January 2010
Examiners’ Examine rs’ Repor Reportt NEBOSH National Diploma in Occupational Health and Safety - Unit C
Examiners’ Report NEBOSH LEVEL 6 DIPLOMA IN OCCUPATIONAL HEALTH AND SAFETY Unit C: Workplace and work equipm ent JANUARY 2010
CONTENTS
Introduction
2
General comments
3
Comments on individual questions
4
2010 NEBOSH, Dominus Way, Meridian Business Park, Leicester LE19 1QW tel: 0116 263 4700
fax: 0116 282 4000
email:
[email protected]
website: www.nebosh.org.uk
The National Examination Board in Occupational Safety and Health is a registered charity, number 1010444 T(s):exrpt s/D/D-C1001
EXTERNAL
DW/DA/REW
Introduction
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]
2
EXTERNAL
General comm ents
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.
3
EXTERNAL
UNIT C – Workp lace and w ork equi pment
Section A – all questions compuls ory Question 1
Outline the main design features of a warehouse and associated traffic routes intended to reduce the risks associated with internal transport.
(10)
In outlining the design features that should be considered in order to minimise risks associated with the movement of vehicles in a warehouse, 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 with vision panels in the access doors; the provision of clearly marked crossing places for pedestrians and designated parking spaces for vehicles to avoid congestion; the provision of protection for racking and other vulnerable items and the use of wheel stops at loading bays and in areas where tipping is necessary; and the provision of adequate ventilation to clear diesel exhaust gasses from the building. While few candidates referred to wheel stops at loading bays and the provision of designated parking spaces, answers were generally to a good standard containing practical solutions which were well outlined.
Question 2
A petrol storage tank in a bund containing three other similar tanks is overfilled during a transfer operation resulting in a large spill of petrol into the bund. The petrol vapour is ignited from a remote source causing a catastrophic explosion and fire involving the whole installation. (a) (b)
Identify the design and construction measures that could have prevented such an event.
(4)
Outline the range of measures that would be necessary to mitigate the effects of such an event.
(6)
For part (a), design and construction measures that could have prevented the incident include adequate segregation between adjacent tanks and the use of separate bunding; an interlocked pumping system with high level alarms with at least double redundancy of the alarms; level detection and vapour detector monitoring systems fitted in the bunds together with foam vapour suppression; the provision of remote shut down systems and a good standard of earthing and bonding. Few candidates referred to the need for vapour detection and monitoring in the bunds or the provision of remote shut down systems.
4
EXTERNAL
When candidates came to answer part (b), many appeared to have no understanding of “mitigation” measures and consequently repeated many of the preventative and protective measures they had included in their answers to the first part of the question. Examiners were looking for an outline of measures such as the provision of adequate fixed foam installations to spray the surface of pools in the bunded areas and spray deluge systems; the installation of foam monitors capable of reaching the tops of tanks; the erection of radiation walls between adjacent bunds to prevent other tanks being heated; an adequate supply of fire fighting water; the redundancy of water pressurisation; the installation of remotely operated pumps and valves to empty affected tanks; easy routes of access for fire fighters; the provision of drainage interceptors to minimise the environmental effects of fire water run-off; regular draining and cleaning to remove firewater from bunds; the preparation of an emergency plan to deal with such an event should it occur and the provision of training for operatives both in the content of the plan and the actions expected of them. Many of the above measures for example the provision of foam sprays, spray deluge systems water supply and the redundancy of water pressurisation rarely appeared in the answers provided.
Question 3
A design for a multi–fuel combined heat and power (CHP) power station allows for either coal, oil or natural gas burning. The proposed site will include the necessary fuel storage facilities and water treatment plant. The installation will be located on the bank of a river estuary and receive deliveries by road, pipeline and ship. Identify potential pollutants AND their related source: (a)
during normal operation;
(5)
(b)
during abnormal operation.
(5)
In answering this question, candidates were expected to identify both the specific pollutants and their sources in the normal operation of the power station and in any abnormal conditions that could be foreseen. During normal operation, it would be likely that there would be emissions of carbon dioxide and oxides of nitrogen during the burning of fossil fuels and of sulphur dioxide and other sulphur compounds when coal or oil were the chosen fuels. Other likely pollutants would include soot and coal dust from incomplete combustion, solid waste from coal and oil ash, VOC emission from oil storage tank vents, acid and alkali effluents arising from the water treatment process, emissions from vehicles delivering fuel to the site, the thermal content of cooling waters and the pollution arising from the inevitable noise and light. Pollution during abnormal conditions would be caused by leaks from oil storage tanks, gas supply pipes and acid and alkali storage tanks; spillage of chemical following a road tanker accident; oil slicks from ships during off-loading operations; carbon dioxide due to incomplete combustion of fuel; particulate from incomplete combustion of oil or coal and accidental combustion such as fires in tanks or coal tip ignition with the resultant fire water run off during fire fighting operations. The question caused difficulties and some candidates were unable to differentiate between normal and abnormal operation. In general, there seemed little awareness of the significant pollutants that might arise from the operation with little reference being made to VOC emissions, effluent from the water treatment system and noise and light. There was a tendency to make a general reference to ‘gases’, even greenhouse gases, without further classification and even when pollutants were identified, their actual sources were not given as required by the question.
5
EXTERNAL
Question 4
A production plant uses a potentially explosive powder. Pressurised nitrogen is the transporting and inerting gas within the plant. (a)
Give the meaning of ‘inerting’.
(b)
Outline practical reasons necessary for this process.
(2) why
inerting
was
considered (3)
(c)
Identify the risks from inert atmospheres during maintenance.
(2)
(d)
Outline control measures that reduce the risks from inert atmospheres during maintenance.
(3)
To obtain the marks available for part (a) of the question, candidates should have stated that ‘inerting’ involves the partial or complete substitution of the oxygen content in a flammable atmosphere with an inert gas. For part (b), an outline of the reasons for the necessity to inert in the process described would have referred to the prevention of explosion within the process and the avoidance of flammable limits; the prevention of air/oxygen being drawn into the process through pipe work or holes in the equipment; the possible existence of air/oxygen within the process due to start up conditions or maintenance and repair work; to negate possible ignition sources from friction or static electricity within the process and to protect against the possibility of the presence of tramp metal producing sparks during the process. In answer to part (c), Examiners were looking for an identification of risks such as cold burns from cold nitrogen supplies; hypoxia, anoxia and asphyxiation due an inadequate supply of oxygen and direct and indirect injury from the release of pressurised gas or product from the plant. Finally, an outline of control measures that would reduce the risks from inert atmospheres when maintenance work was being carried out should have referred to: the effective isolation of the plant by disconnecting the supply of inert gas or by blanking/spading the supply pipe; measuring and monitoring the oxygen and flammability levels in the working area; the use of forced ventilation or breathing apparatus; and establishing control by means of a permit to work system with the activities being authorised and undertaken by trained and informed personnel. Few candidates were able to provide either an adequate meaning for ‘inerting’ nor the reasons for its use in the process described. Asphyxiation but little else was identified as a risk during maintenance work. Best answers were provided for part (d) though there was the occasional reference to the use of a respirator as a control measure. It was concerning to note in the answers a reference to the fact that oxygen and nitrogen form an explosive mixture and another to the use of oxygen as an inerting medium.
6
EXTERNAL
Question 5
The owners of a large distribution warehouse business have secured a contract from a stationery manufacturer. Their insurers have recommended that the proposed storage facility is sprinkler protected. Outline the factors to be considered in providing an adequate sprinkler system for the storage facility.
(10)
An initial design factor to be considered in the provision of an adequate sprinkler system would be the capacity of water required, the existence of an adequate and assured water supply and the availability of an alternative if this was to fail for any reason. The design of the pumping system would also be important with a diesel back up if the decision was taken to install electrically operated pumps. Other factors would include the means of activating the system (frangible bulbs or detector activated); the linkage of the system to alarms; the spray pattern required; the area to be covered and the presence of other combustibles apart from the stationery; the height of the storage racks and their distance from the sprinkler heads with a decision to be taken on the need for in-rack sprinkling; the provision of fire stopping for sprinklers passing through compartmentalisation; the provision of fire water run off; the arrangements to be put in place for testing the equipment and issues concerned with the protection of the sprinkler heads and the electrical system. Many answers lacked technical depth, did not show an understanding of the particular issues raised in the wording of the question and were generalised round fire prevention rather than design measures.
Question 6
With reference to the mechanical hazards associated with the operation of a hydraulic robotic arm on a production line, outline a range of measures aimed at minimising the risk of injury.
(10)
From the outset, it was important for candidates to recognise that the question was asking for an outline of the safety measures needed to protect against the various mechanical hazards presented by robots and not by machinery in general. Better responses were provided by those candidates who took a hierarchical approach, referring to a range of possible technical, procedural and behavioural controls. For example, while it may not be possible to eliminate the hazards entirely, the elimination of a crushing hazard between the robot and another object by increasing the distance between them was one that was worthy of mention. In terms of safeguarding with respect to the operation described in the scenario, distance guarding of adequate height, interlocked and allowing authorised access only, the presence of sensing devices such as photoelectric systems or pressure mats, and the provision of local fixed guards to eliminate drawing in hazards were all relevant. Procedural measures might include software checks to avoid aberrant behaviour mainly related to impact hazards together with maintenance procedures to check the integrity of hydraulic systems and wiring designed to avoid or reduce electrical or signal interference. In the operation described, maintenance personnel would be at particular risk and so procedures involving permit to work systems would be imperative. Additionally, technical measures should be introduced to allow maintenance work to be performed remotely as far as possible. This would also apply to teaching which should be done either remotely or with the robot in slow mode. Should anyone need access to the robot, then measures should be in place to release any stored energy and to protect against hydraulic failure. Finally, in terms of behavioural controls, it would be necessary to provide a warning before the machine starts up and for the workforce to be informed of the dangers, and instructed and trained in the procedures to be followed.
7
EXTERNAL
There were some good answers provided for this question. However, some candidates showed a lack of knowledge of the principles of machinery guarding and many referred only to fencing without being specific as to what this would entail. Others listed a number of hazards associated with robotic systems but then did not indicate what measures should be taken to mitigate their effect.
Section B – three from five questions t o be attempted
Question 7
A property development company has acquired a former Victorian grain warehouse, abandoned for the past twenty years, to convert into luxury apartments. A Principal Contractor has been appointed for the entire project which involves total removal of the building internals followed by construction of the apartments within the building shell. The demolition work is sub-contracted to a specialist company. (a)
Under the Construction (Design and Management) Regulations 2007 (CDM);
(i)
outline the specific duties of the Principal Contractor with regard to the demolition phase of the project. Your answer should exclude requirements to check on client’s duties.
(7)
(ii)
identify additional duties specific to demolition under CDM.
(3)
(b)
Outline the content of the Pre-Construction Information that will be of specific interest to the demolition contractor.
(10)
Part (a) of the question was designed to test candidates’ knowledge of the Construction (Design and Management) Regulations and in particular Regulations 22 to 24. The duties placed upon the Principal Contractor by the Regulations include: the development of a construction phase plan, providing the demolition contractor with a copy of the plan relating to demolition, informing them of the minimum time for planning and preparation before beginning work and ensuring that he/she is competent to manage a demolition sub contract; planning, managing and monitoring the demolition phase to ensure it is carried out without risks to health and safety; ensuring that information relating to their activities is provided to the demolition contractor and ensuring safe working and co-ordination between them and other subcontractors; ensuring that welfare facilities suitable for demolition work such as decontamination units and showers are provided; taking steps to prevent access to the construction site by unauthorised persons; identifying the information relating to the demolition activity required by the CDM coordinator for inclusion in the health and safety file; ensuring that all contract and sub-contract employees are given site induction and any further information and training they might need in relation to health and safety and consulting with employees or their representatives on health and safety issues. The additional duties in the Regulations specific to demolition are found in Regulation 29. They require that the demolition of a structure should be planned and carried out in such a manner as to prevent danger or where it is not practical to prevent it, to reduce the danger to as low a level as is reasonably practicable. The arrangements for carrying out the demolition work should be recorded in writing before the work begins.
8
EXTERNAL
For part (c), candidates should have given examples of information such as the location of site and buried services; details of hazardous and flammable substances stored on the site; possible contamination of the ground or drains; the location of other hazards such as asbestos; the possible presence of anthrax contaminated plaster; the presence of any hazardous machinery or equipment that has been left in the building; details of weaknesses in the structure such as fragile roofs or the presence of rot; ground conditions such as possible instability and the existence of culverts; information on the previous use of the land; means of access to the site and traffic routes particularly those for the removal of waste; the proximity of neighbours; copies of the original building plans if available and details of any restrictions on the hours of work. This was not a particularly popular question and not well answered by those who did decide to attempt it. It may have been that candidates did not have too much knowledge of construction operations. There was a general inability to identify the specific requirements for demolition with candidates opting to identify in their place the general duties contained in the Regulations. Some confused pre-construction information with the design brief. Candidates should again be reminded of the need to study the wording of the question with great care, since despite the instructions given in bold type, there were still a number of candidates who referred to the duties of the client.
Question 8
(a) (b)
Outline a range of factors that may cause instability of a mobile crane.
(8)
Outline control measures that should be taken to reduce the likelihood of a mobile crane overturning during a lifting operation.
(12)
This was a very popular question and generally well answered. Factors affecting crane stability that could have been outlined include issues connected with the load, those affecting the crane directly such as lateral or longitudinal stability and other stability issues. Issues connected with the load include its weight and centre of gravity, incorrect slinging, snatching of the load or shock loading and the load snagging on obstructions. Instability issues which might affect the crane directly include unstable ground that is incapable of bearing the weight of the crane and its load; sloping or uneven ground; outriggers not fully extended and a failure to use spreader plates; exceeding the crane’s safe working load; overruling the rated capacity indicator and/or alarm and slewing or hoisting too quickly. Other stability issues include travelling on gradients under load; driving too fast or extending the jib under load; incorrect rigging of the luffing jib, blocks or sheaves; incorrect tyre pressures; mechanical failure; inadvertent contacts and adverse weather conditions. For part (b), control measures that should be taken involve initially the carrying out of an area survey including a full assessment of the environment such as ground conditions including the presence of voids, excavations or soft ground; over head and proximity hazards; weather forecasts and pre-lift levelling and compaction. This will be followed by procedural control measures such as the preparation of a lifting plan and the appointment of a competent person to supervise the lift; ensuring that the statutory inspections and certification of the crane have been carried out and that it has been regularly maintained; the selection of the correct lifting accessories; cordoning off the lifting area and erecting warning signs and carrying out a test lift. Additionally it will be necessary to ensure that the appropriate engineering con trols are in place and are in good working condition such as a rated capacity indicator and alarm system, speed limiters, the over-hoist limit switch and the motion and performance limit device; to ensure the outriggers are fully extended and positioned on spreader plates; and that visibility is improved where necessary by the provision of CCTV and/or mirrors. Finally consideration will have to be given to behavioural controls such as the competence and training of the driver, slinger and banksman.
9
EXTERNAL
Some candidates successfully outlined a range of factors that might cause instability but then did not go on in part (b) to suggest the appropriate control measures.
Question 9
A serious accident occurred when a threaded steel rod in the braking mechanism of a hoist broke. An investigation revealed that the cause of the breakage was fatigue failure. (a)
Outline the mechanism and characteristics of fatigue failure.
(6)
(b)
Identify THREE factors which can contribute to such a failure AND for EACH factor outline ONE circumstance in which it may occur.
(6)
Outline the measures that could have been taken to minimise the likelihood of such a failure.
(8)
(c)
This question was designed to test candidates’ understanding of the mechanisms and causative factors of fatigue failure and the measures that could minimise the probability of such failure occurring. Part (a) required candidates to outline characteristics such as crack propagation from points of stress concentration, fluctuating stress environments and the characteristic conchoidal fracture pattern (beach marks) which progress as narrow rings at low load extending at full load. There is little or no deformation prior to the final failure which may be ductile or brittle. In part (b), candidates needed to explore factors which could give rise to fatigue failure in practice such as stress concentration particularly at sharp corners and holes; surface and sub surface defects such as flaws, cracks, occlusions and impurities; design and fatigue strength issues; residual stresses imposed during manufacture or assembly; and the effects of factors such as corrosion or temperature. For part (c), candidates should have outlined measures to minimise the likelihood of fatigue failures such as those connected with design, manufacture and installation involving the correct specification of materials and components to match service conditions, correct assembly and quality assurance; the maintenance, inspection and examination (with NDT) particularly of critical components and their replacement at planned intervals; and measures connected with use such as avoiding abuse and remaining within designed operational limits, the provision of training and instruction for those involved in the use and the keeping of service history records. This question was not widely attempted and the answers that were produced were disappointing with most marks being obtained for part (c). Candidates did not seem to understand the mechanism of fatigue failure with few able to identify its characteristics. Some took the opportunity to write at length on the subject of NDT while there were other surprising references to ‘shorelines’ and ‘beechmarks’.
10
EXTERNAL
Question 10
Outline the precautions that can be taken to minimise the risks associated with a cable strike when excavating near underground electrical cables.
(20)
This question concerned a topic that must often be encountered. If excavation work is to be carried out near underground electrical cables, it is essential that the work is properly planned before it starts. This involves seeking advice from the relevant body such as the appropriate electricity supply company or the highway/roads authority; assessing electricity cable plans on the understanding that symbols may vary between utilities and that high and low voltage cables can be shown on separate plans; making the supply dead if this can be done or investigating the possibility of diversion; avoiding the use of mechanical excavation and utilising a permit to work system. Before the actual excavation work starts, it will be necessary to locate the presence of cables by the use of cable avoidance tools (CATs) such as Hum or radio frequency detectors and their identification and routes clearly marked. Should a cable, which is recorded on a plan, cannot be located, assistance and advice should be sought from the appropriate authority with extreme care being taken if excavation work begins before the assistance and advice has been obtained. The excavation work should be carried out only by personnel who have been trained and are competent in safe digging practice. They would need to be aware that although no cables are indicated on plans or located by a detector, they may still be present and though cable depths are often prescribed, they should not assume that this is always the case. Additionally, though cables often have protective covers, the assumption should not be made that this is universal practice. Workers should also be aware that though a cable has been exposed, there may be further cables at a lower level and if cables are found which are terminated with pot ended or bottle ended seals, they may still be live. When cable joints are discovered, they should be supported, should not be moved and should not be roughly treated. Further precautions that should be taken during the excavation work include the need to look out for permanent marker posts or other visible indication of buried cables; to establish positive location by careful hand digging, exposing the cables by digging from the side and using hand held power tools only at a distance of 500 mm or more from the indicated lines of cables. If mechanical excavators have to be used in the vicinity of cables, then damage should be avoided as far as is reasonably practicable. Personnel should be kept well away from the excavator and drivers instructed to stay in the cab if a cable is struck. If they have to leave the cab in such circumstances, they should jump clear. Once cables are exposed, any damage noted should be reported to the cable owners and no work undertaken in the vicinity. Support should be provided if more than one metre of cable is exposed and protection, such as the use of planks or sandbags should be provided to prevent damage from ongoing work. Finally, cables should not be moved aside unless the work is supervised by the cable owners. Answers to this question were not to a good standard and were often lacking in detail. The more general and obvious points were mentioned such as the need to provide shoring for the excavation and to prevent access by the public but there was little reference to the more technical issues such as the precautions to be taken when cables are exposed, safe digging practice and mechanical digging. There seemed to be little understanding of the power and heat involved when high voltage cables are struck. Many were content to rely on the general principles of safe working without referring to the detail contained in HSG 47.
11
EXTERNAL
Question 11
An enclosed reactor vessel 30 metres high with a diameter of 10 metres needs cleaning, inspection and repair. The reactor was previously used for reacting flammable solids and gases that formed a toxic, acidic product. It is not possible to avoid entry and the relevant personnel are suitably fit, trained, informed and supervised. Outline additional arrangements that should be considered in order to comply with the Confined Spaces Regulations 1997.
(20)
In answering this question, candidates should firstly have referred to the necessity to carry out a risk assessment of the operation which would identify that: the remaining residues of reactants and product in the reactor could be toxic by inhalation and/or contact; a flammable atmosphere may persist; there is the possibility of contamination from adjacent sources and plants; access to surfaces inside the tank involves work at height; the atmosphere within the reactor could be contaminated by the cleaning and repair methods adopted; heat exhaustion may be a factor during internal jetting and repairs; and there is the possibility of oxygen depletion or enrichment. In the light of the above, it would be necessary to take appropriate precautions such as: the need to purge the tank with an inert gas; the use of forced ventilation; atmospheric testing before entry and while the work is being carried out; the provision of full body personal protective equipment possibly including air-fed breathing apparatus; the erection of staging within the reactor and the provision of fall arrest equipment; provision of adequate lighting which together with other electrical equipment should be intrinsically safe or flameproof with arrangements provided for earthing; isolation of the reactor to prevent inadvertent entry of products; the use of non-sparking tools; the operation of a permit to work system for entry to the reactor with means of communication with stand-by personnel on the outside; and consideration of issues such as job rotation and fluid intake. There would also be a need to consider the emergency arrangements required by Regulation 5 of the Confined Spaces Regulations which would have to be in place before entry to the reactor was allowed. These should include the provision and maintenance of cutting equipment if access proves impossible or non-existent at low level and a powered hoist for top entry rescue; breathing apparatus together with harnesses and lines; first aid facilities including rescue stretchers and resuscitation apparatus; fire fighting arrangements and liaison with the emergency services. Some candidates referred to the toxic nature of the material that had been stored but did not mention the effect that cleaning might have on the atmosphere in the vessel while others did not identify issues connected with working at height. Some made reference to emergency plans without giving further detail whilst others seemed to confuse a permit to work with a safe system of work. While answers to this question generally addressed the relevant issues, Examiners did note that the presentation and layout of the information could have been improved - a remark that could well have been applied to other questions on the paper.
12
EXTERNAL
The National Examination Board in Occupational Safety and Health Dominus Way Meridian Business Park Leicester LE19 1QW telephone +44 (0)116 2634700 fax +44 (0)116 2824000 email
[email protected] www.nebosh.org.uk
