Unknown BRITISH STANDARD BS EN 13477 1 2001 Non destructive testing — Acoustic emission — Equipment characterization — Part 1 Equipment description The European Standard 13477 1 2001 has the status of[.]
BS EN 13477-1:2001 BRITISH STANDARD CONFIRMED DECEMBER 2007 Non-destructive testing — Acoustic emission — Equipment characterization — Part 1: Equipment description The European Standard 13477-1:2001 has the status of a British Standard ICS 17.140.01; 19.100 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 13477-1:2001 National foreword This British Standard is the official English language version of EN 13477-1:2001 The UK participation in its preparation was entrusted to Technical Committee WEE/46, Non-destructive testing, which has the responsibility to: — aid enquirers to understand the text; — present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; — monitor related international and European developments and promulgate them in the UK A list of organizations represented on this committee can be obtained on request to its secretary Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations This British Standard, having been prepared under the direction of the Engineering Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 March 2001 Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages to and a back cover The BSI copyright date displayed in this document indicates when the document was last issued Amendments issued since publication Amd No © BSI 03-2001 ISBN 580 36956 Date Comments EN 13477-1 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM January 2001 ICS 19.100 English version Non-destructive testing — Acoustic emission — Equipment characterization — Part 1: Equipment description Essais non destructifs — Emission acoustique — Caractérisation de l'équipement — Partie 1: Description de l'équipement Zerstörungsfreie Prüfung — Schallemissionsprüfung — Gerätecharakterisierung — Teil 1: Gerätebeschreibung This European Standard was approved by CEN on 28 December 2000 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 © 2001 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members B-1050 Brussels Ref No EN 13477-1:2001 E Page EN 13477-1:2001 Contents Page Foreword Scope Normative references Terms and definitions 4 Detection 4.1 Sensing element 4.2 Sensor case 4.3 Sensor characteristics 5 Signal conditioning 5.1 Preamplifier 5.2 Cables 5.3 Post-amplification and frequency filtering Signal measurement 6.1 Continuous signal 6.2 Burst signal 6.3 Waveform Analysis and output of results 8 Automated system 8.1 Automated analysis 8.2 Feedback to a control or alarm system © BSI 03-2001 Page EN 13477-1:2001 Foreword This European Standard has been prepared by Technical Committee CEN/TC 138, Non-destructive testing, the Secretariat of which is held by AFNOR This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by July 2001, and conflicting national standards shall be withdrawn at the latest by July 2001 This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association This European Standard is considered to be a supporting standard to those application and product standards which in themselves support an essential safety requirement of a New Approach Directive and which make normative reference to this European Standard This standard about “Non destructive testing — Acoustic emission — Equipment characterization” consists of the following parts: Part 1: Equipment description Part 2: Verification of operating characteristics Part one of this standard gives a description of the main components of an AE monitoring system Part two of this standard gives methods and acceptance criteria for verifying the electronic performance of an AE monitoring system These methods and acceptance criteria are used to routinely check and verify the performance of an AE monitoring system composed of one or more channels during it’s life time According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom © BSI 03-2001 Page EN 13477-1:2001 Scope This European standard describes the main components that constitute an acoustic emission (AE) monitoring system comprising: — detection; — signal conditioning; — signal measurement; — analysis and output of results Normative references This European Standard incorporates by dated or undated reference, provisions from other publications These normatives references are cited at the appropriate places in the text and the publications are listed hereafter For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision For undated references, the latest edition of the publication referred to applies (including amendments) EN 1330-1, Non-destructive testing — Terminology — Part 1: List of general terms EN 1330-2, Non-destructive testing — Terminology — Part 2: Terms common to the non-destructive testing methods EN 1330-9, Non-destructive testing — Terminology — Part 9: Terms used in acoustic emission testing Terms and definitions For the purpose of this standard the definitions given in EN 1330-1, EN 1330-2, EN 1330-9 and IEC 60050 International Electrotechnical Vocabulary and the following apply: average signal level (ASL) rectified, time averaged AE signal Detection A piezoelectric sensor is the most commonly used device for detecting acoustic emission It provides the most effective conversion of elastic waves (acoustic emission) into an electrical signal in the frequency range most commonly used for AE detection, 20 kHz – MHz In its simplest form it consists of a piezoelectric crystalline or ceramic element, mounted in a protective case The sensor detects a combination of wave types: compressional, shear, surface (Rayleigh), plate (Lamb), arriving from any direction © BSI 03-2001 Page EN 13477-1:2001 4.1 Sensing element The sensing material affects the conversion efficiency, operating temperature range and cable drive capability Lead zirconate titanate (PZT), a ceramic, is the most commonly used material It can be manufactured in a wide range of sizes and shapes The size, shape and containment affect the sensitivity, directionality, frequency response and wave-mode response Several elements may be combined to achieve a desired performance 4.2 Sensor case The sensor case (usually metallic) determines the overall size and mechanical characteristics of the sensor It may have an integral cable or a connector The case provides a total electrical screening of the sensing element and is usually common to one pole of the sensing element A faceplate of ceramic or epoxy between the sensor element and test object provides electrical isolation from the structure to avoid ground loop and induced electromagnetic noise Depending on the method of assembly, the sensor can be made single ended or differential In a single-ended device, the screen of a coaxial cable is connected to the sensor case and to one side of the sensing element In a differential device, a screened twisted pair cable is used and the sensing element is usually split or machined so that the screen does not conduct the electrical output signal Differential sensors have normally improved immunity to electromagnetic noise compared with single-ended sensors The case may contain a low noise preamplifier Incorporating the preamplifier inside the sensor case, eliminates the cable link between the sensor element and the preamplifier This reduces signal loss and improves immunity to electromagnetic noise The drawbacks are that the sensor case becomes larger, the maximum temperature rating is limited by the electronics, and the preamplifier is not interchangeable, see also 5.1 4.3 Sensor characteristics 4.3.1 Frequency response Piezoelectric acoustic emission sensors are either resonant with a peak in a certain frequency range, i.e the frequency content of the transient signal is mostly determined by the resonant frequency of the sensing element, or broad-band with a rather flat frequency response if properly damped The response of a sensor is given in terms of its output voltage versus frequency for a standard mechanical stimulus Due to the inertia of piezoelectric sensors their response will be different to continuous and transient stimuli Most piezoelectric devices will be characterised by surface velocity (volts per metre per second) as a function of frequency for a transient input An exception is the “flat response” device that is often characterised in terms of surface displacement (volts per unit displacement) Continuous signal response may be characterised in the same way or in pressure terms (volts per microbar) 4.3.2 Directionality The directionality is a measure of the uniformity of the device response to signals coming from any direction along the surface of the object to which the device is attached It is usually called the polar response and quoted as a deviation about the mean in dB Sensors may be intentionally directional to preferentially monitor a specific area 4.3.3 Wave mode response Sensors may be made responsive to a particular wave mode, such as: shear, compressional or other waves © BSI 03-2001 Page EN 13477-1:2001 4.3.4 Operating temperature This depends on the construction materials and the characteristics of the sensor element It shall be used within the temperature range specified by the manufacturers Signal conditioning Included in this section is preamplification, cables and post amplification 5.1 Preamplifier The main preamplifier characteristics are the input impedance, noise, gain, bandwidth, filter characteristics such as roll-off rate, output impedance, operating temperature range, common-mode rejection ratio (CMRR) and dynamic range Preamplification can be of voltage or charge Voltage preamplification converts the sensor output, usually a high impedance low-level signal, to a low impedance high-level signal for the transmission over long signal lines to the measurement instrumentation, which may be up to several hundred metres away A typical preamplifier has a high input impedance, 40 dB gain and 50 output impedance to drive a coaxial cable The D.C power supply to the preamplifier is commonly supplied on the same cable as the signal output and decoupled at each end using a filter network The preamplifier input may be single-ended, differential or switchable to fit different sensor types For some industrial applications, preamplifiers are an integral part of the AE sensor, providing greater ruggedness, reliability, reduced signal loss due to cable impedance and reduced susceptibility to electromagnetic noise The design of the preamplifier may allow the sensor to be used as a pulser transducer for calibration purposes Charge preamplification eliminates the effect of cable capacitance on the signal but is not widely used 5.2 Cables 5.2.1 Sensor to preamplifier cable This is the most important cable in the system and should be of low-capacitance, (< 100 pF/m), fully screened, and kept as short as possible (< m) where voltage preamplification is used 5.2.2 Preamplifier to instrument cable This is normally a screened coaxial 50 9impedance cable matched to the preamplifier and measurement instrument Care shall be taken to avoid crosstalk problems with multi-conductor cables, particularly if individual conductors are used to transmit a wide band pulser signal for periodic calibration during a test 5.2.3 Screen A single-point ground for all the screens is normally used at the measurement instrumentation The screens of the cables shall not form ground loops © BSI 03-2001 Page EN 13477-1:2001 5.3 Post-amplification and frequency filtering Post-amplification and further analogue filtering is used at the measurement instrumentation to increase the signal level and remove unwanted low or high frequency signals for measurement purposes The input impedance, dynamic range, filter characteristics, gain or attenuation are relevant to this section The input stage usually provides D.C power for the preamplifier and, sometimes, may control pulser operation Signal measurement 6.1 Continuous signal A continuous signal is characterised by the measurement of RMS (Root Mean Square) or ASL (Average Signal Level) with a particular time constant Continuous signal measurement systems are used where there is no requirement to identify and characterise individual emissions (bursts), e.g., process monitoring and leak detection The measured characteristics and their dynamic range define this type of system 6.2 Burst signal Burst signal measurement systems identify and characterise individual acoustic emissions on the basis of their time above an amplitude threshold The parameters of each burst signal may comprise any or all of the following, depending on the type of system and its user set-up: — peak amplitude; — time to peak amplitude; — arrival time; — rise-time, — duration; — ringdown count; — count to peak amplitude; — energy; — average frequency; — RMS level; — ASL; — detection threshold level; — others © BSI 03-2001 Page EN 13477-1:2001 External slow-varying parameter data, such as pressure, temperature, load or strain may also be acquired as part of the data set These parameters may be sampled at the precise time of the AE and or on a time interval basis All these values define an AE data set The rate at which a system acquires discrete bursts is defined by two parameters: — the peak acquisition rate, which is sustainable for a short defined period of time; — the continuous acquisition rate, which is sustainable for an indefinite period of time 6.3 Waveform The complete characterization of an AE “burst” is obtained by digitization and storage of the waveform when it exceeds a set amplitude threshold The difficulty in using this method is the storage capacity required, typically 100 times that of systems measuring only the primary characteristics of the signal, and the rate at which data can be transferred to the storage medium AE waveform capture is usually triggered periodically by certain characteristics of an AE data set Important features of waveform capture systems include their dynamic range, bandwidth, sampling rate, type and capacity of buffering and data transfer rate to disk Analysis and output of results The analysis and the output of results may take the following form: a) listings of AE data sets; b) graph showing: 1) one AE parameter versus time or an external parameter in cumulative or rate mode e.g AE burst energy versus pressure; 2) distribution of an AE parameter, e.g number of AE burst versus peak amplitude; 3) correlation of one AE parameter against another, e.g peak amplitude versus signal duration; 4) location plot, with source clusters; c) waveform display; d) classification by pattern recognition; e) source severity rating if applicable, as a result of combination of different evaluation criteria; f) other Post-test filtering may be used to remove unwanted signals Decisions on the filter characteristics may be based on wave shape analysis or other relevant factors © BSI 03-2001 Page EN 13477-1:2001 Automated system 8.1 Automated analysis Highly developed AE applications may have their user interface developed to a high level where AE sources are detected, located and categorised automatically with little or no AE expertise required This is important in monitoring applications where on-line analysis and data compression is necessary to reduce the amount of data stored These applications are usually highly procedurized and have software that is specific to the application 8.2 Feedback to a control or alarm system For some application the AE data are used to automatically control a process in real-time or to trigger an alarm Here the data are compared with predefined levels in deciding “acceptance” or “rejection” of the component The AE data acquisition is often “gated” with respect to an external parameter reflecting the loading so that only the relevant part of the process is monitored, thereby avoiding mechanical interference and other unwanted noise © BSI 03-2001 BS EN 13477-1:2001 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: 020 8996 9000 Fax: 020 8996 7400 BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of 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