EN 14253:2003
(Main)Mechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance
Mechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance
This European Standard provides guidelines for the measurement and evaluation of whole-body vibration at the workplace.
This European Standard describes the precautions to be taken to make representative vibration measurements and to determine the daily exposure time for each operation in order to calculate the daily exposure value standardized to an 8-h reference period. This European Standard provides a means to determine the relevant operations that should be taken into account when determining the vibration exposure.
This European Standard applies to situations where people are exposed to whole-body vibration at the workplace, transmitted through the buttocks for a seated person or through the feet for a standing person.
This European Standard is restricted to the evaluation of exposure to whole-body vibration using quantities derived from frequency-weighted root-mean-square acceleration. The frequency range considered is 0,5 Hz to 80 Hz. Where the vibration includes shocks or impacts, methods in this European Standard may underestimate the severity of the exposure. There is a need to assess the risks arising from exposure to whole-body shocks and high crest factor vibration. Methods for this are beyond the scope of this European Standard.
Mechanische Schwingungen - Messung und rechnerische Ermittlung der Einwirkung von Ganzkörper-Schwingungen auf den Menschen am Arbeitsplatz im Hinblick auf seine Gesundheit - Praxisgerechte Anleitung
Diese Europäischen Norm enthält Anleitungen zur Messung und Bewertung von Ganzkörper-Schwingungen am Arbeitsplatz.
Diese Europäischen Norm beschreibt die zu treffenden Vorkehrungen, um repräsentative Schwingungs-messungen durchzuführen und die tägliche Einwirkungsdauer jeder Tätigkeit zu bestimmen, um daraus den frequenz-bewerteten energieäquivalenten 8-h-Beschleunigungs-wert zu errechnen. Diese Europäischen Norm stellt Mittel zur Bestimmung der relevanten Tätigkeiten zur Verfügung, die bei der Ermittlung der Schwingungs-belastung einbezogen werden sollten.
Diese Europäischen Norm gilt für Situationen, in denen am Arbeitsplatz Ganzkörper-Schwingungen auf Bedien-personen beim Sitzen über das Gesäß oder beim Stehen über die Füße übertragen werden.
In dieser Europäischen Norm wird die Einwirkung von Ganzkörper-Schwingungen nur mit solchen Größen beschrieben, die aus dem Effektivwert der frequenzbewerteten Beschleunigung abgeleitet sind. Der betrachtete Frequenzbereich beträgt 0,5 Hz bis 80 Hz. Wenn die Schwingungseinwirkung stoß- oder impulshaltig ist und hohe Beschleunigungsspitzen aufweist, liefert die reine Effektivwert-bildung in der Regel einen zu kleinen Wert für die Schwingungsintensität. Es sind dann Verfahren zur Beurteilung der Risiken bei der Einwirkung von Stößen und Ganzkörper-Schwingungen mit hohem Scheitelfaktor notwendig. Solche Verfahren sind in ISO 2631-1 angegeben, werden aber in dieser Euorpäischen Norm nicht benutzt.
Einzelheiten zur Gültigkeit der Verwendung des Beschleunigungs-Effektivwertes sind in ISO 2631-1 enthalten.
Vibrations mécaniques - Mesurage et calcul de l'effet sur la santé de l'exposition professionnelle aux vibrations transmises à l'ensemble du corps - Guide pratique
La présente norme européenne fournit des principes directeurs pour le mesurage et l'évaluation des vibrations transmises à l'ensemble du corps sur le lieu de travail.
La présente norme européenne décrit les précautions à prendre pour effectuer des mesurages de vibrations représentatifs et déterminer la durée d'exposition quotidienne pour chaque opération, afin de calculer la valeur d'exposition quotidienne équivalente pour une période de référence de 8 heures. Elle offre un moyen de déterminer les opérations correspondantes qu'il convient de prendre en compte lors de la détermination de l'exposition aux vibrations.
La présente norme européenne s'applique aux situations où des personnes sont exposées à des vibrations transmises à l'ensemble du corps sur le lieu de travail, transmises par le séant pour les personnes assises ou par les pieds pour les personnes debout.
La présente norme européenne se limite à l'évaluation de l'exposition aux vibrations transmises à l'ensemble du corps utilisant des grandeurs dérivées de l'accélération efficace pondérée en fréquence. La gamme de fréquences considérée est comprise entre 0,5 Hz et 80 Hz. Lorsque les vibrations comprennent des chocs ou des impacts, les méthodes de la présente norme européenne peuvent sous-estimer la gravité de l'exposition. Il est nécessaire d'évaluer les risques engendrés par l'exposition à des chocs et des vibrations à facteur de crête élevé transmis à l'ensemble du corps. Ces méthodes d'évaluation ne relèvent pas du domaine d'application de la présente norme européenne.
Mehanske vibracije – Merjenje in računsko ugotavljanje učinkov na zdravje oseb, ki so na delovnem mestu izpostavljeni tresenju celotnega telesa – Praktično navodilo
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.QDYRGLORMechanische Schwingungen - Messung und rechnerische Ermittlung der Einwirkung von Ganzkörper-Schwingungen auf den Menschen am Arbeitsplatz im Hinblick auf seine Gesundheit - Praxisgerechte AnleitungVibrations mécaniques - Mesurage et calcul de l'effet sur la santé de l'exposition professionnelle aux vibrations transmises a l'ensemble du corps - Guide pratiqueMechanical vibration - Measurement and calculation of occupational exposure to whole-body vibration with reference to health - Practical guidance13.160Vpliv vibracij in udarcev na ljudiVibration and shock with respect to human beingsICS:Ta slovenski standard je istoveten z:EN 14253:2003SIST EN 14253:2004en01-oktober-2004SIST EN 14253:2004SLOVENSKI
STANDARD
SIST EN 14253:2004
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14253November 2003ICS 13.160English versionMechanical vibration - Measurement and calculation ofoccupational exposure to whole-body vibration with reference tohealth - Practical guidanceVibrations mécaniques - Mesurage et calcul de l'effet sur lasanté de l'exposition professionnelle aux vibrationstransmises à l'ensemble du corps - Guide pratiqueMechanische Schwingungen - Messung und rechnerischeErmittlung der Einwirkung von Ganzkörper-Schwingungenauf den Menschen am Arbeitsplatz im Hinblick auf seineGesundheit - Praxisgerechte AnleitungThis European Standard was approved by CEN on 1 September 2003.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards 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 translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and UnitedKingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2003 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14253:2003 ESIST EN 14253:2004
EN 14253:2003 (E)2ContentsPageForeword.3Introduction.41Scope.52Normative references.53Terms and definitions.54Quantities to be evaluated.65Preparation of the measurement procedure.66Measurement of vibration.107Measurement uncertainty.138Calculation of the daily vibration exposure.159Information to be reported.15Annex A (informative)
Examples of the calculation of daily vibration exposure.17Annex B (informative)
Some numerical examples of the determination of daily vibration exposure.19Bibliography.21SIST EN 14253:2004
EN 14253:2003 (E)3ForewordThis document (EN 14253:2003) has been prepared by Technical Committee CEN/TC 231 “Mechanical vibrationand shock”, the secretariat of which is held by DIN.This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by May 2004, and conflicting national standards shall be withdrawn at the latest byMay 2004.Annexes A and B are informativeUsers of this EN, prepared in the field of application of Article 137 (formerly 118a) of the EC Treaty, should beaware that standards have no formal legal relationship with Directives which may have been made under Article137 of the Treaty. In addition, national legislation in the Member states may contain more stringent requirementsthan the minimum requirements of a Directive based on Article 137. Information on the relationship between thenational legislation implementing Directives based on Article 137 and this EN may be given in a national forewordof the national standard implementing this EN.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal,Slovakia, Spain, Sweden, Switzerland and the United Kingdom.SIST EN 14253:2004
EN 14253:2003 (E)4IntroductionOccupational exposure to whole-body vibration can, in some circumstances, contribute to illness. The generalrequirements for measuring and evaluating whole-body vibration exposure are specified in ISO 2631-1. The aim ofthis European Standard is to provide practical guidelines to develop an effective strategy for evaluation of whole-body vibration exposure at the workplace.The use of the strategy described in this European Standard will lead to a realistic picture of the daily exposure of asubject and of the relevant uncertainties.The evaluation of vibration exposure can be broken up into a number of different stages:¾ identifying a series of discrete operations which make up the subject's working pattern;¾ selection of operations to be evaluated;¾ establishing the r.m.s. acceleration value for each selected operation;¾ evaluation of a typical daily exposure time for each operation identified;¾ calculating the daily vibration exposure.SIST EN 14253:2004
EN 14253:2003 (E)51 ScopeThis European Standard provides guidelines for the measurement and evaluation of whole-body vibration at theworkplace.This European Standard describes the precautions to be taken to make representative vibration measurementsand to determine the daily exposure time for each operation in order to calculate the daily exposure valuestandardized to an 8 h reference period. This European Standard provides a means to determine the relevantoperations that should be taken into account when determining the vibration exposure.This European Standard applies to situations where people are exposed to whole-body vibration at the workplace,transmitted through the buttocks for a seated person or through the feet for a standing person.This European Standard is restricted to the evaluation of exposure to whole-body vibration using quantities derivedfrom frequency-weighted root-mean-square acceleration. The frequency range considered is 0,5 Hz to 80 Hz.Where the vibration includes shocks or impacts, methods in this European Standard may underestimate theseverity of the exposure. There is a need to assess the risks arising from exposure to whole-body shocks and highcrest factor vibration. Methods for this are beyond the scope of this European Standard.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies (including amendments).ENV 28041, Human response to vibration — Measuring instrumentation (ISO 8041:1990)EN 30326-1, Mechanical vibration — Laboratory method for evaluating vehicle seat vibration — Part 1: Basicrequirements (ISO 10326-1:1992)ISO 2631-1, Mechanical vibration and shock — Evaluation of human exposure to whole-body vibration — Part 1:General requirementsISO 5347 (all parts), Methods for the calibration of vibration and shock pick-upsISO 5348, Mechanical vibration and shock — Mechanical mounting of accelerometersISO 16063 (all parts), Methods for the calibration of vibration and shock transducers3 Terms and definitionsFor the purposes of this European Standard, the following terms and definitions apply.3.1operationidentifiable activity for which a representative vibration magnitude measurement is made, being a combination of atype of work and a working conditionEXAMPLEThe type of work can be travelling for a lorry, lifting for a fork-lift truck, etc.; a working condition can be good orpoor travelling surface, soft or hard material to excavate, etc.3.2work cycleoperation or series of different operations, which is repeatedSIST EN 14253:2004
EN 14253:2003 (E)64 Quantities to be evaluatedThere are two principal quantities to be evaluated for each operation i during exposure to vibration:¾ The frequency-weighted acceleration in metres per second squared (m/s2), expressed as the root-mean-square (r.m.s.) values awi for each of the three axes at the supporting surface;¾ the total duration per day Ti of vibration exposure for operation i.The daily vibration exposure Al (8), in m/s2, for each direction l is defined as:å=iiwlillTaTkA201)8((1)whereawli is the frequency-weighted r.m.s. value of the acceleration, determined over the time period Tikx = ky = 1,4 for the x- and y-directions; kz = 1 for the z-directionl = x, y, zT0 is the reference duration of 8 h (28800 s)NOTE 1The Physical Agents Directive 2002/44/EC allows an 8-h vibration dose value (VDV) instead of A(8). Where VDV isused, the Al(8) in this European Standard should be replaced by the daily vibration dose value in the l direction. The use of VDVinstead of A(8) will generally result in a different evaluation of the health risk.NOTE 2The values of kl in the x- and y-directions are based on sensitivity of seated persons but the same factors should beapplied for other postures, e.g. standing.NOTE 3If it can be shown that there is clearly a dominant direction it is sufficient to measure only this direction.The individual contribution of an operation or work cycle i to the daily vibration exposure can be calculated as:0)8(TTakAiwlilli=(2)5 Preparation of the measurement procedure5.1 GeneralThe vibration exposure of an individual during a working day may involve a series of different operations, some ofwhich may be repeated. The vibration exposure may vary greatly from one operation to another, e.g. due to theoperator’s behaviour, the use of different machines or differences between the operations, or due to seasonaleffects.Before making measurements, it is first necessary to identify the individual operations which are likely to contributesubstantially to the overall exposure. The location and nature of each operation should be defined accurately andthe total duration associated with the individual worker during the single day should be quantified. A survey shouldbe undertaken to establish an “exposure profile”. This will help to determine the likely relative importance of eachtype of operation in the overall value of A(8), to identify those for which measurements are required, and to assist inthe planning of any necessary exposure controls.The daily vibration exposure A(8) may be determined for a specific individual on a specific day. In some situations itmay also be useful to calculate A(8) for a notional “typical” day’s exposure, using carefully selected representativevibration measurements and carefully considered exposure duration values. There is no method for evaluating theSIST EN 14253:2004
EN 14253:2003 (E)7combined vibration exposure for more than one day. Therefore, to know what is a typical day when vibration variesfrom one day to another, it is recommended to evaluate the variability of the daily vibration exposure A(8) overdays. However, it is not acceptable to determine A(8) by averaging over several days on which different levels ofvariation exposure have occurred.Representative days of measurement shall be selected with care if evaluation concerns the individual risk. Inparticular, variation in exposure due to equipment used, work condition, or environments, shall be evaluated.5.2 Exposure profileThe exposure profile is used to identify those operations which contribute to the overall value of A(8) and to definethe conditions under which measurements are to be made. It is important to make measurements for all themachines and operations which may give a significant contribution to the daily vibration exposure. For eachoperation identified, the following should be established:¾ the machine being used;¾ a full description of the operation (e.g. for a fork-lift truck: travelling or lifting or idling; for an excavator: diggingor travelling; or a combination of these);¾ operation conditions;¾ nature of ground;¾ state and tuning of the seat;¾ the number of times the operation is performed per day;¾ the average duration of the operation;¾ if possible, the nature of the vibration (e.g. continuous, impulsive, shocks, principal direction, source).Identify all changes in the operating conditions where this might affect the vibration exposure.EXAMPLE¾ speed of mobile machines;¾ a fork-lift truck may be travelling on a smooth surface inside a building, on an uneven surface inside (pits, thresholds,cables/hoses, debris, etc.) or on a rough surface outside;¾ a dumper may be travelling unloaded or loaded;¾ additional equipment which might affect vibration exposure, e.g. an agricultural tractor may be fitted with a slurry tanker ora plough.In addition, it may be useful to obtain:¾ information from workers and supervisors on which operations they believe produce the highest vibrationmagnitude;¾ estimates of the potential vibration hazards for each operation, using information from manufacturers onvibration emission values, or using published results of previous measurements on similar machines;¾ manufacturers’ information on vibration magnitudes and the travelling conditions under which they have beenmeasured;¾ subject's posture, seat suspension topping or bottoming, use of backrest.In the case of short, well-defined exposures, different vibration magnitudes may be associated with each of theindividual operations (e.g. loading and travelling over a rough surface with a wheel-loader, travelling and lifting witha fork-lift truck). In such cases, as many measurements as practicable should be performed for each individualSIST EN 14253:2004
EN 14253:2003 (E)8operation identified in the profile, and averaged as shown in equation (3). The daily duration of overall exposure toeach operation should then be used to determine the overall exposure as shown in equation (1).For the case of long uninterrupted operations (e.g. driving a long-distance in a coach or lorry), two possiblesituations can exist. The first consists of essentially stationary vibration data, unchanging in its statisticalcharacteristics; this might be true for a long journey at constant speed on a motorway. The measurement should belong enough to determine an accurate average vibration magnitude (see 5.4).The other possible situation consists of a continuous operation for which the vibration is not statistically stationarybut changes with time. An approximate exposure profile can be obtained by grouping periods of substantiallydifferent vibration that are statistically stationary. Common examples of logical measurement groupings includegrouping by road type (e.g. urban roads, country roads, motorways) or grouping by vehicle operation (e.g.travelling, other operations). As many measurements as possible should then be made for each operationalgrouping to provide a statistical description of the vibration.5.3 Organization of the measurementsIdeally, measurement of the daily exposure will be continuous throughout the working day and some moderninstruments facilitate this. However, this is often impracticable and it is then necessary to establish a method ofsampling appropriate periods of vibration exposure.The organization of the measurements will depend on the types of vibration exposure of the selected relevantoperations.To evaluate the daily vibration exposure, two types of work pattern can be distinguished:a) The daily work consists of long uninterrupted operations (e.g. driving a long-distance in a coach or lorry). In thiscase, vibration measurements are made over a section of an operation or a complete operation, which mayinclude short interruptions, which are valid parts of the normal operation (e.g. stops at traffic lights).In addition to vibration magnitude information, the evaluation of daily vibration exposure requires adetermination of the duration of exposure to vibration per day.b) The daily work consists of operations with different vibration magnitudes over short periods in respect to thedaily working times (e.g. loading and travelling over a rough surface with a wheel-loader, travelling and liftingwith a fork-lift truck). In such cases either the measurements are made separately for each of the differentoperations at the whole work and the results are combined or where the combination of operation duration isavailable the measurements are made directly for this combination.In addition to vibration magnitude information, the evaluation of daily vibration exposure requires adetermination of the exposure duration associated with each operation.Separate measurements shall be made during those operations believed to cause the greatest vibrationmagnitudes in order to establish the highest short-term exposure.When identifying the important operations, it is important to consider events which occur outside the main work. Forexample, driving an agricultural tractor to and from the field may result in more vibration than the operationundertaken in the field.5.4 Duration and number of vibration measurementsThe duration and number of measurements shall be selected so that a representative 8 h frequency-weightedvibration value can be established. Where continuous measurement throughout the day is not possible, theduration of measurements will be determined by the operation characteristics defined in 5.2.a) Where the daily work consists of long uninterrupted operations, a series of sample measurements, each of atleast 3 min duration, should be taken at different times of the day, and averaged so that variations in vibrationthrough the day are accounted for. The number, N, of sample measurements made shall be sufficient to showthat the average value obtained is representative of the vibration occurring throughout the day.SIST EN 14253:2004
EN 14253:2003 (E)9 The average vibration magnitude, in m/s2, of a series of N vibration magnitude samples is given by:å==NjjwjwtaTa121(3) where wjais the measured vibration magnitude for samplej jtis the measurement duration of samplej
å==NjjtT1 is the total measurement duration This procedure shall be carried out separately for vibration in each of the axes measured.b) Where the daily work consists of operations of shorter duration, which are repeated several times during aworking day, measurements for determination of the 8 h energy-equivalent vibration value can be made overcomplete work cycles. The number of work cycles over which measurements are made shall be sufficient toshow that the average value obtained is representative of the vibration from the operation throughout the day.c) Where no operations are repeated, the vibration from every operation shall be measured.d)Where there is no repeated work cycle of operations of short duration and the individual operations are shorterthan 3 min, the operations can be repeated in order to collect measurements over a minimum of 3 min, seeexample in clause A.3. As an alternative, simulated operations may be organized for making measurements of3 min duration.NOTEThe requirement of a minimum of 3 min is due to statistical reasons.5.5 Estimation of exposure timeThe total daily exposure duration shall be obtained for each operation or work cycle for which a vibration magnitudehas been established. This may be based on;a) a measurement of the actual exposure duration of a single operation or work cycle; andb) information on the number of operations or work cycles per working day.The first of these will be a measurement to determine how long an operator is exposed to vibration, and from whatsource, during a specified period. Various techniques may be used, for example:¾ use of a stopwatch;¾ analysis of video recordings;¾ activity sampling.A source of information may be work records, e.g. the number of lorries loaded and unloaded by fork-lift trucks.However, it is important to ensure that the information is compatible with the information required for an evaluationof daily vibration exposure. For example, work records might give very accurate information on the number ofcompleted work items at the end of each day, but where there is more than one operator, or unfinished work itemsat the end of a shift, this information may not be directly applicable to a vibration exposure evaluation.NOTEOperators asked for information on their typical daily vibration exposure duration will normally give an estimatewhich includes periods of time when there is no vibration (e.g. idling, lifting for a fork-lift truck). Therefore, such an approachoften results in an overestimation of the exposure duration.SIST EN 14253:2004
EN 14253:2003 (E)106 Measurement of vibration6.1 Measuring equipment6.1.1 GeneralVibration measurement systems generally use accelerometers to detect the motion of the vibrating surface.Measurement systems shall be checked before and after measurements.Calibrated measurement systems shall be used.Vibration measurements may be made using simple single-unit vibration meters featuring built-in frequencyweightings and integrating facilities. These systems are designed primarily to evaluate the vibration exposure at theworkplace; they are generally sufficient for most situations covered by this European Standard.More sophisticated measurement systems are often based around some form of frequency analysis, (e.g. narrowband or one-third-octave bands); they may use digital or analogue data recorders to store time information. Theymay use computer-based data acquisition and analysis techniques. These systems are more costly and complex tooperate than the single-unit systems. Frequency analysis will provide information on any dominant frequencies andharmonics which may help to identify effective vibration control measures.Where there is any doubt about the quality of the acceleration signal, it is useful to inspect the acceleration timehistory.Measuring and analysing equipment shall meet the requirements of ENV 28041, which specifies minimumperformance requirements (e.g. frequency weighting characteristics, tolerances, dynamic range, sensitivity, linearityand overload capacity) for appropriate measuring and analysing equipment.Type 2 instrumentation can normally be used for evaluation of human exposure.6.1.2 Accelerometers6.1.2.1 GeneralAccelerometers shall normally be used for measurement of vibration. In general, the choice of accelerometer willbe defined by the expected vibration magnitude, the required frequency range, the physical characteristics of thesurface being measured and the environment in which they are to be used.6.1.2.2 Vibration magnitudeThe accelerometers chosen for the measurement shall be able to operate at the greatest acceleration magnitudesexpected and have a suitable dynamic range to cope with smaller magnitudes at low frequencies.If the accelerometer responds at zero Hertz (e.g. piezoresistive accelerometers) the dynamic range shall besufficient to accommodate both the gravitational component and the vibration.6.1.2.3 Environmental conditionsAccelerometer’s sensitivity to temperature, humidity and other environmental factors shall be considered (seeENV 28041).6.1.3 Location and mounting of accelerometers6.1.3.1 GeneralAccelerometers shall be located so as to indicate the vibration at the interface between the human body and thesource of vibration.SIST EN 14253:2004
EN 14253:2003 (E)11Accelerometers oriented in different directions at a single measurement location shall be as close together aspossible.The vibration shall be measured on the seat of seated persons and on the floor of standing persons.NOTE 1On a mobile machine the measuring equipment should be secured with belts, straps, double-sided adhesive tape,etc. Some equipment such as recorders should be protected against shocks or transients. Different suspension systems may beused; a layer of soft foam placed between the secured equipment and the vibrating surface is generally sufficient.NOTE 2If machines are operating on a slope, the accelerometers should be aligned with the operator's body rather thanwith the vertical and horizontal directions. Use of piezoelectric accelerometers or high-pass filtering is recommended to removethe DC component.6.1.3.2 Seated personsThe vibration shall be measured on the seat surface. For a non-rigid or resilient seat, the accelerometers shall bemounted in a semi-rigid disc as described in EN 30326-1.NOTEThere is no need to attach the disc on the seat since the fixing due to the operator mass is adequate in the range offrequencies being measured. Nevertheless the disc may be maintained in place by an adhesive tape.6.1.3.3 Standing personsThe vibration shall be measured on the surface on which the feet are most often supported. The accelerometersused for the measurement at the feet shall be rigidly fixed on the working platform.The vibration shall be measured on the supporting surface closely adjacent to the area of contact between the feetand that surface (usually within 100 mm of the centre of this area).If the working platform is covered by a resilient material, the accelerometers may be mounted in the middle of arigid plate (about 300 mm x 400 mm) with the person standing on the plate. The mounted resonance shall be morethan five times the maximum frequency of interest (see ISO 5348).Different mounting systems may be used to attach the accelerometer to the vibrating surface such as a powerfulmagnet (the force should be at least 1 kN), glue, double-sided thin adhesive tape, etc.6.1.4 Frequency weightingDetails on the parameters and tolerances for frequency weighting and band limiting are given in ENV 28041 andISO 2631-1.Frequency weighting can be achieved by;¾ analogue or digital filtering of the time signal;¾ application of weighting factors to one-third-octave band or narrower-band frequency analysis spectra.It is important that digital methods, such as digital filtering and Fast Fourier Transform (FFT) analysis, are properlycapable of providing accurate analysis over the full frequency range. The analyses should provide good resolutionat low frequencies, and use a sample rate high enough to obtain accurate information at high frequencies.For most time signals, the Hanning window function is recommended for FFT analyses.NOTEIf it has been established that the frequency range below 1 Hz is not relevant nor important, the range between thecorner frequencies of the frequency weighting may be limited to 1 Hz to 80 Hz.6.1.5 Use of data recordersData recording can be achieved either using analogue or digital recording techniques. In all cases the datarecording shall have sufficient dynamic range to ensure that vibration signals over the full frequency range can bereliably recorded.SIST EN 14253:2004
EN 14253:2003 (E)12NOTE 1Analogue data recorders often have dynamic ranges from 40 dB to 50 dB. Digital systems offer better dynamicrange characteristics (e.g. 90 dB), although care still needs to be taken to ensure best use of the available range.NOTE 2Some analogue and some digital recording systems use data compression techniques to minimise the space takenby the data; these techniques should be avoided, unless it can be shown that such systems do not lose signal information.Measurement instrumentation that includes a data recording element, shall conform to the requirements ofENV 28041.6.1.6 Measurement rangeSome instruments allow the user to select the maximum acceleration magnitude that the instrument can measure.This setting defines the actual measurement range of the instrument. Where the instrument has user-selectabl
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