C July 2011

Front 1

Outline the issues that need to be addressed when planning a fire evacuation procedure for a multi-storey office building. (10)

Back 1

*Action that needs to be taken on discovering a fire, hearing the alarm and in summoning the emergency services.
*Consider the number of employees and members of the public that need to be evacuated.
*Travel distances and the various escape routes available.
*Need for liaison between different organisations within the building.
*Location of assembly points with adequate signage and access for the emergency services.
*Arrangements to account for persons evacuated or those still in the building.
*Security considerations when the building is evacuated, with door marshals to prevent re-entry.
*Provision and training of fire wardens and marshals.
*The possible need for a staged evacuation and arrangements for nonemployees on the premises such as contractors and visitors.
*Arrangements for disabled persons, such as refuges and evacuation chairs.
*Arrangements for fire drills and testing the alarm system.
*Prominent display of fire notices and signage for exit routes.
*Fire training for all employees.
*Clarification of responsibilities for escorting and directing visitors.
*Arrangements for liaison with the emergency services and likely response time.
*Arrangements to disable or secure lifts in the building.

Front 2

In order to install a large item of machinery such as a turbine rotor, it is sometimes necessary to perform adjustments while the rotor is in motion. These adjustments are necessarily undertaken with the rotor in an unguarded condition.
Outline the elements of a safe system of work for this activity. (10)

Back 2

*Use experienced workers fully trained in the systems to be approved (not be carried out by the young or inexperienced).
*Provision and use of a single one piece close fitting overall with no external pockets.
*Arrangements to ensure there are no other entanglement hazards present such as the wearing of jewellery, pendants for example, or long hair.
*Use of temporary guards on or the isolation of parts of the machine which are unnecessarily exposed;
*Where practicable the use of jigs to ensure workers’ hands are distanced from the unguarded rotor.
*Provision of a “stand by” man in direct contact with the person carrying out the work with means of immediate communication such as telephone or radio to ensure an emergency response should the need arise.
*Emergency stop controls or braking arrangements should be readily accessible.
*Use of an inching device to minimise the free rotation period or using the slowest speed possible consistent with the task.
*Provision of adequate lighting.
*Introduction of a permit to work which sets out in writing all relevant checks and controls that need to be undertaken before work can start.
*Erection of barriers and signs to prevent the close approach of personnel not involved in the task.

Front 3

Maintenance work on electrical distribution panels and control circuitry commonly involves diagnostic testing and fault finding on live systems.
Outline the requirements of the Electricity at Work Regulations 1989 that apply to this situation AND the practical precautions that should be in place before the work is undertaken. (10)

Back 3

Three conditions for working on a live system
–that it is unreasonable for it to be made dead and
–that it is reasonable to work on it while it is live
–that suitable precautions are taken.
*Distribution panels should have protection rating of at least IP2X by the provision of test points that do not allow access to fingers or tools other than test probes for example test points of 2mm in diameter.
*Test probes should be insulated and fused and the test meter must be checked prior to use.
*Area should be cordoned off by the use of barriers to prevent unauthorised access
*Insulating mats and/or gloves may be required and, depending on the circumstances.
*All live working should be subject to a permit to work system.
*Engineer should be technically competent or to be closely supervised, having regard to the nature of the work, by someone who is competent.
*Persons involved with the work should possess recognised qualifications and have experience in the type of work being undertaken.
*All incoming and outgoing supplies should be suitably insulated and shrouded. Additional shrouding may be required.
*Cabinet should be connected to the main earth and the cabinet door earth-bonded to the cabinet.
*Ensure sufficient working space, suitable access and adequate lighting.

Front 4

X-ray radiography is a non-destructive testing (NDT) technique that is sometimes used to examine the internal structure of fuel tanks in the wings of large passenger aircraft.
(a) Outline the principles of operation when using X-ray radiography for this application. (4)

Back 4

Radiation would be generated by a portable electrically powered machine such as a generator focussed into a beam by lead shielding. The beam would be directed to penetrate the wing skin to reach a film or electronic sensor placed inside the tank on the opposite side of the wing. An image of the intervening structure within the wing is created on film after photographic development or on the electronic sensor after electronic processing, with defects being revealed by the contrast between light and dark areas. The image has light areas where less radiation reaches the film or sensor after passing through unbroken or sound structure, whereas the image has darker areas where more radiation reaches the film or sensor through voids or cracks in a structural element which is faulty.

Front 5

X-ray radiography is a non-destructive testing (NDT) technique that is sometimes used to examine the internal structure of fuel tanks in the wings of large passenger aircraft.
(b) Other than visual inspection, explain why different forms of NDT might not be appropriate for this application. (4)

Back 5

*Gamma radiography would be impractical and too expensive;
*Eddy current can experience spurious defect indications and does not provide a permanent record;
*Dye penetrant shows only surface cracks with accessibility to tanks being impossible;
*Magnetic particle testing does not work on non-ferrous metal and there would again be the problem of tank inaccessibility;
*There would be no indication of fault location from tap testing.

Front 6

X-ray radiography is a non-destructive testing (NDT) technique that is sometimes used to examine the internal structure of fuel tanks in the wings of large passenger aircraft.
(c) Identify TWO disadvantages in the application of X-ray radiography. (2)

Back 6

*Manual handling of heavy equipment.
*There is the possibility of exposure to x-rays.
*Training in interpretation skills is necessary for the operators and
*Its use is relatively expensive.

Front 7

Outline the key safety features of a facility that is to be used for the storage of highly flammable solvents in 200 litre drums. (10)

Back 7

*Bunding to contain spills, including a facility to collect and dispose of spillages;
*Building to be erected on an impermeable base with an adequate separation distance from other buildings and constructed of fire resistant materials with a light weight roof or blast panels;
*Facility for the segregation of materials;
*Adequate access and egress including a ramp to facilitate the handling of drums;
*Provision of high/low ventilation and of sprinklers/ fire extinguishers to be used in the event of an emergency;
*Clearance of vegetation round the storage area and finally security features such as the provision of locks and warning signs.
*Provision of an impermeable base and clearance of vegetation

Front 8

The use of a tower crane on a construction site must be notified to the Health and Safety Executive before it is brought into first use.
Outline the safety concerns in relation to the use of tower cranes on construction sites that have influenced the introduction of this legal requirement. (10)

Back 8

Mis-assembly of structural components, undetected component defects and a failure to carry out a pre-use inspection of the crane which would have identified defects such as the incorrect installation of the slewing ring and/or jib, and the mis-specification of the independent crane to be used in the erection.
Additionally, there were concerns regarding the inadequate support of components during extension or dismantling with stability being compromised during an extension operation often because of poor communication as a result of the distance from the ground.
There were also instances of inadequate clearance zones where more than one tower crane was used on a site and over flight of areas outside the curtilage of the construction site.
Finally there were concerns about the access to the control cab, often by climbing vertical ladders which required a high standard of fitness and that inadequate cab welfare such as heating and the ability to take refreshment might lead to human error.

Front 9

A storage tank requires inspection, cleaning and repair. It is 6 metres in diameter and 10 metres high and was previously used for storing leaded
petrol.
Outline the arrangements that should be considered in order to comply with the Confined Spaces Regulations 1997. (20)

Back 9

No person should enter a confined space unless it is not reasonably practicable to achieve the intended purpose without such entry.
Consider whether the work or any part of it, could be done without entering the tank for example by using remotely controlled cameras, robotic inspection systems or a cleaning lance operated from outside the tank.
If not possible, a safe system of work in relation to any of the relevant specified risks such
-fire and explosion and
-loss of consciousness due to asphyxiation or high temperatures.
to develop the safe system of work, a full risk assessment would have to be carried out where consideration would have to be given to the likelihood of flammable atmospheres from the previous contents of the tank, the possibility of air contamination from the cleaning or repair methods used and the build-up of heat within the tank. The assessment would also need to look at other issues from the work to be carried out including working from height and the toxic effects of lead.
Arrangements that the risk assessment might find to be necessary relate to the possible need to purge the tank with an inert gas, the use of forced ventilation, atmospheric testing before and during entry and the provision of personal protective equipment possibly including air-fed breathing apparatus.
Attention would also need to be paid to the requirements for electrical equipment (for example intrinsically safe or flameproof) and earthing arrangements.
If heat were to be a foreseeable problem, then consideration should be given to issues such as job rotation and fluid intake.
Additionally, consideration should be given to the prevention of falls from height and the means of access and egress in the event of escape and rescue.
Procedural arrangements would centre on the establishment of well-defined systems of work, the
implementation of an entry permit system, limiting the number of people working in the tank, communication with standby personnel and drawing up the emergency arrangements.
The emergency arrangements to be considered, and which should be in place before entry is allowed would include issues such as the provision and maintenance of cutting equipment, hoists for top entry rescue, fire-fighting equipment, personal protective equipment such as breathing apparatus, first aid facilities including resuscitation apparatus and liaison with the emergency services.
Additionally, arrangements should be in place to ensure that all personnel involved in the operation including the emergency response team, have received sufficient training in the work methods, the precautions needed and the procedures to be followed in the event of an emergency.

Front 10

(a) With reference to the Pressure Systems Safety Regulations 2000, explain what is meant by a ‘pressure system’. (4)

Back 10

A system comprising a pressure vessel, its associated pipework and protective devices; the pipework with its protective devices to which a transportable pressure receptacle is, or is intended to be, connected; or a pipeline with its protective devices, which contains or is liable to contain a relevant fluid but does not include a transportable pressure receptacle.

Examples of a ‘relevant fluid’ such as steam; a liquid which has a pressure 0.5 bar above atmospheric at the temperature of the liquid or at 17.5º C; a fluid or mixture of fluids which is at a pressure greater than 0.5 bar above atmospheric pressure when in equilibrium with its vapour at either the actual temperature of the liquid or at 17.5 degrees Celsius; or a gas dissolved under pressure in solvent contained in a porous substance at ambient temperature and which could be released from the solvent without the application of heat.

Front 11

(b) Outline FOUR examples of the mechanisms of mechanical failure in pressure systems. (8)

Back 11

Overpressure – occurs if pressure relief valves fail coupled with other devices failing. This will lead to the pressure level rising beyond safe working and design limits which normally lead to catastrophic results.

Hydrogen attack - occurs when hydrogen seeps into gaps in the molecular framework of the metal and causes stresses from within the framework causing embrittlement.

Overheating – can occur if alarms and controls fitted to prevent this have not been tested or maintained or inappropriate controls have been fitted originally.

Creep - when a material is under constant load or stress, it may undergo progressive plastic (permanent) deformation over a period of time. This time dependent deformation is called ‘creep’

Abnormal external loading – occurs when being struck by something like fork lift truck or fuel delivery vehicle causing concentrated stresses from the impact.

Corrosive failure – occurs through chemical or electro-chemical attack by atmosphere, moisture or other agents causing deterioration of a material.

Front 12

(c) Outline the technical AND procedural measures to minimise the likelihood of failures in pressure systems. (8)

Back 12

*Correct design specification ensuring the system was fit for purpose;
*Fitting specific safety features such as pressure relief valves and level sensors;
*Ensure quality control during the manufacture;
*Introduction of inspection and maintenance procedures including statutory examination with the scheme of examination being prepared by a competent person;
*The role of non-destructive testing; ensuring the system operates within its design parameters and, in the case of boilers, the filtering and treatment of water.

Front 13

(a) Describe the effects of a fire in a workplace on the following structural materials:
(i) steel; (4)
(ii) concrete; (4)
(iii) wood. (4)

Back 13

(i) Steel expands - it also conducts heat, and therefore materials away from the source of fire can be affected, and it becomes weaker as the temperature rises, potentially causing plastic deformation and buckling. It may regain its strength on cooling, but its load-bearing properties may change.

(ii) Concrete has limited expansion and acts as an insulator at lower temperatures. Concrete surfaces can spall and break away when heated. If there is steel reinforcement in the concrete this acts as a conductor, expands and increases spalling. Structural strength and integrity is lost on cooling.

(iii) Wood thin sections will burn and promote fire the charred surface of thicker structural members may act as an insulator to protect the inner timber. However, burning timber generates smoke and fumes and allows the surface propagation of fire. Some varieties of timber are more resistant to fire than others while large timbers generally tend to retain their structural integrity.

Front 14

(b) Outline the precautions that could be taken to prevent failure of these materials in the event of fire. (8)

Back 14

Steel can be insulated with sprayed concrete. Compartmentalisation can be used to control the consequences of heat transfer through steel, or over-engineering to compensate for loss of structural support.
Concrete can be specially selected for fire resistance, as can timber. Increasing timber thickness to allow for a charring layer, or impregnating timber with fire retardant material, will improve its fire resistance. In addition, intumescent coatings and non-flammable surface cladding, such as plaster board, will also give added protection.

Front 15

Part 4 of the Construction (Design and Management) Regulations 2007 require that certain places of construction work are to be inspected by a competent person.
(a) Identify:
(i) when statutory inspections of supported excavations must be carried out; (3)
(ii) the information that should be recorded in a statutory excavation inspection report. (5)

Back 15

(i)
An excavation must be carried out at the start of every shift before work commences, after an event that may have affected the stability of the excavation and following an unintentional fall of material.
(ii)
*Name and position of the person making the report.
*Name and address of the person on whose behalf the work was carried out.
*Description of the place of work inspected including the plant and equipment in use
*Date and time of the inspection.
*Details of any matter identified that could lead to risk, the action to be taken to prevent the risk and the details of any further action necessary.

Front 16

(b) Outline the particular features of an excavation that could result in it being considered unsafe. (12)

Back 16

*Its proximity to adjoining structures.
*Inadequacy or incomplete nature of the means of support for the type of soil where the excavation was sited.
*Damage to or the dislodgement of the supports provided such as metal sheets or walings.
*Presence of excess water either from damaged pipes or land drains.
*Damaged services and the presence of fallen rock, earth or other materials in the excavation.
*Failure to provide adequate means of access and egress.
*Presence of spoil or materials placed too close to the edge of the excavation.
*Failure to provide stop blocks despite the use of vehicles in close proximity to the excavation.
*Presence of gas or fumes or biological or chemical hazards and a failure to provide adequate barriers and
*Warning signs to prevent persons from approaching and falling into the excavation.

Front 17

(a) With respect to UK mains voltage electricity, outline the factors that determine the severity of the effects of an electric shock. (6)

Back 17

The voltage, the nature of the current (whether alternating or direct), the body resistance of the individual with reference to age, gender, the amount of moisture (perspiration) on the body and the type of footwear worn, the route taken by the current through the body, the speed of action of any protective measures and the environmental conditions, such as the floor material and the presence of water.

Front 18

(b) For EACH of the following protective devices, describe their principles of operation:
(i) residual current devices; (3)
(ii) fuses; (3)
(iii) 110v centre tapped to earth reduced voltage systems. (3)

Back 18

Residual current device is designed as a shock limiting device and not for system protection.
It operates on an earth leakage fault. Any differential in the current passing through the line (neutral) and phase (live) conductors is detected, operating a switch to cut off the electrical supply to the apparatus and preventing severe electric shock. The nominal operating current is 30mA and the device should operate within 30 to 50 milliseconds of the fault being detected.

A fuse is a device placed in the live side of a circuit, designed to automatically cut off the power supply to the circuit within a given time when the current flow in the circuit exceeds a given value and produces sufficient heat to melt the fuse which is designed to do so at a predetermined temperature. It prevents the overload of an electrical system and overheating of electrical wiring. However, its speed of operation is generally too slow to protect people from electric shock. There are still candidates, however, who claim that fuses are a protection device for humans rather than the system.

One of the better ways of reducing the risk from electricity is to reduce the voltage, achieved by the use of a step down transformer. A common reduction is to 110volts and a transformer used to attain the reduction is described as centre tapped to earth in that the secondary winding of the transformer is earthed to its centre thus ensuring that the maximum voltage from live to earth involved in an electric shock will be 55 volts.

Front 19

(c) Outline other design features of electrical systems intended to improve safety. (5)

Back 19

*Selection and colour coding of cables and placing them out of reach wherever possible;
*Provision of effective means of isolation to ensure the secure disconnection and separation of electrical equipment from every source of energy;
*Use of earthed systems and Class 1 equipment or double insulated Class 2 equipment;
*Use of circuit breakers and the introduction of earth free zones.