Examiners’ Report NEBOSH International Diploma in Occupational Health and Safety (Unit IC)
Examiners’ Report NEBOSH INTERNATIONAL DIPLOMA IN OCCUPATIONAL HEALTH AND SAFETY Unit IC – International workplace and work equipment safety JANUARY 2010
Comments on individual questions
2010 NEBOSH, Dominus Way, Meridian Business Park, Leicester LE19 1QW tel: 0116 263 4700
fax: 0116 282 4000
email: [email protected]
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NEBOSH (The National Examination Board in Occupational Safety and Health) was formed in 1979 as an independent examining board and awarding body with charitable status. We offer a comprehensive range of globally-recognised, vocationally-related qualifications designed to meet the health, safety, environmental and risk management needs of all places of work in both the private and public sectors. Courses leading to NEBOSH qualifications attract over 25,000 candidates annually and are offered by over 400 course providers in 65 countries around the world. Our qualifications are recognised by the relevant professional membership bodies including the Institution of Occupational Safety and Health (IOSH) and the International Institute of Risk and Safety Management (IIRSM). NEBOSH is an awarding body to be recognised and regulated by the UK regulatory authorities:
The Office of the Qualifications and Examinations Regulator (Ofqual) in England The Department for Children, Education, Lifelong Learning and Skills (DCELLS) in Wales The Council for the Curriculum, Examinations and Assessment (CCEA) in Northern Ireland The Scottish Qualifications Authority (SQA) in Scotland
NEBOSH follows the “GCSE, GCE, VCE, GNVQ and AEA Code of Practice 2007/8” published by the regulatory authorities in relation to examination setting and marking (available at the Ofqual website www.ofqual.gov.uk). While not obliged to adhere to this code, NEBOSH regards it as best practice to do so. Candidates’ scripts are marked by a team of Examiners appointed by NEBOSH on the basis of their qualifications and experience. The standard of the qualification is determined by NEBOSH, which is overseen by the NEBOSH Council comprising nominees from, amongst others, the Health and Safety Executive (HSE), the Confederation of British Industry (CBI), the Trades Union Congress (TUC) and the Institution of Occupational Safety and Health (IOSH). Representatives of course providers, from both the public and private sectors, are elected to the NEBOSH Council. This report on the Examination provides information on the performance of candidates which it is hoped will be useful to candidates and tutors in preparation for future examinations. It is intended to be constructive and informative and to promote better understanding of the syllabus content and the application of assessment criteria. © NEBOSH 2010
Any enquiries about this report publication should be addressed to: NEBOSH Dominus Way Meridian Business Park Leicester LE10 1QW Tel: 0116 263 4700 Fax: 0116 282 4000 Email: [email protected]
Many candidates are well prepared for this unit assessment and provide comprehensive and relevant answers in response to the demands of the question paper. This includes the ability to demonstrate understanding of knowledge by applying it to workplace situations. There are always some candidates, however, who appear to be unprepared for the unit assessment and who show both a lack of knowledge of the syllabus content and a lack of understanding of how key concepts should be applied to workplace situations. In order to meet the pass standard for this assessment, acquisition of knowledge and understanding across the syllabus are prerequisites. However, candidates need to demonstrate their knowledge and understanding in answering the questions set. Referral of candidates in this unit is invariably because they are unable to write a full, well-informed answer to the question asked. Some candidates find it difficult to relate their learning to the questions and as a result offer responses reliant on recalled knowledge and conjecture and fail to demonstrate any degree of understanding. Candidates should prepare themselves for this vocational examination by ensuring their understanding, not rote-learning pre-prepared answers. Common pitfalls It is recognised that many candidates are well prepared for their assessments. However, recurrent issues, as outlined below, continue to prevent some candidates reaching their full potential in the assessment.
Many candidates fail to apply the basic principles of examination technique and for some candidates this means the difference between a pass and a referral.
In some instances, candidates are failing because they do not attempt all the required questions or are failing to provide complete answers. Candidates are advised to always attempt an answer to a compulsory question, even when the mind goes blank. Applying basic health and safety management principles can generate credit worthy points.
Some candidates fail to answer the question set and instead provide information that may be relevant to the topic but is irrelevant to the question and cannot therefore be awarded marks.
Many candidates fail to apply the command words (also known as action verbs, eg describe, outline, etc). Command words are the instructions that guide the candidate on the depth of answer required. If, for instance, a question asks the candidate to ‘describe’ something, then few marks will be awarded to an answer that is an outline.
Some candidates fail to separate their answers into the different sub-sections of the questions. These candidates could gain marks for the different sections if they clearly indicated which part of the question they were answering (by using the numbering from the question in their answer, for example). Structuring their answers to address the different parts of the question can also help in logically drawing out the points to be made in response.
Candidates need to plan their time effectively. Some candidates fail to make good use of their time and give excessive detail in some answers leaving insufficient time to address all of the questions.
Candidates should also be aware that Examiners cannot award marks if handwriting is illegible.
The International Diploma in Health and Safety is taught and examined in English. Candidates are therefore expected to have a good command of both written and spoken English including technical and scientific vocabulary. The recommended standard expected of candidates is equivalent to the International English Language Testing System (IELTS) level 7 (very good user). It is evident from a number of scripts that there are candidates attempting the examination without the necessary English language skills. More information on the IELTS standards can be found at www.ielts.org
UNIT IC – International workplace and work equipment safety
Section A – all questions compulsory
In 1988 a disaster occurred on the Piper Alpha platform in the United Kingdom. (a)
Identify mechanical failures that contributed to the initial explosion.
Outline the systems failures associated with the permit-to-work system that contributed to the initial explosion.
In answering part (a) of the question, candidates should have referred to the removal of a safety pressure valve and its replacement with a blank flange assembly which was incorrectly fitted and was not leak tight. A running condensate pump tripped and a stand by pump, associated with the blanked flange was operated. Condensate and gas escaped from the blanked flange and the gas exploded. For part (b), good answers would have referred to the failures with the permit to work system which was in operation for the removal of the pressure valve including a failure in communication at the end of the working day with the suspended permit returned to the control room but not displayed and a failure to check that the blanked valve was leak tight at the time; a failure in communication at shift handover with the absence of any written procedures for this event; the absence of formal training for those with the responsibility of issuing permits; inadequate written procedures for the permit to work in that there was no reference to locking off or tagging valves to prevent inadvertent operation, no mention of the need to cross reference permits, no place on the permit for the issuer to declare that the work had been left in a safe condition, no attention drawn to the potential dangers associated with the ‘suspension’ of permits, and finally inadequate monitoring and auditing by management of the permit to work procedure. This question was poorly answered with most candidates unable to identify the mechanical failures that led to the incident for part (a), and, for the second part, referring to a lack of communication at shift change over but little else.
Outline the issues that should be included in a fire safety training session for workers.
Most candidates were able to outline a good range of issues to be covered in a fire safety training session for workers which would include: the consequences of fire such as the effects of smoke inhalation on those involved the potential costs to the business; the principles of the fire triangle; the basic elements of fire prevention such as the storage of flammable materials, good housekeeping and the need to prevent the accumulation of rubbish; the action to be taken on discovering a fire such as raising the alarm, the procedure for calling the fire service and the action to be taken by personnel on hearing the alarm; the location and use of fire fighting equipment with practical training for selected workers; the escape routes and exits from the premises together with the assembly points and the roll calls that would have to be carried out; the arrangements for the evacuation of people with disabilities and for assisting visitors and members of the public; the identity and role of fire wardens and marshals; the importance of fire evacuation practices and drills and issues directly concerned with personal behaviour such as refraining from re-entering the building after evacuation until instructed to do so.
Coal is delivered by train to a power station and is transported by conveyors to a furnace. Conveyor workers check that the coal moves along the conveyors efficiently. These workers have received suitable information, instruction and training and are supervised. Outline additional control measures that could reduce risks to conveyor workers.
For this question, candidates were expected to refer to control measures such as ensuring suitable guarding was in place for the conveyors for example fixed guards on the conveyor drums, nip guards between the belts and rotating rollers and enclosures or distance guards to prevent access to the conveyors; edge guards or rails to prevent the coal from falling off the conveyors; trip wires or emergency stops that were clearly visible to enable the belts to be stopped in the event of an emergency; the provision of adequate space between the conveyors; positioning the conveyor belts at a convenient height to facilitate the loading and unloading of the coal; carrying out maintenance on the conveyors on a regular basis by competent personnel; carrying out a noise assessment and providing the workers with hearing protection if this was found to be necessary; monitoring the presence of dust and ensuring a good level of general ventilation together with suppression sprays; providing a level of lighting that will enable work to be carried out safely and importantly introducing procedures for inspecting the machinery at the beginning of each shift to ensure that the guards and safety devices were in position and installing a start up warning device. Most candidates referred to the need to provide guards for the conveyor but did not indicate the type and location of the protection required. Some concentrated on general working conditions such as exposure to dust and dirt and wrote of job rotation and welfare issues while a few who perhaps did not read the question with sufficient care discussed traffic management and the use of forklift trucks rather than the hazards associated with the use of the conveyors.
Outline the features of a ‘fixed guard’ in relation to machinery safety.
Outline the factors to be considered in the design and use of fixed guards that minimise risks to workers.
In outlining the features of a fixed guard candidates could have referred to it as a guard with no moving parts affixed in such a manner (eg by screws, nuts ,welding) that it can only be opened or removed by the use of tools or destruction of the affixing means. It provides appropriate protection against mechanical hazards when infrequent or no access is required to dangerous parts of a machine during its normal operation. Some candidates outlined features which were more appropriate for an interlocked rather than a fixed guard. In outlining the design features of a fixed guard, candidates should have referred to factors such as: the material of construction, which should be sufficiently robust to withstand the rigours of the workplace and be able to contain any ejected material, but still allow sight of the process when required; the method of fixing, usually requiring the use of a special tool for the guard’s removal; the need to ensure that any necessary openings in guards are such that they do not allow access to the dangerous parts (a function of the size of any opening in relation to the distance to the hazard); and the need to address the possibility of the guard reverberating and exacerbating a noise problem. Most candidates recognised that a tool would be required for the removal of a guard but then wrote about hazards rather than outlining the essential properties of the guard. Factors to be considered in the use of fixed guards include monitoring and supervision to ensure that the guard is not compromised; safe systems of work for carrying out maintenance operations with the guard removed and the provision of information and training for both operators and maintenance staff. Answers to this part of the question were to a reasonable standard though there were a few suggestions that the guard should be interlocked to stop the machine if it was removed.
Direct contact with live parts of an electrical supply within a workplace can result in serious injury or death. Outline a range of control measures that may prevent or limit the effect of such contact.
In answering this question, the most obvious control measure that should have come to mind would have been the possibility of isolation with the supply locked off to enable ‘dead’ working. If this were not possible, then contact with live parts might be prevented by the complete insulation of live parts such as cables, bus bars and connections. Contact might also be prevented or at least deterred by placing barriers across the usual direction of access or enclosures to prevent contact from any direction. There are also occasions when contact is unintentional where consideration should be given to positioning live parts of the supply out of reach taking into account activities which might include the use of ladders or long metal tubes. In addition to the above measures, in the event of contact, its effect might be limited by the use of residual current devices (RCDs) while other possible control measures include the use of fuses or circuit breakers to protect against over current, procedural measures such as permits to work and physical measures such as mats and the use of appropriate tools. Answers provided were generally not to a good standard with many candidates referring to control measures more suited to portable equipment.
A worker suspended in a fall protection harness is at risk of suffering from suspension trauma with the potential for serious injury or death. Outline the precautions an employer could take to reduce the risks to the worker in this situation.
In answer to this question, candidates were expected to outline precautions such as the initial selection of the harness, particularly with respect to its shock absorbency and its construction to a recognised standard; to implementation of plans to prevent prolonged suspension in the fall protection harness but if prolonged suspension were to occur, to the drawing up of procedures for carrying out rescue and providing treatment as soon as possible. There will also be a need for workers wearing harnesses and those performing rescue operations to have training in determining if the harness is properly fitted and correctly worn and performs as intended; how suspension trauma/orthostatic intolerance occurs together with the procedures that should be followed in a rescue operation and the methods of reducing risks while suspended. The procedures for rescue should contain contingency based actions such as if self or prompt rescue is impossible, the worker should be trained to pump their legs frequently; the need for rescue workers to elevate the worker’s legs and rescue them in the direction of gravity to avoid negative hydrostatic force; the need for continuous monitoring of the suspended worker for signs and symptoms of suspension trauma/ orthostatic intolerance; ensuring the worker receives appropriate first aid treatment once rescued such as supplementary oxygen administered by trained personnel; the need to call for medical assistance if the worker is unconscious in harness suspension and monitoring the worker after rescue and ensuring evaluation by a healthcare professional. It is essential that the signs and symptoms of suspension trauma are recognised. These include light headedness, palpitations, poor concentration, fatigue, nausea, dizziness, headache, sweating, weakness, paleness, breathlessness, and unusually low heart rate and blood pressure. Only a few candidates appear to have knowledge of suspension trauma with others describing standard precautions for working at height in order to prevent workers arriving in a position where they were suspended.
Section B – three from five questions to be attempted
Workers in a vehicle maintenance workshop spray-paint vehicles using a highly flammable solvent-based paint. Outline the measures needed to assess and control the risks associated with the spray-painting activity.
One of the first measures to be taken in this situation would be to carry out an assessment of the risks involved in carrying out the activity which would include the hazardous properties of the paints and solvents used (normally by reference to safety data sheets), the circumstances in which the work was carried out, possible ignition sources and the likelihood that a fire or explosion would occur. The control measures to be taken would be firstly to ensure that the workshop was constructed of fire resistant material, and then to give consideration to the possibility of replacing the paint in use with one that was less flammable.
An external fire resistant storeroom would have to be provided for the paints and solvents with the quantities present in the workshop reduced to a minimum and kept in non-spill containers provided with lids. Procedures would have to be put in place for the containment and clean up of spillages and for the cleaning of the spray guns. Local exhaust ventilation would have to be provided in the workshop with care taken to ensure all electrical equipment was to the standard appropriate for the conditions that might prevail, such as flameproof or intrinsically safe. Fire fighting equipment would have to be provided together with adequate fire escape routes and emergency procedures drawn up and communicated to the workforce who would also need instruction and training on the risks involved in the operation and the precautions to be observed. While candidates were generally able to identify many of the control measures necessary, they had more difficulty in suggesting how the risks associated with the process should be assessed. Some lost marks because they produced lists rather than the outline required.
Outline the features and arrangements that should be considered in order to minimise risks associated with the movement of vehicles in the workplace.
In outlining the design features that should be considered in order to minimise risks associated with the movement of vehicles in the workplace, candidates should have referred to matters such as the provision of traffic routes with a smooth and stable surface and of sufficient width and headroom for the types of vehicle that will use them; the elimination of sharp bends, blind corners and steep gradients with the siting of convex mirrors on those corners that cannot be avoided; the installation of a one way system to minimise the need for reversing; the inclusion of passing places for vehicles; the introduction of speed limits and the provision of speed retarders; the provision of a good standard of lighting for the routes and particularly for the transition areas between the inside and outside of buildings; the segregation of vehicles and pedestrians including separate access and egress and the provision of clearly marked crossing places. As for procedural arrangements, they would include the selection and training of competent drivers who would be subjected to regular health screening; the provision of information on site rules for visitors including drivers visiting the site; the introduction of procedures for the regular maintenance both of the traffic routes and of in-house vehicles and for the reporting of defects; the rigorous enforcement of speed limits and the provision and use of high visibility clothing by workers working in close proximity to traffic routes. The question was well answered by the majority of candidates though some again produced lists rather than the additional detail required to satisfy an ‘outline’ question.
An independent scaffold is to be used as a working platform to carry out repairs to a two-storey building. (a)
Outline factors which should be considered in order to confirm that the scaffold is safe to use. Identify the inspection requirements for the scaffold.
Factors to be considered in order to confirm that the scaffold is safe to use include that: it has been designed to carry all loads likely to be placed upon it including sheeting, chutes and nets and has been erected by a competent person; it is constructed of sound materials and fittings and has been erected on firm level ground avoiding all voids and drains; that the standards are supported on base plates on suitable sole plates with care being taking to ensure joints are staggered; that longitudinal and diagonal bracing and ledger braces have been used; that the working platforms are fully boarded, are wide enough for the work to be undertaken with the boards fully supported without any overhang; that guard rails, toe boards and brick guards or sheeting have been provided; that there is safe access to the scaffold with ladders extending to at least one metre above the working platform; that appropriate methods for dealing with waste such as chutes have been fitted together with the means for raising and lowering materials such as hoists or closed containers and that if the scaffold is erected in a position where there is likely to be movement of vehicles, protection has been provided to prevent damage from any collision that might occur. For part (b), inspection by a competent person is necessary following erection, at specified intervals, following any alterations or damage or after a period of inclement weather. Records of the inspections should be retained and the scaffold tagged as having been inspected. Answers to this question were generally to a good standard despite the fact that a few candidates included inspection requirements in their responses to part (a) and thus were left with nothing more to identify for the second part of the question.
Prevention of pipework failures is critical in preventing major leaks and incidents. The construction of a new chemical plant is nearly complete and some parts are being prepared for start-up. (a)
Outline an inspection strategy that could prevent pipework failures within this plant.
Outline the items that could be included on a checklist when inspecting pipework after construction.
In answering part (a) of this question, candidates would first need to make the point that any current inspection would need to be more thorough than those which may have been carried out in the past. The strategy would involve the use of NDT techniques such as dye penetrant for the detection of surface faults and ultrasonics or radiography to detect those that were more serious. The techniques would involve the use of qualified personnel to interpret the results and management should resist the temptation to use unqualified personnel for any type of pipe work inspection. Inspection should take place during and after construction has been completed and should be ongoing throughout the life of the plant. Those carrying out the inspections should preferably include a member of the design team who will be able to detect departures from the design intentions and also a member of the start up team who suffer most from the results of construction defects.
For part (b), candidates were expected to outline items such as that: the construction of the pipe work is from the grade of steel specified and the required tests have been carried out; the pipes are not secured too tightly and are free to expand; the flanges on liquid lines are not located above cables; temporary supports have been removed and permanent supports correctly installed; springs and hangers are not fully compressed or extended; no sub-standard joints exist, no screwed joints have been used and all joints have been leak tested; temporary branches, nipples and plugs have been removed and replaced with welded plugs; pipes do not touch the ground, are not laid underground and do not pass through pits or depressions containing water; relief valve drain lines are not too close to the ground so that blocking and freezing is avoided; reinforcement pads are vented; dead ends, dead legs and water traps have been avoided; bellows are not distorted and support rings are not loose; vibrating pipes have been avoided and all pipe work has received hydrostatic testing. This was not a popular question and answers that were submitted were not to a good standard. For the first part, candidates produced little more than a list of different types of NDT while for the second, only vague and general descriptions of the items that could be checked were given. ______________________________________________________________ Question 11
In November 1984 the San Juanico gas storage facility near Mexico City exploded with catastrophic consequences. (a)
Outline the circumstances of the disaster.
Outline how a Boiling Liquid Expanding Vapour Cloud Explosion (BLEVE) occurs with a gas storage vessel constructed of metal.
Outline the immediate rescue and restoration measures that took place.
A major fire and a series of catastrophic explosions occurred at the San Juanico LPG terminal near Mexico City. As a result of the incident, some 500-550 people died and the terminal destroyed. The terminal was supplied with LPG from three refineries on a daily basis. On the day of the incident it was being supplied from a refinery some 400km away. Two large spheres and 48 cylindrical vessels (torpedoes) were filled to 90% capacity and four smaller spheres to 50% capacity. A drop in pressure was noticed in the control room but the operators were unable to identify the cause of the pressure drop. An 8 inch pipe between a sphere and a series of cylinders had ruptured. The gas accumulated around surrounding tanks and over an area measuring 150 metres by 200 metres. The gas cloud drifted to a flare stack and exploded. A number of ground fires from the original point of fracture were directed at adjacent cylinders. A series of BLEVEs occurred involving four of the six spheres and a number of the cylindrical vessels. Injuries sustained were caused by radiated heat and burning droplets of LPG. In answer to part (b), candidates should have outlined that gases such as butane and propane are stored under pressure in metal storage vessels. When the valve to the vessel is opened, the resulting drop in pressure restores the LPG to the gaseous state. If, however, the vessel is involved in a fire, the liquefied gas boils and the contents of the vessel will revert to the gaseous phase with a resulting increase in pressure inside the vessel. The pressure relief valve opens and vaporised liquid escapes and the liquid level drops. As there is less and less liquid left to absorb the heat, the vessel above the liquid level absorbs the heat and the metal starts to change and weaken and ultimately ruptures as a result of ductile failure. The remaining contents burst out and vaporise under atmospheric pressure sending debris from the vessel into the surrounding area. The vapour cloud which includes gas droplets finds an ignition source and explodes.
Following the explosion, some 4,000 emergency workers were drafted into the terminal. The primary measures were concerned with the temporary evacuation and transport of the injured. Further measures were aimed at the prevention of an epidemic, the removal of debris and identification of those who had been killed. Fires were extinguished, temporary shelters provided and arrangements made for the mass internment of those who had died. This question was not popular and was answered by only a few candidates. While many were able to give a reasonable description of the mechanics of a BLEVE it became obvious that they had little knowledge of the circumstances of the Mexico City incident.
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