C July 2006

Front 1

Unless appropriate precautions are taken, chemical reactions in a batch manufacturing process can give rise to conditions which can lead to a ‘runaway reaction’. (a) Explain what is meant by ‘runaway reaction’ and identify the conditions that may give rise to such an event.

Back 1

Where reactions involve the release of energy in quantities or at rates too high to be absorbed by the immediate environment of the reacting system the increase in the temperature causes a runaway reaction.

Causes - Failure of temp control (reaction cooling); Strong exothermic reaction; Presence of containment catalysis (speeds up reaction)

Front 2

(b) Describe the design and operational features of chemical processes necessary to prevent such an event.

Back 2

Design features - Conduct HAZOP study; Appropriate temperature control system e.g.. matrix cooler; High integrity temperature detection linked to cooling/reaction addition protection; Pressure rise detection linked to cooling/venting/auto shut down; Vessel protected by correctly sized bursting disc linked to safe haven e.g. secondary vessel to dump reaction to; Agitation of liquids to promote even temp distribution.
Operational features - High calibre of operator experienced and appropriate level of qualification to operate process; Ensure that maintenance activities/raw material handling don't introduce potential catalysis into reaction

Front 3

Describe the principles and the effects of a boiling liquid expanding vapour explosion (BLEVE). Give examples of actual incidents to illustrate your answer.

Back 3

Cylinder/container containing flammable gas under pressure e.g. butane pressure turns gas into liquid state; Valve opened reduces pressure turning liquid into gaseous state; Cylinder exposed to heat source e.g. caught in a fire liquids absorbs heat; Liquids starts to vapour and is vented off; Liquid level falls heat continues; Area of cylinder just above liquid level starts to weaken/thin with heat; Area unable to hold internal over pressure and ruptures.
Sudden release of contents resulting in - Blast wave (low); Radiation (thermal) high; Missiles travelling long distances
San Carlos July 1978 Mexico city - crashed over loaded road tanker - explosion - 216 Dead 200 Injured

Front 4

A company produces waste in the form of a hazardous sludge. Disposal of the waste is currently via a licensed contractor to a landfill site but this is becoming increasingly costly. Outline the various options that the company might consider to reduce the cost and environmental impact of dealing with the waste.

Back 4

Identify recycling opportunities at all stages of the process; substitute process materials for ones that give rise to a non-hazardous waste; improve production efficiency to produce less waste; treat waste on-site to reduce quantity (e.g. de-watering); treat waste to reduce hazardous properties; select waste contractors that can process the sludge; seek opportunities to exchange waste streams with companies that can use waste as raw material; explore other disposal means (e.g. incineration); explore becoming licensed to save costs.

Front 5

(a) Summarise the legal duties placed on employers by the Provision and Use of Work Equipment Regulations 1998 in respect of mechanical power presses that are additional to general machine safety requirements.

Back 5

Competent person to carry through examination of power presses guards and protection device; ensure it correctly installed and safe to operate; test of the power press, guard, protection device and closed tool to ensure it is working properly and give no indication of fault; Installation; routine examination;

Front 6

(b) Review the factors other than legislation that may have influenced the decline in the number of power press accidents over the last 40 years.

Back 6

Decline of the manufacturing industry; replacement of power presses by hydraulic and pneumatic presses; improved guarding and Non-Distructive Testing (NDT) techniques; increased interest in and development of health and safety management systems.

Front 7

(a) Explain the purpose of non-destructive testing (NDT) on items of plant.

Back 7

The purpose of non-destructive testing (NDT) is to check for faults (cracks etc) in components before they develop into total failure without affecting the integrity of the component.

Front 8

(b) Other than visual inspection, outline the principles, advantages and disadvantages of TWO NDT techniques.

Back 8

Impact or ‘tap’ testing involves detection of the change of pitch of reverberant sound after striking. It is cheap as no specialist equipment is required but it gives no indication of where the fault is and relies on individual sensitivity / skill.
Magnetic particle method involves coating the surface of the item involved to be tested with magnetic particles that may be in powder form or within a liquid. It is a simple and quick operation that is very sensitive to surface cracks and, in certain circumstances, can detect sub-surface defects, its drawback is that the interpretation of results may be difficult, particularly on the inside surface of a pressure vessel.

Front 9

Outline the health and safety issues which should be identified during a lighting audit of a factory which includes production, maintenance workshops and offices.

Back 9

Availability of natural light; Compliant with workplace (health, safety & welfare) regs; Requirements for pedestrians/vehicles; Close working tasks; Task specific lighting; DSE work station lighting; Avoidance of glare; Avoidance of stroboscopic effects with regard to rotating machinery; Equipment lighting to comply with PUWER requirements; Lighting fort non-daytime external areas; Emergency lighting; Level of luminance; Illumination ratio; Psychological effects; Maintenance, cleaning and testing considerations; Consideration of flammable atmospheres etc EX rating

Front 10

A three-storey building is situated with one side fronting on to a pedestrian walkway. The building is to undergo extensive maintenance to the external fabric which includes a sloping roof.
(a) Outline the safety aspects of the work that will need to be considered before work starts.

Back 10

Public safety - Falling objects; Screening; Segregations/barriers; Security; Fencing; Dust damping; Noise levels. Building workers safety - Safe systems of work; Provision of PPE; Fall protection; Scaffolding; Edge protection; Signage; Hazardous materials present e.g. asbestos
Plant and equipment requirements – Suitability; Availability. Welfare facilities – Washing; Toilets; Rest/eating etc. Storage of materials – Hazardous; Flammable; Housekeeping; Lay down areas
Traffic management – Deliveries; Plant; MEWPS etc. Emergency arrangements – Alarm; Muster points; Escape routes. Access & Egress - Maintenance workers; Pedestrians; Building workers; Vehicles

Front 11

(b) Describe, with sketches, the means of providing safe working places for those working at height.

Back 11

no answers

Front 12

During a fire drill exercise at a large multi-storey office premises, the majority of the occupants evacuated the building in less than three minutes. However, all of the people based in one area of the building, failed to leave the building until a further four minutes had elapsed.
(a) Outline factors that may have contributed to the delay in evacuation

Back 12

Human factors - Hearing disabilities; Belief that false alarm; Belief that above evacuating; Waiting for direct notification e.g.. phone call; Routine violations
Fire Alarm Design/maintenance – Quiet; Does not extend into all parts of building; Poorly maintained sounders; Faults within infrastructure leading to partial failure in some areas
Deficiencies in procedure - Difficult to understand; Poorly communicated; Not exercised; Poorly planned escape routes; Untrained staff
Execution of procedure - Delayed response to alarm; Staff not reacting quickly; Finishing of phone calls; Switching off equipment; Fire marshalls not following procedure; Blocked escape routes; Staff not trained; Poor response perhaps many false alarms have occurred in past

Front 13

(b) Describe the advantages of undertaking regular fire drills in workplaces.

Back 13

Regular practice of an evacuation procedure allowed compliance with legislation, smooth and quick evacuations in future and allowed occupants to be familiar with: the procedure and their duties, escape routes and the use of panic bars/bolts, etc, alarm signals and to react to future alarms in a calm and orderly manner. Targeted retraining or communication of the procedure; investigation into the need for amending the procedure; and investigation into the need for fire alarm redesign.

Front 14

(a) Outline the factors related to construction work that can increase the risks from electricity on a construction site.

Back 14

Working environment (including the weather), water, damp, soil or mud; damage by activities; severing/abrasion of cables due to nature of work; equipment supply by contractors (whose standards might vary); the possible temptation to use long trailing cables; damage by vehicles; the difficulties in managing a range of people and activities on site.

Front 15

(b) Describe the control measures that may be used to address the problems outlined in (a).

Back 15

Use reduced voltage systems, cordless equipment etc; use protective devises such as RCDs; have robust procedures to control the selection, inspection and testing of portable equipment and fault reporting along with control and co-ordination of equipment brought onto site; and cable detection.

Front 16

A company is planning a move from premises containing a ‘manual’ warehouse to one in which the warehouse contains automated order picking and automated guided vehicle (AGV) goods transfer facilities.
Identify and describe the risks which might be reduced by such a move, together with the new factors or increased risks which might arise from the changes.

Back 16

Risks Reduced - Manual handling; Pedestrian/vehicle collision; Racking Collisions; Falling objects less; likely to contact person; WAH access to racking; Reduction of noise; FLT collisions; Incorrect order picking
Risks Increased - Programming dangers (teachers); Interference in signal; Proximity sensors to prevent pedestrian contact; AGV collision; Guarding of order picking machinery; Dropped loads to be dealt with in automated area; Maintenance activities for equipment; Software failure

Front 17

It has been found necessary to repair the explosion venting system at the top of a 15 metre high grain silo on a farm. Fixed external and internal access will be required for fitters/welders.
Prepare a summary of the essential precautions to be taken before and during the repair work.

Back 17

Planning & Organising - Consider work to be carried out and devise RA & MS; Nominate supervisor for task; All workers briefed on general & specific risks; Suitable equipment for task e.g.. PPE, tools, access etc
Preparation of Silo – Emptied; Locked off to prevent filling movement of parts; Residue removed before hot works; Damped down
Confined space entry - PTW control; Ventilation; Trained staff; Emergency rescue plan defined and trained; Ensure suitable access and egress; Oxygen monitoring; Signage erected of work in progress etc
Working at height - Use of platforms; Handrails; Toe boards; Harnesses if required; Protection of fragile sections of silo top;
Working area - Excluding non-essential personnel; Erecting barriers; Sighting of warning signs