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23 Cards in this Set
- Front
- Back
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Exothermic chemical processes rely on efficient control of temperature and pressure to prevent the phenomenon of 'runaway reaction’ (thermal
runaway) when mixing chemicals in a reactor. Outline the methods used to control temperature and pressure in such circumstances. |
*Install high integrity temperature detection linked to the cooling and reactant addition systems with pressure rise detection linked to cooling, venting or auto shut-down
*External cooling of the reactor by chilled water jacketing, an air cooled heat exchanger or the use of material with high heat conductivity in the construction of the reactor or internal cooling by the use of water or fluid refrigerant cooled coils. *A further method would involve the control of the reactant by pre-chilling it, limiting the rate of its addition to the reactor, controlling the subsequent reaction by high efficiency temperature detection loops and the depth and level of reaction by pocketed thermal probes. *Prevention of reactant bulk insulation can be prevented by efficient mixing with a mechanical stirrer while it would be advisable to locate the reactor away from external sources of heat and to introduce a system of regular internal cleaning to prevent the build up of insulating residues. |
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(a) In relation to automatic fire detection and alarm systems, outline
the basic principles of operation of: (i) heat detectors; (ii) smoke detectors. |
Heat detectors:
*Fixed temperature detectors use a thermocouple or other device to detect a set temperature. *Rate of temperature rise use electronic circuitry to detect an abnormally fast temperature rise. Smoke detectors: *Optical detectors detect the obscuration or scattering of a light beam by smoke particles. *Ionising detectors respond to the electrical current generated by ionising of smoke particles by a radioactive source |
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(b) Identify the circumstances in which EACH type of detector
would be inappropriate. |
Heat detectors:
Inappropriate where sudden temperature changes might be experienced in normal circumstances, or where there might be slow burning materials Smoke detectors: Inappropriate where the detector might be affected by smoke, steam or vapour in a non-fire situation such as in kitchens and hotel bedrooms |
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(a) Outline the principles of gamma radiography.
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Gamma radiography uses the transmission of gamma rays from a sealed ionising radiation source (isotope) through a test object onto a film placed on the opposite side. The film records the intensity of the radiation received and since cracks and flaws are hollow, a greater intensity of rays pass onto the film showing up defects as darker regions
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(b) Outline the advantages and disadvantages of gamma radiography as a form of non-destructive testing.
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Advantages
*Internal defects can be identified *Produces a permanent record of the test *Can be used to test most materials *Has an in-situ capability *Coupling with the surface of the test piece is not required Power source not required Disadvantages *Requires full compliance with the requirements of the Ionising Radiation Regulations *Poses a radiation exposure hazard to operators requiring specific SSOW to be implemented *Can be time consuming, expensive and there is a delay in obtaining the results *Equipment can be bulking and difficult to move *Specialist operators are required and staff to interpret results *Results may take a long time to receive *Can be an expensive process to run |
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The Lifting Operations and Lifting Equipment Regulations 1998 specifiy fixed intervals between thorough examinations of lifting equipment but also includes an option for thorough examination to be carried out in accordance with an ‘examination scheme’. Outline the factors that a competent person would need to take into account when deciding whether less frequent examinations might be justified.
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*Age of the equipment
*Standards and specifications to which the equipment had been designed and manufactured *Quality conformance of materials at the time of manufacture *Manufacturers’ recommendations on testing, inspection and maintenance and whether there has been compliance with these recommendations History of the equipment: -Extent of use -Loads lifted -Environments in which it has been used and *Current and anticipated future use *Equipment’s history of accident, breakdown and repair *Equipment’s records of modifications, alterations and the fitting of replacement parts *Typical performance history of similar items of equipment *Records of previous thorough examinations *Any insurance company requirements. |
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The residents of a village have recently been affected by a fallout of dust on their cars and property. They allege that the dust comes from a cement works situated a few miles away. Outline the steps that should be taken by those responsible for the cement works in order to investigate whether emissions from the works are the cause of the problem.
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Management to conduct desk top survey (feasibility study) involving residents to look at:
*Historical records *Weather patterns *Links with wind direction *Identification of other potential sources of dust in the area *Check plant for obvious faults and conduct continuous monitoring of the emissions on site together with offsite background monitoring (background) *Conduct analysis of dust collected from village to establish if it matches that produced from plant *Consult and liaise with officials from the Local Authority as well as Environment Agency or the Scottish Environmental Protection Agency dependent on the location of the works *Check supervisor reports over period of alleged fall out for abnormalities in process/ check maintenance logs for break down e.g.. LEV systems |
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In relation to a newly designed machine that falls within Schedule 2 Part 4 Annex (iv) of the Supply of Machinery (Safety) Regulations 2008, outline the procedures that must be followed, and the requirements that must be met, before such a machine is placed on the market for sale in the European Economic Area.
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*Machine designer/manufacturer to ensure the machine satisfies the Essential Health and Safety Requirements (EHSRs) by reference to relevant EN standards and to compile a technical file.
*If the machine is found to be safe, and has been designed and manufactured according to EN standards, the manufacturer may either ensure that the machine is manufactured in accordance with the technical file by carrying out internal checks or develop a quality assurance (QA) system and have it approved by an approval body or obtain EC type approval from an approval body. *When any of these procedures is completed satisfactorily, the approved body issues either an EC type examination certificate or approval for the quality assurance system. *If the machine is not designed and manufactured according to EN standards, the manufacturer may again either develop a QA system and have it approved or obtain EC type approval from an approval body. A successful completion of either of the above will again result in the issue of an EC type examination certificate or approval for the QA system. *Manufacturer should ensure the machine conforms with other non-machinery directives before issuing a declaration of conformity and fixing the CE mark to the machine |
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A company has been contracted to undertake maintenance work on the
roof of a building that is partly constructed of fragile material. (a) Identify the characteristics of the fragile material that may contribute to the risk of falls through the roof. |
*Age/condition of the material - corroded, rotten or water sodden
*Type of material e.g. fibre board/asbestos *Thickness of the material *Span between roof support *Condition of fixing *Fragile material might well be camouflaged by deposits of dirt and other material. |
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(b) Outline the measures to be taken to minimise the risk to persons involved with the work.
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*Completing a full risk assessment of the operation
*Production of a method statement detailing the safe system of work to be followed. This would describe: *Proposed means of access to the area of work e.g. provision of scaffolds and crawling boards *Erection of edge protection comprising guardrails and toe boards to prevent the falls both of persons and materials from the roof *Identify areas of the roof containing fragile materials, to mark them with barriers or signs and to prevent falls through them by the use of covers *Provide safety nets and/or air bags under the areas of the roof, which contained fragile materials. *Use of safety harnesses with adequate fixing points might also be necessary *Arrangements for e.g. hoist to transport tools, equipment and materials to the roof and *Use of chutes should be considered for the removal of rubbish. *Use of competent personnel fully briefed and aware of the risks involved and the precautions to be observed and to draw up procedures to deal with any emergency that might occur *Erection of barriers and signs to prevent occupants of the building from passing beneath areas of the roof where work was being carried out and also members of the public from passing in close proximity to the building. |
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Contractors are required to work in a sewer chamber that is accessed via a vertical shaft. Due to their enclosed nature, the shaft and chamber may have to be categorised as confined under the Confined Spaces Regulations 1997. (a) Outline the hazards the contractors could be exposed to when undertaking this activity.
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*Unsafe access and egress and
*Working on slippery surfaces which could result in falls *Presence of gases and vapours either toxic and/or flammable and an atmosphere that was deficient in oxygen *Possibility of the sudden ingress of water which could contain chemical or biological contaminants *Hazard of working in a restricted space with low headroom *Poor standard of lighting *Danger of material falling down shaft *Possible presence of sharps in the sewer chamber *Thermal issues that might occur when working in hot or alternatively cold temperatures |
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(b) Outline the risks that would be classed as ‘specified risks’ under the Confined Spaces Regulations 1997.
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*Injuries arising as a result of a fire or explosion
*Loss of consciousness or asphyxiation arising from gas, fumes, vapour or a lack of oxygen *Drowning due to the increase in the level of liquid *Loss of consciousness arising from an increase in body temperature |
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(c) Outline the issues to consider when developing emergency arrangements that will be provided during this activity.
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*Carrying out dynamic risk assessments
*Raising the alarm and *Carrying out a rescue operation *Trained and competent emergency rescue team *Procedures for summoning the public emergency services if required and providing them with relevant information *Provide means of communication for those inside the chamber with those on the outside *Provide rescue and resuscitation equipment e.g. lifelines, lifting equipment and breathing apparatus *Provide PPE e.g. overalls, footwear and head protection for members of the rescue team *Precautions to be taken in the event of fire e.g. provision of fire extinguishers *Identify plant in the vicinity that may need to be shut down during an emergency rescue *Availability of first aid equipment and trained first aid personnel until the arrival of professional medical help *Ensure access to the point of entry for carrying out the rescue operation bearing in mind the possible remoteness of the site |
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An external lift on a construction site has an interlocked guard to prevent the lift operating when the gate is open. With reference to the diagram:
(a) identify the TWO types of switch shown (Switch A AND Switch B); |
*Switch A is wired normally closed and is a positively operated switch while
*Switch B is wired normally open and is negatively operated. |
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(b) identify the functional components associated with BOTH switches;
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*Cam follower or plunger
*Internal spring compressed from the bottom *Internal electrical contacts attached to the cam follower with the gate acting as the cam |
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(c) outline the normal sequence of operation for the electrically operated, cam-activated switch assembly when the gate opens and closes;
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*When the gate is closed the normal sequence of operations would be the depression of the plunger on switch B and the compression of the internal spring and the release of the cam follower on switch A causing de-compression of the spring. This would allow electrical contact to be made in both switches, so making the circuit and allowing the operation of the lift.
*When the gate is open, the cam follower on switch A is depressed and the internal spring compresses while the cam follower in switch B is released causing decompression of the spring. The electrical contact is broken in both switches thus breaking the circuit and preventing the operation of the lift. |
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(d) outline ways in which electrically-operated, cam-activated switches may fail to operate as intended.
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*Faulty installation with incorrect wiring
*Failure of or damage to the internal spring which prevents the appropriate contact being made; *Damage to other internal parts of the switch *Presence of debris or dirt within the body of the switch *Contact weld through electrical arcing; a misalignment between cam and cam follower or a wiring fault *Wear of or damage to parts such as a bent plunger *Damage due to a corrosive atmosphere and sabotage such as deliberate disconnection of wiring or the ‘taping up’ of parts to simulate activation by the gate. |
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In relation to dust explosions: (a) explain the conditions that must be present for a primary dust explosion to occur;
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*Dust must be combustible,
*Must be capable of becoming airborne and *Mixing with air and *Its particle size and distribution must be capable of propagating flame. *Additionally the concentration of dust must fall within the explosive limits, *An ignition source of sufficient heat energy must *Come in contact with the dust and the *Atmosphere must contain sufficient oxygen to sustain combustion |
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(b) explain the additional conditions necessary for secondary explosions to occur;
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*Dislodgement of accumulated dust from
*Horizontal surfaces within the affected building by the *Pressure wave and *Consequent air turbulence created by the *Primary explosion and the *Airborne suspension of *Combustible dust throughout the affected area which is *Ignited by the *Original primary explosion ignition source or by the *Combustion of products from the primary explosion or by *Any other ignition source with sufficient heat energy within the affected area. |
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(c) identify the causes and effects of the General Foods dust explosion, Banbury 1981;
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*Initial failure of a pneumatic conveying system which resulted in the overfilling of a holding bin.
*Air pressure caused the outlet filter to fail resulting in the emission and build up of a cloud of corn starch powder which was ignited by an electrical arc from a broken cable. *The explosion caused substantial damage to an external wall and nine men were injured. |
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(d) identify the design features that would minimise the likelihood and effect of a dust explosion.
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*Design the ducting and equipment to withstand the effects of an explosion
*Ensure that the ducting was dust tight *Provide LEV at points of transfer *Install explosion relief or suppression systems together with systems for suppressing fire *Use screw conveyors instead of pneumatic systems for moving materials *Provide a magnetic extraction system for removing metal from product fed to the plant *Interlocking equipment to prevent overfilling of vessels and over-pressurisation *Use instrument systems with integral emergency shutdown *Use intrinsically safe electrical equipment and bonding all metal work to earth *Prevent dust build up in the plant by the use of sloping surfaces and *Introduce a mechanised system for the humidification of the air |
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A corrosive substance has a flash point of 20°C. An electrical subcontractor has been employed to design and install the electric supply to an open air production plant which is used to manufacture the corrosive substance. This plant is located next to the sea. (a) Outline the aspects of this situation which the designer of the electrical supply must address to ensure that the installed system will be compliant with the Electricity at Work Regulations 1989.
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Mechanical damage:
*Caused by impact, stress and strain, abrasion, wear, vibration and pressure Weather impact, *Resistant to: effects of rain, snow loading and UV degradation from sunlight Adverse environmental contaminants *Damp, dirt, corrosive leaks, salt laden air and water and steam leaks, Flammable atmosphere *Present as a result of vapour leaks, spills and effluents Environmental factors relevant to the use and maintenance of the intended supply. *Lighting of switch gear and instrument panels and that provided for winter maintenance in restricted work spaces and during periods of low temperature |
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(b) Describe the types of fault that may be found in fixed electrical systems under such conditions.
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*Equipment unsuitable for wet or corrosive conditions
*Exposed live conductors, *Damaged or perished insulation *Damage to the protection on cable conduits. *Corrosion of parts e.g. transformer casings could facilitate the ingress of fluids resulting in short circuits *Poor earthing and a lack of earth continuity together with damage caused to the means for isolating the supply to parts of the plant *Inadequate excess current protection because fuses with incorrect ratings have been fitted. |
