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HSE information sheet

Safety in electrical testing: Productson production lines

What is this guidance about?

This information sheet contains specific advice aboutsome of the ways of avoiding injury during the electricaltesting of products on production lines. Further advice isgiven in Safety in electrical testing at work: Generalguidance1 and other guidance on electrical safety listedunder Where can I get more information on page 3.

How can injuries happen during testing?

The most significant danger to people carrying out

electrical testing work is that they might suffer an electricshock. Any simultaneous contact of a part of the bodywith a conductor that is live at a dangerous voltage, egas one that is connected to the mains supply whileanother part of the body is connected to an earth, willresult in an electric shock. There is also a risk of burninjuries resulting from arcing when conductors areaccidentally short-circuited.

An electric shock can lead to serious injury, sometimesfatal. Injuries can also occur when a person reacts to anelectric shock, for example by falling or touching anotherhazard. Factors which are likely to increase the risk ofreceiving an electric shock include the following:

(a) People carrying out electrical testing work onproduction lines are often unskilled or semi-skilledin relation to electrical competence;

(b) Some equipment, such as washing machines ordishwashers, could also be using water in itsoperation. This may lead to an increased risk ofshock because water can conduct electricity andreduces the resistance of the skin;

(c) Serious injury can also occur if accidental contactis made with the two poles of a supply, whether thesupply is earth-referenced or not. Similarly, contactwith both poles of internally generated sources cancause electric shocks;

(d) For much of the equipment tested there will becomparatively large areas of earthed metal thatmay be easily touched. There is therefore anincreased possibility of electric shock from contactwith a single live conductor;

(e) Test equipment and instruments applied to theequipment being tested may themselves generatehazardous voltages;

(f) As well as the risk of accidental contact byauthorised test operatives, unauthorised people

Engineering Information Sheet No 38

might have ready access to a test station on aproduction line.

Carrying out a risk assessment

To help you to identify the precautions that are

necessary for carrying out electrical testing work safely,you need to do an assessment of the risk of injury posedby the work being done. When assessing the risk, you

need to think about the hazards that are present, whomay be harmed and how, and the effectiveness of

existing precautions. Bear in mind the examples of

factors given in this guidance which might increase therisk.

When carrying out a risk assessment for electrical

testing, ask yourself the following questions:

(a) Can the work be done with the equipment dead?

(b) Can the testing be done automatically, without

human intervention?

(c) Is it absolutely necessary for someone to be

working on or near equipment that is live atdangerous voltages or current levels?

(d) Have suitable precautions been taken to avoiddanger and, where necessary, to prevent injury?

(e) Is the person doing the work competent for that

type of work, or, if not, adequately supervised?

What precautions should I take?

Where possible, the work should be done with the

equipment dead (this is a requirement of the Electricityat Work Regulations 19892). Otherwise, adequateprecautions, which should be identified in your risk

assessment, must be taken to ensure safety.

The following precautions are recommended as part of asafe system of working for electrical testing of thisequipment.

Test areas

Wherever testing is to be done on a production line, thetest area should be clearly designated as such, to

reduce the risk of unauthorised people entering it. This isusually done by using fixed barriers to prevent

unauthorised access. Make sure that the barriers aresited so that enough space is left around the testers toallow them to work safely.

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In addition, use visual indicators, such as warning lights,to show when testing is being done.

Access to live parts

Where testing is carried out on live equipment, the risk ismost effectively controlled by preventing access to thelive parts. This can be achieved in a number of ways:

(a) Where possible, units should be tested with allcovers in place;

(b) Where this standard cannot be achieved, coverexposed conductors during the testing procedure.This protection can be in the form of temporaryinsulation, for example purpose-built attachmentsthat can be quickly attached before the test andthen removed once testing is complete;

(c) Where equipment has to be worked on for a longerperiod of time, transparent screens with aperturesfor applying test instrument probes can be used;

(d) Suitable precautions should be taken to minimiseexposed earthed metalwork in the test areas.

Test equipment

Test equipment, leads and cables should be handledcarefully to avoid injury. The following precautions arerecommended:

(a) All leads and cables which can be energised atdangerous voltages should be robustly insulatedand properly terminated. All connections ofconductors which can be energised at dangerousvoltage should be electrically and mechanicallyrobust to prevent conductors becomingaccidentally exposed. There should be no exposedconductors at dangerous voltages at any purpose-built connectors or jigs into which the product isfixed for testing;

(b) Test equipment connecting leads, probes andconnectors should be sufficiently protected toprevent accidental contact when being applied toand removed from live parts;

(c) Where practicable, place the equipment under testinto interlocked enclosures. This allowsconnections to be made while the equipment isisolated;

(d) Where practicable, apply test leads while theequipment is isolated and then energise it. Tomake sure that the equipment is isolated a suitable

isolating device should be used which must be:

(i) appropriate and convenient for the intendeduse;

(ii) suitably located;(iii) readily identifiable (eg by durable marking) as

to which circuits or part of the test area isserved;

(iv) provided with adequate means to prevent thesupply isolator being switched on (eitherinadvertently, mistakenly, or by anunauthorised person).

High-voltage insulation (flash) testing

This type of testing is required for the majority ofproducts and should be done using proprietary testequipment. To prevent dangerous shocks the testinstrument output current should be limited to no greaterthan 5 mA (traditionally 5 mA ac has been used, butsince May 20013 new equipment should be limited to

3 mA ac). Proprietary equipment has this feature, whichallows simple hand-held test probes to be used whenthe current is automatically limited to these values.

Where a higher test current is absolutely necessary,additional precautions will be needed. Theseprecautions will include the use of heavily shrouded andinsulated test probes. The tips of the probes should becovered by retractable, insulated sleeving. The testvoltage may be applied by a switch built into theinsulated handles of the probes.

People doing the testing need to be thoroughly trained. Itwill be necessary to prevent the test operator, andothers, from coming into contact with all hazardousvoltages present during testing. It may be necessary todischarge safely any stored energy which may remain inthe equipment after the test has been carried out beforeallowing any further contact with the equipment.

Supplementary protection

(a) Where practicable, the power supplies to all theequipment should include a residual current device(RCD) with a rated tripping current of, at most,

30 mA.

(b) The level of supervision and monitoring will varydepending on the protection arrangementsadopted. The risk assessment will need to takeaccount of this when the test facility is being set up.Ensure that the assessment is revised to take intoaccount any product design changes, methods ofworking and changes of personnel.

What are the legal requirements?

The Electricity at Work Regulations 19892 are theprincipal legislation relating to electrical testing activitiesand regulation 14 is particularly relevant to live testingactivities. In addition, employers are required underregulation 3 of the Management of Health and Safety at

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Work Regulations 19994 to assess the risks to the healthand safety of their employees while they are at work, inorder to identify and implement the necessaryprecautions for ensuring safety.

References

1 Safety in electrical testing at work: GeneralguidanceLeaflet INDG354 HSE Books 2002 (singlecopy free or priced packs of 5 ISBN 0 7176 2296 7)

2 Memorandum of guidance on the Electricity atWork Regulations 1989. Guidance on RegulationsHSR25 ISBN 0 11 883963 2

3 BS EN 50191: 2001 Erection and operation ofelectrical test equipment

4 Management of health and safety at work.

Management of Health and Safety at Work Regulations1999. Approved Code of Practice and guidanceL21(Second edition) HSE Books 2000 ISBN 0 7176 2488 9

Where can I get more information?

Electrical test equipment for use by electriciansGuidance Note GS38 ISBN 0 7176 0845 X

Electricity at work: Safe working practicesHSG85ISBN 0 7176 0442 X

While every effort has been made to ensure theaccuracy of the references listed in this publication, theirfuture availability cannot be guaranteed.

Further information

HSE priced and free publications are available by mailorder from HSE Books, PO Box 1999, Sudbury, SuffolkCO10 2WA Tel: 01787 881165 Fax: 01787 313995Website: www.hsebooks.co.uk (HSE priced publicationsare also available from bookshops.)

For information about health and safety ring HSE'sInfoLine Tel: 08701 545500 Fax: 02920 859260 e-mail:hseinformationservices@natbrit.com or write to HSEInformation Services, Caerphilly Business Park,Caerphilly CF83 3GG. You can also visit HSEs website:www.hse.gov.uk

British Standards are available from BSI CustomerServices, 389 Chiswick High Road, London W4 4ALTel: 020 8996 9001 Fax: 020 8996 7001Website: www.bsi-global.com

This leaflet contains notes on good practice which arenot compulsory but which you may find helpful inconsidering what you need to do.

This publication may be freely reproduced, except foradvertising, endorsement or commercial purposes. Theinformation is current at 03/02. Please acknowledge thesource as HSE.

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Printed and published by the Health and Safety Executive 03/02 EIS38 C150