HSE Human Factors Briefing Note No

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HSE Human Factors Briefing Note No




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HSE Human Factors Briefing Note No. 6 Maintenance Error Briefing Note 1 – ‘Introd cing Human Factors’ e plains the background to these Briefing Notes. Human erro rs and violat ions in servicing and rep ir tasks ha ve man of t he same root causes a errors in oth r types of task (see Briefing Notes on competence, humans and risk, p ocedures, communications and fatigue). However, in maintenance, a fa ult introduce into the system by hu man error today might have no effect for several mon hs and then cause a su dden unexpected hazar dous breakdown. Case st udies A well-known loss

preve tion expert Professor Tr evor Kletz asked for an unusual retir ment gift – a filing cab net . He put his collect ion of accident re cords in th is and when he sorted the into categories, by far the largest categor y was ‘preparation for maintenance’. Source: OTO 01007 An example of poor preparation for maintenance is an accid ent that occurred during maintenance work on a fir fighting sy stem for a tank in the be nzene stora ge area of a petrochemical plant. Maintenance was carrie out even though the ta nk was full o benzene. Coordination and communication between maintenance and

production depart ents was poor. Production did not supply critical information to maintenance such a : the tank was filled wi th benzene; a component was missing allowing be nzene into t he fire fighting foam pipes and, the t ank did not have nitrogen blanketing. One person was killed a nd 3 injured in the explosion that occurred. Only after the accident, d d the company prepare written procedure and a QA procedure f r maintenance. Source: Mars database incident no. 233 ‘One way of reducing the number of accident s associated wit maintenance operation is to carry out less mainte nance’. Klet

z in Ref. 3 maintenance problem There’s only one way to remove the 8 rings from the peg. Only 1 way in 4 ,000 puts them back in the same order and the same way up as they started! How would you make sure they went ba ck the right way? Your answers will apply to most maintenance tasks. Example a swers – se e below.
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HSE concerns Companies focus their attention on accidents during maintenance that could injure the maintenance fitter rather than the major accident potential of the maintenance fitter’s error. Human errors in servicing and repair can render unavailable syst ems

needed for safety reasons or could introduce faults that make the equipment unsafe. Maintenance checklist: If your company manages maintenance well, you should be able to tick most of the boxes below. When it comes to maintenance, we: ..are fully aware of what maintenance work can lead to a major hazard accident ..have good defences in place to make sure these accidents are very unlikely, including: Physical barriers and guards ‘Administrative’ controls (permits, procedures, checklists) Management controls (supervision and checking of tasks) Highly competent maintenance teams Well designed

maintenance tasks (interesting, no time pressure, comfortable conditions) ..base our maintenance programme on major accident risk assessment ..communicate well during shifts and between shifts ..take special care of temporary or inexperienced maintenance technicians and contractors ..do walk around inspections of maintenance tasks in progress ..have considered the ease of maintaining systems and continually improve it ..look for early signs of problems (e.g. a large backlog of jobs; excessive repair times; adverse feedback from staff) ..investigate near misses and accidents to learn from human

failure in maintenance and to improve our systems The ‘ring and pegs’ problem: 1. Redesign to make it impossible to reassemble it incorrectly or so that ring order and direction doesn’t actually matter 2. Try to make this task more interesting! 3. Put a colour code, number or other marking to show when the rings are on the right way 4. Design the task to give the person doing it enough time and low stress conditions to do it 5. Make sure a second person checks the order and direction of the rings after they have been assembled.
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Learning more about maintenance error The diagra

below shows that, as with most human errors, the root ca use of maintenance erro rs can usually be tr aced back t management. One way of lookin g at this is t hat management are responsible for putting in ‘defences against erro r. Defences are anything designed t prevent or reduce the chance of hu man errors or to deal wi th the conse quences of unpreventable or unforeseen accident s. However, ac cident report often sho that mana gement are responsible for breaking down defences by chan ges in administration. Poor mana geme t decisi ons rking cond itions th at ou ra ge human errors Errors (

‘unsafe acts’ ) Near misses or ccidents (Major Haz rd or ‘Occupati l’) Can lead to Can lead to Can lead to The table be low illustrate s a human error analysis of a general maintenance task and shows the types of defences that should be co nsidered to pr event maj r accident hazards arising from human errors in the . Task Need to Ph ical Defences Administrative Defences Plan the job Identify safety critical pa rts of the job and h w t manag e them (risk as se ssm ent Physical b rri rs a und ite s that could b damag ed by maintena nce; maintainabl system s (d esi gned for e si er maintena nce);

barrie s to contain or co ntrol h rd s if relea ed (e.g. bund s; wate r curtai ns; fire detectio and fighting syste s; prote tive clo hing; refuge s) Safety Management Syste ; good safety cultu and morale; permit to work sy stem; pro ed ures fo r shift hand over if task exten s ov er 2 or more shifts; g ood commu ni cation s betwe en mai tenan ce a operatio ns person nel; m anag e po ssi e fatigue or time of day effects on ta sk; team sele ction; site emerg y plan; incid ent analy is system Isolate the sy st em Use be st means of contai ning h ards. ‘Blinds’ in pip s etc rathe than rely on

valves; bleed valves; remove circui t breakers rat her than rely on switch es; take readi ng s to check isolation Permit syste shoul d sp ify defen ce s to be use ; con ct sp ot che ks of pe rmits in use; p ocedu re update syste Gain ac cess to the system Open u covers/hat ch es us ek ee ng s to k ep track of tools and compo ts; physi cal protection of surroundi ng area s if openi ng up re qui re s force Spare , tools and con uma les stora ge an d a issuing syst em Carry out serv e o repai r task Test by eye o usin g instrum ents; repla e d ma ged or worn out item s; reple ish fluids Mostly

admini trative but, could make sy st em s mor ‘maintaina ble (easi r to ma intain) and ma ke it impossibl e to do key tas inc rrec tly (e.g. des ign comp one nts that will only fit in one way Comp etent techni cia s; up to date maintena nce pro ed ures/ checkli ts/ job aid ; inde pend ent ch ecks by se con t ch cian o su pe isor; system d sig ned to acce pt only corre t co mp onent s; good calib ration pro ed ures; team traini ng i required; stagg er mai tenan ce ta sks so that multiples of the sam item are not servi ed at th e same time by the same crew (same fault cou d be introdu ce d into

each item); system of remin ders to ensure n thin g is left out
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Task Need to Physical Defences Administrative Defences Reassemble Align the system correctly; do not leave any components out; don’t leave foreign object in system Design of system to resist errors (e.g. by providing only one means of reassembly; components that cannot be damaged by forcing) Housekeeping system to ensure that all replacements have been fitted and all old ones accounted for. Independent checking, random checking during reassembly Remove isolation Make sure it is safe to refill or restart system

Isolations physically locked; barriers against the specific hazard (e.g. screens; protective clothing) Strict procedure for reinstating equipment; observe for signs of problems; be able to re-isolate the system quickly Commission and test the system; put back into service Make sure the system works properly and is in the correct state (running or standby) Allow only authorised personnel access to the system Good test procedures; clear measures or criteria for pass/fail; independent checks References 1. Major Accident Reporting System (MARS) entry 2335

http://mahbsrv2.jrc.it/MARS/servlet/ShortReports 2. HSE (2000) ‘Improving Maintenance: a Guide to Reducing Human Error’. ISBN 0 7176 1818 8 3. HSE (2000) ‘Maintenance - Reducing the risks’. OTO 2001/007 ISBN 0 7176 2075 1 4. Reason, J and Hobbs, A (2003). ‘Managing Maintenance Error’. Ashgate. ISBN 0 7546 1591 X


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