures particle volumes and reports in the range about from 0,6 ?m to 1 600 ?m. 2Terms and definitions For the purposes of this International Standard, the following terms and definitions apply. 2.1 dead time time during which the electronics are not able to detect particles due to the signal processing of a previous particle 2.2 orifice small-diameter hole through which suspension is drawn 2.3 sensing zone volume of electrolyte solution within, and around, the orifice in which a particle is detected 2.4 sampling volume volume of suspension that is analysed 3Symbols Dorifice diameter, in ?m Kdcalibration constant of diameter Kdcalibration constant of mean diameter ? Kd standard deviation of mean calibration constant mmass of sample in beaker, in g VTvolume of electrolyte solution in which m is dispersed, in ml Vmanalysis volume, in ml ?Ninumber of counts in a size interval i ?mass of the particles per volume of the electrolyte it displaces, in g?ml?1 Viarithmetic mean volume for a particular size interval i, in ml Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 13319:2000(E) 2© ISO 2000 All rights reserved Vivolume of the particle obtained from the threshold, or channel boundary and instrument units; without an arbitrary calibration to particle diameter (i.e. Vi= tIA, where t = threshold level, I = current through aperture and A = attenuation factor), in ml xdiameter of a sphere with volume equivalent to that of the particle, in ?m x50, x10, x90the values of x corresponding to the 50 %, 10 % and 90 % percentile points of the cumulative per cent undersize distributions, in ?m 4Principle The response, i.e. the electrical pulse generated when a particle passes through the orifice, has been found both experimentally and theoretically to be proportional to the particle volume (see Bibliography). A dilute suspension of particles dispersed in an electrolyte solution is stirred to provide a homogeneous mixture and is drawn through a small orifice, or aperture, in an insulating wall. A current applied across two electrodes, placed on each side of the orifice, enables the particles to be sensed by the electrical impedance changes as they pass through the orifice. The particle-generated pulses are amplified and counted and the pulse height is analysed. After employing a calibration factor, a distribution of the number of particles against the volume-equivalent diameter is obtained. This distribution is usually converted to percentage by mass versus particle size, where the size parameter is expressed as the diameter of a sphere of volume and density equal to that of the particle. See Figure 1. Key 1Volumetric metering device6Output 2Valve7Pulse-height analyser 3Pulse amplifier8Stirred suspension of particles in electrolyte solution 4Oscilloscope pulse display9Aperture 5Counting circuit10Counter start/stop Figure 1 Diagram illustrating the principle of the electrical sensing zone method Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 13319:2000(E) © ISO 2000 All rights reserved3 5General operation 5.1Response If the particles are spherical, the electrical response is proportional to the volume of the particles. This has also been shown to be true for particles of other shapes; however, the constant of proportionality (i.e. the instruments calibration constant) may be different. In general, particles should have a low conductivity with respect to the electrolyte solution, but conducting particles can be measured. 5.2Size limits The lower size limit of the electrical sensing zone method is generally considered to be restricted only by thermal and electronic noise. It is normally stated to be about 0,6 ?m, but under favourable conditions a lower limit is possible. There is no theoretical upper limit, and for particles having a density similar to that of the electrolyte solution, the largest orifice available (normally 2 000 ?m) may be used. When the particle density is high, the upper size limit is reached when the particles can no longer be kept in homogeneous suspension. In this case, the viscosity and/or the density of the electrolyte solution has to be increased, for example by the addition of glycerol or sucrose. The size range for a single orifice sensor is proportional to the orifice diameter, D. The response has been found to depend linearly on D over a range from 0,015 D to 0,80 D (i.e. 1,5 ?m to 80 ?m for a 100 ?m orifice), although the orifice may become prone to blockage at levels greater than 0,60 D. This range can be extended by using two or more sensors (see annex B) but in practice this procedure can be avoided by the careful selection of the diameter of one sensor, to achieve an acceptable range. The response of the instrument is dependent on the effective electrical resistance of the particle, which is usually high. The measurement of conducting particles (e.g. metals, carbon, silicon and many types of cells and organisms, such as blood cells) requires more time to implement. The particles can become electrically translucent (i.e. give a smaller electrical pulse than their volume indicates) if a voltage, typically of 10 V to 15 V or more, is applied between the electrodes. To obtain acceptable results, a distribution is obtained under normal conditions. The analysis is then repeated using half the current and twice the gain (1/attenuation). The distributions should be the same. If they are not, the procedure should be repeated using an even lower current. 5.3Effect of coincident particle passage Ideal data would result if particles traversed the orifice singly, when each particle would produce a single pulse. When two or more particles arrive in the sensing zone together, the resulting pulse will be complex. Either a single large pulse will be obtained, resulting in a loss of count and effectively registering a single larger particle, or the count will be correct but the reported size of each will be increased, or some particles will not be counted. These effects will distort the particle distribution obtained but can be minimized by using low concentrations. Table 1 shows counts per millilitre for the coincidence to be 5 % (i.e. approximately only one particle in twenty is affected). Counts per millilitre should always be less than these quoted values. Since particle size distributions should not be a function of concentration, the effect of coincidence can be tested by obtaining a distribution at one concentration and comparing it with that obtained when the concentration is halved. In such a test, repeat such dilutions until the reduction in count in a channel with the largest number decreases in proportion to the dilution. This should always be done when analysing very narrow size distributions, as this is where the effect of coincidence is most noticeable. 5.4Dead time In some modern instruments, pulse-height analysis routines are used to process the data. Since it takes a finite time to process each pulse, it is possible that the analyser may not count particles for a given time after receiving a pulse. This means that, for a relatively high count rate, a significant proportion of the counts may be lost. Since dead time is not a function of the pulse height, the loss will be proportional to the counts in each channel and will not affect the size distribution. However, if concentration is to be reported or the mass integration method of calibration (see 6.11.3) is to be used, the effect can be kept to a minimum by using dilute suspensions (e.g. at 5 % coincidence) and setting up the instrument so that the pulses in the lowest channels are not counted. This is Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Qatar Petroleum/5943408001 Not for Resale, 04/12/2007 03:12:27 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 13319:2000(E) 4© ISO 2000 All rights reserved done by first obtaining a count distribution and observing the number of counts per channel. A typical result is shown in Figure 2. By restricting the counts in the lowest channel to that shown by A, the dead time will be minimized. In normal operation, this dead time will not cause any distortion of the size distribution since all particles will have the same chance of not being counted, provided that a large number of particles, at least 100 000, are counted. However dead time will affect the accuracy of the mass integration method of calibration (see 6.11.3), when there will be an apparent loss of mass. Counts at channels below A are noise counts. True particle counts are at the higher channels Figure 2 Typical results 5.5Repeatability of counts It has been shown that, in a correctly performed analysis, the number of counts in each channel is a random variable which follows Poisson's law. This means that the standard deviation of a number of counts N approximates toN. Thus, in a series of replicate runs the number of counts in a channel, Ni,1, Ni,2, Ni,3, etc., which yield a mean count Niwith 95 % confidence, the replicate counts