1、 IEC/TR 62781 Edition 1.0 2012-09 TECHNICAL REPORT Ultrasonics Conditioning of water for ultrasonic measurements IEC/TR 62781:2012(E) colour inside THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2012 IEC, Geneva, Switzerland All rights reserved. Unless otherwise specified, no part of this publica
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8、ervice Centre - webstore.iec.ch/csc If you wish to give us your feedback on this publication or need further assistance, please contact the Customer Service Centre: csciec.ch. IEC/TR 62781 Edition 1.0 2012-09 TECHNICAL REPORT Ultrasonics Conditioning of water for ultrasonic measurements INTERNATIONA
9、L ELECTROTECHNICAL COMMISSION S ICS 17.140.50 PRICE CODE ISBN 978-2-83220-376-7 Registered trademark of the International Electrotechnical Commission Warning! Make sure that you obtained this publication from an authorized distributor. colour inside 2 TR 62781 IEC:2012(E) CONTENTS FOREWORD . 4 INTRO
10、DUCTION . 6 1 Scope . 7 2 Normative references . 7 3 Dissolved gases . 7 3.1 General . 7 3.2 Chemical methods . 8 3.2.1 General . 8 3.2.2 Addition of sodium sulphite 8 3.3 Physical methods 9 3.3.1 General . 9 3.3.2 Vacuum degassing 9 3.3.3 Reduced pressure recirculation . 9 3.3.4 Degassing contactor
11、s 11 3.3.5 Boiling . 11 3.4 Verification methods 11 3.4.1 General . 11 3.4.2 Electrical verification methods . 12 3.4.3 Optical verification methods . 12 3.5 Re-gassing 12 4 Dissolved ionic content . 13 4.1 General . 13 4.2 Chemical methods . 13 4.2.1 General . 13 4.2.2 Ion exchange devices 13 4.3 P
12、hysical methods 13 4.3.1 General . 13 4.3.2 Distillation . 14 4.3.3 Reverse osmosis . 14 4.4 Verification methods 14 4.5 Reionization 14 5 Biological content . 15 5.1 General . 15 5.2 Chemical methods . 15 5.2.1 General . 15 5.2.2 Addition of chlorine-based chemicals . 15 5.2.3 Addition of copper-ba
13、sed chemicals 15 5.2.4 Addition of silver-based chemicals . 16 5.3 Physical methods 16 5.3.1 General . 16 5.3.2 UV filtration . 16 5.3.3 Cavitation methods 16 6 Suspended particulate content . 16 6.1 General . 16 TR 62781 IEC:2012(E) 3 6.2 Physical methods 17 6.3 Particulate re-contamination 17 7 Wa
14、ter temperature 17 7.1 General . 17 7.2 Thermal sources in an ultrasonic measurement tank . 18 8 Examples of low-cost water treatment systems . 18 8.1 Hydrophone measurement water tank 18 8.2 RFB measurement vessel 19 Bibliography 21 Figure 1 Dissolved oxygen concentration as a function of time for
15、2, 4 and 6 g/l of sodium sulphite in de-mineralised water and for different surface areas and volumes of water 9 Figure 2 Dissolved oxygen concentration in water as a function of time during reduced pressure recirculation degassing . 10 Figure 3 Re-gassing profile for a body of water following reduc
16、ed pressure recirculation degassing . 12 Figure 4 Example water treatment system for hydrophone measurements . 19 Figure 5 Example water treatment system for RFB measurements . 20 Table 1 Conditions for degassing by boiling . 11 4 TR 62781 IEC:2012(E) INTERNATIONAL ELECTROTECHNICAL COMMISSION _ ULTR
17、ASONICS CONDITIONING OF WATER FOR ULTRASONIC MEASUREMENTS FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-op
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28、 Standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example “state of the art“. IEC 62781, which is a technical report, has been prepared by
29、 IEC technical committee 87: Ultrasonics. The text of this technical report is based on the following documents: Enquiry draft Report on voting 87/494A/DTR 87/507/RVC Full information on the voting for the approval of this technical report can be found in the report on voting indicated in the above
30、table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. TR 62781 IEC:2012(E) 5 The committee has decided that the contents of this publication will remain unchanged until the stability date indicated on the IEC web site under “http:/webstore.iec.ch“ in the data re
31、lated to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. A bilingual version of this publication may be issued at a later date. IMPORTANT The colour inside logo on the cover page of this publication indicates that it
32、contains colours which are considered to be useful for the correct understanding of its contents. Users should therefore print this document using a colour printer. 6 TR 62781 IEC:2012(E) INTRODUCTION Many ultrasonic measurements are conducted in water, as it provides an inexpensive and readily avai
33、lable medium with characteristic acoustic impedance comparable to biological tissue. However, basic tap water is far from optimum for ultrasonic measurement as it contains many dissolved, absorbed and suspended contaminants. Measurements can be affected in many ways by these impurities. For example:
34、 dissolved gases readily dissociate from the water in the presence of high rarefactional pressures or heat giving rise to bubble formation. These bubbles not only are unwanted point reflectors but also increase the likelihood of cavitation. dissolved ionic components result in a raised conductivity
35、of the water, which in turn can affect the measured output from some unshielded hydrophones. Furthermore experimental equipment left in an ionic solution for any period of time will gradually develop a layer of deposit (e.g. calcium carbonate) on its surface. biological activity within an untreated
36、water tank will result in the creation of an unpleasant film on all available surfaces. If left long enough this biological activity will result in an undesirable environment for the operator and may also be a health hazard. To minimize these effects it is necessary to undertake a water treatment pr
37、ocess. These problems are well known and many IEC standards have sought to address these issues, often by means of an informative annex. This technical report aims to provide a unified resource for operators wishing to establish a water treatment process for ultrasonic measurements. This technical r
38、eport discusses each of the stages within a water treatment process and provides examples of suitable treatment methods. TR 62781 IEC:2012(E) 7 ULTRASONICS CONDITIONING OF WATER FOR ULTRASONIC MEASUREMENTS 1 Scope This Technical Report describes methods: for degassing water to be used in ultrasonic
39、measurements, to decrease the ionic content of water to be used in ultrasonic measurements, to decrease the biological content of water to be used in ultrasonic measurements, to reduce the suspended particulate content of water to be used in ultrasonic measurements. This technical report is applicab
40、le to all measurements of ultrasonic fields where water is the transmission medium. The quality and treatment methods for water used within a radiation force balance (RFB) may be different from that required for hydrophone based acoustic measurements. Chemical based methods of water treatment (e.g.
41、algaecides) may be appropriate for these applications. However, in this document, chemical means are noted but appropriately discouraged for acoustic pressure/intensity measurements. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and
42、are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 62127-1, Ultrasonics Hydrophones Part 1: Measurement and characterization of medical ultrasonic f
43、ields up to 40 MHz 3 Dissolved gases 3.1 General Tap water is often super-saturated with dissolved gases (although not in the same relative quantities as in air). Bubbles can be a cause of major experimental problems since they act as near perfect reflectors of ultrasound. This can perturb the ultra
44、sonic field being measured. Also, if a bubble forms directly in front of the active element of a hydrophone it will prevent any propagating ultrasound from being measured by that hydrophone. Finally acoustic pressures greater than approximately 100 kPa can cause cavitation, i.e. they can bring bubbl
45、es out of solution and it is well established that measurements can be strongly affected by acoustic cavitation. Trapped gas on particulate is also a significant source of cavitation and removal of suspended particulates is considered in Clause 6. Cavitation is the growth, oscillation and collapse o
46、f previously existing gas- or vapour-filled micro-bubbles in a medium. This will result in the production of spurious acoustic signals both below and above the driving frequency (for stable and inertial cavitation respectively). Particular care should be taken to avoid inertial cavitation as bubble
47、collapse is a particularly destructive event. If such a collapse happens on the surface of a hydrophone, damage to the hydrophone may occur. It is useful to note that macroscopic bubbles are visible to the naked eye. However, microscopic bubbles may be much harder to visually detect, and can be just
48、 as much of a problem. There is thus a need to define means of obtaining a suitable medium in which the effects of cavitation are minimized. 8 TR 62781 IEC:2012(E) A measurement method to detect the onset of cavitation is described in 1,2 1 . Specifically, the onset of inertial cavitation is often c
49、haracterized by the presence of the sub-harmonic of the fundamental operating frequency or additional broadband noise. Examples of acoustic spectra acquired using a needle and membrane hydrophones is presented in 3,4. 3.2 Chemical methods 3.2.1 General Whilst chemical methods of removing dissolved gases can be very effective both in terms of initial degassing rate and rate of subsequent re-gassing, they have a number of drawbacks. Firstly, chemical methods tend to be single
