Examination and Testing of Portable and Transportable Electrical Equipment

Transcription

1 UNIVERSITY OF NEWCASTLE UPON TYNE Examination and Testing of Portable and Transportable Electrical Equipment January 1997 (First Printed August 1996)

2 1) INTRODUCTION This document sets out university policy in relation to the examination and testing of portable and transportable electrical equipment. (This is referred to throughout the text as "portable equipment". Other publications may use the expression "portable appliances" and "portable appliance tester" is the common expression for testers, also used in this text). It is the aim of the policy to comply with the legal requirements and with HSE guidance which recommends that the risks are assessed, managed and controlled by establishing an examination test and maintenance system appropriate to the risk. Guidance is given as to the frequency of examination and testing and the minimum standards to be achieved. 2) LEGAL REQUIREMENTS There are legal duties on manufacturers and suppliers covering the initial integrity and safety of new work equipment. The particular legal requirements relating to the use and maintenance (and by implication, examination and testing) of electrical equipment are contained in the Electricity at Work Regulations 1989 (EAW). Regulation 4(2) states: "As may be necessary to prevent danger, all systems shall be maintained so as to prevent, so far as is reasonably practicable, such danger." 'System', as defined in the Regulations, includes portable equipment. Thus, the Regulations require certain safety objectives to be achieved but do not prescribe in detail the measures to be taken. Instead precautions must be selected appropriate to risk, depending on particular work activities. In order therefore to ensure that portable equipment is maintained in a safe condition the University has adopted a formal system of visual examination and testing. 3) UNIVERSITY APPROACH AND APPLICATION OF THE POLICY A distinction has been made between portable and fixed equipment because the electrical connections to portable equipment are more vulnerable to harsh treatment and damage; a person holding portable equipment is more likely to receive a shock if a fault develops, and a shock in such circumstances is more likely to be fatal. The policy applies to all portable equipment owned by the University or in use on University premises. Portable equipment provided by the University in connection with living accommodation e.g. desk lamps, kettles etc. is included. Departments must devise their own rules for equipment brought from home. Ideally it should be banned. If this is not practicable, it should be examined and tested prior to being brought 2

3 into use. The worst case is a ban which is not effective, resulting in use of untested equipment. The private property of students and other residents in University accommodation, and electrical apparatus bought or hired by student union or student organisations is not dealt with under this policy; separate instructions and guidance applies in each case. 4) RESPONSIBILITY The responsibility for the safety of portable equipment (and thus maintenance, inspection and testing) lies with the Head of Department. The local arrangements for inspecting, testing and maintaining it must be set out in Departmental Safety Policies. Guidance on the contents of such a statement, taken from circular MR5, is set out in Appendix 5. Departments may arrange for the work to be carried out by the Estates Department via the Engineer's section. This will attract charges. Departments will remain responsible for ensuring the system operates and that where appropriate adequate user checks are carried out. (See para 6, and the Table on page 4). Alternative arrangements may also be made with external contractors to carry out inspection and testing. This however may only be done through the Engineer's section. 5) CONTENTS OF PROGRAMME a) Equipment which is subject Students personal equipment, and equipment hire in, is excluded (see para 3). Portable equipment is not part of a fixed installation, but can be connected to a fixed installation or generator by means of a flexible cable and a plug. It may be either hand-held or hand operated while connected to the supply. Voltages less than 50 v ac or 120 v dc are not subject to this Policy. Within this broad category, it could be earthed (supplied by a 3-core cable) or it could be double insulated (supplied by a 2-core cable and bearing the BS kite mark). Examples are:- drills, extension leads, lamps, grinders, floor cleaners, kettles etc.: i.e. domestic-type equipment. portable office equipment such as computers and word-processors: i.e. electronic equipment audio visual equipment: i.e. overhead projectors (OHPs), slide projectors, etc. portable laboratory equipment. Special care must be taken to include all electrical equipment in the testing scheme and this includes equipment used in outstations, houses, on fieldwork, excavations etc. 3

4 Equipment which has been decommissioned or taken out of frequent use will not be needed to be included in the testing programme. It will require formal inspection and testing before bringing into re-use. b) Portable Appliance Testers The portable appliance testers available to Departments from University Central Stores are designed to be used by people with no special technical knowledge. Note however that they are not suitable for use on computers, word-processors or other equipment with electronic components since it may damage them. (See also the comments in 5(c) below). See Appendix 3 for details of use. c) Appropriate Examinations and Tests For the office electronic equipment mentioned above, testing is not considered necessary, and only a visual examination for signs of damage is required. See Appendix 2 for details of visual examinations. d) Frequency The programme should initially be annual. Following experience of operating the system over a number of years together with information on faults found it is possible to review the frequency. If significant numbers of defects continue to occur, this should be reduced to six months. Where few or no defects recur at yearly intervals, the period may be stretched, but not beyond that set out in the Table below. Departments wishing to reduce the frequency from annual should inform the Safety Office. The various points addressed in the sub-paragraphs above are summarised in the following table. 4

5 TABLE: Warning: Initial frequency is annual: this gives MAXIMUM intervals to be justified by experience (see para 6(d)). User Checks Formal Visual Examination Combined Examination and Test Electronic equipment e.g. No Yes. 4 Years No computers, word-processors Double insulated NOT handheld. Moved occasionally (e.g. desk lamps) No Yes. 4 Years Yes. 4 Years Double insulated and hand-held. Yes Yes. 1 Year Yes. 2 Years Earthed equipment e.g. electric kettles, most electric fires Yes Yes. 1 Year Yes. 2 Years e) Labelling, Recording and Reporting All equipment which is examined and/or tested should carry a dated, initialed label: green for "Pass" and red for "Fail". These come with the Portable Appliance Tester from Central Stores. An adequate record should be kept. Progress with the programme should be reported annually to the Head of Department (see University circular MR5). f) Failed Equipment and Repairs Any equipment which fails a visual inspection or test and cannot be readily and safely repaired by a competent person must not only be labelled with a red Fail label, but unplugged and withdrawn from use. The equipment should be investigated, repaired and re-tested by a qualified person, and only qualified staff may carry out any repairs to equipment. Such staff should be aware of the risks from charged capacitors. Repairs should be carried out with the equipment unplugged and the system de-energised. 6) APPOINTING STAFF Preamble Users of hand-held equipment should check for signs that equipment is not in sound condition before they use it, particularly when it has been in storage for some time (see Table on page 4). Reference should be made to guidance in Appendix 1. a) Domestic-Type Equipment and Office Equipment No special technical knowledge is required, but the following qualities are necessary: i) An ability to follow simple instructions. 5

6 ii) An ability to work thoroughly and keep records. iii) Willingness, coupled with a willingness to call for help or advice when any difficulties are encountered. N.B. Repairs require technical knowledge, and should not be part of the person's duties unless he or she possesses appropriate additional technical knowledge. b) Laboratory Equipment Some laboratory equipment may be little different to domestic equipment, when similar considerations apply. In other cases however this will require special technical knowledge, and may well require use of a more sophisticated Portable Appliance Tester than the standard model available from University Central Stores. Departments should ensure in such cases that the person appointed has appropriate knowledge and equipment. 6

7 GUIDELINES FOR USE OF PORTABLE ELECTRICAL EQUIPMENT APPENDIX 1 General Many but not all University circuits are protected by RCD's (Residual Current Device, or Earth Leakage Circuit Breaker). Where they are not, use of a portable RCD will improve the safety of the situation, particularly in a hostile environment. A. User Checks (Visual) Serious Defect - Equipment to be withdrawn immediately. Users must carry out a visual inspection of plugs and leads before using any item of electrical equipment which is earthed or normally hand held (see Table on page 4). Look out for: An electrical test pass sticker, green pass, red fail. Damage to the cable (apart from light scuffing) e.g. kinks, cuts, abrasions. Damage to the plug e.g. cracked casing, bent pins. Equipment with intermittent fault. Inadequate joints e.g. taped "chocolate block" connectors. The outer sheath of the cable should be effective and secured where it enters the plug or equipment. There should be no exposed wires. Damage to external casing of equipment e.g. loose parts, or screws. Evidence of overheating e.g. burn marks or discoloration. Has equipment been subjected to conditions for which it is not suitable e.g. is it wet or contaminated. Protective cable grommets, which protect cables passing through sharp metal cases - these should be effective. Damaged or loose grommets are a frequent cause of premature cable failure. B. User-Safe Operating Guidelines Do not attempt to repair or make alterations to equipment and never remove permanently fixed covers from appliances. Report any defects and label equipment "out of order". 7

8 Do not use damaged or defective equipment and equipment which has failed a test. Remember to switch off equipment and unplug before cleaning or fitting new parts. Always remove plugs by holding the plug and not pulling on the cord. Ensure that cables are not squashed under furniture, doors or touching warm radiators. Do not overload socket outlets. Avoid or minimise the use of adapters. Overloaded sockets can lead to fire hazards. If necessary, use a fused 13 amp block extension board to BS 1363A. Do test the residual current device if fitted. Do not use electrical equipment in a wet environment. Avoid drinking near electrical equipment. Do not bring personal items of equipment into the work place without first having it checked by your Departmental Safety Officer. Do find out how to deal with an electrical shock incident. Your Departmental Safety Officer and/or first-aider will be able to advise. Do find out the correct fire extinguisher to use on an electrical fire. Plugs & Fuses You do not need to dismantle the plug as part of a user check, or have it dismantled for you, unless you are suspicious of its condition. If you do so and find a fuse has been illegally "wired out" with a nail or a paper clip, or the fuse rating is simply too high, then remove it from use and have it checked. Fuse ratings examples: 3 amp Desk, lamp, radio, hi-fit Up to 600 watts 5 amp Iron, TV Up to 1,000 watts 7 amp Hair dryer Up to 1,400 watts 13 amp Kettle Up to 3,000 watts 8

9 APPENDIX 2 TECHNICAL STANDARD FORMAL VISUAL EXAMINATION Precautions 1) Exercise caution before unplugging equipment from a socket - turn off at the socket switch, where there is one. Take care that the back of the plug is securely fastened to the body of the plug, and there is no damage which exposes metal terminals which you could touch. 2) In moving equipment about, remember to comply with the Local Rules relating to manual handling, and avoid creating tripping hazards with the cables. Action Check the action of the ON/OFF switch - if unsatisfactory FAIL and refer for repair. Disconnect the equipment and remove the plug from the socket. A visual examination should include the following: 1) Electrical Supply Leads A careful examination of the electrical supply lead. Extension leads should be totally unwound, vacuum cleaner leads etc., totally extended. Care will be needed in the case of pre-formed coiled leads (i.e. "curly leads" ) to ensure that all surfaces are thoroughly examined. Check the whole length for outs, abrasions, nips, perished areas, taped joints. It is seldom possible to adequately repair a damaged electrical supply lead other than by use of proprietary couplers. Any repairs, other than using couplers (male connection of machine side, female on the supply side) must be failed. Chocolate block connectors are not approved connectors and must be failed. If in doubt, consult a qualified person (consult HSE Guidance Note GS 37, flexible leads, plugs, sockets etc.). Supply leads should not be located so as to give rise to a tripping hazard or allow for potential damage to the cable itself. Profiled rubber cable protector strips should be used where necessary. Check that double-insulated flex or lead is used i.e. each conductor is insulated and there is a second layer of insulation around all conductors. If not doubleinsulated, remove and fail. If twin flex (i.e. two conductors with no third earth conductor) is used on equipment which does not bear the double insulated stamp kite mark (class II equipment) refer the equipment to a qualified person. Single-insulated twin-flex is not now acceptable on mains power equipment and must be changed. 2) Equipment 9

10 The equipment should show no signs of obvious damage: in particular no live metalwork should be exposed. 3) Plugs The electric plug must be complete and in perfect visual order. It should be marked with the appropriate BS specification. CHECK FOR: Backs not securely fastened to fronts. Broken or cracked parts Burn marks or other signs of overheating Wetness or contamination Broken or missing pins FAIL THE PLUG IF ANY OF THE ABOVE ARE NOTED. CHECK FOR: The cable being secured by a cabling clamp. This should clamp the outer cable sheath, not the inner cables (cores). New plugs, 13 amp, should have partially shield pins. Plug Inspections and Fuses The foregoing is essential. What follows is highly desirable for earthed equipment and equipment normally hand held. The plug should have the back taken off and be inspected. Check that the internal wiring is firm and the leads go to the correct terminals. Live brown (red) Neutral blue (black) Earth green/yellow (green) Refer to diagram (page 10). If a lead with different coloured conductors is present, consult a qualified person and label the lead. The supply lead MUST have an earth core correctly terminated to the plug earth pin UNLESS the appliance is marked with the double insulation symbol i.e. kite mark. ALL terminations should be tight (check with screw driver). ALL cores insulated up to the point of termination and free of loose whiskers of cable with no sign of overheating. 10

11 Check the fuse rating. The fuse must be correct rating for both the rating of the appliance and the supply lead. If this is not marked on the appliance, check the power rating and fit a fuse according to the table below. Wattage Fuse Rating Examples Up to 400w 2 amp Desk lamps, radios w 3 Laboratory hot plates w (1kw) 5 Fridges, irons, TV, OHP 1kw - 2kw 10 Water baths 2kw - 3kw 13 Electric fires, cookers, kettles, vacuum pumps Where the wattage is not given or there is doubt about the current consumption of the apparatus, advice should be sought from a qualified person. 4) Multi-way Adaptors Unfused multi-way BS 1363 or BS 546 plug adapters shall be failed on the visual inspection and withdrawn from service. Subsequent action Record a pass or fail on the equipment inventory. Label appliance accordingly. Diagram illustrating correct wiring for earthed appliances 11

12 APPENDIX 3 TECHNICAL STANDARD USE OF PORTABLE APPLIANCE TESTER Test Equipment The Safety Office has purchased two METROHM PAT portable appliance testers for use on mains voltage portable equipment They may be booked out from Central Stores. They should not be used on electronic equipment. A qualified person may use other equipment which they consider will achieve the test requirements. Multimeters/AVO will not normally achieve this The test carried out depends upon the type of apparatus. a) Class I.: Earthed Equipment Metal-cased equipment which relies on insulation and the connection of metal parts to the earth lead. b) Class II: Double-Insulated Appliances marked with the kite mark. These appliances have only two wires (live and neutral) and will often be made of plastic or other electrically insulating materials. There is no earth lead. External metal work is insulated from live parts. Earthed Equipment should have three leads in the cable (live, neutral and earth) - if only two are fitted refer to qualified person to test. Two tests are required the Earth Continuity Test and the Insulation Test. Below is a technical description of how the University PAT carries out these tests. The nontechnical reader may omit this section and go direct to "Test Procedure". i) Earth Continuity Test The requirement is that the resistance between exposed metal parts of the apparatus and the earth pin of the plug should not exceed 0.1 ohm. An alternating current of at least 1.5 times the appliance cable rating is passed down the earth lead and is returned by the earth clip connection to the framework of the appliance to check that the earth continuity between earth pin and framework is less than the pre-set value. If the earth continuity is greater than this value a trigger circuit is operated which stops the test and illuminates the CONTINUITY FAIL lamp. If the appliance earth is poorly terminated or damaged, the earth conductor will be fused if the fusing capacity of the number of strands secured is less than 1.5 times the rated current at the 0.1 ohm level. 12

13 Note: Appliances with long main lead may fail this test even though in good order. Appliances failing this test should be referred to a qualified person who can decide whether a resistance of up to 0.25 ohm or even 0.5 ohm is acceptable in particular circumstances. Guide to Maximum Lead Lengths Pat Range The PAT can check appliances with flexible cable ratings from 5 amp to 15 amp. Guide to maximum cable length for continuity trip setting: At 0.1 Ohm level: At 0.25 Ohm level: 2 metres of 0.5 mm 2 for 3 amps 5 metres of 0.5 mm 2 for 3 amps 3 metres of 0.75 mm 2 for 6 amps 8 metres of 0.75 mm 2 for 6 amps 4 metres of 1.00 mm 2 for 10 amps 10 metres of 1.0 mm 2 for 10 amps 6 metres of 1.5 mm 2 for 15 amps 15 metres of 1.5 mm 2 for 15 amps Note: Appliances with a smooth metal surface where clipping of the test lead cannot be achieved, or where metal parts are not accessible must be tested by a qualified person using a megger or other apparatus. Note: The test device usually puts 25 amps for 5 sec through each circuit for this test. ii) Insulation Test The requirement is that the measured insulation resistance between the (temporarily) shorted live and neutral pins, and the earth pin shall exceed 0.5 Meg ohm at 500 volts. Live and neutral pins of the appliance under test are shorted together and 500 DC is applied between shorted live/neutral and earth to check that the insulation resistance between live parts and framework is greater than 0.5 Meg ohms. If the insulation resistance is less than 0.5 meghoms a trigger circuit is operated which discontinues the test and illuminates the INSULATION FAIL lamp. Note: Electronic equipment may be damaged by this test. Refer to a qualified person. 13

14 TEST PROCEDURE Class I Appliances Follow the instructions printed on or with the tester. A full visual examination must be carried out as detailed in Appendix 2. Any equipment failing a visual examination MUST not be tested. Setting Up 1) Connect the mains plug to mains and switch to the 'on' position. The PAT is now active, indicated by the STANDBY lamp illuminating. 2) Select continuity trip level required on key-lock switch. (See guide to maximum cable lengths, page 12). Operation Lamp Indication and Meaning of the Lamp Signals STANDBY - LAMP ON The PAT is in the STANDBY condition ready to begin a test. Connect the appliance to be tested into the test socket located on the front panel of the PAT. Connect the earth clip to the framework of the appliance ensuring good electrical contact to an exposed conducting area. If an on/off switch is fitted to the appliance, set it to the 'on' position otherwise the insulation test results will be invalid. Operate the 'START' push switch. TEST IN PROGRESS - LAMP ON The PAT is in the TEST IN PROGRESS condition for the duration of the test, after which the test results are displayed on the appropriate lamps. INSULATION FAIL - LAMP ON CONTINUITY FAIL - LAMP ON Remove the appliance from the test socket, disconnect the earth clip or operate the RE-SET push switch to return the PAT to STANDBY ready for the next test. NB: The Continuity Fail lamp will illuminate if the earth clip is not properly connected to the framework of the appliance or if the earth connection is open circuit when the START push switch has been operated. TEST SUCCESSFUL - LAMP ON The INSULATION RESISTANCE and EARTH CONTINUITY of the appliance under test are satisfactory. 14

15 The run push-switch can now be operated if appropriate. Note: If the current rating of the appliance exceeds 15 amps then the run test should not be carried out. This supplies mains power to the appliance for normal running. Reset the PAT by removing the appliance from the test socket and disconnecting the earth clip, or by operating the RE-SET push switch to return to the STANDBY condition, ready for the next test. Repeat tests cannot be made without re-setting the PAT. Record results and label equipment accordingly. (See section 5) Note: With kettles and water heating equipment, the earth test lead must be clipped to the outside of the heater element. Ensure water is covering the element before the RUN part of the test is allowed to proceed. Note: All appliances FAILING must be referred to a qualified person for further test or repair and must be marked FAIL and taken out of service. Note: If any doubt, refer to qualified person. Class II Appliances: i.e. Double insulated appliances marked with the kite mark. The operation of the PAT is the same as above, except that the TEST-IN PROGRESS button must be depressed for the duration of the test. 15

16 APPENDIX 4 USING THE UNIVERSITY ENGINEER This is an option for Departments who do not wish to appoint their own staff: a charge will be made by the Engineer. A Department will still have responsibility to ensure that user checks are carried out, and visual checks should still be carried out by inspecting staff during self inspections. (For selfinspection programme see circular MR5). A list of portable equipment within the department should be maintained by the Department and submitted to the Engineer on request. The Department will be responsible for providing safe access to rooms and equipment, and making appropriate arrangements in high risk areas such as laboratories or containment areas. Manual handling implications may also need to be considered and equipment made readily accessible for the electrician. N.B. Cables running beneath carpets or taped down may need to be lifted and examined. The following matters will need to be agreed between the Department and the University Engineer. 1) All matters with regard to cost of the service etc. A cost based upon a standard cost per appliance will be applicable but additional charges may apply in the event of i) Agreed working outside of normal working hours. ii) Non productive time attributable directly to the Department. iii) Minor site repairs (see page 16). 2) The dates that the inspecting electrician will be on site. 3) Whether any equipment needs to be tested outside normal working hours. 4) A schedule of any items to be excluded from the testing service e.g. equipment not owned by the University, IT equipment. 5) Who will carry out repairs, and under what circumstances. It is NOT permissible under any circumstances for any faulty item of equipment to be returned to service, prior to the fault(s) being repaired and the equipment re-tested. 6) Arrangements regarding the powering down of any sophisticated equipment by the usual operator of the equipment, prior to the testing and the powering up and the subsequent trial use of such equipment by the usual operator immediately after the testing is completed. 7) The procedure to be followed in the event of any alleged damage having been caused by the electrician or the testing process. 16

17 8) The name of the Departmental contact person. OUTSIDE CONTRACTORS Departments may also engage the services of an outside electrical contractor to carry out examination and testing, but this must be done through the Engineer. As all contractors are vetted by the University for competence, insurance, etc. Contractors should use the labelling system identified in section 5(e). MINOR SITE REPAIRS CARRIED OUT BY UNIVERSITY ENGINEER In order to increase the efficiency of the service provided by the University Engineer and to minimise any inconvenience caused as a result of a failed inspection (by returning the appliance to service as soon as possible) the University Engineer/Electrician shall, if authorised by the Department, undertake minor on-site repairs if these can be done at the time of noting the defect. The following minor on-site repairs, limited to the following list, will be carried out free if done at the same time as the test. They will not normally include anything which required any dismantling of the appliance. a) Changing of an incorrectly sized fuse within a plug. b) Retermination of the plug, and in the case of a detachable lead, or extension lead etc. retermination of the socket at the other end of the lead. c) Replacement of the plug. All plugs and fuses provided by the University Engineer's section shall be marked with the appropriate BS specification number and in the case of 13 amp BS1363 plugs shall have partially shrouded live and neutral pins. It is confirmed that the portable appliance will be tested after repair and before being returned to service. If any other repairs are necessary these may be carried out on a time and materials basis. They must be requested via the Electrical Foreman who, if resources permit, will authorise the Electrician to complete the repair. The Foreman may require the department to confirm the request via the Engineering Section Help Desk. 17

18 APPENDIX 5 EXAMPLE: PERFORMANCE STANDARD FOR A DEPARTMENTAL PORTABLE APPLIANCE TESTING AND SAFETY INSPECTION PROGRAMME ESSENTIAL ELEMENTS 1) Specify equipment to which it applies. (HSE guidance for Office type environment is shown overleaf). 2) Specify work which will be done i.e. whether visual inspection or visual inspection plus PAT tester. (See guidance overleaf). Include details such as: Dated label to be attached to each piece of equipment or its plug (but not the back of the plug, which is easily interchangeable). 3) Specify frequency: University policy is that where PAT testing is to be done, it should be done annually (subject to revision upwards or down-wards by agreement with the University Safety Officer in the light of experience operating the programme). 4) Specify which PAT: choice is Department's own equipment or University PAT available from University Stores. (N.B. University PAT is not required and is not suitable for portable equipment with electronic components such as P.C.'s and typewriters). 5) Specify who shall do it, the time apportioned to them for carrying it out, and when they shall do it 6) Specify that on completion, the "doer" shall report in writing to the Head of Department that it has been done, and indicate what defects have been identified and what remedial action has (or is being) taken. 7) Issue an instruction that: i) equipment with either a red "do not use" label or no label at all may not be used, and ii) equipment with an outdated "tested" label should be submitted for re-test at the earliest opportunity. 8) Maintain a simple Departmental record of the dates when the exercise has been carried out. ADDITIONAL DESIRABLE BUT NON-ESSENTIAL FEATURES 1) Preparation of a Departmental inventory of portable equipment. 2) Use of a Departmental PAT which produces a print-out of equipment tested and the results. 18