health and safety executive vibration...
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Health and Safety Executive
Vibration solutionsPracticalwaystoreducetheriskofhand-armvibrationinjury
This is a free-to-download, web-friendly version of HSG170 (First edition, published 1997). This version has been adapted for online use from HSE’s current printed version.
Youcanbuythebookatwww.hsebooks.co.ukandmostgoodbookshops.
ISBN 978 0 7176 0954 3Price £13.75
This book is aimed at managers in industry who experience problems with vibration tools, which can cause hand-arm vibration syndrome and vibration white finger. It features case studies to demonstrate how vibration levels can be reduced and by how much. It describes solutions which have been adopted by industry and how much they cost using charts, illustrations and photographs to accompany a description of the methods used.
HSE Books
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© Crown copyright 1997
Firstpublished1997
ISBN9780717609543
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans(electronic,mechanical,photocopying,recordingorotherwise)withoutthepriorwrittenpermissionofthecopyrightowner.
Applicationsforreproductionshouldbemadeinwritingto:TheOfficeofPublicSectorInformation,InformationPolicyTeam,Kew,Richmond,SurreyTW94DUore-mail:[email protected]
ThisguidanceisissuedbytheHealthandSafetyExecutive.Followingtheguidanceisnotcompulsoryandyouarefreetotakeotheraction.Butifyoudofollowtheguidanceyouwillnormallybedoingenoughtocomplywiththelaw.Healthandsafetyinspectorsseektosecurecompliancewiththelawandmayrefertothisguidanceasillustratinggoodpractice.
Health and Safety Executive
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ContentsIntroduction 5
How to approach a vibration problem 6
Avoiding pitfalls when introducing vibration control 10
Reduction in vibration exposure case studies 12Tableofcasestudiessortedbyvibrationsource 14
Case studies 181 Semi-automaticcutoffmachine 182 Off-linegrindingwheelpre-forming 193 Introductionoflow-vibrationanglegrinders 214 Crushingconcrete 235 Waterjetting 246 Burstingconcreteinsteadofbreaking 267 Diamondwirecutting 288 Pipelineinsertionmethodavoidstrenching 309 Directionaldrillingavoidstrenching 3210 Mountedroadbreaker 3411 Reduced-vibrationroadbreakers 3612 Maintainingchainsawanti-vibrationrubberbushes 3813 Chainsawmaintenanceandtrainingprogramme 4014 Reduced-vibrationchippinghammer 4215 Sleeveforchippinghammerchisel 4416 Isolatedcastingcutoff 4517 Automaticfettlingofcastings 4718 Air-carbonarcgougingreplacestraditionaltools 4819 Castingshellknockoutincabinet 5020 Maintenanceoflow-vibrationtools 5221 Reduced-vibrationneedleguns 5422 Shotblastingcabinetreplacesrotaryfiles 5623 Descalingwithabrasiveblasters 5724 Jobrotationanduseofpedestal-mountednutrunners 5825 Automaticboltfitting 6026 Automatedpalletstripping 6227 Low-vibrationpowersaw 6328 Outdoorpowertoolspurchasingpolicy 6429 Low-vibrationfastenersystem 6630 Nocontactcastingshellknockout 6831 Low-vibrationrivetersandreactionbars 6932 Specialformworkavoidsscabbling 7133 Paint-onmaterialavoidsscabbling 7334 Gritblastinginsteadofscabbling 7435 Reduced-vibrationpolescabbler 7536 Deburringwithrumbler 7737 Beltgrindingandpolishingofmetalfabrications 7838 Groupworkingwithsuspendedtools 7939 Installationofhydrauliccroppingmachine 8040 Excavatorreducesvibrationexposureinquarry 8241 Toolstockauditandpurchasingpolicy 8442 Hands-freelinishing 8543 Beltgrindingandpolishingofceramicware 8644 Isolationforgrindingoperation 8745 Lasercutterreplacesnibblingmachine 89
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Maintaining blood circulation case studies 9146 Glovestowarmhands 9247 Ductawayexhaustair 9348 Heatedhandles 9449 Hotairtowarmhands 95
Health surveillance 9650 Healthsurveillanceonaconstructionsite 9751 Screeningandsurveillancemethodsinanaero-enginemanufacturer 98
Table of case studies by industry 100
Table of case studies by reduction method 101
References 102
Further reading 103
Glossary 104
Acknowledgements 106
Further information 107
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IntroductionBackground
Vibrationexposurefromprolongedandregularworkwithpoweredhand-heldtools,equipmentorprocessescanhaveadverseeffectsonthehandsandarmsofusers.Withouteffectivecontrols,workersusingsuchequipmentmaysuffervariousformsofdamage,collectivelyknownas‘hand-armvibrationsyndrome’(HAVS).Thisisapainfulconditionandtheeffectscanincludeimpairedbloodcirculation,damagetothenervesandmuscles,andlossofabilitytogripproperly.Thebestknownformofdamageis‘vibrationwhitefinger’(VWF),whichisaprescribedindustrialdisease.
Legislation and HSE guidance
Underhealthandsafetylegislation1,2,3employersandmachinemakersmustconsiderwhatactionisnecessarytoreduceriskstohealth,sofarasisreasonablypracticable.HSEhaspublishedauthoritativeguidance,Hand-arm vibration(HS(G)88),4asasourceofreferenceforthoseinvolvedinidentifyingandcontrollingtherisksofHAVS.Itcontainsextratechnicaldetailstocomplementthecasestudiesandincludessectionson:hazardandcontrolprogrammes;technicalwaystoreducevibration;clinicaleffectsandthehealthsurveillanceprogramme;andmeasuringhand-armvibration.Alistofotherrelevantpublicationsisincludedinthe‘Furtherreading’section.
Aim of the book
Thisbookisaimedatmanagersandshowsthatvibrationproblemscanbesolvedinmanyways-butitisnotexhaustive.Itoffersrealexamplesofhowsomecompanieshavereducedvibrationatwork.Althougheachindustryhasitsownworkingpractices,manyvibrationproblemsandsolutionsarenotuniqueandarerelevantinseveralindustries.Vibrationreductionshouldbeconsideredattheprocessandproductdesignstages,whenselectingandpurchasingtools,andwhenindividualworktasksandworkstationsarebeingdesigned.
Check-list and advice for managers
Thisbookincludesacheck-listformanagersonapproachingtheproblemofvibrationandadviceonavoidingpitfallswhenintroducingvibrationcontrols.
The case studies
Thecasestudieshavebeenorganisedintothreesections,eachwithashortintroduction.Theseare:
(a) reductionofexposuretovibration;
(b) maintainingbloodcirculation;and
(c) healthsurveillance.
Thetablesatthebeginningandendofthebookprovideaneasycross-referencetocasestudiesforparticularindustriesandtoparticularmethodsofvibrationcontrol.
Someemployershavedevelopedthesolutionsin-house.Otherorganisationshavefoundthatemployingvibrationconsultantswithwideexperienceininvestigatinghand-armvibrationexposureatworkhasledtoeffective,value-for-money
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solutions.Tohelpemployers,HSEhaspublishedguidanceonemployinghealthandsafetyconsultants.5
Someofthelanguageistechnicalandsoaglossaryisincludedattheendofthebook.Thecasestudiesaredesignedtogivemanagersanideaofwhatisachievableandarenotmeanttoreproducetechnicalmanuals.
Acknowledgements
HSEcommissionedAVTechnologyLimitedtogatherinformationforthecasestudymaterialinthisbook.Wewouldliketothankthemandthecompanieswhoagreedtobeinvolvedwiththispublication(listedonpage106).
How to approach a vibration problemAnyworkerwhousespoweredhand-heldorhand-guidedtoolsasamajorpartoftheirjobmaybeatriskofdevelopingvibrationinjurytotheirhandsandarms.Manyworkerswhoneedtoholdworkpiecesindirectcontactwithmachinerymayfacesimilarrisks.Inparticular,anyjobthatcausestinglingornumbnessinthefingers,orwherefingerblanchingoccurs,shouldberegardedassuspect.Onecourseofactioncouldbetomeasurethevibration,assesstheexposureandtakeactioninaccordancewithHS(G)88.4Forpoweredhandtools,itmaybeeasiertoassumethereisaproblemwhenthereisregularandprolongeduse.
Thecheck-listisdesignedtohelpyoudecidewhereproblemsmightoccur.Itisfollowedbyadviceonvibrationcontroltechniquesthatmightbeusedtogetthevibrationhazardundercontrol.Youmaywishtodiscussyourconclusionswithavibrationcontrolengineer.
Find out where the main problems are
Observetheworkprocessesandthetoolsused.Wherepracticableandsafe todoso,trythetoolyourself.
Howmanyemployeesusepoweredhand-heldtoolsandwheredotheywork? Isthereahighturnoverofpeopleinanydepartmentsusingpoweredhand- heldtools?
Askoperatorsaboutvibrationlevelswhenthetoolormachineisinuse. Dotheygetnumbnessortinglingintheirfingers?
Haveoperatorscomplainedaboutrecurrentpainorthrobbingintheirhands, ordifficultieswithgrippingobjects,orcompletingfiddlytaskssuchas fasteningorunfasteningabutton?
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Look at the process
Couldyouredesigntheprocesstoavoidorreducetheuseofpowered hand-heldtools,egbysubstitutionormechanisation?
Arealternativelowervibrationprocessesormethodsavailable?
Couldyouintroduceremoteorpower-assistedcontrol?
Couldyouusemechanicalaidstohelpmovethecomponentsortools?
Look at the installation
Couldyoureducevibrationfromfixedmachinesbyimprovingthemounting?
Couldyouisolatethevibrationdirectly?
Couldyouusejigstoholdcomponentsfirmlyinplace?
Look at the task
Couldyoureduceormechanisetheforcewhichtheoperatorhastoexert todothejob?
Couldyouusebalancersortensionerstotaketheweightofthetoolfrom theoperator’shands?
Look at the tools
Areyouprovidingthemostappropriatetoolsforthejob?Checkwithsuppliers whetherlowervibrationtoolsorcomponentsareavailable.
Couldyouuseanalternativetypeoftool,forexampleagrinderinsteadofa chippinghammer,toreducevibrationexposure?
Couldyoubuybetter-balancedwheelsordiscsforcuttingorgrinding?
Areyouusingtheoptimumqualityandgradeofcuttingorgrindingwheels anddiscs?
Arethetoolsandmachineryperforminginaccordancewiththevibration valuesdeclaredbythemanufacturer?
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Couldyoureducetheairlinepressureonhammeractiontoolsandmaintain cuttingrates?
Check maintenance requirements
Doyourmaintenanceschedulesconformtothemanufacturer’sspecifications?
Areyourmaintenancearrangementsadequatelysupervised,monitoredand recorded?
Doyouknowhowoftentoolsortheircomponentsshouldbereplaced? Doyouneedtoreplaceanti-vibrationmountsordampers?Askthe manufacturerorsupplierforinformation.
Couldyoumakebalancechecksonyourtoolsandmachines?
Doyoukeepthetoolssharp?Couldvibrationexposurefromtoolsharpening operationsbereduced?
Look at the work schedule
Couldyoureduceexposurebyintroducingjobrotation?
Arethereenoughbreaksintheworkforrecoveryduringtaskswithariskof highvibration?
Check operator usage
Areoperatorsusingthetoolscorrectlyinaccordancewithmanufacturer’s instructions?
Doyoutrainoperatorstousethecorrecttoolforthejob?
Arethecorrecttoolsavailable?
Shouldyouintroducea‘permittouse’systemfortoolsandprocesseswith ahigh-vibrationrisk?
Wouldclosersupervisionhelp?
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Consider operator protection
Dooperatorsknowwhattheycandotominimisevibrationrisks?
Couldyouimproveoperators’information,instructionandtraining?
Istheworkplacewarmenoughtomaintaingoodbloodcirculation,so preventinghandsandfingersfrombecomingcold?
Dooperatorsneedglovesorclothingtohelpkeepthemwarm?
Doestheexhaustairfrompneumatictoolsneedtobedivertedawayfrom theoperator’shands?
Look at the costs and benefits
Comparethecostsandbenefitsofthevariouscontrolmeasures.How manyemployeeswillbenefit?
Arethereotherbenefits,egreducednoiseorimprovedproductivity?
Whatwillbethecostperemployeeprotected?
Look for symptoms
Haveyouinstitutedaprogrammeforidentifyingearlyadversehealtheffects?
Doyouhaveaccesstoamedicalpractitionertosupervisetheprogramme andforreferralofsymptoms?
Doworkersknowwhattolookoutforandaretheyencouragedtoreport symptomssuchasfingerblanching?
Doyoukeepadequaterecordsofthesereports?
Doyouinvestigateanyadversehealtheffectsreported?
Doyoufeedyourfindingsbackintoyourriskassessmentandcontrol measures?
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Avoiding pitfalls when introducing vibration controlThefollowingvibrationcontroltechniquesaredescribedinoneormoreofthecasestudies.
Process redesign
Waysofimprovingtheprocesscanoftenbefoundwhichnotonlyreduceexposuretohazardousvibrationbutalsoimproveproductivityandquality.However,considerthefollowingpoints:
Ensurethatwheneliminatingonehazard,egbyintroducinganewtechnique orproductsuchaschangingfrommechanical(buffing)tochemicalpolishing methods,youdonotcreateadifferenthazard.
Beawarethatimprovementsinproductivityresultingfromprocessredesign couldincreasethevibrationexposureofindividualemployees.
Redesignmaytaketimeandrequiresomeinvestment.Other,possibly temporary,measuresmaybeappropriatetointroduceuntiltheredesign hasbeencompleted,egintroducingjobrotation.
Theproductoftendeterminestheprocess.Forexample,thechoiceof decorativefinishforbuildingsurfacesandtheprocessusedtoachieveitcan affecttheexposureofconstructionworkerstovibration.Cancustomer requirementsbevariedtominimiseworkerexposuretovibration?
Isolation
Isolationisthereductionofvibrationpassingfromthevibratingmachine,toolorcomponenttotheoperator’shands.Thiscanbeachievedbytheuseofrubberbushes,sleevesandanti-vibrationmounts.Considerthefollowingpoints:
Thismethodisonlylikelytobepracticalinalimitednumberofcasesandwith expertadvice.Eachworksituationshouldbeassessed.Askforspecialist advicefromtheanti-vibrationmountormaterialsupplier.
Incorrectapplicationofthistechniquecouldincreasevibrationlevelsandmay createadditionalphysicalhazards.
Ifyouapplyittonewmachines,youshouldcheckthemanufacturer’s guaranteestomakesurethattheywillnotbeinvalidated.
Checkthatanti-vibrationhandlesaresuitableforthemachineinquestion andwillnotaffecttheoperationofthemachine.
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Ensurethatresilientsleevesarecapableofreducinglow-frequencyvibration. Isthesleeveorwrappingthickenough?Getadvicefromthesupplieror vibrationexpert.
Theresonantfrequencyoftheanti-vibrationmountmustbewellbelowthe mostimportantmachinefrequencies-usuallytheoperatingspeedandrelated frequencies.Getadvicefromthesupplierorvibrationexpert.
Makesurethatthemountsarenotsosoftthatthetoolormachinebecomes uncontrollable.
Makesurethatamountoranti-vibrationhandlefailurecannotcreatea hazard.Getadvicefromavibrationexpert.
Gloves Glovescanplayanimportantroleinreducingtherisksfromhand-armvibration.Incoldconditionsgloveswillkeepthehandswarm,helpingtomaintaingoodcirculationtothefingers.Glovesmayalsobenecessary,oradvisable,forphysicalprotectionofthehands.Ifyouwishtosupplyglovestoyourworkers,youwillneedtoensurethattheyareappropriateforthetoolsandthetasksothatthewearerfindsthemcomfortableandisabletomanipulatethetoolsandcontrolsproperlywithoutincreasinggriporforce.
Variousgloveswithspecialsoftliningsintendedtoprovidevibrationisolationarecommerciallyavailable.Theseglovescanoftenreducehigh-frequencyvibrationbuthavelittleeffectatmidandlowfrequencieswhicharethosemostlikelytodamagebloodflowinthehand.Anti-vibrationglovesshouldbeassumednottoreducevibrationexposureunlessyouhavetestdatathatshowsotherwiseforthecombinationofgloveandtoolused.Manufacturerscontinuetoconductresearchtodevelopbetterperformingmaterialstoreducevibrationatthehazardousfrequencies.
New tools
Askforvibrationdataforanytoolsthatyouareconsideringusingorbuying.SomehelpfulquestionsaresuggestedinAppendix1ofHS(G)88,4andtheyarereproducedonpage12.
Doyouknowwhatthesupplier’svibrationdatameans?Rememberthatthedatawhichthesupplierhastoprovideisintendedtohelpyouchoosetherightmachineforthejobandyouremployees.
Thevibrationmagnitudesquotedbymanufacturers/machine-makersareintendedtoenablethepotentialpurchasertocompareonemaker’smachineswithmachinesofasimilartypeofferedbyanothermanufacturer.Thevibrationmagnitudesofthemachineswheninnormalusemaybedifferent.Askthemanufacturerformoreinformation.
Ensureemployeesareawarethatsomelow-vibrationtoolswillfeeldifferentinuseandmayrequireadifferentoperatortechniquetothetraditionaltoolswhichtheyreplace.Trainingandaperiodforemployeestogetusedtousingthenewtoolsmaybenecessary.
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Purchasing new tools and equipment
Whenpurchasingnewtoolsandequipment,employersshouldasksuppliersforinformationonvibration.Thefollowinglistsuggestssomepossiblequestions.
1Isthevibrationofanyhandleorothersurfacetobeheldbytheuserlikelytoexceedanaccelerationof2.5m/s2,innormaluse?
Iftheanswertoquestion1isYES,
2Whatisthefrequency-weightedacceleration:(a)underoperatingconditionsproducingthehighestvibration?(b)undertypicaloperatingconditions?(c)underotherstandardconditions?
3Underwhatoperatingconditionswerethemeasurementsmade?
4Ifthetestswereinaccordancewithapublishedstandard,providedetailsandindicatetheextenttowhichthevibrationmaydifferfromthequotedvaluesundernormalconditionsofuse.
5Whatmeasureshavebeentakentominimisevibration?
6Areadditionalvibrationreductionmeasurespracticable?Givedetailsofanydesignchanges,theadditionalcostandanyproductionpenalties.
7Whatisthemaximumfrequency-weightedaccelerationthatthetoolorequipmentcanbeguaranteednottoexceed?
8Whattestswouldbecarriedouttoconfirmanyclaimsmadeinanswertoquestion7?
9Whatothermeasuresarerequiredtominimisethevibrationhazardtowhichemployeesareexposedwhenusingthetoolorequipmentinquestion?Givedetailsofanyspecialmaintenancerequirements.
Reduction in vibration exposure case studiesThesestudieshavebeenplacedinorderbyvibrationsource.Eachcasestudyinthissectiondescribesthenatureofthevibrationproblem,thesolutionappliedbythecompany,thecost(at1995prices)andthevibrationreductionandotherbenefitsgained.Vibrationreductionshavebeenachievedbyusingtoolsormachineswhichproducelessvibration,byreducingtheamountoftimespentusingthetoolormachine,orbyintroducinganewwayofworkingwhichremovesallexposuretovibration.
Thevibrationdataforeachcasestudyissummarisedinatable.
Understanding the vibration measurements and data tables
Vibration magnitude
Hand-transmittedvibrationmagnitudeismeasuredintermsoftheaccelerationofthesurfaceincontactwiththehand.Theaccelerationofthesurfaceisnormallyexpressedinunitsofmetrespersecondsquared(m/s2).Hazardtohealthisusuallyassessedfromtheaverage(root-mean-squareorrms)accelerationlevel,usinganinstrumentwithastandard‘frequencyweightingnetwork’orfiltertoreduceits
ExtractfromHS(G)88Hand-arm vibration
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sensitivityatthehighfrequencies.Thisgivesthe‘frequencyweightedacceleration’(ah,w)inm/s2,where‘h’indicateshand-transmittedvibrationand‘w’indicatesthatthemeasurementhasbeenfrequencyweighted.BritishStandardBS6842:19876describesaprocedureformakingthesemeasurements.
Thevibrationmagnitudefiguresquotedinthestudiesrelatetospecifictoolsinspecificcircumstances.Eachsituationshouldbemeasuredseparately.Thefiguresmayofferaguideonlytothelikelyvaluewhensimilartoolsareusedinsimilarprocesses(seeHS(G)884).BS6842:1987hassincebeensupersededbyBSENISO5349-1:2001,butthevibrationmagnitudesinthisbookwereobtainedusingBS6842:1987.
Daily vibration exposure
Thevibrationexposure,or‘dose’,ofaworkeroveraworkingdaydependsonthedurationofexposureaswellasthevibrationmagnitudeatthegrippedsurface(s)ofthetool(s)used.Exposureshouldbeadjustedtoastandardreferenceperiodof8hours(A(8))toallowdifferentexposurepatternstobecomparedandfortheassessmentofhealthrisk.Programmesofpreventativemeasuresandhealthsurveillancearerecommendedwhereworkers’dailyvibrationexposureregularlyexceeds2.8m/s2A(8).
Vibration data table
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 5 2.5hours 3hours 3
After 0 - 0 -
Thetablegivesthevibrationmagnitude(ah,w)anddetailsofdailyexposurebeforeandafteractiontoreducevibrationexposurehasbeentaken.Inmanycasesthevibrationisreducedtozerobythemodification.TheseverityofthevibrationhazardisindicatedincolumnBwhichshowsthepermittedtimebeforethedailyexposureexceeds2.8m/s2A(8):theshorterthetimeindicated,thegreaterthevibrationhazard.Actiontoreducetheriskmayberequiredafteronlyafewminutesdailyexposureforsomehigh-hazardtools.Therelativeriskofdevelopinghand-armvibrationinjurycanbegaugedbycomparingeithertheactualdailyvibrationexposuretime(columnC)withthetimebeforethedailyexposureexceeds2.8m/s2(columnB),ortheactualdailyvibrationexposure(columnD)with2.8m/s2A(8).
Insomeofthecases,forexampleCaseStudies11and40,theexposurevaluesafterthecontrolmeasureshavebeenappliedremaininexcessoftherecommendedHSEactionlevel.Inthesecases,additionalactionshouldbetakentoaddresstheriskstohealth,forexample,increasingthefrequencyordetailofhealthsurveillance.
Explanation of ‘before’ and ‘after’ terms
‘Before(estimated)’-thismeansthatthedataisbasedonestimatesoftheexposurethatwouldhavebeencausedbyaprocessnolongerinexistence,orthatthedatahasbeenprovidedtogiveanindicationoftheexposurethatwouldhaveoccurredifahigh-vibrationprocesshadbeenused.
Exampleoftable A B C D
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‘Before(potential)’-thisisbasedontheworstcasehypotheticalprocessthatcouldhavebeenusedtodothework.
‘Before(typical)’-thisreflectsthefactthattheoldtechniquecouldproduceawiderangeofexposuresduetodifferentvibrationmagnitudesandvaryingexposuretimes.Thefiguresinthetablegiveagoodaverageforthetypeofwork.
‘After(potential)’-thisisestimateddatawherethesolutionwasnotcompleteatthetimeoftheresearch.
‘After(typical)’-thisiswherethesolutionmayleadtoarangeofvibrationexposuresduetovariationsinvibrationmagnitudeandexposuretime.
Table of case studies (sorted by vibration source)
Case Title Vibration source Industry Exposure reduction technique
1 Semi-automaticcutoffmachine Abrasivedisccutter Investmentfoundry Process automation
2 Off-linegrindingwheelpre-forming Grindingwheeldresser Precisionengineering Process automation
3 Introductionoflow-vibrationangle Handtool Shipbuilding Tooldesign grinders (anglegrinder)
4 Crushingconcrete Handtool(breaker) Construction Changeofmachine
5 Waterjetting Handtool(breaker) Construction Changeofprocess
6 Burstingconcreteinsteadof Handtool(breaker) Construction Changeofprocess breaking
7 Diamondwirecutting Handtool(breaker) Construction Changeofprocess
8 Pipelineinsertionmethodavoids Handtool(breaker) Utilities Changeofmachine trenching
9 Directionaldrillingavoidstrenching Handtool(breaker) Utilities Changeofprocess
10 Mountedroadbreaker Handtool(breaker) Utilities Isolation
11 Reduced-vibrationroadbreakers Handtool(breaker) Utilities Tooldesign
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Case Title Vibration source Industry Exposure reduction technique
12 Maintainingchainsawanti-vibration Handtool(chainsaw) Forestry Maintenance rubberbushes
13 Chainsawmaintenanceand Handtool(chainsaw) Watercourse Management trainingprogramme maintenance
14 Reduced-vibrationchipping Handtool(chipping Foundry Tooldesign hammer hammer)
15 Sleeveforchippinghammerchisel Handtool(chipping Steel Isolation hammer) 16 Isolatedcastingcutoff Handtool(disccutter) Foundry Isolation
17 Automaticfettlingofcastings Handtool(grinder) Foundry Process automation
18 Air-carbonarcgougingreplaces Handtool(grinder) Powerengineering Changeofprocess traditionaltools
19 Castingshellknockoutincabinet Handtool(hammer) Investmentfoundry Isolation
20 Maintenanceoflow-vibrationtools Handtool(needlegun) Construction Maintenance
21 Reduced-vibrationneedleguns Handtool(needlegun) Construction Tooldesign
22 Shotblastingcabinetreplaces Handtool(needlegun) Shipbuilding Changeofprocess rotaryfiles
23 Descalingwithabrasiveblasters Handtool(needlegun) Shipbuilding Changeofprocess
24 Jobrotationanduseofpedestal- Handtool(nutrunner) Automotive Isolation mountednutrunners
25 Automaticboltfitting Handtool(nutrunner) Automotive Process automation
26 Automatedpalletstripping Handtool(powersaw) Palletrepair Process automation
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Health and Safety Executive
Case Title Vibration source Industry Exposure reduction technique
27 Low-vibrationpowersaw Handtool(powersaw) Palletrepair Tooldesign
28 Outdoorpowertoolspurchasing Handtools(outdoor) Watercourse Management policy maintenance
29 Low-vibrationfastenersystem Handtool(rivetinggun) Aerospace Changeofprocess
30 Nocontactcastingshellknockout Handtool(rivetinggun) Investmentfoundry Isolation
31 Low-vibrationrivetersandreaction Handtool(riveter) Aerospace Tooldesign bars
32 Specialformworkavoidsscabbling Handtool(scabbler) Construction Changeofprocess
33 Paint-onmaterialavoidsscabbling Handtool(scabbler) Construction Changeofprocess
34 Gritblastinginsteadofscabbling Handtool(scabbler) Construction Changeofprocess
35 Reduced-vibrationpolescabbler Handtool(scabbler) Construction Tooldesign
36 Deburringwithrumbler Handtool(straight Turbinemanufacture Changeofprocess grinder)
37 Beltgrindingandpolishingof Handtool(straight Turbinemanufacture Changeoftool metalfabrications grinder)
38 Groupworkingwithsuspended Handtools(various) Automotive Management tools
39 Installationofhydrauliccropping Handtools(various) Foundry Changeofprocess machine
40 Excavatorreducesvibration Handtools(various) Quarrying Changeofprocess exposureinquarry
41 Toolstockauditandpurchasing Handtools(various) Shipbuilding Management policy
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Health and Safety Executive
Case Title Vibration source Industry Exposure reduction technique
42 Hands-freelinishing Linishingmachine Investmentfoundry Isolation
43 Beltgrindingandpolishingof Pedestalgrinder Ceramics Changeofmachine ceramicware
44 Isolationforgrindingoperation Pedestalgrinder Foundry Isolation
45 Lasercutterreplacesnibbling Sheetmetal Turbinemanufacture Changeofprocess machine
Note:CaseStudies46to51donothaveavibrationsource.
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Health and Safety Executive
1 Semi-automatic cut off machineThe task
Cutting multiple cast components from their runners and risers.
The problem
Oneofthetraditionalmethodsforcuttingoffcastcomponentsistouseanabrasivecuttingdiscmountedinacircularsawbench.Inatypicaldayatonefoundrytheoperatorofsuchamachinecouldspendupto3hoursexposedtovibrationmagnitudesofupto5m/s2.Theoperationisalsoverynoisyandthereispotentialriskofinjuryfromcontactwiththeexposedcuttingdisc.
The solution
Twofully-enclosed,semi-automaticcut-offmachineswerebought,principallytoimprovequalityandefficiency.Themultiplecastingsareclampedinrotatingfixtures,trunnionmounted,andcutoffwithanabrasivedisc.
The cost
Thetotalprojectcostswereapproximately£70000.
The result
n Theoperatordoesnotneedtotouchanyvibratingcomponents.n Theoperatorcontrolsthepositionandalignmentofthecastingsandcutting
discsatadistance.n Manualhandlingofthecomponentsandexposuretonoise,dustandsparksis
reduced.n Thecycletimeiscut.n Lessmetalhastobegroundoffafterwards,whichalsosavestimeinthefettling
shop.n Theriskofinjuryfromcontactwiththecuttingwheeliseliminated.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 5 2hours30minutes 3hours 3
After 0 - 0 -
Automaticcut-offmachine
Automaticcut-offmachinesavailablefromFlexovit(UK)Limited
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Health and Safety Executive
2 Off-line grinding wheel pre-formingThe task
Dressing precision grinding wheels.
The problem
Somecompanieshavetogrindcomponentstopreciseshapes,dimensionsandsurfacefinishes.Thisisoftendonewithgrindingwheelsthatareprofiledtogivetherequiredshape.Duringuse,thesewheelshavetobefrequentlydressedtorestoretheircorrectshapeandsurfacequalities.Thisisusuallydonewithadresserattachmentmountedonagrindingmachine,whicheithersemi-automaticallyorfully-automaticallyprofilesthesurfacewithadiamondtool.
Newgrindingwheelsaresuppliedinsetwidths,withnoprofiling.Cuttingacompletenewprofilewiththedresserattachmentisverytimeconsuming,somostcompaniespre-formtheirwheelsbeforethedresserisused.Thetraditionalmethodofpre-formingistouseahand-heldpieceofcarbide.Thisisextremelydangerous,bothbecauseoftheriskofcontactwiththegrindingwheelandbecausetheoperatorisexposedtohighvibrationmagnitudes.Theactualvibrationexposurevariesdependingonthesizeofthewheelandthepieceofcarbideinuse.Operatorsreportedseverewristpainandnumbnessofthehandsafterjustafewsecondsofthework.
Off-linegrindingwheeldresser/pre-former
CasecourtesyofIndustrialMachineToolServicesLimited
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Health and Safety Executive
The solution
Thewheelsarepre-formedanddressedonanoff-linedressingmachine,whichusesamechanicallydrivendiamondtoolguidedbyaspeciallyprofiledsteelfixturetocuttheprofileintothegrindingwheel.Themachineisfullyautomaticwithalidwhichmustbeclosedbeforethecuttingcyclecanbeginandcannotbeopeneduntilthecycleiscomplete.
The cost
Anoff-linedressingmachinewouldcostabout£12000.
The result
n Theoperatorsarenotexposedtovibration.n Thereislittleriskofcontactwiththegrindingwheel.n Productivityisincreasedbyavoidingproductionmachinedowntime.n Theoperators’exposuretonoiseisalsoreduced.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(estimated)
40(estimated) 2.4minutes 5minutes 4.1(estimated)
After 0 - 0 -
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Health and Safety Executive
3 Introduction of low-vibration angle grindersThe task
Weld dressing and fettling of metal fabrications.
The problem
Atoneshipyardthebulkofthisworkisdonewith225mm(9in)electrichigh-frequencyanglegrinders.Thesearelargeheavytoolswhichoftenhavetobeheldoverheadorinawkwardpositionsbytheoperatorforanaverageof1to3hoursaday.Thecompanyhasjustunder200ofthesetoolswhichproduceaveragevibrationmagnitudesof7m/s2,givingapotentialexposureofover4m/s2A(8).
The solution
Thecompanyintroducedatemporarysolutiontorestrictthetimeforwhich225mm(9in)grinderscouldbeused,andtoencouragetheuseoflesspowerfultoolswithlowervibrationvaluesforsmalljobs.
Thelong-termrequirementwastouseagrinderwithbothhighperformanceandlowvibration.In-houseengineersreviewedallthegrindersavailableonthemarketatthetimeanddecidedthatanewdesignofpneumatic225mm(9in)grinderfeaturingautomaticcorrectionfordiscimbalanceshouldbebought.Initialtestsshowedthatthesenewtoolsusingthecompany’susualgrindingdiscsachievedalowermetalremovalratecomparedwiththeoldelectricgrinders.Furthertestingrevealedthatbychangingtoasoftergradeofdisc,thepneumaticgrinderscouldgiveametalremovalrate40%higherthanthatachievedbytheoldtool/disccombination.Theuseofthenewtoolssignificantlyincreasedtherequirementforcompressedairintheshipyardanditwasnecessarytoupgradetheairdistributionsystemtocopewiththeextrademand.
The cost
Self-balancingpneumatic225mm(9in)anglegrindersareapproximately£700each.Theresearchanddevelopmenttook1month.Thealterationstotheairdistributionsysteminvolvedsignificantexpenditure.
Reduced-vibrationanglegrinder
EquipmentprovidedbyAtlasCopcoToolsLimited
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Health and Safety Executive
The result
n Vibrationmagnitudesarelower.Inextendedtestingonrealjobsintheyard,thenewgrindersproducedanaveragevibrationmagnitudeof3.5m/s2.
n Efficiencyisimprovedbecauseofthehigherrateofmetalremoval.n Thetoolsaremuchlighterandsotheyareeasierandlesstiringtooperate.n Therearefewerrisksassociatedwithtrailingelectricalleadsintheworkingarea.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 7 1hour17minutes 3hours 4.3
After 3.5 5hours7minutes 3hours 2.1
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Health and Safety Executive
4 Crushing concreteThe task
Demolishing concrete structures.
The problem
Aspartoftherefurbishmentofahospitalmaternityblock,itwasnecessarytodemolisha15mlongsectionofconcretewall.Thiscouldhavebeendonewithsmallpneumaticbreakerswhichmighthavecausedtypicalworkervibrationexposuresof7m/s2A(8)andcreatedintrusivelevelsofnoise.
The solution
Thewallwascutawayfromthebuildingpillarsbydrillinglinesofoverlappingholes(stitchdrilling)usingadiamonddrill.Thediamonddrillingmachinewasheldinaclampandsotheoperatorswerenotexposedtovibration.Eachsectionwasthenbrokenupby‘biting’offpieceswithahydraulicconcretecrusher.Thejawsofthisdevicecloseslowly,allowingtheoperatorstoloosentheirgripbeforecrushingtakesplace.
The cost
About50%morethanthecostofusingpneumaticbreakersonthesamejob.
The result
n Theoperator’sexposuretovibrationisnegligible.n Verylowvibrationispassedintothestructurewhichhelpstoreducedamage
andstructure-bornenoise.n Thismethodislessmessythanusingbreakersasthedebrisisinlargerpieces
andlessdustisproduced.n Noiselevelsareverylow,bothfortheoperatorsandtheenvironment.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
12 26minutes 3hours 7
After 0 - 0 -
Left Demolishingconcretestructures.
CasecourtesyofSpecialistServices(CuttingandDrilling)Limited
Right Concretecrusherdemolishingawall
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Health and Safety Executive
5 Water jettingThe task
Removing damaged or weathered concrete surfaces.
The problem
Thedeckandsidewallsofareinforcedconcreteroadbridgehaddecayedtotheextentthatsurfacerepairswereneeded.Thetopfewcentimetresofconcreteneededtoberemovedandreplacedwithnewmaterial.Thetraditionalmethodofremovingtheoldmaterialistousehand-heldpneumaticbreakers,whichcanexposeworkerstotypicalvibrationmagnitudesof12m/s2forabout3hoursperday.Theuseofpercussivetoolscanalsodamagethereinforcementbar,whichthenhastoberepairedorreplaced,andcausecrackinginthebaseconcretewhichmayweakenthestructure.Theoperatorsworktoaspecifieddepth,oftenunnecessarilyremovingsoundmaterialandleavingareasofdeepdamagedmaterial.Thesurfacealsorequiresthoroughcleaningbeforenewconcretecanbeapplied.Thejobwouldhavetakenabout60workerdayswiththebreakers,aswellasadditionaltimetorepairthereinforcementbarandotherdamage.
The solution
Thejobwasdonewitharobot-mountedwaterjettingmachine.Thisprocessusesanextremelyhighpressurewaterjettowearawaytheolddamagedconcrete.Thejetremovesallconcreteuptoacertainstrength,regardlessofdepth,leavingthegoodmaterialandremovingallofthedamagedmaterial.
The cost
Acontractorusingthewaterjettingmachinetook15daysatapproximately£1200perdaytocompletethejob(totalcost£18000).Todothejobusinghand-heldbreakerswouldhaveinvolved60workerdaysatapproximately£150perday(totalcost£9000),plusthecostofrepairstothereinforcementbarandbaseconcrete.Thesereinstatementcostsoftenresultintotalprojectcostssignificantlyhigherthanthoseforthewaterjettingmethod.
Robotmachinewaterjettingabridgesidewall
Concretesurfaceafterwaterjetting
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Health and Safety Executive
The result
n Operatorsarenotexposedtoanyhand-armvibration.n Thereinforcementbarwascompletelyunaffectedandtherewasnodamageto
thebaseconcretestructuresoitwasimmediatelyreadyfortheapplicationofnewconcrete.
n Thenewconcreteadheresbettertothejettedsurface.n Airbornedustlevelsareverylowasthedebrisiswashedawaybythewater.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
12 26minutes 3hours 7
After 0 - 0 -
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Health and Safety Executive
6 Bursting concrete instead of breakingThe task
Demolishing concrete structures.
The problem
Duringtherenovationofalargewarehouse,atemporaryconcreteretainerwasbuilttosupporttheexternalwallswhilethefloorswereremovedandreplaced.Whenthestructuralworkwascomplete,theretainer,whichwas1mx1minsectionandranroundtheentire300mperimeterofthebuilding,hadtoberemoved.Traditionallythisisdoneusingsmallhand-heldpercussivebreakers,asthevibrationsfromlargerplantcoulddamagethebuildingstructure.Suchsmalltoolshavelowmaterialremovalratesandexposeoperatorstovibrationmagnitudesintherangeof5to20m/s2.
The solution
Themaincontractorhiredasmallspecialistcompanytobreakuptheretainerusinghydraulicbursting.Thisinvolvesforcingtheconcreteapartwithaspecialhydraulictoolinsertedintoholesspeciallydrilledforthepurpose.Althoughtheburstingprocessitselfdoesnotexposetheoperatortoanyvibration,inthiscasetheholesweremadewitharockdrillwhichwouldhaveexposedtheoperatortovibrationmagnitudesashighas15m/s2.Therockdrillworksfast,sothetotaldailyexposuretimewasonlyabout10minutes,whichwouldgiveapotentialvibrationexposureofabout2m/s2A(8).Vibrationexposurecouldbeeliminatedaltogetherbyusingaclamp-mounteddiamondcoredrilltomaketheholes.Thiswouldtakeslightlylongerthantherockdrill.
The cost
Therockdrillandburstingmethodcostapproximately30%morethanusingbreakers.Thediamonddrillandburstingmethodcostapproximatelytwicethatofusingbreakers.
Hydraulicburstingtoolbeingusedtodemolisharetainingwall
CasecourtesyofSpecialistServices(CuttingandDrilling)Limited
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The result
n Thedailyexposuretimeoftheoperatorsisreduced.Thismethodismuchquickerthanequivalentlowimpactmethods.
n Verylowvibrationmagnitudesaretransmittedtothebuildingstructure.n Burstingproducesverylownoiselevelsandlessdustandflyingdebristhan
pneumaticbreakers.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
12 26minutes 3hours 7
After(actual)
15 17minutes 10minutes 2.2
After(potential)
0 - 0 -
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Health and Safety Executive
7 Diamond wire cuttingThe task
Removal of sections of brick or concrete structures.
The problem
Aspartoftherefurbishmentofarailwaystation,anewstairwellwastobecutthroughthetopofabrickarchedtunnel.Directlyabovethetunneltherewasasolidfloor,whichwas1mthickinthemiddleofthetunneland4mthickatthesides.Theaperturewastobecutthroughallofthismaterialacrossthefull7mwidthofthetunnelforalengthofapproximately3m.Thisjobcouldhavebeendonewithhand-heldpneumaticbreakers.However,toavoiddamagetothebasestructure,onlylow-poweredunitscouldhavebeenusedandthejobwouldinvolvefrom40to60workerdaysofwork.Astoolsofthistypeproducetypicalvibrationmagnitudesintherange5to20m/s2andmaybeusedforlongperiods,vibrationexposuresof7m/s2A(8)orgreaterarepossible.
The solution
Theaperturewasmadewithalargepercussivebreakermountedonanexcavator.Normallythiswouldhaveledtoseveredamagetotheremainingarchstructure,butthiswaspreventedbycuttingrightthroughthebrickworkalongtheedgesoftheareatoberemoved.Thisisolatedthedelicatepartsofthestructureandallowedthematerialtobebrokenupinapproximately2hours.Thecutsweremadeinfoursectionswithadiamondwiresaw.Thisconsistedofadiamond-toothedsawwirewhichwaswrappedaroundthestructuretobecutanddrivenbyatrack-mountedmechanism.Asthewirecuts,itispulledthroughthestructurelikeacheesecutter.Forthisjobthewirewasthreadedthroughpilotholesdrilledthroughtothetunnelfromthefloorabove.Thiswasdonewithaclamp-mounteddiamondcoredrill.
The cost
£4500,comparedwithabout£5000forthesamejobusinghandbreakers.
Diamondwirecutter(NBThesafetyguardshavebeenremovedforthephotograph)
Mountedbreakerknockingaholethroughabrickarchshowingdiamond-drilledpilotholes
CasecourtesyofSpecialistServices(CuttingandDrilling)Limited
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The result
n Theoperatorsarenotexposedtoanyvibrationfromthecuttingordrilling.n Thismethodismuchquicker,whichmeanslessdisruptiontotheoverallwork
programme.Inthiscase,thetotaltimeonsitewasreducedtoatotalof3days,ie1.5daysdiamonddrilling,1daydiamondwiresawingand2hoursbreaking.
n Thereislessnoiseandlessdamagetothestructure.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
12 26minutes 3hours 7
After 0 - 0 -
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8 Pipeline insertion method avoids trenchingThe task
Replacing old cast-iron gas and water mains.
The problem
Thetraditionalmethodofreplacingoldutilitymainsistodigatrenchdowntotheoldpipeandlayanewonebyitsside(knownasfull-lengthtrenching).Thisinvolvesalotofworkbothindiggingthetrenchandinreinstatementafterwards.Thereisalsoachancethatotherburiedservicesmightbedamagedintheprocess.Inurbanareasitisalsonecessarytobreakroadandpavementsurfaceswithpercussivetools,whichmayresultinhighhand-armvibrationexposures.
The solution
Itisnowpossibletoreplaceoldpipeswithoutfull-lengthtrenching.Onetechnique,whichcanbeusedinareaswithcompressiblesoil,involvessplittingtheoldpipeundergroundandinsertinganewoneinthevoid.Twoholesaredugabout3mwideand100maparttoexposesectionsoftheoldpipe.Alargepneumatichammerfittedwithapipesplittingbladeisthenpulledfromoneholetotheotheralongtherouteoftheoldpipewithapowerfulwinch.Thebladebreaksupthepipewhilethehammerbodyforcesthefragmentsaparttomakespaceforthenewpipelinewhichispulledalongbehindthepipesplittingblade.Additionalsmallholesaredugdowntoreconnectbranchestothenewpipeandtoremoveoldleakrepaircollarswhichthebladeoftencannotsplit.Ittookoneutilitiescompanyapproximately2hourstoreplaceabout100mofpipe.
Pipelinereplacementequipment
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The cost
About£10000forpneumaticequipmentor£30000forhydraulicequipment.Thisequipmentisalsoavailableforhire.
The result
n Thismethodreducesthetimetheoperatorsareexposedtovibration.n Itismuchquickerthanfulltrenching(about25%ofthetime)anditreducesthe
chanceofdamagingotherburiedutilitiesortreeroots.n Thereislessdisruptiontootherroadusersandresidentsasthereisless
excavationandreinstatement.n Inareaswithsuitablesoilitispossibletoinsertapipe25%largerthantheold
onewhichreducestheneedforridermains(ieextrapipesonthesameroutetocopewiththeadditionalvolume).
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
12 26minutes 3hours 7
After(potential)
12 26minutes 30minutes 3
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9 Directional drilling avoids trenchingThe task
Laying new utility mains.
The problem
Thetraditionalmethodforlayingutilities,egwater,gasandtelephonelines,istodiganopentrenchoverthefulllengthofthejobandplacethepipeinthetrenchinsections.Thetrenchingoperationcausesconsiderabledisruptionandmess,andcanbeexpensive.Roadandpavementsurfacesneedtobebrokenupandreinstatedusingpercussivetools.Workersareexposedtotypicalvibrationmagnitudesintherange5to20m/s2foranaverageof3hoursperday.
The solution
PipesforanewwatermainwerelaidwithouttrenchingacrossamotorwayinnorthernEngland.Theutilitycompanyhiredacontractorwhouseddirectionaldrillingtolaythepipe.Thistechnique,whichcanbeusedinareaswithsoftground,involvesdiggingapitateachendofthepiperunanddrivingasteerableboringtoolhorizontallyundergroundfromonepittotheother.Theheadofthetoolissteeredfromthesurfaceusingamobiletransmitter.Aftertheboringiscomplete,thenewpipeispulledbackthroughthehole.Smallholesaredugfromthesurfacedowntothenewpipetoconnectthesidebranchestothemain.Thereisariskofdisturbingotherburiedutilities,whichcanbeavoidedbyfollowingtheHSEguidancebook,HS(G)47, Avoiding danger from underground services.7
Directionaldrilling
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The cost
Equipmentcostsabout£30000.Thetotaljobcostsabout75%offulltrenching.
The result
n Vibrationexposuretimeisreducedfromanaverage3hoursto15minutesperday.
n Thismethodismuchquicker(about25%oftimeforfulltrenching).n Thereislessreinstatementandlessdisruptiontoroadusersandresidents.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
12 26minutes 3hours 7
After 12 26minutes 15minutes 2
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10 Mounted roadbreakerThe task
Breaking road surfaces.
The problem
Themostcommontoolusedtobreakuproadandpavementsurfacesisthehand-heldpercussivebreaker.Thesetoolstypicallyproducehand-armvibrationmagnitudesofbetween8and25m/s2withanaverageofaround12m/s2.Afull-timebreakeroperatorworkingonaroadexcavationjobmightbeexposedtothisvibrationforanaverageof3hoursperdaywhichwouldgiveatypicalexposureof7m/s2A(8).Theamountofworkthatanoperatorcandowithoneofthesetoolsinadayvariesdependingonthedepthandhardnessofthesurfacetobebrokenup.
The solution
Insomecircumstancesitispossibletogreatlyreducethevibrationexposurebyusingalargerbreakerattachmentmountedonthearmofanexcavator.Thismethodwasusedbyautilitiescontractorfordiggingtelecommunicationstrenchesintheroadinabusyurbanarea.Therewasalreadyanexcavatoronsitefordiggingoutthetrenchesoncethesurfacehadbeenbroken,andthebucketwasreplacedwithabreakerattachment,whichtookabout5minutes,wheneverrequired.Thebreakerispoweredusingtheexcavatorhydraulicsandisactivatedbyafootpedal.Thearmpositioniscontrolledbyapairoflevers,passingverylittlevibration(vibrationmagnitudeislessthan1m/s2)totheoperator’shands.Ahand-heldbreaker,fittedwithasharpcuttingtool,wasusedforabout5minutesatthebeginningofthedaytoscoretheedgesoftheareatobebrokenupwiththemountedbreaker.
The cost
Mountedbreakerattachmentsstartataround£3000.
Mountedbreakerbeingusedtobreakroadway
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The result
n Thismethodreducesthetimetheoperatorsareexposedtovibration.Theexposureforthehand-heldbreakeroperatorwasreducedtolittlemorethan1m/s2A(8).
n Onthetypeofsurfacefoundinthisexample,themountedbreakerworksapproximately10timesasfastasonepersonwithahand-heldtool.
n Theattachmentsontheexcavatorcanbechangedveryquickly.n Overallthereislessdisruptionandnoise.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
12 26minutes 3hours 7
After 12 26minutes 5minutes 1.2
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11 Reduced-vibration roadbreakersThe task
Breaking concrete and asphalt road surfaces.
The problem
Wheninstallingormaintainingundergroundservicesitisoftennecessarytodiguproadways,pavementsandotherareasofhardstanding,whichusuallyinvolvesbreakingthesurfacewithpercussivepneumaticorhydraulicbreakers.Oneutilitycontractoremployedteamsofworkerstodothisusingarangeofbreakersofvarioustypesandages.Onetool,whichwasoldbutstillinregularuse,producedavibrationmagnitudeof23m/s2measuredwhilebreakingaroadsurface.Onaverage,toolsfromthecompany’sstocksproducedvibrationmagnitudesofabout12m/s2.Theworkershadavarietyoffunctionstoperformsotheactualexposuretovibrationfrombreakersvariedfromdaytoday.Takingatypicalexposuretimeof3hours,anexposureofover7m/s2A(8)couldbeexperienced.
The solution
Manybreakermanufacturersnowmaketoolswhichtheyclaimproducelowervibrationmagnitudesthanoldertypeswithnolossofperformance.Thesemayfeatureredesignedmechanismsorsomeformofvibrationisolationinthehandle.Thecompanyboughtorborrowedaselectionofreduced-vibrationtoolsfromitsregularsuppliersandallowedaroadgangonarealjobtotrythemoutandcomparethem.Thevibrationmagnitudesproducedbythetoolsweremeasuredandtheoperatorswereaskedtocommentontheirperformanceandeaseofuse.
Oneofthenewtools,whichfeaturedsoftlysprunghandles,producedthelowestmeasuredvibrationmagnitudeof5m/s2.Theoperatorfeltthatthesoftspringsmadethetooldifficulttocontrolsothathehadtoholdthehandlesmoretightlythantheothertools,increasingfatigue.Thenextlowestvibrationmagnitudemeasuredonanotherofthenewtoolswithstiffer(risingrate)springswas8m/s2.Theoperatorfoundthistoolcomfortabletouseandeasiertocontrolthanalloftheothertoolsontest.Infuturethistoolwillbeboughtbythecompanyastheyfeltitofferedaconsiderablereductioninvibrationexposureovertheexistingtoolswhilestillhavinggoodperformanceandcontrollability.
Left Aselectionofbreakers
Right Oneofthepreferredbreakersinuse
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The cost
Vibration-reducedbreakerscost25%morethantheequivalentstandardtypes.
The result
n Thevibrationmagnitudeisreduced.n Tooloperatorsareinvolvedinchoosingthepreferredtool.n Operatorsfoundthepreferredbreakerlesstiringtouseanditallowedgreater
precisionthantheothers.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Traditionalbreakerdesign(typical)
12 26minutes 3hours(estimated)
7.3
Newbreakerdesign
8 1hour 3hours(estimated)
5
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12 Maintaining chainsawanti-vibration rubber bushesThe task
Cutting wood with chainsaws.
The problem
Mostmodernchainsawsarefittedwithrubberbusheswhichisolatethehandlesfromthevibratingpartsofthemachines.Overtimethesebushesdeterioratethroughcontactwithoilandhightemperatures.Generallytheyarereplacedwhentheyhavesplitorfailedcompletely.Theirabilitytoprotecttheoperatorfromharmfulvibrationwillbereducedsignificantlywellbeforecompletefailureoccurs.Oneforestrycompanyhadachainsawthathadbeenininfrequentuseforapproximately3years.Thesawhadbeenwellmaintained,withregularinspectionandservicingandwiththechainkeptsharpandatthecorrecttension.Theanti-vibrationbusheswerestillintactbuthadbecomesoftenedtotheextentwheretheycouldbe‘bottomedout’bypressureonthehandles.Inanormalwoodsawingoperation,avibrationmagnitudeof9.7m/s2wasmeasuredwhichwouldleadtoavibrationdoseof2.8m/s2A(8)beingreachedinabout40minutes.Thetypicalusageofsuchatoolmightbe2hoursperday.
The solution
Thebusheswerereplacedonaregularbasisaspartofamonitoringandmaintenanceprogramme.
The cost
Typicalbushescostabout£5eachandcanbereplacedinabout1hour.
Vibrationaccelerationmeasuredonachainsawbeforeandafteranti-vibrationbushreplacement
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The result
n Thevibrationmagnitude,measuredwiththesameoperatorcuttingthesamepieceofwoodasbefore,wasreducedto5.4m/s2.Thiswouldallowover2hoursuseinadaybeforereachinganexposureof2.8m/s2A(8).
n Theoperatorhadmorecontrolofthetoolandfounditmorecomfortabletooperate.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
9.7 40minutes 2hours 4.8
After 5.4 2hours 2hours 2.7
Dismantledchainsawwiththefiveoldanti-vibrationbushes
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13 Chainsaw maintenance and training programmeThe task
Use of chainsaws for cleaning river banks and watercourses.
The problem
Riverbanksandwatercoursesareclearedusingchainsawsandotherpowertools.Onecompanyintroducedatoolpurchasingpolicydesignedtoreducethevibrationexposureofstaffto2.8m/s2A(8).Thiswasdonebybuyingchainsawswithamaximumvibrationof5.6m/s2,basedonatypicaldailyexposuretimeof2hours(seealsoCaseStudy28).Theeffectivenessofthispolicydependedonthisvibrationperformanceandworkratebeingachievedinthefield,anditispossiblethatpoormaintenancemayleadtoanincreaseinthevibrationproducedbychainsaws.Forexample,inatestitwasshownthatpartiallyperishedanti-vibrationbushesincreasedthevibrationmagnitudeproducedbyonesawfrom5.6m/s2to9m/s2.Inanothertest,abluntchaincutatapproximatelyathirdofthespeedofasharponefittedintothesamesaw,operatedbythesameperson,cuttingthesamepieceofwood.Sincetheworkershaveafixedamountofworktodo,itwaspossiblethatusingbluntchainscouldtriplethevibrationexposuretime.
The solution
Theorganisationapproachedtheproblemintwoways.Firstly,theydevelopedaplannedmaintenanceprogrammewhereeverytoolwasservicedbyacompetentmechanicevery12months.Foreachtoolthereisaservicerecordsheetwhichhastobecompletedshowingtheconditionofallmajorcomponentsincludinganti-vibrationequipment.Thisshouldensurethatpartsarereplacedbeforetheystopworkingandthattoolsarekeptingoodcondition.Secondly,thetooloperatorsthemselvesweregiventraininginthecorrectmaintenanceoftheirtools(suchaschaintensioningandregularsawsharpening),therisksofhand-armvibrationandtheconsequencesofpoormaintenanceandbluntchains.Thiswasdoneaspartofthegeneralchainsawsafetytrainingtheoperatorsreceive.
Chainsawinuse
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The cost
Toolservicingcouldcostapproximately£50.Additionaltrainingcostswereminimalasitwasdoneaspartofanexistingtrainingprogramme.
The result
n Thevibrationmagnitudeproducedbythetoolswasreduced.n Efficiencyimprovedandtherewasareductioninunexpectedtoolbreakdown.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Poorlymaintainedtools
9 46minutes 6hours 8
Correctlymaintainedtools
5.6 2hours 2hours 2.8
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14 Reduced-vibration chipping hammerThe task
Removing mould materials from the cores of large castings.
The problem
Manyofthecastingsmadeinthefoundryofapumpmanufacturingcompanyarehollow.Theyarecastaroundasandcorewhichhastoberemovedwhenthemetalhascooled.Thisisdonewithahand-heldimpulsivechippinghammer.Thecompanyhadseveraloldtoolswhichtypicallyproducedvibrationmagnitudesof8m/s2.Althoughtheworkwasnotdoneeverydayitwaspossiblethatonsomeoccasionsworkerswereexposedtovibrationfromthesetoolsforupto4hoursperday.Thisgaveapotentialvibrationexposureofabout6m/s2A(8).Theextendedperiodsofusewerealsoquitephysicallytiring.
The solution
Theworkisnowdonewithavibrationreducedchippinghammerwhichexposestheworkertoavibrationmagnitudeof3.7m/s2.Thevibrationhasbeenreducedbytheredesignoftheinternalcomponentsofthetoolusingspringsandcompressedairtoisolatethetoolbodyfromtheimpactingparts.
Low-vibrationchippinghammerknockingoutacasting CasecourtesyofSvedalaLimited
Cross-sectionoftoolshowingthemetalandairspringsusedforvibrationisolation
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The cost
Thelow-vibrationchippinghammerusedinthiscasecostabout25%morethanthepriceofanequivalentnormalone.
The result
n Thevibrationmagnitudeproducedbythetoolhashalved.n Thenewtoolismuchmorecomfortabletouseforlongperiods.n Toolperformanceisasgoodasequivalenthigh-vibrationunits.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
8 59minutes 4hours 5.6
After(potential)
3.7 10hours 4hours 2.6
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15 Sleeve for chipping hammer chiselThe task
Removing defects in steel castings using a chipping hammer.
The problem
Atalargesteelworks,defectsinsteelcastingsareremovedusingpneumaticchiselsorchippinghammers.Generallythetoolpiece(chisel)isheldinonehandwhilethetriggerisoperatedbytheother.Bothhandsareexposedtovibrationbutthechiselhandisexposedthemost.Ononetoolavibrationmagnitudeofapproximately26m/s2wasmeasured.Theexposuretimeforthesetoolscannotbepredictedasitvariesfromdaytoday.However,theHSErecommendedactionlevelof2.8m/s2wouldbeexceededifthetoolwasusedforabout5minutesinoneday.
The solution
Workingtogetherwithasupplierofindustrialrubberproducts,thesteelcompanyhasdevelopedaresilientsleevetowraparoundthechisel.Thisismosteffectiveatreducingvibrationalongthelineofthechisel.
The cost
Sleevescostapproximately£5each.
The result
n Theoverallvibrationmagnitudehasreducedto13m/s2,halfofitsoriginalvalue.
n Thesleeveprovidesthermalinsulationbetweenthechiselandtheoperator’shandandismorecomfortablefortheoperator.
Note:Inadditiontothedevelopmentofthechiselsleeve,thecompanyhasintroducedreduced-vibrationgrinderswhichareabletoremovemostdefects.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 26 5minutes Varies Varies
After 13 20minutes Varies Varies
Chiselfittedwithresilientsleeve
CasecourtesyofBritishSteelPLC,SwindenTechnologyCentre,Rotherham
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16 Isolating casting cut offThe task
Cutting runners and risers from cast components.
The problem
Inasmallalloysteelfoundry,runnersandrisersusedtobecutfromcastingsusing225mm(9in)pneumatichand-helddisccutters.Overatypicalworkingcycle,thisoperationproducedanaveragevibrationmagnitudeof5m/s2.Operatorscouldhavebeenexposedtothisvibrationforupto5hoursaday,givingapotentialvibrationexposureof4m/s2A(8).Theeightworkersinthefettlingareaused25000cuttingdiscsperyear.Theworkalsoresultedinhighnoiseexposureandalotofmanualhandling.
The solution
Aspartofageneralprogrammetoimproveergonomicsandreducevibrationexposureinthefettlingarea,thecompanyboughtanenclosedremote-controlledcut-offmachine.Thecastingismountedinasimplefixtureandcutbyalargeabrasivedisconapneumaticarm.Theoperatorwatchesthecuttingthroughawindowintheenclosureanddoesnotcomeintocontactwithanyvibratingcomponents.
The cost
£135000forthecut-offmachine.Disccostshavereducedbyapproximately80%.Themachinepaidforitselfin2yearsboththroughimprovedproductivityandgreatlyreduceddiscconsumption.
Cuttingoffacastingwithahand-heldtool
Automaticcut-offmachineshowingacastinginafixture
CasecourtesyofTerrillBros.(Founders)Limited
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The result
n Theoperatorsarenotexposedtoanyvibration.n Ithashelpedintheprogrammetoreducebackinjuriesatthefoundry.n Theexposuretonoise,dustandfumeshasreduced.n Theriskofinjurybycontactwiththecutterorhotmetalisreduced.n Moreworkcanbeprocessedbythesamenumberofworkers.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 5.5 2hours 5hours 4
After 0 - 0 -
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17 Automatic fettling of castingsThe task
Fettling spheroidal carbon steel castings.
The problem
Thecompanyoperatesafoundrythatcastscomponentsinspheroidalcarbonsteels.Thesematerialsareveryhardand,asaresult,fettling(theremovalofexcessmaterialaftercasting)hastobedonewithhigh-performancetools.Peopleworkinginthefettlingareacanbeexposedtogrindervibrationforupto3.5hoursaday.Thelargehigh-frequencyelectricgrindersusedatthefactorycanproducetypicalvibrationmagnitudesofaround7m/s2,soitispossiblethatpeopledoingthisworkreceivedavibrationexposureofabout5m/s2A(8).
The solution
Muchofthefettlingisnowdonewithafully-automatedrobot-basedmachine.Thecastingsaremountedonspecialfixturesandplacedontoaconveyorsystem.Arobotarmthenpicksupthefixtureandmanipulatesthecastingsothattheunwantedmaterialisremovedbylargegrindingandcut-offwheels.Thecontrolsequencesarepre-programmed,soalltheoperatorhastodoismountthecastingsontothefixtures.
The cost
About£250000foreachautomaticfettlingmachine.
The result
n Theoperatorsarenotexposedtoanyvibration.n Thereisimprovedproductivityandmoreconsistentquality.n Thereisreducedexposuretonoise,dustandfumes.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 7 1hour17minutes 3.5 4.6
After 0 - 0 -
Insidethefettlingmachine,showingacastingmountedinafixtureandthegrindingwheel
CasecourtesyofTriplexWilliamsLimited
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18 Air-carbon arc gouging replaces traditional toolsThe task
Rectifying defects in large castings.
The problem
Anengineeringcompanyneededtorefurbishtwosteamchests,whicharelargespecialiststeelcastingsweighingabout20tonneseach.Theyhadbothbeeninserviceforsomeyearsandhadmanydefectsfromuseandpreviousrepairs.Non-destructivetestingtechniqueswereusedtodetectandlocatethedefects,whichincludedcracksandholesinthesurface,hiddenvoids,andareaswhereanincorrectmaterialhadbeenadded.Torepairthedefects,approximately2tonnesofmaterialneededtoberemovedfromeachcastingbygouging.Traditionaltools,suchaschippinghammersandgrinders,wouldhavetakenateamofworkersseveralmonthstocompleteandtheywouldhavebeenexposedtoahighvibrationmagnitude.
The solution
Thecompanyremovedthematerialusingair-carbonarcgouging.Thisprocessusesanarcweldingpowersourceandaspecialhandsetwithanozzlethatblastscompressedairontothearc,blowingawaythemoltenmetal.
Steamchestcastingshowinglargearearemovedbythermalgouging
Air-carbonarcgouginginprocess
CasecourtesyofMitsuiBabcockEnergyServicesLtd
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The cost
Air-carbonarcgougingequipmentcostsapproximately£7000perset.
The result
n Theoperatorswerenotexposedtoanyvibration.n Thismethodgaveahighermaterialremovalratethanchippingandgrinding,
whichledtolargesavingsintimeandcost.Forexample,thejobwascompletedbyfourmeninabout1month.
Note:Theprocessproducedcopiousvolumesofairbornefumeandspatter.Operatorsmustbeprotectedandotherpeopleremovedfromthearea.Failuretodosowillputthehealthofoperatorsatseriousrisk.Companiesshouldperformadetailedassessmentoftheriskstothehealthandsafetyofoperatorsandensurefumelevelsarecontrolledtotheappropriatelevel.Thismayresultinadditionalcosts.Itmayalsoproducehighnoiselevelsfromwhichoperatorsmustbeprotected.
Therearevariousothermethodsofthermalgougingwhicharesuitablefordifferentapplicationsandmanyhavelowerexposuretotheseotherhazards.Thetwomainalternativesareoxy-fuelgasflamegougingandplasmagouging.
Operation Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
GrindingChipping
913
46minutes22minutes
3hours3hours
5.58
After - 0 - 0 -
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19 Casting shell knockout in cabinetThe task
Removing ceramic mould shells from precision cast components.
The problem
Atonesmallfoundry,ceramicmouldshellsusedtoberemovedbyhandusingalumphammer.Thiswasverytimeconsumingandnotparticularlyeffectiveatremovingallofthemouldmaterial.Handhammeringoperationslikethisexposeworkerstohighmagnitudesofshockvibration-overatypicalworkingcycle,valuesashighas27m/s2arecommon.Eachmouldshelltookabout2minutestoknockout.Thenumberdoneperdayvariedandtheworkwassharedbetweentwoorthreepeople.Ifonepersonknockedouttenmouldsinadaytheirvibrationexposurewouldhavebeenabout6m/s2A(8).
The solution
Thecompanyboughtaknockoutcabinet.Thisconsistsofachippinghammermountedinasteelframeinsideanacousticallytreatedenclosure.Thecastingisplacedinthecabinetandthechipperwillonlyoperatewhenthedoorisclosed.
The cost
£5000topurchaseandfitoutthecabinet.
Left Castinginsidecabinetbeforeoperationbegins
Right Castinginsidecabinetaftermouldremoval
Automaticknockoutcabinetandoperator
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The result
n Theoperatorisnotexposedtovibration.n Thereisasmallreductioninmanualhandling.n Itisamuchfastermethod(eighttimesfasterthantheoldmethod)andmore
effective.n Noiseexposuresarelowerthanalternativemethods.n Thereislessmessaroundtheworkshopastheremovedceramicisallinone
place,reducingcleanuptime.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
27 5minutes 20minutes 5.5
After 0 - 0 0
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20 Maintenance of low-vibration toolsThe task
Using a needle gun.
The problem
Aspartofaprogrammetoreducehand-armvibrationexposure,oneconstructioncompanytriedoutanewvibration-reducedneedlegun.Themanufacturerclaimedavibrationmagnitudeof4m/s2(testedtotherelevantlaboratorystandard).Thiswasconsideredacceptablebythecompanyasthetoolswouldnotbeusedformorethan4hoursperdayandtheoperatorswouldnotbeexposedtovibrationfromothersources.Thetoolwasusedonalargesiteforafewmonthswithoutanyregularmaintenance.Duringacheckonvibrationlevelsperformedon-site,theneedlegunproducedavibrationmagnitudeof15m/s2.Thecompanyreturnedthetooltothemanufacturersforrepairsandcomment.
The solution
Thetoolwasdismantledanditwasdiscoveredthatonlysixoftheoriginal28needleswerestillintactandthatpartofoneofthebrokenneedleswasjammingthevibrationisolationsystem.Therewasnodamagetotheotherinternalcomponentsofthetoolwhichhadstillbeenusableeveninitsdamagedstate.Theneedlesandneedleguidewerereplaced,thetoolwasreassembledandtestedforvibrationagain.Undersimilarloadconditionstobefore,amagnitudeof4m/s2wasmeasured.Thevibrationexposurecausedbythepoorly-maintainedtoolwillbeavoidedinfuturebymorerigorousmonitoringofthetool’scondition.
The cost
Basicmaintenancecanbedonein-house.Thecostofamanufacturer’sservicewilldependonthetypeoftool.
Vibrationaccelerationmeasuredonaneedlegunbeforeandafteritwasrepaired
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The result
n Thevibrationmagnitudeisreduced.n Properlymaintainedtoolstendtolastlongerandretainperformanceand
productivity
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 15 19minutes 4 10.6
After 4 4hours 4 2.8
Therepairedneedlegun
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21 Reduced-vibration needle gunsThe task
Large-scale concrete construction.
The problem
Thebuildingoflargeconcretestructuresofteninvolvesscabbling.Thisinvolvesroughingupconcretewithpercussivetoolstoformabondingsurfacewhichwillmakeagoodjointwhereadditionalconcreteistobeadded.Thiscanbedonewithavarietyoftoolsdependingonaccessrequirements.Ononesite,hand-heldneedlegunswereusedtoscabblearangeofsurfaces.Someofthesetoolsweretestedatthesiteandproducedvibrationmagnitudesofbetween9and13m/s2whilescabbling.Asthetoolsmaybeusedforupto2hoursinatypicalday,thiswouldgiveamaximumvibrationexposureof6.5m/s2A(8).
The solution
Thereareseveralmethodswhichcouldreducevibrationexposureduetoscabbling.Oneinvolvestheuseofnewlow-vibrationneedlegunswhichwereusedasdirectreplacementsfortheoldtools.Ononeofthenewtools,avibrationmagnitudeof4m/s2wasmeasuredwhilescabblingconcrete,whichwasasignificantimprovementovertheoldertoolsonthesite.Theinternaldesignofthetoolusessprings,rubberandcompressedairtoisolatethevibrationfromtheoperator.
The cost
Thetoolinthiscasecostsabout10%morethanthepriceofanequivalentnormaltool.
Vibration-reducedneedlegun
Cross-sectionoftoolshowingvibration-isolatingspringsandfloatingcylinderbody
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The result
n Thevibrationmagnitudehasreduced.n Operatorsreportthatthetoolismorepleasanttouse.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
13 22minutes 2hours 6.5
After(potential)
4 4hours 2hours 2
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22 Shot blasting cabinet replaces rotary filesThe task
Descaling very large castings.
The problem
Submarinebuoyancytankscontainlargeintricatelyshapedventscalledgrillagesthroughwhichwaterandairarepumpedinandout.Thesegrillagesaregenerallymadeofcastmetalandrequirefettlinganddescalingbeforetheycanbefittedtotheship.Becauseoftheircomplexshape,atoneshipbuildingcompanythisjobwasdonebyateamof30peoplewithrotaryfiles.Theywouldworkalldayforseveralweeksoneachgrillageandcouldbeexposedtovibrationmagnitudesover5m/s2.Noiseanddustlevelswerealsoextremelyhigh.
The solution
Thecompanyalreadyhadaverylargeshotblastingcabinetwhichwasusedforsurfacepreparationofotheritems.Thiscabinetwasadaptedsothatthegrillagescouldpassthroughonaconveyorsystem.Amachineusescompressedairtoblastsmallmetalballs(shot)atthesurfacesofthegrillage.This‘shot-blasting’dislodgesandremovesthescale.Oneoperatorisrequired,whostandsawayfromthenoiseanddust,andisnotexposedtoanyhand-armvibration.
The cost
Approximately£50000.
The result
n Theoperatorisnotexposedtovibration.n Thereisreducedexposuretonoiseanddust.n Whatusedtotakeateam3weekscannowbedonebyonepersonin1day.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 5 2hours30minutes 6hours 4.3
After 0 - 0 -
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23 Descaling with abrasive blastersThe task
Cleaning the insides of large storage tanks to remove rust, scale and other impurities after fabrication.
The problem
Alargeshipbuildingcompanyusedtocleanouttanksusingneedlescalers.Thisoperationexposedstafftovibrationmagnitudesintherange11to23m/s2oftenformorethan7hoursaday.Conditionsinsidethetankwerealsoextremelyunpleasantwithhighnoiselevelsandcloudsofdust.
The solution
Theneedlescalerswerereplacedwithportablevacuumblastingmachineswhichcleanthesurfacesbyblastingthemwithanabrasivematerialandthensuckingitandanydebrisawaytoaholdingtank.Theoperatorisexposedtovibrationmagnitudesbelow1m/s2.
The cost
About£1000forthevacuumblastingmachine.
The result
n Areductioninvibrationmagnitudefromupto23m/s2tolessthan1m/s2.n Alargereductioninbothnoiseanddustlevels.Thevacuumactionofthe
equipmentremovesdustanddebriswhichpreviouslymadetheworkenvironmentveryunpleasant.
n Asmallerteamofoperatorsisrequiredtocleanthetankswhichhasledtoimprovedproductivityandcostsavings.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 23 7minutes 7hours 21
After 1 Morethan24hours 7hours 1
Vacuumblastingmachine
Educt-o-maticmachineavailablefromHodge-ClemcoLimited
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24 Job rotation and use of pedestal-mounted nutrunnersThe task
Tightening threaded fastenings and attachments.
The problem
Ononeengineassemblyline,atemporaryadapterisnecessaryforfeedingoiltotheenginesumpduringon-linetests.Itisscrewedintoathreadedholeonthesideoftheengineblock.Itdoesnotneedtobetightenedtoaspecifictorquebutneedstobequitetight.Thisusedtobedonewithahand-heldpneumaticratchetgunofthetypeusedingaragestotightenwheelnuts,whichcouldproducevibrationmagnitudesupto8m/s2.Amaximumof2400enginesareassembledperday,which,withperhaps3secondsratchetingoneach,wouldgiveanexposureof4m/s2A(8).Theworkwasdonebyagroupofaboutfivepeople.
The solution
Thecompanyimplementedajobrotationschemewherebyoperatorsmovedbetweenfourorfivedifferenttasksallaroundthesameareaoftheproductionline.Someoftheotheractivitiesinvolvesomevibrationexposure,butingeneraltherotationhashalvedindividualexposuretime.Tofurtherreduceexposure,thecompanyoptedtousepedestal-mountednutrunnersinsteadofratchetgunstodothejob.Theseareverysolidlymountedandsopassverylittlevibrationtotheoperator.
Ahand-heldratchetguninuse
Apedestal-mountednutrunner
CasecourtesyofFordMotorCompany
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The cost
About£5000forthepedestalmountingandtool.
The result
n Vibrationmagnitudeisreduced.n Lessnoiseisproducedbythepedestal-mountedtoolthantheratchetgun.n Operatorsreportthatthegroupworkingreducesboredomandfatigue.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 8 1hour 2hours 4
After Lessthan1 Morethan24hours 1hour Lessthan1
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25 Automatic bolt fittingThe task
Fitting main bearing caps to car engines.
The problem
Thecompanyusedtofitmainbearingstoengineblocksmanually.Usingthismethod,theretainingboltsarestartedbyhandandthenrun-upandtightenedup,or‘torqued’,usinghand-heldpneumaticorelectrictools.Thesetoolsoftenproducedhighvibrationmagnitudesupto8m/s2andwereinalmostconstantuseasenginespassedontheproductionline.Ittooktwopeopletofitthebearingcapsquicklyenoughtokeepupwiththeotherpartsoftheline.
The solution
Inoneplanttheprocesshasbeenautomated.Thebearingcapsareplacedinafixturebyrobotarmsandfittedbyadedicatedmachinewhichpicksandplacesallfivecaps.
The cost
Tenspindleautonutrunnerscost£100000.
Themachineinoperationshowingarowoffivebearingcapsabouttobeliftedontoacylinderheadandfasteneddown
Multipletighteningspindlesofthetypeusedtosimultaneouslytightenthetenbearingcapbolts
CasecourtesyofFordMotorCompany
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The result
n Theoperatorsarenotexposedtoanyvibration.n Thenoiseexposureofoperatorshasreduced.n Consistencyandproductivityhasimproved.Forexample,whatwasdoneby
twofull-timepeoplecannowbedonebyone,whoalsohashandsfreeforothertasks.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
8 1hour 6hours 7
After 0 - 0 -
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Left Hand-heldnailsawusedtodismantleapallet
Right Stringerstrippingmachine
26 Automated pallet strippingThe task
Repairing wooden pallets.
The problem
Thecompanyownandleaseoutpallets.Whenthepalletsaredamagedtheyarerepairedinspecialdepotsaroundthecountry.Onarrivalatthedepot,thepalletsaresortedandtheirdefectsidentified.Damagedpartsarethenremovedbyprisingapartthejointsandcuttingthroughthenailswithapneumaticsaw.Thesawsusedhaveareciprocatingactionandareusedinshortburstsforatotalofabout1hourperday.Thecompanywantedtoreducetheresultinghand-armvibrationexposurebyasmuchaspossible.
Themosttime-consumingpalletelementstoremovearethestringers.Thesearethestrongpieceswhichrunacrossthepallettosupportthetopplanksandareheldinplacewithmorenailsthantheotherparts.Thestringernailsarealsomoredifficulttoaccess,whichresultsinalotofmanualhandling.
The solution (BRISTOL DEPOT)
Aspartofanoverallprogrammetoreducearangeofhazardsandimproveefficiency,approvedbyanergonomist,thecompanydecidedtoautomatethestringerstrippingprocess.Theyintroducedspeciallyconstructedstringerstrippingmachineswherethepalletsareclampedtoabenchandacircularbladeisforcedthroughthenails.Workersintheplantrotatejobs,sosomevibrationexposureisstillexperiencedduetotheuseofthesawsonthenon-stringerparts.
The cost
Nocostsavailable.
The result
n Thestringerstrippersdonotexposetheiroperatorstoanyvibrationandtheygreatlyreducetheamountofmanualhandling.
n Thetimetheoperatorsareexposedtovibrationduringthedayhasreduced.n Overalltheintroductionofthestringerstrippershasreducedthevibration
exposureofworkersby13%andreducedtheoccurrenceofupperlimbandbackinjuries.
Twodepotsinthecompany-BristolandBirmingham-introduceddifferentsolutionstotheproblem.
CasecourtesyofChep(UK)LimitedBristol depot
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27 Low-vibration power sawThe solution (BIRMINGHAM DEPOT)
Atoneofitssitesthecompanyhastakenadvantageofadvancesintooldesignandboughtnewsawsofsimilarperformancewhichproducemuchlowervibrationmagnitudes.Thenewsawshavebeencarefullydesignedtohaveamorebalancedandsmoothoperationthantheoldertypes.
The cost
Anewlow-vibrationsawcostsabout11%morethantheoldtype.
Summary - the combined effect Inthefuture,thecompanyintendstointroducethebenefitsofbothsolutionstotheirotherdepotstofurtherreducetheexposureofoperatorstovibration.Wherebothsolutionsareusedtogether,thetotalreductioninvibrationexposurewillbe60%.
The result
n Thenewsawsproduceavibrationmagnitude53%lowerthanthetypicaloldsawsandtheycanbeintroducedwithoutanychangetotheworksystem.
n Thenewtoolisdesignedtoreduceinternalwearofpartsandsomaintenancecostsarereduced.
CasecourtesyofChep(UK)LimitedBirmingham depot
Explodeddiagramofthenewsawshowingpivotmechanismandcounterbalanceweights
SawsmanufacturedbyCengar,UniversalToolCompanyLimited
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28 Outdoor power tools purchasing policyThe task
Using chainsaws and strimmers.
The problem
Themaintenanceofwatercoursesofteninvolvesusingchainsaws,strimmersandbrushcutterstoclearvegetationfromriverbanksandsimilarareas.Localdepotsofanationalorganisationwerefreetopurchasetoolsoftheirchoicefromlocalsupplierswhenrequired,whichresultedinthecompanyowningalargerangeoftoolsfromavarietyofmanufacturers.Atestsessionwasheldatwhichthevibrationproducedbyaselectionofthetoolsinusewasmeasuredundersimulatedworkconditions.Thechainsawsproducedanaveragevibrationmagnitudeof13m/s2withseveraltoolsreportedtoproducevaluesabove25m/s2.Thestrimmersgaveanaveragevibrationmagnitudeof8m/s2withasignificantnumberproducingmorethan15m/s2.Itwasverydifficulttodeterminearepresentativevibrationexposuretimeforthetools,however,discussionbetweentooloperatorsandotherstaffrevealedthatdailyexposuresofmorethan2hoursforachainsawand4hoursforastrimmerwereunlikely.Thismeantthatpersonnelhadpotentialexposuresof13m/s2A(8)forchainsawsand11m/s2A(8)forstrimmers.
The solution
Acommittee,includingrepresentativesofmanagement,theunionsandtheoperators,reviewedtheexistingsituationanddiscussedthemostappropriatemeasurestoreducevibrationexposure.Theobjectivewastoreduceitto2.8m/s2A(8),which,usingtheestimatedexposuretimes,couldallowchainsawstoproduceamaximumvibrationmagnitudeof5.6m/s2andstrimmersamaximumof4m/s2.Therewasalengthyperiodofconsultationwithtoolsuppliers,toolusersandotherstoensurethatasufficientrangeoftoolsmeetingthesecriteriawouldbeavailableandthatalloftheorganisation’sneedsandobligationscouldbemet.Apurchasingpolicywasthenprepared,underwhichallofthechainsawsandstrimmersinstockwouldbereplacedwithtoolswhichmetthecriteriawithin4years.Thechangeswillbephasedinwithtoolsproducingvibrationmagnitudesofmorethan20m/s2beingwithdrawnfromuseimmediately,alltoolsproducingmorethan12.5m/s2within1year,andtheultimateobjectiveachievedwithin4years.
Strimmerinuse
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The cost
Minimalastoolswouldbereplacedattheendoftheirlifeanyway.
The result
n Ageneralreductioninvibrationmagnitudesproducedbythetoolsused.n Thenewertoolsareoftenbetterdesignedandlessnoisy.n Theoperatorsofthetoolswereinvolvedinthedevelopmentofthepolicywhich
helpedtoincreasetheirawarenessoftheproblem.
Tool Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Old ChainsawStrimmer
2615
6minutes17minutes
2hours4hours
1311
New ChainsawStrimmer
5.6maximum4maximum
2hours4hours
2hours4hours
2.82.8
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29 Low-vibration fastener systemThe task
Assembling lightweight structures.
The problem
Aircraftwingsproducedatonefactorywereassembledusingnutsandbolts.Withthismethod,toensuretheintegrityofthejoint,theboltsareslightlylargerthantheholesdrilledinthewingtotakethemandhavetobeforcedintoplacewitharivetinggun.Inasimulatedworkingcycle,arivetinggunproducedanaveragevibrationmagnitudeof9.5m/s2.Aworkermightbeexposedtothislevelforupto1houradaywithasimilarperiodspentusinganutrunner(vibrationmagnitudeofapproximately3m/s2)andtherestofthedaydrilling(vibrationmagnitudeoflessthan1m/s2).
The solution
Thewingsarenowassembledusingapin/collarfastenersystem.Thissystemusesswagedmetalcollarstosecurepins(bolts)withsimpleparallelgroovesratherthanspiralthreads.Thepinsarestillslightlylargerthantheholesinthewingbutarepulledintoplacewithaspecialpneumatictoolratherthanpushedthroughwitharivetinggun.Ametalringorcollaristhenplacedovereachpinandasecondspecialtoolsimultaneouslypullsonthetailofthepinandpushesaconicaldieover
Theoperationofthepin/collarfasteningsystem
CasecourtesyofBritishAerospace,AirbusLimited
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thecollar.Thisactionclampsthejointtogetherandlocksitbydeforming(swaging)thecollarintothepingrooves.Thetailofthepinthensnapsoff,leavingitflushwiththenewlyswagedcollar.Theonlysourceofvibrationinthisprocess,otherthandrillingtheholes,istheshockproducedbythepintailbreaking.Thisresultsinanaveragevibrationmagnitudeof1.5m/s2overatypicalworkingcycle.Eachoperatorspendsbetween1and2hoursadayfittingthefastenersandtherestofthetimedrillingholes.
The cost
Thefastenersaresimilarincosttothenutsandboltspreviouslyused.Toolscostabout£1000each.
The result
n Thereisareductioninboththevibrationmagnitudeproducedandthetimetheoperatorsareexposed.
n Thenoiselevelsaregreatlyreduced.n Thecycleisfasteroverallwhichincreasesproductivity.n Thequalityofworkhasimprovedbecausetheclampingforceishigherand
moreconsistentandthefinishedjointismoreresistanttolooseningfromvibration.
Tool Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before RivetinggunNutrunnerDrill
9.53Lessthan1
42minutes7hoursMorethan24hours
1hour1hour6hours
Totalof3.6
After Pin/collartoolsDrill
1.5Lessthan1
Morethan24hoursMorethan24hours
1hour30minutes6hours30minutes
Totalof1.1
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30 No contact casting shell knockoutThe task
Knocking out multiple-component ceramic moulds used in the ‘lost wax’ casting process.
The problem
Aprecisioncastingcompanyusedahand-heldrivetinghammer,ofatypeusedinshipyards,toknockoutcastingsfromtheceramicshellsinwhichtheyhadbeencast.Thisprocesstakesapproximately20minutestocompletepermultiplecomponentmould,exposingtheoperatortovibrationmagnitudesofupto12m/s2.Typicallyanoperatorwouldknockout18suchmouldsadaygivingapossibleexposureof10m/s2A(8).
The solution
Thecompanydevelopedanin-housesolutionbymountingapneumaticbreaker,similartothetypeusedtodiguptheroad,inacustom-builtsteelsupportframe.Themouldtobeknockedoutisheldintheframewithpneumaticjawsandvibratedbyaspecialtoolpiecefittedinthebreaker.
The cost
Approximately£2500forthebreaker,steelworkandpneumaticsplusengineer’stime.
The result
n Theoperatordoesnotcomeintocontactwithanyvibratingparts.n Thetimetoknockoutonemouldtreereducedfrom20minutesto5minutes.n Thereisareducedriskofbackproblemsaslessliftingisrequired.n Themachinecanbepartiallyorfullyenclosedtoreducetheoperator’s
exposuretonoise.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 12 25minutes 6hours 10
After 0 - 0 -
Knockoutmachineshowingbreakermountedinsupportframe
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31 Low-vibration riveters and reaction barsThe task
Riveting aeroplane wings.
The problem
Aircraftwingsareoftenassembledusingrivets.Aholeisdrilledthroughthecomponentstobejoinedandarivetinserted.Thejointisthenmadebyflaringthepointoftherivetwithanimpulsivetool(rivetinggun)whiletheotherendissupportedwithareactionbar.Inatypicaloperationatonefactorythewingcomponentswereheldinajigwhiletherivetingwasdonebytwoworkers.Oneworkeroperatedtherivetinggunandtheotherheldthereactionbar,asolidblockofmetal,inplace.Afullday’srivetingrequiresabout2hoursuseofthetools,givingvibrationexposuresofabout2m/s2A(8)and9m/s2A(8)forrivetingandreactingrespectively.
The solution
Thecompanyinvestedinnewtoolswiththespecificintentionofreducinghand-armvibrationexposure.Theyboughtvibration-reducedrivetinggunsandvibration-isolatedreactionbarswhichhavereducedthevibrationmagnitudeexperiencedbybothoperatorsto3m/s2.Thegunhasanimprovedinternaldesignandthereactionbarfeaturesapassivespring/dampersystemtoreducethevibration.
The cost
Low-vibrationriveterscostabouttwicethepriceofnormalones.Vibration-dampedreactionbarscostabout£300.
The result
n Vibrationmagnitudehasreducedforboththerivetingandreactingoperations.n Thenewtoolsaremorecomfortablefortheoperatorstouse.
CasecourtesyofBritishAerospaceAirbusLimited
Low-vibrationtoolsbeingusedtorivetanaircraftwing
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Operation Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before RivetingReacting
517
2hours30minutes13minutes
2hours2hours
2.58.5
After RivetingReacting
33
7hours7hours
2hours2hours
1.51.5
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32 Special formworkavoids scabblingThe task
Construction of large concrete structures.
The problem
AconstructioncompanywasawardedacontracttobuildoneofthestationsfortheLondonUndergroundJubileeLineExtension.Thestationdesignincludedareinforcedconcretebaseslab300mlong,25mwideand3mdeep.Theslabwascastin situin43sections,each7mlong.Thesectionswerecastoneafteranotherusingtheprevioussectiontosupportonesideandaspeciallyconstructedformworkstopendtosupporttheother.Withthismethodofconstructionitisimportantthatthenewconcretemakesaneffectivebondwiththeold.Whenwoodenformworkisused,thisbondcanonlybeachievedbyremovingthetopsurfaceoftheconcretetorevealtheaggregateunderneath.Thisisoftendonewithimpulsivetoolsinaprocessknownasscabbling.Inthiscase,thetoolswereusedforabout2hoursperdayandexposedoperatorstohighvibrationmagnitudes(typically15m/s2).Atthatworkrate,eachstopendwouldhavetakenapproximatelyeightworkershiftstoscabblewithavibrationexposureofabout8m/s2A(8).
The solution
Thecompanyusedanexpandedmetalmaterialtoconstructtheformworkforthestopendmatingsurfaces.Thematerialwasribbedandfeaturedbenttabsofmeshwhich,whenconcretewaspouredbehindit,becomeembeddedintheconcrete,
Scrapingawayexcessmaterialduringpouring
Exampleofin situcastconcreteshowingexpandedmetalformwork
CasecourtesyofTarmacBachyJointVenture
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formingabond.Theformworkwasleftinplaceoncetheconcretehadcuredandwhenthenextsectionwaspoured,itformedabondwiththeoutersurfaceoftheexpandedmetalthatwasasstrongasatraditionalscabbledjoint.Noscabblingwasnecessary.
The cost
Theexpandedmetalformworkcostapproximately£7perm2.
The result
n Theoperatorswerenotexposedtoanyvibration.n Itwasinstalledmorequicklythanusingwoodenformworkasitallowedthenext
sectionofconcretetobepouredbeforetheprevioussectionwasfullycured(set).
n Noiseanddustlevelswerealsoreduced.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(estimated)
15 17minutes 2hours 7.5
After 0 - 0 -
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33 Paint-on materialavoids scabblingThe task
Preparing cast concrete for adhesion to new material.
The problem
Largeconcretestructuresaregenerallycastinstagesbypouringliquidconcreteintofabricatedmoulds.Toensurecorrectadhesionbetweenstagesitisnecessarytoroughen,orscabble,thematingsurfacesofthehardenedconcrete.Ononesite,needlegunsthatexposedoperatorstovibrationmagnitudesof9m/s2weresometimesusedforthisoperationfornearly2hoursperday.
The solution
Thecompanyusedaretarder.Thisisamaterialwhichcanbepaintedontotheinsideofthemouldintheareaswherescabblingwouldhavebeennecessary.Thispreventsthesurfaceconcretefromcuringsothatthetopfewmillimetresofmaterialcanberemovedwithastandardpressurewasherafterremovalofthemould,leavingasurfaceidealforadhesion.Thematerialcanbeusedsafelybyfollowingthehandlinginstructionsonthesafetydatasheetssuppliedbythemanufacturer.
The cost
Approximately£180foradrumofretarderwithacoverageofabout100m2.
The result
n Thereisnovibrationexposurefortheoperators.n Itincreasesproductivity,egajobwhichwouldhavetakenhalfadaywith
needlegunscannowbedonein10minuteswithreducedcost.n Noiseanddustexposurearereduced.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 9 46minutes 2hours 4
After 0 - 0 -
Removingexcessmaterialwithjetwasher
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34 Grit blasting insteadof scabblingThe task
Constructing concrete structures.
The problem
AconstructioncompanywasbuildingoneofthestationsfortheLondonUndergroundJubileeLineextension.Themainstructureofthestationisconcretewhichwasbeingcastin situinstages.Themeetingsurfacesofeachsectionhavetobepreparedbeforetheadjacentsectioniscasttoensureaneffectivebond.Insomepartsofthestructure,thiswasdoneusingaspecialexpandedmetalmaterialwhichformsthebonditself(seealsoCaseStudy32).However,thismaterialisnotsuitableforuseonthinsectionsofconcretewhichmeantthejointsinthesesectionshadtobepreparedinsomeotherway.Theycouldhavebeenpreparedusingimpulsivescabblingtoolssuchasneedleguns,butworkerswouldhavebeenexposedtovibrationmagnitudesof15m/s2forupto2hourspershift.Thesetoolsalsoproducehighnoiselevels.
The solution
Thesurfaceswerepreparedbygritblasting.Asub-contractgangwasabletoblastabout300m2ofthesurfacesperdayperworker.Beforetheworkbegan,screenswereerectedaroundtheareatobeblastedtopreventdustfromblowingaroundthesite.Thegritblastingmethodcomparesfavourablywiththeuseofimpulsivescabblerswhichmayprepareaslittleas8m2ofthesurfaceperdayperworker.
The cost
Sub-contractedgritblastingonthisprojectcostabout£3perm2.
The result
n Theoperatorsarenotexposedtoanyvibrationwithgritblasting.n Gritblastingismuchfasterthanscabblingbutmayincreaseexposuretodust
andnoisewhichwillrequirefurtherassessmentandcontrolmeasures.
CasecourtesyofTarmacBachyJointVenture
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
15 17minutes 2hours 7.5
After 0 - 0 -
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35 Reduced-vibrationpole scabblerThe task
Making large, in situ cast concrete structures.
The problem
Aconstructioncompanyneededtomakemanylargeconcretecomponentsatthesiteofalargebridgebuildingproject.Thecomponentswerecastinstages.Abatchofconcreteispouredintoamouldandallowedtohardenbeforethenextbatchispouredon.Toensurethatthesuccessivestagesbondtogethereffectively,thesurfaceofeachisroughedor‘scabbled’onceithashardened.Onflathorizontalsurfacesthiscanbedonewithapolescabbler,areciprocatingtoolfittedwithasharppointwhichbreaksuptheconcrete.Thevibrationproducedbythesetoolscanbeveryhigh,forexampleamagnitudeof40m/s2wasmeasuredononeoldtoolusedatthebridgesite.Thisparticulartoolisrarelyusednow,butanaveragedailyusageof1hourwouldgiveanexposureof14m/s2A(8).
The solution
Polescabblerswhichincludevibrationreducingfeaturesarenowavailable.Onesuchtoolwasusedatthebridgesiteandproducedavibrationmagnitudeof7.5m/s2.With1hour’suseadaythiswouldgiveanexposureoflessthan3m/s2A(8).Thetoolfeaturesspring/dampersystemstoabsorbthevibrationproducedbytheimpactofthepoint.Thismakesthetoolheavierthantheoldtypebuttheeffectsofthishavebeenreducedbyfittingahandletotheshaftwhichimprovescontrol.
Cross-sectionofvibration-reducingfeaturesoftool,showingisolatingsprings
Newreduced-vibrationpolescabbler
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The cost
Thereduced-vibrationpolescabblerusedinthiscasecostsabout50%morethananequivalentnormaltype.
The result
n Thevibrationmagnitudeproducedbythenewtoolsisreduced.n Theoperatorssaytheypreferusingthenewtools.n Thenewtoolisfittedwithahandleontheshaftwhichimprovescontrol,
particularlyonflatsurfaces.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
40 2minutes 1hour 14
After 7.5 1hour5minutes 1hour 2.6
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36 Deburring with rumblerThe task
Removing sharp edges from small pressed components.
The problem
Atonefactorysmallpressedcomponentsweredeburredusingemerybandsmountedonrubbercylindersfittedtostraightgrinders.Thecomponentisheldinonehandandthetoolintheothersobothhandsareexposedtovibration.Themagnitudeofthevibrationexposurevariesdependingonthesizeandtypeofcomponent.Atypicalaveragevibrationmagnitudewouldbe2m/s2andexposurecouldbeaslongas7hours,witheachcomponenttakingabout2minutestocomplete.
The solution
Thecomponentsarenowdeburredbyrumbling.Thisprocessinvolvesplacingabatchofcomponentsinacontaineralongwithalargequantityofsmallpiecesofabrasivematerial.Thecontaineristhenvibratedvigorously(rumbled)whichcausesthecomponentsandabrasivepiecestorubagainsteachother,removingtheburrs.Abatchofabout500componentstakes20minutestodeburrinthemachine.
The cost
Deburringmachinescostapproximately£5000each.Abrasivematerialcostsarereducedsignificantly.
The result
n Theoperatorsarenotexposedtoanyvibration.n Therehasalsobeenasignificantincreaseinproductivity.n Rumblingmachinesmayproducehighnoiselevelsfromwhichoperatorsmust
beprotected.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 2 16hours 7hours 1.9
After 0 - 0 -
Therumblingmachinenowusedtodeburrsmallcomponents
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37 Belt grinding and polishing of metal fabricationsThe task
Fettling and preparing metal fabrications.
The problem
Atalarge-scaleprecisionengineeringfactory,smallfabricationsarefettledusingarangeoftools.Themajorityofthetoolsusedarestraightgrindersofdifferentsizesfittedwithavarietyoftoolpieces.Onetool,fittedwitharotaryburr,producedanaveragevibrationmagnitudeof2m/s2overatypicalworkingcycle.Theactualexposuretimeforeachtoolvariesfromdaytoday.
The solution
Thecompanyrecentlystartedusinghand-heldbeltgrinderswhichtypicallyproducevibrationmagnitudesofaround0.5m/s2.Thesetoolscanbeusedformostofthejobspreviouslydonewithstraightgrinders,givingasignificantreductioninvibrationexposureandseveralotheradvantages.
The cost
Beltgrindersareavailableinseveralsizesandcostabout£700comparedwith£100to£200forequivalentstraightgrinders.Overall,thecostofabrasivebeltsissimilartoothertypesoftool.Thebeltsareavailableinarangeofwidths,lengthsandabrasivegrades.
The result
n Thevibrationmagnitudeproducedhasreduced.n Thetoolsareeasiertocontrolandlesspronetowanderandkick.n Thebeltscanbechangedveryquickly.n Theoperatorneedstoapplylessforcetooperatethebeltgrinder.n Accesstoawkwardareasismuchimproved.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 2 16hours Varies Varies
After 0.5 Morethan24hours Varies Varies
Left Rotaryfilebeingusedtofettleacomponent
Right Hand-heldbeltgrinderbeingusedtofettleacomponent
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38 Group working with suspended toolsThe task
General assembly tasks in a car engine plant.
The problem
Engineassemblyinvolvesmanydifferenttasks.Alongtimeisspentsorting,checkingandaligningcomponentsandputtingtogethersub-assemblies.Therearealsomanythreadedconnectionswhichhavetobestarted,run-upandtightenedtoaspecifiedtorque.Thesetasksaredonebyonepersonusingpneumatichandtoolsthatproducevibrationmagnitudesashighas8m/s2.Althoughthetoolsarenotinconstantuse,theyareusedforaboutanhourperday,anddailyvibrationexposuresarelikelytoreachtheHSErecommendedactionlevelof2.8m/s2A(8).Thesetoolsareheavywhichmayputastrainonthewrist,worseningsomeoftheeffectsofhand-armvibrationsyndrome.
The solution
Ononenewengineassemblylineaworkgroupsystemisused.Thisinvolvesagroupoffourorfivepeoplepershiftsharingvariousassemblytasks.Inthegeneralassemblyarea,thishalvesthetimeforwhichanyindividualisexposedtovibrationinaday.Nutrunningandtorquingupisdonewithlowstall-torqueclutch-operatedtools(iethetoolkeepsturningthenutuntilitreachesapre-settorque)whichproducesvibrationmagnitudesofapproximately2.5m/s2.Thesetoolsandothersaresuspendedfromoverheadcounterbalancesystems,whichtakestheirweightandholdsthematanappropriateheightfortherequiredtask.
The cost
Toolscost£1000each.Thesuspensionmechanismcostsabout£1500.
The result
n Areductioninvibrationmagnitudeisproduced.n Theriskofwriststrainisreduced.n Ergonomicsareimprovedassuspendedtoolscomeeasilytohand.n Operatorsreportthatgroupworkingreducesboredomandfatigue.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
8 1hour 1hour 2.8
After(typical)
2.5 10hours 30minutes Lessthan1
CasecourtesyofFordMotorCompany
Suspendedhandtoolinuse,showingsupportcable
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39 Installation of hydraulic cropping machineThe task
Removing flash and excess metal (fettling) from nodular iron castings.
The problem
Atonefoundry,castexhaustmanifoldsusedtobefettledbytwogroupsoffiveworkersusinghandtools.Inthisprocess,oneworkerknocksoffthelargerpieceswithalumphammerandthenputsthecastingsontoaconveyor.Thecastingiscarriedtothreeotherswhointurnoperatealargepedestalgrinder,achippinghammerandastraightgrinder.Finallyafifthpersoninspectsthecastingsforanydefects.Thechipperandstraightgrinderusedaretypeswhichcanproducevibrationmagnitudesashighas12m/s2and6m/s2respectively.Thepedestalgrinderisofthetypewhichcanexposeoperatorstomagnitudesofaround10m/s2.Lumphammeroperationsofthistypeproduceatypicalmagnitudeof27m/s2.Observationshowedthateachoperationresultedinvibrationexposureforabout15%ofthetime,andasthegrouprotatedbetweenthefivejobs,thetotalexposureforeachgroupmembercouldhavebeennearly6m/s2A(8).
The solution
Thecompanyinstalledahydrauliccroppingmachine,inwhichthecastingsareheldinafixtureandthebulkoftheflashisremovedwithasingleblowfromaspeciallymadetool,pushedbyahydraulicpress.Someworkstillhastobedonewiththegrinders,althoughmuchlessthanbefore.Thelumphammerisnolongerusedatall.Withthenewmachine,asingle,rotatinggroupofsixpeoplefettlemarginallymorecastingsinadaythanthetwooldgroupstogether.Vibrationexposureisabout1.7m/s2A(8).
Left Castingbeforefettling
Right Castingafterfettling
Croppingmachineshowingcastingsinfixtures
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The cost
£600000forthecroppingmachine,including£100000fortooling.
The result
n Dailyvibrationexposurefortheoperatorshasreduced.n Themachinehasimprovedquality,andproducesamoreconsistentandneat
finish.n Productivityhasimprovedbyabout80%.
Operation Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(withtypicaltools)
PedestalgrinderStraightgrinderLumphammer
10627
38minutes2hours30minutes5minutes
15minutes15minutes15minutes
5.8
After(withtypicaltools)
PedestalgrinderStraightgrinder
106
38minutes2hours30minutes
5minutes5minutes
1.2
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40 Excavator reduces vibration exposure in quarryThe task
Quarrying for masonry stone.
The problem
Masonrystonecanoftenbequarriedwithouttheuseofexplosives.Blocksofstoneareloosenedfromthegroundwithhand-heldtoolsandliftedawaywithmobilecranes.Onlylargeblocksofregularshapeandcolourareofuse.Irregularandsmallblocksarebrokenupwithpneumaticbreakersandremovedbyhand.Goodblocksaresquaredupbyrockdrillingrowsofholesandsplittingthestonebyhammeringwedgesintotheholes.Pneumaticbreakersandrockdrillsproducetypicalvibrationmagnitudesof12m/s2and15m/s2respectively.Alsosledgehammersareusedwhichexposetheoperatortoshockvibrationwithatypicalmagnitudeofaround25m/s2.Inonesmalllimestonequarry,itisestimatedthatapproximately1.25hourswasspentrockdrilling,1.5hoursbreaking,and8minuteshammeringinanaverageday,givingatypicaldailyexposureofnearly9m/s2A(8).
The solution
Alarge360otrackedexcavatorisusedtopullblocksofstonefromthequarryfaceandbreakuptheunwantedmaterial.Blocksareextractedbyscrapingoutandenlargingnaturalfissuresintherockaroundtheblockandleveringthemout.Goodblocksarethenfinishedwiththerockdrillsasbefore.Unwantedmaterialisremovedbytheexcavatorsonopneumaticbreakingisnecessary.Thereisasmallreductionintheuseofrockdrillsandsledgehammersgivingatypicaldailyexposureof6.1m/s2A(8).Thenextstepforthecompanyistobuymodern,low-vibrationrockdrillswhentheexistingunitsneedreplacement.
The cost
Theexcavatorisleasedfor£800perweekincludingthedriver.
Left Rockdrillinginprogress
Right Excavatoratworkinaquarry
CasecourtesyofRatteeandKettLimited
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The result
n Nopneumaticbreakingisnecessarywhichreducesthetimetheoperatorisexposedtovibration.
n Dustandnoiseexposureisreducedasworkersarenotclosetothebreakingrocks.
n Productivityhasimproved.
Operation Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before RockdrillingBreakingHammering
151225
17minutes26minutes6minutes
1hour15minutes1hour30minutes8minutes
8.6
After RockdrillingHammering
1525
17minutes6minutes
1hour7minutes
6.1
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41 Tool stock audit and purchasing policyThe task
Preparation and dressing of metal fabrications and castings.
The problem
AlargeshipyardinNorthernEnglandhadmorethan400straightgrindersofvarioussizesinstock.Thetoolswereusedallovertheyardandtheirdailyusagevariedgreatly.Itispossiblethatduringafulldayanoperatorcouldusearangeofsimilartools.Thehighestvibrationmagnitudemeasuredonastraightgrinderatthesitewasabout7m/s2.
The solution
Thecompanydecidedtomeasurethevibrationmagnitudeproducedbyeverytoolinstock.Todothistheyboughtavibrationmeterandtransducersetandtrainedstaffmemberstousethem.Thisexerciseproducedresultsintherange1to7m/s2.Thetoolsproducingthehighestvibrationwerequarantinedimmediatelyandwherepossible,theuseofthelow-vibrationtoolswasencouraged.Alongsidethisprogramme,thecompanymadevibrationperformanceaconditionofpurchasefornewtooling.Itwasdecidedthatbyonlybuyinggrindersthatproducedvibrationmagnitudeslowerthan2.8m/s2,vibrationexposureshouldbekeptatareasonablelevelregardlessofexposuretime.Thedecisiontobuyatoolisbasedbothonmanufacturer’sclaimeddataandtestsperformedattheyard.Thevibrationperformanceofthetoolswillbemonitoredatintervalstocheckfordeterioration.
The cost
Qualityhand-armvibrationmeasurementequipmentstartsataround£3000.Alternatively,instrumentationcanbehired.Staffcanbetrainedtousetheequipmentinonedayandassistancemaybeprovidedbytheinstrumentvendor.
The result
n Thevibrationmagnitudeproducedhasreducedby60%.n Themeasurementequipmentcanalsobeusedtomonitorvibrationinother
partsoftheyard.n Theprocesshasimprovedcontroloftheexistingstockoftools.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(potential)
7 1hour15minutes Varies Varies
After 2.8 8hours Varies Varies
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42 Hands-free linishingThe task
Using linishers (abrasive belt grinders) to remove excess material from castings (fettling).
The problem
Inthefoundryindustry,manypedestal-mountedlinishersareused.Ontheselinishers,theoperatorholdsthecomponentstobefettledandpushesthemagainsttheabrasivebelt.Althoughthevibrationexperiencedbytheoperatorvariesdependingonthetypeofcomponentandthepressureapplied,vibrationmagnitudesofabout8m/s2aretypical.Itisunlikelythatanoperatorworkingatthemachineforafullshiftwouldbeexposedtothevibrationformorethan2hours,givingapossibleexposureof4m/s2A(8).
The solution
Atonefoundrythemanuallinisherswerereplacedwithautomaticones.Thecomponentisheldinaspeciallymadejigandpushedontothebeltbypneumaticrams.
The cost
Eachnewgrindercostsbetween£20000and£30000.Themountingfixturetoholdthecastinginplacewasmadein-housebymaintenancestafffrommildsteel.
The result
n Theoperatordoesnotcomeintocontactwithanyvibratingparts.n Thecycletimeforeachcomponenthasbeencutfromabout5minutesto30
seconds,andproducesamoreconsistentfinish.n Noiseexposureandthepotentialriskofinjuryduetocontactwiththebelthas
reduced.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 8 1hour 2hours 4
After 0 - 0 -
Left Hand-heldlinishingmachine
Right Automaticlinishingmachine
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43 Belt grinding and polishing of ceramic wareThe task
Polishing out blemishes on ceramic ware.
The problem
Thetraditionalmethodforrectifyingblemishesonceramicwareistopolishthewareusingpedestalgrindersfittedwithpolishingstones.Inuse,thesestonesquicklyweartoanirregularshape,resultinginhighvibration.Theoperatorsarehighlyskilledandworkveryfast,polishingupto100piecesperhourfor7hoursaday.Duringasimulatedworkingcycle,anaveragevibrationmagnitudeof4m/s2wasmeasuredonaplatebeingpolishedononesuchmachine.
The solution
Thepedestalgrinderswerereplacedwithspeciallydesignedbench-topbeltgrindingandpolishingmachines(linishers).Theserequirelessskilltooperateandaremuchfaster(upto250piecesperhour)withatypicalworkcycleaveragevibrationmagnitudeof2m/s2.
The cost
£2500forabench-toplinisher.Thepolishingmaterialcostsperpiecearesimilartothetraditionalmethod.
The result
n Thevibrationmagnitudeproducedhashalved.n Thenewmachinesproduceamoreconsistentfinishandgivemorecontrolto
theoperator.n Theyproducelessnoise.n Theycanbeusedonawiderrangeofmaterialsandaremuchpreferredbythe
operators.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before 4 4hours 7hours 3.7
After 2 16hours 7hours 1.8
Warebeingpolishedwithapedestalmachine
Warebeingpolishedwithabench-toplinishermachine
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44 Isolation for grinding operationThe task
Fettling cast components with a pedestal grinder.
The problem
Afoundryusedalargepedestalgrindertoremoveflashandotherunwantedmaterialfromaluminiumcastings.Inthisprocess,anoperatorholdsthecastinginbothhandsandsupportsitinafixturewhilepushingit,withsomeforce,againstthegrindingwheel.Thefixturewassupportedbyaflimsyfabricatedbracketmountedonthebodyofthegrinder.Mechanicalvibrations,duetoout-of-balanceforcesinthemachine,causedthebrackettoresonatewhichinturncausedthefixtureandthecastingtovibrate.Thistransmittedveryhighvibrationmagnitudestotheoperator’shands.Theoperatorcouldbeincontactwiththevibrationforupto4hoursperdayandadailyvibrationexposuregreaterthan14m/s2A(8)waspossible.
The solution
Afirmofconsultantswasemployedtoinvestigatethecauseofthevibrationandfindasolution.Thecastingfixturesupportbracketwasidentifiedastheprincipalcauseoftheproblem.Areplacementwasdesignedwithamorerigidconstructiontobemounteddirectlyonthefloorratherthanonthemachine.Thenewbracketwasmadeandfittedbythecompany’sownengineeringstaff.
The cost
£20formaterials.Approximatelyhalfaday’slabourplusconsultant’stime.
CasecourtesyofIndustrialNoiseandVibrationCentre
Castingfixturesupportmethodsshowinghowtheoperatorwasisolatedfromthevibration
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The result
n Thevibrationexperiencedbytheoperatorhasreducedtolessthanatenthoftheoriginal.
n Improvedcontrolofthecomponenthasresultedinamoreconsistentfinish.
Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Originalsupport Morethan20 Lessthan9minutes 4hours Morethan14
Newsupport 1.5 Morethan24hours 4hours 1
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45 Laser cutter replaces nibbling machineThe task
Cutting shapes from thick metal sheets.
The problem
Atonelarge-scaleprecisionengineeringfactory,sheetmetalusedtobecuttoshapeusinganibblingmachine.Thisisalargepunchpressfittedwithasmalltoolwhichpiercesthemetalapproximatelytentimespersecond.Thecutismadebyguidingthesheetbyhandsothatthetoolslowly‘nibbles’aslotatapproximately10mmpersecond.Theaveragevibrationmagnitude,measuredatthepointwherethehandwasholdingonesheetof3mmsteel,was9m/s2.Thecompanyhadfoursuchmachinesinuse,whennecessary,operatedbyalargepoolofworkerswhospenttheremainderoftheirtimeperformingothergeneralfabricationduties.Themachinecouldnotcuttoprecisedimensions,leavingaroughedgeonthesheet,sothatgrindingwasnecessarytobringthecomponentstothecorrectsizeandfinish.Atypicaldaymighthaveincluded2hours’grinding(withtoolsproducingvibrationmagnitudesof2m/s2)and1houronthenibblingmachine.Thiswouldgiveatotaltypicaldailyvibrationexposureofover3m/s2A(8).
The solution
Thecompanyinvestedinaflat-bedcarbon-dioxidelasercutterwhich,withonetrainedoperator,doestheworkpreviouslydonebythefournibblingmachines.Themachineiscomputercontrolledandthereisnocontactwithvibratingsurfaces.Italsocutsmoreaccuratelythanthenibblersonogrindingisnecessary.Theotherstaffnowconcentrateonotherdutieswithnoexposuretovibration.
Nibblingmachine
Lasercutting
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The cost
About£400000tobuythelasercutterplus£20000peryearfortoolingandgases.Thepunchpresseswouldcostabout£50000each.Inothersituationsasmallerlasercuttingmachine,oroneusingplasmaorflamecutting,couldbeused,whichcouldbemuchcheaper.
The result
n Theoperatorsarenotexposedtoanyvibration.n Thelaserisveryefficientwithfastandmoreaccuratecutting.n Itcancutmuchlargersheets.n Ithasremovedtheriskofinjuringhandsinthepunchpressandhasreduced
noiseexposure.
Operation Vibration magnitude ah,w in m/s2
Time before daily exposure exceeds 2.8 m/s2 A(8)
Daily exposure time
Daily exposure (m/s2 A(8))
Before(typical)
NibblerGrinding
92
46minutes16hours
1hour2hours
3.3
After - 0 - 0 -
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Maintaining blood circulation case studiesTheprimarycauseofHAVSisworkwhichinvolvesholdingvibratingtoolsorworkpieces.Theriskdependsonboththevibrationmagnitudeandhowlongpeopleareexposedtoit.Severalotherfactorsalsoaffecttheseverityoftherisk,althoughthereisstillonlylimitedscientificinformationontheirimportanceandthewaytheyinteract.Theseincludefactorsaffectingbloodcirculation,suchastemperatureandsmoking,whichmaybeparticularlyimportantinthedevelopmentofvibrationwhitefinger(VWF).
Althoughthemainaimistoreducetheexposureofworkerstohand-armvibration,thereareotheractivitieswhichcanhelptoimproveworkingconditions.Keepingthebodyandhandswarmhelpstomaintainagoodbloodflowtothefingersandmayreducetheriskofinjury.Wherepeoplehavetoworkincoldareas,specificmeasuresmightincludewearingwarmweatherproofclothing;usingtoolswithheatedhandles;wearinggloves;andmakingarrangementstoallowworkerstowarmtheirhandsandbodiesbeforestartingwork.Glovesareusefulbothforkeepinghandswarmandprovidingphysicalprotection.
Encouragingemployeestohaveanadequateregularfoodintake,andtheavailabilityofhotdrinksincoldwetweatherwillhelptomaintainbodytemperatureandbloodcirculationtotheextremities.Massagingandexercisingfingersduringworkbreakswillalsohelpthebloodcirculation.Avoidingorcuttingdownsmokingshouldbeencouraged.
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46 Gloves to warm handsThe task
Continuous drilling of large holes in heavy-gauge steel.
The problem
Inoneshipyardholesaredrilledthroughthickmetalstructuresinnon-stopoperations.Thejobisdonewithlargemagneticallymounted,multivanepneumaticdrills.Althoughthevibrationexposureoftheoperatorsisnotparticularlyhigh,perhapsamagnitudeof1.4m/s2foramaximumof7hours,someoftheoperatorsshowedsymptomsofvibrationwhitefinger(oneoftheconditionsthatmakeupHAVS).Staffattheyardfeltthatthismaybeduetothechillingeffectoftheexhaustairfromthedrills.Thedrillsranconstantlyforverylongperiods,becomingencrustedwithiceondampdays.
The solution
Operatorsweresuppliedwithstandardlattice-coatedknittedgloves,chosenspecificallytokeeptheirhandswarm.Ifcuttingoilisused,theyareusedincombinationwithrubberglovestopreventthepotentiallyharmfuloilcomingintocontactwiththeskin.
The cost
Approximately£1apair.
The result
n Operatorsreportgreatlyimprovedcomfort.
Althoughthissolutiondoesnotaffecttheactualmeasuredvibrationexposure,handandbodytemperaturedoaffectperipheralcirculationandarebelievedtohaveaneffectonthedevelopmentofvibrationwhitefinger.
Gloveofthetypeusedtokeepdrilloperators’handswarm
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47 Duct away exhaust airThe task
Preparing, modifying or finishing metal components using pneumatic tools.
The problem
ConcernaboutexposuretodustledaMidlandsfoundrytostopusingpneumatictoolswhichwereblowingexhaustairontotheworkpiece.Unfortunately,alternativetoolstendtoexhausttheairinthedirectionoftheoperator’shands.Thecoolingeffectofthisaircancausediscomfortanditisbelievedthatcoldhandsmaybemoresusceptibletotheeffectsofvibrationwhitefinger(oneoftheconditionsthatmakeupHAVS),evenifthevibrationexposureremainsthesame.
The solution
Tokeeptheexhaustairawayfromtheoperator’shands,anexhaustductwasmadeupfromscraptubingandoldgauntletsandtapedtothesupplyhosetodischargeairawayfromthehandlesofthetool.
The cost
Scrapmaterials,alittletapeandafewminutesoftime.
The result
n Operatorsreportimprovedcomfort.n Theductgivessomeprotectiontotheconnectionbetweenthetoolandtheair-
line(thetool-hoseunion).n Proprietarysystemsareavailablewhichincorporatesilencers.
Althoughthissolutiondoesnotaffecttheactualmeasuredvibrationexposure,handandbodytemperaturedoaffectperipheralcirculationandarebelievedtohaveaneffectonthedevelopmentofvibrationwhitefinger.
Left Smallanglegrinderfittedwithanoldgauntletsleevetoductexhaustairawayfromtheoperator’shands
Right Smallstraightgrinderfittedwithalengthofpipetoductawayexhaustair
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48 Heated handlesThe task
Using chainsaws in forestry.
The problem
Incommercialforestry,workersareoftenrequiredtoworkoutsidealldayinverycoldconditions.Thecoldreducesthebloodflowtothehandsandfingersoftheforestryworkerswhichmayincreasetheeffectsofvibrationproducedbytoolssuchaschainsaws.Astheworkmaybealongwayfromshelter,keepingthehandswarmcanbedifficult.
The solution
Chainsawsareavailablewithheatingmechanismsinthehandles.Thesegenerallyfeatureelectricheatingelementswhichcanbeswitchedonandoff.Incombinationwithgloves,thesehandlescankeepthehandswarmalldayifnecessary.
The cost
Heatedhandlesaddapproximately10%tothecostofaprofessionalchainsaw.
The result
n Warmhandsaremorecomfortablethroughouttheday.
Althoughthissolutiondoesnotaffecttheactualmeasuredvibrationexposure,handandbodytemperaturedoaffectperipheralcirculationandarebelievedtohaveaneffectonthedevelopmentofvibrationwhitefinger.
Typicalchainsawuse
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49 Hot air to warm handsThe task
Using grinders and linishers in a precision foundry.
The problem
Atalargeprecisionfoundry,peopleworkinginthefettlingareahavetousevariouspiecesofequipmentwhichcanexposethemtopotentiallyhazardoushand-armvibration.Manyoftheoperatorswalkorcycletoworkandinwintertheycanoftenarrivewithverycoldhands.Thisresultsincirculationproblemswhichcouldincreasetheriskofinjuryfromvibration.
The solution
Thecompanyinstalledanordinarywarm-airhanddryerintheworkshoplockerarea.Theworkersareabletousethistowarmuptheirhandsbeforestartingtousethevibratingequipment.
The cost
Dryerscostabout£150andcanbeleased.
The result
n Warmhandsaremorecomfortableaswellaslesspronetovibrationdamage.
Althoughthissolutiondoesnotaffecttheactualmeasuredvibrationexposure,handandbodytemperaturedoaffectperipheralcirculationandarebelievedtohaveaneffectonthedevelopmentofvibrationwhitefinger.
Operatorusinghotairhanddryertowarmhandsbeforebeginningwork
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Health surveillanceEmployersarerequiredbylaw2toprovideappropriatehealthsurveillancefortheiremployeestakingaccountofrisksidentifiedinariskassessment.Thepurposeofhealthsurveillanceistodetectadversehealtheffectsatanearlystagesothatactioncanbetakentopreventfurtherharmtoemployees.Healthsurveillancecanalsogiveyoufeedbackonyourriskassessmentandtheeffectivenessofyourcontrolmeasures.
Whateffectsonindividualstherearelikelytobefromexposuretovibrationcannotbeknownwithanycertainty,andHSEthereforerecommendsaprogrammeofhealthsurveillanceforallemployeeswhoworkregularlywithvibratingtoolsormachines.
Agoodprogrammeshouldincludecheckingworkersunderthegeneralsupervisionofamedicalpractitioner,preferablyonewhohastrainingandexperienceinoccupationalmedicine.Ideallythecheckshouldincludeaquestionnaireandclinicalexaminationandbeundertakeninitiallyatpre-employmentandthenonaregularbasis,usuallyannually.WorkersshouldbeencouragedtoreportanyHAVSsymptoms,egfingerblanching(whichshouldbeinvestigated),toadesignatedperson.Adequaterecordsanddocumentationshouldbekeptofroutinehealthsurveillanceproceduresandofanyreportedsymptomsandtheirassociatedinvestigation.
Theexamplesinthissectionillustratesomemethodsavailableforobjectivetesting.HSEiscurrentlyundertakingworktoinvestigatethestandardisationofthetestsandguidancewillbepublishedgivingagreedmethodsforthesetests.
MoreadviceabouthealthsurveillanceiscontainedintheHSEguidancebookonhand-armvibration(HS(G)88).4
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50 Health surveillance on a construction siteThe problem
Constructionsiteworkersareexposedtoseveralpotentialsourcesofvibration.Awidevarietyoftoolsisusedwithunpredictableregularity,forvaryinglengthsoftimeandoftenincoldorwetconditions.This,coupledwiththefactthatsomepeoplearemoresusceptibletotheeffectsofHAVSthanothers,canmakeappropriatecontrolofvibrationexposureverydifficult.
The solution
Atonesite,allworkerspotentiallyexposedtohazardousvibrationareexaminedatregularintervalsforsignsofvibrationwhitefinger(VWF).Everyoneisexaminedatleastevery6months,withanyoneshowingsymptomsbeingseenmoreoften.Thecompanyhascompiledalistofthevibrationmagnitudesproducedbyallthetoolsonsitefrominformationsuppliedbythemanufacturers.Thisinformationhasbeenusedtocalculateanexposuretimeforeachtoolthatwouldgiveavibrationexposureof2.8m/s2A(8).Programmesofpreventivemeasuresandhealthsurveillancearerecommendedwhereworkers’exposureregularlyexceeds2.8m/s2A(8).
WorkersshowingnosymptomsofHAVSarenotrestrictedintheuseoftools,buthavebeenadvisedoftherisksandasaresultvariousformalandinformaljobrotationschemesexisttoavoidhighvibrationexposures.PeopleshowingsymptomsofVWFuptoStageOneoftheStockholmScalearerestrictedtoexposurewhichisbelow2.8m/s2A(8),andkeptonlightdutiesfortherestofthetime.AnyoneexhibitingsymptomsaboveStageOneoftheStockholmScaleisremovedfromallpotentialvibrationexposure.
Inthisexample,theexaminationswerecarriedoutintheon-sitemedicalcentre.Analternativecouldbetousedoctorsspecialisinginoccupationalhealthonaconsultancybasis.
AdviceonthesymptomsofHAVS,VWFandtheStockholmScaleisgiveninHSE’sguidanceHand-arm vibration.4
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51 Screening and surveillance methods in an aero-engine manufacturerThiscasestudyillustratesonecompany’sapproachtotheuseofdifferentmethodsforobjectivetesting.
Thecompanyintroducedasurveillancesystemfortheirworkersexposedtohand-armvibration.Thiswasorganisedbytheirmedicaldepartment.Theassessmentconsistedofsixpartsincludingaquestionnaire.Theworks’doctorconsideredandreviewedtheresultsofallthetestsbeforeanyconclusionsweredrawn.
Thesixpartsincludedthefollowing:
1 Questionnaire
Alltheworkerscompleteaquestionnaire,similartotheoneinHSE’sHand-arm vibration.4Therangeofquestionsincludeshandsymptoms,socialhistory,leisurepursuits,vibrationexposureandareportofthehandexamination.Thehandexaminationisdoneinthetestroom,whichiskeptat24oC(plusorminus2oC),sothatthesubjectcanacclimatiseandtheeffectoftheoutsidetemperaturecanberemoved.Acclimatisationgenerallytakesabouthalfanhourbutinverycoldweathermaytakelonger.
2 Cold provocation test
Thepurposeofthistechniqueistodemonstrateobjectivelyanabnormalresponseofthefingertocoldstimulation.Thefingersofeachhandare‘wired’upwiththermocouplesandplaced(inawaterproofglove)inatankofwaterat15oCfor5minutes.Therateatwhichthefingersrewarmafterremovalfromthetankisloggedbyacomputertogiveatracewhichcanbeinterpreted.EarlystudiessuggestthatthistestmayhavethepotentialtodistinguishbetweenVWFandprimaryRaynaud’sphenomenon(alsoknownas‘constitutionalwhitefinger’whichisaninheritedcondition),astherearedifferencesbetweenthepatternsofthefingerrewarmingtracesproducedbythetwoconditions.ThetestisnotuncomfortableandisnotdesignedtoprovokeanattackofVWF.
Handfittedwiththermocouples
Handin15oCwatertankforcoldprovocationtest
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3 Thermal aesthesiometry
Usingafingertemperaturepad,thesubject’shotandcoldtemperaturethresholdsaredeterminedbyincreasingordecreasingthetemperaturefromareferenceof32.5oC.Thesubjectreactstoafeelingofhotorcoldbypressingaresponsebutton.ThedifferencebetweenthethresholdofhotandcoldtemperaturesisrecordedastheTemperatureNeutralZone.
4 Grip strengths
Thestrengthofgripforeachhandismeasuredusingagripstrengthdetector.
5 Vibrotactile threshold measurement
Thethresholdofsensitivitytovibrationat32.5Hzand125Hzismeasuredusingacounterbalancedvibrationexciter.Thesubject’sresponseisrecordedbypushingaresponsebutton.
6 Gap detection aesthesiometry
Thegapdetectionabilityoffingersistestedbyplacingthefingeronataperinggroovecutintoaperspexblock.Theblockismovedslowlytoincreasethegapuntilthesubjectcanfeelthegroove.Theminimumgroovewidththatthesubjectcanfeelwiththefingerisrecorded.
Thermalaesthesiometrytestinprogress
Gapdetectionaesthesiometryequipment
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Table of case studies by industryIndustry Study
Aerospace 29,31,51
Automotive 24,25,38,
Ceramics 43
Construction 4,5,6,7,20,21,32,33,34,35,50
Forestry 12,48
Foundry 14,16,39,44,47,49
Investment foundry 1,17,19,30,42
Pallet repair 26,27
Power engineering 18
Precision engineering 2
Quarrying 40
Shipbuilding 3,22,23,41,46
Steel 15
Turbine manufacture 36,37,45
Utilities 8,9,10,11
Watercourse maintenance 13,28
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Table of case studies by reduction methodMethod Study
Change of machine 4,8,43
Change of process 5,6,7,9,18,22,23,29,32,33,34,36, 39,40,45
Change of tool 37
Isolation 10,15,16,19,24,30,42,44
Maintenance 12,20
Management 13,28,38,41
Process automation 1,2,17,25,26
Tool design 3,11,14,21,27,31,35
Maintaining blood circulation 46,47,48,49Health surveillance 50,51
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References1 Health and Safety at Work etc Act 1974 Ch37TheStationeryOffice1974ISBN0105437743
2 Management of health and safety at work. Management of Health and Safety at Work Regulations 1999. Approved Code of Practice and guidanceL21(Secondedition)HSEBooks2000ISBN0717624889
3 The Supply of Machinery (Safety) Regulations 1992SI1992/3073TheStationeryOffice1992ISBN0110257197asamendedbytheSupply of Machinery (Safety) (Amendment) Regulations 1994SI1994/2063TheStationeryOffice1994ISBN0110450639
4 Hand-arm vibrationHSG88HSEBooks1994ISBN0717607437
5 Need help on health and safety? Guidance for employers on when and how to get advice on health and safetyLeafletINDG322HSEBooks2000(singlecopyfreeorpricedpacksof10ISBN0717617904)
6 BS6842:1987Guide to measurements and evaluation of human exposure to vibration transmitted to the hand(nowsupersededbyBSENISO5349-1:2001Mechanical vibration. Measurement and evaluation of human exposure to hand-transmitted vibration. General requirements)BritishStandardsInstitution
7 Avoiding danger from underground servicesHSG47(Secondedition)HSEBooks2000ISBN0717617440
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Further readingHand-transmitted vibration: Occupational exposures and their health effects in Great BritainCRR232HSEBooks1999ISBN0717624765
Hazards associated with foundry processes: Hand-arm vibration - symptoms and solutionsFoundriesInformationSheetFNIS9HSEBooks1996
Hazards associated with foundry processes: Hand-arm vibration - the current pictureFoundriesInformationSheetFNIS8HSEBooks1996
Health risks from hand-arm vibration: Advice for employees and the self-employedLeafletINDG126(rev1)HSEBooks1998(singlecopyfreeorpricedpacksof15ISBN0717615545)
Health risks from hand-arm vibration: Advice for employersLeafletINDG175(rev1)HSEBooks1998(singlecopyfreeorpricedpacksof10ISBN0717615537)
Health surveillance at workHSG61(Secondedition)HSEBooks1999ISBN071761705X
Reduction and control of noise and vibration in shipyardsAvailableonsubscriptionfromtheShipbuildersandShiprepairersAssociation(SSA),MarineHouse,ThorpeLeaRoad,Egham,SurreyTW208BFTel:01784223770Fax:01784223775
RIDDOR explained: Reporting of Injuries, Diseases and Dangerous Occurrences RegulationsLeafletHSE31(rev1)HSEBooks1999(singlecopyfreeorpricedpacksof10ISBN0717624412)
Safe use of work equipment. Provision and Use of Work Equipment Regulations 1998. Approved Code of Practice and guidanceL22(Secondedition)HSEBooks1998ISBN0717616266
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GlossaryAngle grinderRotarygrinderinwhichthegrindingwheelrotatesatanangletothemotoraxis.Canbefittedwithgrindingorcuttingdiscs,shapedgrindingstonesandmetaltools.
Anti-vibration mountsSoftmounts,usuallyacombinationofrubberandmetal,forvibratingmachinery,designedtopreventvibrationfromthevibrationsourcepassingtothesupportingstructure.Alsosee‘Isolation’.
BalancerToolsuspensionsystems,usingacounterbalanceandpulleys,designedtopreventtheoperatorhavingtoliftthefullweightofthetool.
Core drillDrillwhichcutsleavingasolidcorewhichcanberemoved.
CuringThechemicalprocessbywhichamateriallikecementbecomeshardandstrong.
Daily vibration exposureThecombinationofvibrationmagnitudewiththeperiodofexposureinaday,usuallynormalisedtoan8-hourperiodandexpressedasm/s2A(8).DailyvibrationexposurescanbecomparedwiththeHSEactionlevelof2.8m/s2A(8).
DampingReducingvibrationbyattachingvibration-absorbingmaterialsordevices.
DeburringRemovingsharpedgesfromanobjectduringmanufacture.
DescalingRemovingmill-scale(oxidisedsurface)frommetalobjects.
Declared (vibration) valuesThevibrationvaluegivenbythetoolmanufacturer.Thisvalueisobtainedfromastandardtestprocedure.Thevaluegivenbythemanufacturermaynotbethesameasthevibrationwhenthetoolisbeingused.Thedeclaredvibrationvaluesareintendedtoallowcomparisonbetweensimilartoolsfromdifferentmanufacturers.
Dressing(ofagrindingwheel)Removingthetopsurfaceofagrindingwheeltorestoreitsshapeandabrasiveproperties.
FettlingRemovingunwantedmaterialfromacasting.
FixtureAspeciallymadeholderdesignedtofitacomponentperfectlyandsupportitastheworkisdone.
FormworkTemporarystructuresusedasmouldsforconcretecastinginbuilding.
Frequency (Hz)Ameasureoftherateatwhichavibratingsurfacemovesbackandforth.ThefrequencyismeasuredinHertz(Hz),equivalenttothenumberofcyclespersecond.
IsolationReductionofvibrationpassingfromonepartofamachine(egthemotor)toanother(egthehandles)usingflexibleconnectingsystems.
Investment castingProcessformanufacturingmetalobjectsbymakingatemporarymouldaroundareplicamadefromasoftmaterialsuchaswaxbycoatingitinaceramicmaterial.Astheceramicmaterialisfired,thewaxflowsawayleavingahollowmouldintowhichthemoltenmetalispoured.
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LinisherAgrindingmachinewhichusespaperorfabricbeltscoatedwithabrasivematerial.
Pedestal grinderAgrindingmachineusingasolidwheelofabrasivematerialmountedonapedestal.
Resilient materialsSoft,pliantmaterialswhichprovidesomevibrationisolation.
Resonant frequencyThefrequencyatwhichastructurewillvibrateeasily,producingrelativelylargevibrationsfromsmallinputmotions.
Root-mean-square (rms)Averagingmethodusedforoscillatingsignals(thesquare-rootofthearithmeticmeanofasetofsquaredvalues).
Rotary burrAmetaltoolpiecefittedtoagrinder.
Rotary fileAstraightgrinderfittedwithametaltoolpiece.
RumblingDeburringsmallobjectsbyshakingalargenumberofthemtogetherwithabrasivematerial.
Runners and risersThewastepartsofacastingwherethemoltenmetalflowedintothemouldandbetweencomponents.
Shot blasting (or direct pressure blasting)Asurfacepreparationtechniqueusingsmallfragmentsofmaterialsuchasslagormetal(shot)whicharepropelledbycompressedair.
Straight grinderRotarygrinderinwhichthegrindingwheelrotatesinlinewiththeaxisofthemotor.Itcanbefittedwithgrindingorcuttingdiscs,shapedgrindingstonesandmetaltools.
Stockholm ScaleAclassificationsystemusedtoclassifythevascularandneurologicalsymptomsofHAVS.
SwagingFormingmetalbyapplicationofpressurebyametaltool.
TensionersAtoolsuspensionsystemdesignedtopreventtheoperatorhavingtoliftthefullweightofthetool.
TorqueAmeasureofthetightnessofanutorbolt.
Vibration exposureSee‘Dailyvibrationexposure’.
Vibration magnitudeAmeasureoftheaveragevibrationlevel,usingaroot-mean-squareaverage.
(Frequency) weighted vibrationAmeasureofvibrationmagnitudewhichemphasisesvibrationsatthefrequenciesthoughttobemostdamagingtothehandandarm.
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Vibrationsolutions Page106of107
Health and Safety Executive
AcknowledgementsTheHealthandSafetyExecutiveacknowledgesthegenerosityofthefollowingcompanieswhosuppliedinformationforcasesorphotographs/illustrationstohelpcompilethispublication:
ARMUtilityServicesLimited,LeylandAtlasCopcoToolsLimited,HemelHempsteadBritishAerospaceAirbusLimited,ChesterBritishSteelPLC,SwindenTechnicalCentre,RotherhamCengarUniversalToolCo.Limited,HalifaxChep(UK)Limited,BirminghamDepotChep(UK)Limited,BristolDepotCompairPowerToolsLimited,SwanseaCornwallCountyCouncil,RedruthEuropeanGasTurbines,IndustrialProducts,LincolnFlexovit(UK)Limited,CongletonFordMotorCompany,BridgendForestryCommission,DumfriesHodge-ClemcoLimited,SheffieldIndustrialMachineToolServicesLimited,RochesterIndustrialNoiseandVibrationCentre,SloughMitsuiBabcockEnergyServicesLimited,TiptonNationalRiversAuthority,Almondsbury,BristolOutdoorPowerProductsLimited,Denton,ManchesterRattee&KettLimited,CambridgeRollsRoycePlc,DerbySECOEngineeringCo.Limited,EversleySpecialistServices(CuttingandDrilling)Limited,PortsmouthSpodeLimited,Stoke-on-TrentSvedalaLimited,StAustell,CornwallTarmacBachyJointVenture,LondonE14TerrillBros.(Founders)Limited,HayleTriplexWilliamsLimited,CardiffTTUKLimited,BedfordVickersShipbuildingandEngineeringLimited,Barrow-in-Furness
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Further information
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PublishedbyHSE01/10 Page107of107
Health and Safety Executive