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Nebosh unit ic questions matrix - ans


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Nebosh unit ic questions matrix - ans

  1. 1. 1 NEBOSH UNIT-IC Questions Matrix S# - UNIT - S. # Questions Dates Element IC1 General workplace issues 1-IC1 - 09 A sewage drain has collapsed and it is necessary to inspect the damage prior to its repair. The inspection requires entry into a confined space 10 metres deep. OUTLINE the possible risks to those entering the sewer. Marks-10 - Restricted space for entry causing RISK of head injury, slip and trip, - Risk associated with the presence of gases and vapours either toxic and / or flammable - Risk of oxygen deficiency which could lead asphyxiation and /or suffocation - Working on slippery surface and the presence pipe, cables or tools which could result in falls - The possibility of the sudden ingress of water with the danger of drowning - The presence of chemical or biological contaminants either on the surface water or in the sludge deposited in the sewer with the risk of contracting illness such as weil’s disease. - Working in a restricted space with low headroom which might lead to musculoskeletal injuries. - Thermal issues such as heat exhaustion that might occur when working in high temperatures. - Contact with sharps with the resultant needle stick injuries - The ever present risk of entrapment which could be caused by the collapse of the sewer Jul 2012 Jan 2011 2-IC1-05 (a) OUTLINE the possible health and safety effects of inadequate workplace lighting. Marks-4 (b) OUTLINE the factors that should be considered to ensure that lighting in a workplace is adequate. Marks-16 a). Health effects includes: headache, visual fatigue , eye strain, blurred vision; -inadequate posture creating neck and backache to get adequate VIEW for the tasks to be performed. - Safety implications : likely to increase the incidents such as slip, trip and fall, striking with objects because of insufficient lighting arrangements causing unidentified objects – wrong type of lightings which are creating stroboscopic effects - Human error which may put others at risk - Factors that should be considered: - The type of work to be taken - The amount of precision required and whether tasks require general, local and/or localised lighting - The level of natural light available - The workplace layout giving attention to the effects of screens, furniture or racking - the considerations of those objects casting shadows - The different types and level of lightings required for stairs, corridors and outside security lights. - The level of lighting in adjacent areas in order to avoid the effects of moving from a strongly lit area to one which is dimly lit and vice versa; - The individual needs of the employee whether on account of age or disability - The possibility of glare on display screen - The colour and type of lighting fitted o prevent stroboscopic effects - The need for emergency lighting particularly for fire escape routes - The need for portable lighting when work has to be carried out in confined space - The ease of maintenance whether replacing spent bulbs or cleaning the light fittings for probable - All glazed windows and skylights used for the lighting of workrooms shall, so far as is practicable, be kept clean on both the inner and outer surfaces and free from obstruction, OUTLINE the health and safety issues which should be identified during a lighting audit of a factory which includes production, maintenance workshops and offices Jan, 2012 Jan, 2009
  2. 2. 2 3-IC1 - 01 A contractor is to repair the felt roofs of an office. OUTLINE the measures that should be taken to reduce the risks to workers and members of the public. -10 1-Selection of contractor 2– Risk Assessments, SSW, method statements 3– Access and egress 4– Correct use of ladders 5– Edge Protection / Fall protections 6 – Means for transporting tools, materials 7– Garbage chute – 8 Competent employees 9 – Precautions while handling gas cylinders 10– Precautions for possible contacts with hazardous substances such as tar, asbestos 11– PPE (knee pad etc) 12 – Additional measures / protection of public: Barriers, Signs at ground, Arrangement for vehicle movement – Restricted access / security, Traffic control / flagman. Jan -09 4-IC1 -02 A rectangular warehouse building (40m x 100m ground area and 18m high) was constructed on a structural steel framework, with a flat roof and coated steel walls. During a storm, the warehouse suffered a catastrophic failure of one of its long walls which in turn caused the collapse of the roof and buckling of the other walls. (a) OUTLINE the possible causes of this structural failure. -10 (b) OUTLINE the health and safety issues to be considered when planning the subsequent Demolition of the damaged warehouse. -10 - Cause of failure – 1.Exceeded the designed wind loading due to adverse weather, - 2.Overloading of structure by excess weight on roof due to accumulation of snow or rain water. – 3.Alteration to the structural members which had invalidated the original design calculations. – 4.Collapsing or nearby excavations and tunneling operations creating instability – 5. Vibrations caused by the volume of passing traffic 6. Wind variations which would result in fatigue. – 7. Poor workmanship - Even superior quality materials, if used imperfectly, may not successfully serve the planned function, or be as durable as designed. -8. Faulty Construction- occurs when inappropriate material is used for construction. Faults that result in structural failures include bad welds, improper torque used on nuts and bolts, sand that is too salty for concrete, bad riveting and inferior steel. -9.Bad Foundation - cause displacement which alters the stress distribution of the building so the construction and design are changed and no longer meet the necessary specifications. - Safety issues for demolition: 1-Selection of Demolition contractor (competency) 2– Risk Assessments, SSW, method statements 3– Access and egress 4– Correct use of ladders 5– Edge protection / fall protections 6.Identifications / insulations of buried services (EWG), 7. Inspection, examination and maintenance of plants / equipment 8 – Means for transporting tools, materials 9– Garbage chute – 10 Competent employees 9 – Precautions while handling gas cylinders 10– Identification, Precautions for possible contacts with hazardous substances such as lead paint, asbestos, 11. Protections of adjoining property 12– PPE 13 – Additional measures / protection of public: Barriers, Signs at ground, Arrangement for vehicle movement – Restricted access / security, Traffic control / flagman. Jan, 2009, Jan 2007 SSW – safe system of work EWG – electricit y, water, gas 5-IC1 -03 A company has been contracted to undertake maintenance work on the roof of a building, which is partly constructed of fragile material. a. IDENTIFY the characteristics of the fragile materials that may contribute the risk of falls through the roof. 5 b. OUTLINE the measures to be taken to reduce the risks to those involved in the roof work and those who may be affected by it. 15 a / Characteristics: The age and condition of material; The type of material such as fiber board, asbestos or polycarbonate and thickness; The sheet profile; The span between roof supports; The design of supporting structure such as the purlins; The July 2008
  3. 3. 3 condition of the fixings; The slippery nature of the surface and The fact that the fragile materials might well be hidden by deposit of dirt, grass etc. b/ 1-Selection of Demolition contractor (competency) 2– Risk Assessments,3. Consequent production of a method statement detailing the SSW, - 4. The SSW should be followed, which will include - Access and egress, access scaffolds, crawling board 5– Edge protection / fall protections - harness with suitable anchorage 6. Identification and demarcation of areas of the roof containing fragile 7. Demarcation can be done using barriers and signages 8- Suitable Cover can also be used to prevent fall through the fragile areas 9- Provision of Safety nets or and air bags under the areas of the roof which contain fragile materials can provide additional safeguards 10- Means / hoists for transporting tools, materials, equipment 11– Garbage chute – 10 Competent employees 11– PPE 12 – Additional measures / protection of public: Barriers, Signs at ground, Arrangement for vehicle movement – Restricted access / security, Traffic control / flagman 06-IC1 - 06 It is proposed to inspect, clean and repair the inside of a tank that is 6 metres in diameter and 10 metres high and which has previously been used for storing leaded petrol. OUTLINE the arrangements that should be considered in order to comply with the Confined Spaces legislation. Or, OUTLINE the steps that should be considered in order to enter this confined space and to carry out the work safety. The relevant specified risks in this case relate to fire and explosion, and loss of consciousness due to asphyxiation or high temperatures, works at height. A SSW is required for entering confined space, to comply with confined space legislation and to carry out work safely – To develop a safe system of work a full RISK ASSESSMENT needs to be carried out considering the likelihood of - Toxic effects of lead, - Flammable atmospheres from the previous contents of the tank - Air contamination from the cleaning or repair methods used - The build-up of heat within the tank – hazard associated with Working at height - Completion of the risk assessment would point to appropriate arrangements / preventive measures / precautions such as - Initial Arrangements - The need to purge the tank with an inert gas, - The use of forced ventilation, - Atmospheric testing before and during entry, and - The provision of PPE including air-fed breathing apparatus - The requirements for electrical equipment (e.g. intrinsically safe, 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. - The physical arrangements for working at height would need to be considered in terms of both prevention of falls from height and, means of access and egress in the event of escape or rescue. - Procedural arrangements would centre on the - Implementation of an entry permit - 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 would include issues such as The provision and maintenance of cutting equipment, - Tripod / Hoists, - Fire-fighting equipment, - PPE (e.g. breathing apparatus) - First-aid facilities including CPR apparatus and Liaison with emergency services Additionally, Arrangements should also be in place to ensure that all personnel involved in the operation have received sufficient training in the work methods, the precautions needed and emergency procedures. JUL 2008, JUL 2005 SSW – safe system of work 07-IC1 - 08 (a) GIVE the meaning of the term ‘confined space. Marks-2 (b) OUTLINE the factors that should be considered to ensure that emergency rescue arrangements for confined space work Jul 2007, Jul 2009
  4. 4. 4 are suitable and sufficient. Marks-8 Confined spaces are defined as ‘any place . . . in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk’ (i.e. of serious injury, drowning or asphyxiation). Or any enclosed o partially enclosed place such as a chamber, tank etc or other similar space in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk such as lack of oxygen or the possibility of drowning in free flowing solids. - Confined spaces include: Chambers, Tanks (sealed and open-top), Vessels, Furnaces, Ducts, Sewers, Manholes, Pits, Flues, Excavations, Boilers, Reactors and Ovens. - The risks identified and how an emergency rescue might take place and could include - o The means provided for emergency access / egress, o The equipment required e.g. Life lines, lifting equipment (Tripod / Hoist), air fed breathing apparatus, o Methods for raising the alarm with others outside the confined space e.g. Radio, personal alarms etc, to initiate rescue procedures o The availability of first aid assistance until the arrival of professional medical help. o Ensuring that there are persons present who are competent to undertake (CPR) resuscitation procedures, o The number and competence of those who would be involved in the rescue operation. o Precautions taken to protect rescuers from the risks to health and safety identified in the risk assessment o Precautions taken in the event of fire such as the provision of fire extinguishers; o Identification of plant which may need to be shut down during an emergency rescue and o Means provided for contacting public emergency services and supplying them with relevant information. o Training or refresher trainings for emergency personnel. 08-IC1 - 05 A vegetable packing plant employing 200 men and 60 women is about to open. OUTLINE the specific welfare arrangements that need to be provided before the plant opens. Marks-10 / 20 Sanitary Conveniences: Sufficient numbers of well-lit and ventilated sanitary conveniences - Maintained in a clean and tidy condition. - Provision of Toilet paper, a coat hook - Separate rooms or blocks for men and women (or capable of being locked from inside if the sanitary conveniences in the same room). Washing Facilities: Sufficient numbers of well-lit and ventilated washing facilities - Changing rooms and Showers to be provided and maintained in a clean, tidy condition - Supply of hot and cold or warm running water, - Soap and a means of drying Drinking Water: An adequate supply of drinking water with cups - Readily accessible, located away from sources of contamination - Marked conspicuously Accommodation for Clothing / Facilities for Changing Clothing: Clothing accommodation with a hook/peg located in a clean, warm, dry, ventilated place should be provided for each worker to hang their own clothes if not worn during the working day. - Changing facilities separate for men and women and contain means of drying wet clothing and separate storage of contaminated clothing - Decontamination facilities with shower and a clear division between clean and dirty areas JUL 2010 JUL 2008
  5. 5. 5 Facilities for Rest and to Eat Meals: Rest and eating facilities - Readily accessible, contain adequate seating and tables - Be maintained in a clean condition - Arrangement for preparing and heating food and for boiling water - Means or procedure for preventing contamination of the area where food and drinks are taken - Rest rooms and areas should be arranged to ensure that non-smokers do not have to be exposed to smokers - separate rooms/areas, prohibition. - Adequate Facilities for nursing mothers and pregnant women to rest. First aid facilities including trained personnel taking into account the number of persons employed and the proximity of emergency services 09-IC1-12 OUTLINE the main design features of a workplace designed to reduce the risk of injury associated with INTERNAL TRANSPORT. OR. OUTLINE the main design features of a ware housing operation design to reduce the risk of injuries associated with INTERNAL TRANSPORT. Features that could have been included are: - 1. SEGREGATION of vehicles and pedestrians. - Separate pedestrian access and egress; Inclusion of passing places and refuges; barriers, guard rails, raised walkways and curbs to protect pedestrians, and clearly marked crossing places. 2. TRAFFIC ROUTE should be sufficient width, on stable leveled ground, Suitable road surfaces; Design of layout to avoid sharp bends and blind corners and to avoid the need to reverse, through use of one ways systems. Provision Convex mirrors on blind corners to improve visibility; Route should have speed limit, speed retarder and suitable road marking. Provisions of hazard signs – to warn blind corners, crossings, low-head rooms or width restrictions. All the routes should be well lit – including color balance, avoidance of glare in the transitions area between inside and outside the buildings, - 3. VEHICLE Movements should be carried out in safe area with sufficient space and operatives provided with high visibility clothings. Vehicle should be fitted with reverse alarm and flashing beacon lights. Designated parking spaces to avoid congestion. 4. PROCEDURAL ARRANGEMENTS – control of visitors in the premises, training and certification for the drivers, prevention of unauthorized use of vehicles; training and information to pedestrians on the risks, selection for suitability and maintenance of vehicles , monitoring and reporting the defects, maintenance of traffic routes, enforcement of speed limits and the use of banksman will further reduce the risks. Protection of racking or other vulnerable items, to reduce the likelihood of items falling and to avoid from collision with moving vehicles. Provision of suitable and sufficient Jan 2008, Jan 2010 Q of Me.IC07. 01 END OF UNIT 1
  6. 6. 6 Element IC2 Principles of fire and explosion 10-IC2-04 Compartmentation in buildings consists of fire resisting doors, walls, floors, ceilings and windows. Window frames are potentially a weak point in this fire resistance. (a) OUTLINE how window frames made with the following materials might behave in a fire: (i) wood; Marks-3 ; (ii)metal; Marks-3; (iii)plastic. Marks-3 (b) IDENTIFY which of these window frame materials gives the best overall fire resistance. Mark-1 Jan 2012 July 2009 11-IC2-07 You have been asked to investigate a boiler explosion at one of your company’s sites. The maintenance manager has drawn you a sketch showing the position of the water column isolating valves at the time of the explosion (see below diagram will be given). (a) Describe the chain of events that could have led to an explosion due to the water column valve being closed. 6 (b) Other than the safety feature on the water column, identify FOUR other safety features that you would expect to find on the boiler. Marks-4 Jan 2012 July 2010 12-IC2-02 In relation to dust explosions: (a) Outline the conditions that must be present for a primary dust explosion to occur; Marks-4 (b) Outline the additional conditions necessary for secondary explosions to occur; Marks-4 (c) IDENTIFY FOUR factors that may affect the reliability of a nitrogen inerting system used in a powdered aluminium process; Marks-4 (d) IDENTIFY the design features that would minimise the likelihood and effect of a dust explosion. Marks-8 a. Conditions that must be present for a primary dust explosion: - The dust must be combustible – the concentration of dust must fall within the explosive limits – The ignition source must come in the contact with the dust – Sufficient Oxygen should be present in the atmosphere to sustain the combustion. (the dust must be capable of becoming air born and mixing with air, the particle size must be capable of propagating flame) b. Conditions necessary for Secondary Explosions: Dislodgement / Force removal of accumulated dust from horizontal surface within the affected building by the pressure wave and consequent air turbulence. Ignition: When lying dust is distributed by the primary explosion and form a second dust cloud , the dust cloud then can be ignited – By the combustion of products from primary explosion - By the heat released through the primary explosion - Any other source of ignition within the area with sufficient heat energy c. Factors that may affect the reliability of a nitrogen inerting system: The number and location of sampling points - The type and calibration of the sensors - The presence of containments in the system which could interfere with readings Inadequate provision of a safe means of shut down if oxygen levels are too high - The adequacy of supply of inerting gas - The number of locations where air can enter the plant or process and the reliability of the electronic control system d. The design features that would minimise the likelihood and effect of a dust explosion Jul 2012 Jul 2011 Jan 2009
  7. 7. 7 - The initial design of ducting and equipment to withstand the effects of an explosion, - Ensuring that the ducting was dust tight, - Providing local exhaust ventilation at point of transfer, - Installing explosion relief or suppression systems together with systems for suppressing fire, - Using screw conveyors instead of pneumatic systems for moving materials Providing a magnetic extraction system for removing metal from product fed to the plant, - Interlocking equipment to prevent overfilling of vessels and over pressurization, - Using instrument systems with integral emergency shutdown - Using intrinsically safe electrical equipment and bonding all metal work to earth, - Preventing dust build up in the plant by the use of sloping surfaces and introducing a mechanised system for humidification of the air. 13-IC2-01 A diesel engine is being used to power a machine in a potentially flammable atmosphere. (a) IDENTIFY the sources of ignition from the diesel engine. Marks-4 (b) OUTLINE the protection that should be applied to the engine to minimize the risk of an explosion. Marks-6 OR, (a) Identify the sources of ignition from a typical diesel-engined fork-lift truck. (b) Outline the protection that should be provided on such a truck in order to minimise the risk of explosion when it is required to work in a potentially flammable atmosphere. a. Source of ignition: Flame and sparks from the exhaust and inlet system – sparks arising of Trucks electrical system – sparks arises to static electricity – through over speeding / over loading – from frictions / surface temperature – Fuel get hotter than Flash point b. Precautionary measures: 1. Fitting of spark. Flame arrestors to prevent flash back to the atmosphere, - 2. Inspect, test and maintenance of electrical joints on diesel engine systems – 3. Electrical equipment on the truck should be suitable for zones 1 and 2 4. Electrical starters wired to plug and socket in a safe area. 6. Inspect, test and maintain cooling systems on diesel engine systems – 7. The use of a water jacket on the exhaust system together with thermal sensors and air cooling for ‘hot spots’ would provide additional protection. 8. Mechanical alternatives (e.g. fuel gauge) should be fitted where possible. 9. The use of electrically conducting materials for parts such as tyres and drive belts would reduce static build up 10 The engine and exhaust system should be designed in such manner that their surface temperature are always below the flash point of flammable substances – diesel etc. Jan 2011 Jan 2007N A process plant stores and use large quantities of a substance that has the potential for giving rise to an explosive atmosphere. OUTLINE a range of control measure which will minimize the possibilities of explosion. 10 marks - Avoid / minimize release by using enclosed systems and maintenance of plant to prevent loss of containment. - Control release at source by using early detection and auto shut off systems - Prevent formation of an explosive environment by using ventilation or inert atmosphere - In case of release – ensure that it is suitably contained, safely collected and removed to a safe place, or otherwise contained safe by use of bunding. - Emergency arrangement – for tackling major spillage. - Avoid ignition source by ensuring that areas are zoned, and flame proof electrical equipment are selected and used. a. Build of static charge is obvious – therefore all the storage tanks, pump needs to be properly grounded, suitable clothing, Safety shoes (anti-static) to be worn by the operatives. b. No Smoking policy must be adhered and PERMIT to Work system to be followed.
  8. 8. 8 - Avoid adverse conditions by protection of storage vessels against weather and vehicle - Finally ensure segregation of incompatible dangerous substances. 14-IC2-03 OUTLINE the principles of a vapour cloud explosion AND give an example of a major incident associated with a vapour cloud explosion. -8 OUTLINE the effects of a vapour cloud explosion. Marks-2 Or With examples of actual incidents, describe the principles and effects of a vapour cloud explosion. Principle: A vapour cloud explosion may be confined (in a tank, vessels or building etc) or un confined when released in large quantity in the air. - For Explosion to occur – The presence of flammable vapour concentration above the lover explosive limits, the source of ignition such as a spark, is required with energy greater than the minimum ignition energy. - The (unconfined) vapour cloud can travel large distances before igniting / explosion and Cloud dispersal may bring the mixture below the lower exposure limit depending on the condition - The vapour cloud may be produced by a rapid release of liquefied gas following vessel rupture due to overpressure and subsequent vaporisation. It may also be produced by an uncontrolled build-up of vapour above the lower explosion limit inside a vessel. The effects of Vapor cloud explosion: Overpressure, Fire, explosion, and thermal effects and debris over a wide area from confined vapour cloud explosion. In confined Explosion – vessel or containment rapture may occur resulting in a rapid release of liquefied gas. Example - The explosion in process vessels at the Hickson and Welch chemical plant In unconfined explosion – damage to people and property may be caused by pressure wave and thermal radiation – Example - the explosion in flixborough July 2010 Jan, 2008 With examples of actual incidents, describe the principles and effects of a BLEVE – boiling liquid expanding vapour explosions. Principle of BLEVE: A BELEVE (boiling liquid expanding vapor explosion) is initiated by an external heat source applied to a container of liquid. A drum of petrol on a bonefire is a simple example. The vessels loses containment, by rapture or pressure release valve opening, which vents the vapour with subsequent ignition. There is rapid spread of boiling liquid and vapour and a fire ball ensues. Effects: The explosion generates debris and missiles from the vessels and also a thermal radiation shockwave. The explosion of tanker carrying a flammable substance at the san carlos de la rapita Spanish campsite is a notable example. LPG cylinders in fire situation are a typical example. July 2012
  9. 9. 9 15-IC2-R The investigation of an accident at a food processor handling corn starch products concluded that the explosion had taken place in two stages, a preliminary explosion followed by a more severe secondary explosion. a) IDENTIFY the principles underlying the control measures that may be needed to prevent or minimize the effects of such an accident. b) For each of principles identified, suggest control measures which are based upon the principle. a. Principles needed to prevent or minimize the effects of such an accident. - Elimination of sources of ignition; Limitation of dust cloud generation and Minimizing harm by controlling explosion. b. Control measures to eliminate ignition sources are: - To ensure electrically conducting safety footwear is worn; - The use of non sparking tools and correctly rated ex electrical equipment; - No smoking; - Prevention of equipment hot spots; - Magnetic extraction of rogue ferrous metals; - Electrical bonding and earthing; - Carrying out an assessment to meet the requirements of relevant legislation (e.g. DSEAR The Dangerous Substances and Explosive Atmospheres Regulations 2002 of the UK) and; - Correct zoning of areas. Dust cloud suppression could be achieved by: - Damping down combined with the use of a pressure monitoring device; - Having LEV at point of transfer; - Use of an interlock to prevent overfilling of silo; - Good housekeeping to prevent dust build up and - Ensuring all ducting is dust tight. Controlling explosion could be by use of: Equipment that is able to withstand explosion; - Explosion relief venting and explosion panels; - Ensuring building integrity. ETA, RRC 16-IC2-05 In 1974 a plant in Flixborough, United Kingdom, producing highly flammable pressurized gas developed a leak on the fifth of six reactors. In order to continue production the fifth reactor was removed from service and a bypass assembly then installed between the fourth and sixth reactor. The bypass assembly subsequently ruptured and an UNCONFINED VAPOUR CLOUD EXPLOSION followed. (a) DESCRIBE the mechanism for an unconfined vapour cloud explosion. Marks-3 (b) OUTLINE the technical failings that contributed to this major accident. Marks-7 a. There were 6 numbers of reactors (R1 to R6), R5 got some repair works. Therefore to get the production continues it was decided to make some bypass pipe between R4 and R6. This decision initiated the trouble- and given chance to uncontrolled release of gas, cyclohexane, from that temporary pipeline which was used to bypass a reactor R5 taken out for service for repair. - On release the gas formed a flammable mixture in air within the explosive limits. - The large vapour cloud either immediately came across a source of energy or - Travel some distance to find an ignition source where it was quickly detonated causing rapid flame propagation. b. Probable technical failure: -The absence of professionally qualified mechanical engineer / work manager who could oversee the modification between R4 and R5. - A plant modification had been done without assessment of the potential consequences of its installation. - The constructed assembly was of unknown strength: Pneumatic test were carried out for leak testing and not in order to assess the strength of the assembly - Only limited calculation were undertaken on the integrity of the bypass line: The flow and pressure calculation were taken on straight pipe line not the fitted by pass dog leg pipe, No calculation had been taken for the dog leg shaped Jul 2009
  10. 10. 10 assembly to withstand the likely strains - No reference were made to any recognized standards - No drawing was proposed for the assembly - No reference were taken from the designers’ guidelines so that the bellows were used out of line without adequate support. - and insufficient support were provided for the newly installed pipework 17-IC2-05 In November 1984 the San Juanico gas storage facility near Mexico City exploded with catastrophic consequences. (a) OUTLINE the circumstances of the disaster. Marks-8 (b) OUTLINE how a Boiling Liquid Expanding Vapour Cloud Explosion (BLEVE) occurs with a gas storage vessel constructed of metal. Marks-8 (c) OUTLINE the immediate rescue and restoration measures that took place. Marks-4 a. Circumstances of the Disaster: At approximately 5:35 hours, 19 NOV 1984 a major fire and a series of catastrophic explosions occurred at PEMEX LPG terminal at San Juanico Near Maxico city. As a result some 5000 people died and 6000-7000 people suffered from severe burn and the LPG terminal was completely destroyed. - The terminal was supplied with LPG from 3 refineries on daily basis, The terminal was being filled from a refinery 400 km away. As on the previous day it had become almost empty. Two large sphere and 48 cylindrical vessels were filled upto 90% and 4 smaller sphere to 50% capacity. - A drop in pressure was observed in control room but the operator was unable to know the cause of such pressure drop, actually an 8 inch pipe between a sphere and a series of cylinders had raptured causing the release of LPG. This uncontrolled release was continued for 5-10 minutes. And the gas was accumulated around the surrounding tanks measuring 150m to 200m and 2m high, which was drifted to flare stack and exploded. - This resulted in numbers of ground fire. Also a series of BLEVE occurred four of SIX spheres and numbers of cylindrical vessels. Injuries were caused by radiated heat and burning droplets of LPG. b. BLEVE with a gas storage vessel made of metal: The gas such as butane and propane are stored under pressure in the liquid form in the metal storage vessels. When the valve to the vessels is open, the resulting drop in pressure restores the LPG in gaseous state. - BOILING LIQUID: If the vessels involve the fire, the liquid gas boils and the content of vessels will revert to gaseous state with a resulting increase in pressure inside the vessels. - EXPANDING: The pressure relief valve opens and vaporized liquid escapes causing liquid level in vessel dropped. The less liquid cannot absorb the heat and then the metal start to deform and weaken, ultimately rapture as result of ductile failure. - Vapour Cloud Explosion: The remaining contents burn out and vaporize under atmospheric pressure sending debris from the vessels to the surroundings area. The vapor cloud which includes the LPG droplets find the ignition source and EXPLODES. C. Following the explosion, some 4000 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 died. Jan 2010 July 2009 18-IC2-08 In 2004 at ICL Plastics Glasgow nine people were killed and 45 seriously injured by an explosion in the unventilated basement of a building. Liquid Petroleum Gas (LPG) had leaked from a crack in a corroded unprotected underground pipeline that had been laid 35 years earlier. The LPG leak had migrated into the building Describe how corrosion occurs in buried LPG metal pipework. Marks-6 Outline how buried LPG metal pipework can be protected against corrosion. Marks-4 Jul 2010
  11. 11. 11 (a) Excluding corrosion protection, outline additional factors to consider in preventing a recurrence of an explosion in similar LPG pipework installations. Marks-10 a. The corrosion in the buried LPG pipework is an electro-chemical process which is caused due to - Presence of moisture together with the possibility of containments in the soil, - The presence of corrosion cells such as pitting of the metal pipework, - The roles played by anode, cathode and electrolytes, - The liberation and transfer of electrons b. Protection against corrosion by - Wrapping with protective tape, Coating it with bitumen, Galvanizing, Sleeving with a dry envelop, Providing cathodic protection or a sacrificial anode c. Identification and prioritizing at risk installations such as o Those where hazardous features arise from the design and layout of the building; o where there are inherent hazards in the layout or the condition of installation and pipework such as the presence of unventilated voids o those which are least well maintained or located in the most corrosive soils o The older installations and the extent of their existing protection. o For inspection and maintenance of the systems, plan and drawings will be required, though it must be acknowledged that disturbing the pipe work may increase the risk of leaks. o There will also be a need for the introduction of a systematic programme of replacement of metallic pipes with polypropylene pipe and the condition of at risk systems will need to be monitored pending the replacement 19-IC2.10 new Many household aerosol canisters contain propellants that are a mixture of highly flammable materials such as iso-propane and iso-butane. These canisters are used for multiple purposes including cleaning products, furniture polishes, cosmetics, deodorants, (a) DESCRIBE how a fire and explosion may occur when large quantities of these canisters are stored in a commercial warehouse. Marks-5 (b) OUTLINE the fire precautions that could be taken to limit the spread of any resulting fire and explosion in such a warehouse. Marks-5 a. The canisters may have suffered damage for example to the valve or body of the canister, leading to loss of containment and the formation of flammable vapours which if between the upper and lower flammable limits can be ignited by a heat source, perhaps a nearby fire or hot work and even by direct sunlight. The canisters may then be propelled from their original position as projectiles as the radiant heat from the initial fire causes boiling of the contents of adjacent canisters. This causes the release and ignition of additional vapour sources resulting in multiple BLEVEs. a) b. Fire precautions that can be taken to limit the spread of any resulting fire and explosion in a similar type of warehouse include  The segregation of the canisters from other flammable products;  The separation of high flammability canisters by physical barriers;  Using compartmentalization within the warehouse with fire resistant partitions;  The provision of containment cages to prevent projectiles;  The installation of automatic fire detection and alarm systems;  The use of automatic extinguishing systems and venting and explosion reliefs.  The canisters should be fitted with pressure relief valves. July 2011
  12. 12. 12 END OF UNIT 2 Element IC3 Workplace fire risk assessment 20-IC3-02 OUTLINE the issues that should be included in a fire safety training session for workers. Marks-10 Presentation on training - 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; Fire Types / Classification - 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 fire such as RACE – raising alarm, alerting concerned/ procedure for calling fire services, and the action to be taken by personnel on hearing fire alarm (confined fire, evacuate) - The procedure for calling the fire service; - The action to be taken by personnel on hearing the alarm; - The location and use of firefighting equipment with practical training for selected employees - The escape routes and exits from the premises together with the assembly points - The head counts / roll call that would have to be carried out - The arrangements for the evacuation of people with disabilities, 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 behavior such as refraining from re-entering the building after evacuation until instructed to do so July 2012 Jan, 2010 Jan, 2008 21-IC3-05 A factory manufactures upholstery using fabrics and plastic pellets. These raw materials are delivered to a warehouse. The fabrics and plastic pellets are machined to form furniture coverings and cushions. The finished product is then stored in a dispatch warehouse prior to distribution. The movement of goods around the premises is carried out by Liquid Petroleum Gas (LPG) fuelled forklift trucks. The company is located on the outskirts of a small town and employs 230 people. OUTLINE the range of factors that must be addressed to ensure an on-site Fire Risk Assessment is made for the premises. 20 Fuel (LPG, flammable cover, untreated fillings, material of construction )– Ignition source(electricity, smoking, hot work, arson) – People issues (no of person to be evacuated, visitors, disabled employees) – Preventive actions (Compartmentalization, separate store for LPG-with fixed sprinkler, use of fire resistance cover materials, minimizing amount of combustibles ) – Mitigation actions (Detection – Suppression – Alarm system,)– Means of access (clear, fire doors, travel distance, sign and emergency light) – Assembly points. Jan 2012 July 2009 22-IC3-01 A four-storey general Hospital is to be refurbished and upgraded on a floor by floor basis, with three floors of the hospital remaining operational at all times. OUTLINE the factors to be considered when writing fire evacuation procedures for the parts of the hospital that remain operational during the project. Marks-10 - The various sections and activities of hospital – such as ward, operation theater, ICU, offices, outpatient, visitors etc. - The number of patient and staff to be evacuated - The mobility of patient including their health condition and age - Identifying the temporary procedure and means of route to evacuate the be ridden patient - Review ing the current evacuation procedure and considering the escape routes, assembly points and fire brigade access - Ensuring that the escape routes and assembly points are clear from construction materials - The provision of emergency lighting and appropriate sign ages - Considering of two stage evacuation procedure Jan, 2009
  13. 13. 13 - Considering the possibility of emergency zoning and classification for example – full or partial evacuation, area wise nearest assembly point as per zone (burz khalifa) - Assessing the effect of construction work on the existing fire detection system, Alarm and firefighting equipment and the possibilities that might increase the risk of fire. - Assessing the need for first aid provision and firefighting and fire protection provisions. - Adequate training for the existing hospital employees as well as the construction employees. 23-IC3-08 OUTLINE the issues that need to be addressed when planning a fire evacuation procedure for an office building occupied by a number of different companies. Your answer should include examples where appropriate. ERP for Al thurath 1. Identification of emergency scenario – such as Fire, Earthquake, Riot etc. 2. Selection for employees to form an emergency control team – Described responsibilities, - Adequate training to Fire warden , Security and other members 3. Means of Raising Alarm and Alerting Building occupants 4. Liaison with emergency services – such as their access requirements and appropriate locations of assembly areas. 5. Considering the health situation of occupants and member of visitors in the building , their sensory disabilities and physical disabilities etc. to be considered 6. Physical Measures – Such as travel distance, number of access, Emergency lights, Exit signs, Evacuation routes etc. 7. Firefighting Equipment – Alarm, Smoke detector, heat detector, Suitable Fire extinguishing media (DCP, CO2, sprinkler system, Hose reel etc.) 8. First Aid measures – First aid providers, first aid medicines, first aid equipment, CPR arrangements etc. 9. Emergency Rescue Equipment – Stretcher, Wheel chair etc. 10. Providing door marshals to prevent entry or re-entry to the store. 11. Security considerations such as minimizing the opportunity for theft would also be an issue. 12. Assembly points - Well defined, Displayed and communicated 13. The procedure, once drawn up, would need to be summarized on prominently displayed fire notices and tested with regular fire drills. ETA 27 24-IC3-02 A large shopping complex is arranged on four levels, with retail outlets on basement, ground floor and first floor levels and with restaurant facilities on the top level. Movement between floors is achieved by the use of escalators, lift and stair. LULU center i. Review, with valid reasoning, the systems that might be installed in the building to detect, suppress and warn of fire ii. Describe the design features of the building to assist in the safe evacuation of persons in the event of fire. i. Fire Detection System: might include Heat sensors in the restaurant areas, Smoke Detectors in general areas, Flame Sensors in furnishing areas and CCTV – closed circuit television to monitor throughout. Fire Suppression System: Sprinkler system, Provision fire hose reel, Portable Fire Extinguishers, Fire blankets in kitchen Fire Alarm System: could be automatically triggered on detection of FIRE, but controlled manual activation might be preferable to avoid panic situation. The alarm itself could be bells, sirens or verbal instructions over public addressing system. Consideration might be taken for zoning and a staged alarm system. ii. Design features of the building to assist in the safe evacuation of persons in the event of fire RRC – IC 3 –LA-Q 1
  14. 14. 14 - Escape routes – distance / requirements: The building design should primarily take the consideration of escape route distances and travel distances - Fire resistance of materials / Fire doors: Design features for evacuation should include escape route requirements such as fire resistance of materials used, and protection against fire and smoke using fire doors in staircases and corridors - Maximum numbers / location of persons on the premises: Account must be taken to the expected maximum number of the persons and their locations , such as higher concentration of persons in the dining areas – food court - Number and width of stair case: other design feature should include the numbers and width of staircases - Protected areas / Control of use of lifts : The need of protected areas and control of use of lifts, particularly for mobility impaired persons and fire fighters - Compartmentalization: would need to be considered, although difficult in common areas in an open plan store, and - Protection of dust and voids: Also protection of ducts and voids to minimize and content the spread of smoke - Smoke extraction: through automatic roof vents and sprinklers and auto shut off of the ventilation system in the event of fire - Signage / Emergency lighting: Finally signages would need to be provided and emergency lighting where appropriate. 25-IC3-03 (a) In relation to automatic fire detection and alarm systems, outline the basic principle AND operation of: (i) Heat detectors; Marks-4 (ii) Smoke detectors. Marks-4 (b) IDENTIFY the circumstances in which EACH type of detector would be inappropriate. Marks-2 i) Heat Detector: detects a rise in temperature two types of heat detectors – a. Self Resetting – (Fixed rate heat detector and rate of rise type) b. Fusible - Fixed rate heat detectors operate when a fixed, set, temperature is reached, / Has a sensing element fixed at particular temp. By means of a thermocouple or similar arrangement, it detects when the predetermined temperatures is reached - A rate of rise heat detectors operate when either the temperature rises at more than a certain rate, or when its fixed temperature is reached / detects abnormally fast temperature rises by means of electronic resistors or thermistors ii) Smoke detector: - Smoke detectors are of two main types: ionisation and optical (or photoelectric). - The ionisation type uses a small radioactive source, smoke passing into the detector is ionised, which is then detected by an electronic sensor. The detector reacts and sound alarm when the pre-set flow of electric current is reduced as smoke enters the detector. - The optical type of detectors are designed to operate by either - The absorption (obscuration) of light ray by smoke particles passing through them - The scattering (Refraction) of light from an optical ray. July 2011 July 2008
  15. 15. 15 26-IC3-04 A conference center is planning to extend its existing building to incorporate childcare facilities on the ground floor and additional conference rooms to hire out to local businesses on the upper floors. OUTLINE the range of factors that would need to be reviewed following completion of the planned work to enable the company’s fire risk assessment to be updated. Marks-20 DOHA Mall Fire case …relate to The Planning and Construction phase: The design of the extension need to be addressed, - The material used for the constructions, - Competent advise need to be obtained from the Fire Authority / civil defence, - And the means of access should be remain clear from any obstructions and maintained at all the time. On completion of the planned extension the additional risk factors would arises from the additional users such as: - The small children, - Worried parents in case of fire, - The extra persons on premises attending the events in conference areas, - The possibility that the delegates can be under influence of alcohol, - The allowance of smoking by the delegate in such areas. The above added risk factors would call for additional precautions such as - Escape routes - Procedures and conducting fire drills for children and delegates - Extension to the existing alarm system - Additional firefighting equipment, Emergency lightings, notices and signage - Requirements of additional fire marshal experience in handling children in event of fire for evacuation - Train employees in revised procedures July 2007 27-IC3-06 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. Fortune tower Fire incident (a) OUTLINE factors that may have contributed to the delay in evacuation. Marks-15 (b) OUTLINE reasons for conducting regular fire drills in workplaces. Marks-5 a. Fire Alarm: Fire Alarm too quit due to low volume; - number of fire alarm are insufficient; - Alarm may sound similar to other alarming system creating confusion among people; - Alarm may be inactive due to maintenance work; - signal of alarm may be weaken due to wall and doors or other obstruction. Design of buildings: inadequate escape routes which are greater than recommended travel distance; - too complex to traverse ; - too narrow slowing down the evacuation; less numbers of access comparing to strength of occupants; even blocked and locked; inadequate lighting or no emergency lighting in the escape routes; incorrect signs showing emergency exits; Deficiency in existing Evacuation procedure: FEP too difficult and complex to understand; - - the procedure may not be communicated adequately; -no or insufficient instructions for staff mentioned in the procedure; - actions / responsibilities are not well communicated; - fire marshal duties may not be well defined; - inadequate number of fire marshal deputed; - insufficient training / drills conducted for the occupants of the building. Execution / Compliance of Procedure: possible noncompliance of procedure during actual exercise ; - Delay in response to the alarm by finishing work, finishing telephone call, by shutting of PC, gathering their belonging or may be investigating why alarm sounded; No response at all Assuming the Alarm as FALSE alarm or a Drill. Human factors: hearing disabilities; physical disabilities; general apathy; lack of will to participate; lack of familiarity with the July 2010
  16. 16. 16 layout of the building. b. REASONS FOR REGULAR FIRE DRILLS: Quick evacuation; - Familiarity with procedure; - familiarity with evacuation routes, Alarm, assembly points and DO’s and Don’ts in case of such situations; - legal compliances; - Insurance requirements; - identification of troubles / defects to find out the scope for improvements; - Amendments in procedure to suit the requirements maintaining its efficiency and suitability. 28-IC3-07 21a-IC3-02 19-IC3-01 For a large supermarket with restaurant facilities: a) OUTLINE the automatic fire protection systems that should be in place; Marks-6 b) OUTLINE the factors to be considered when developing a safe means of escape for the supermarket. Marks-14 a) Fire Detection System: might include Heat sensors in the restaurant areas, Smoke Detectors in general areas, Flame Sensors in furnishing areas and CCTV – closed circuit television to monitor throughout. Fire Suppression System: Sprinkler system, Provision fire hose reel, Portable Fire Extinguishers, Fire blankets in kitchen Fire Alarm System: could be automatically triggered on detection of FIRE, but controlled manual activation might be preferable to avoid panic situation. The alarm itself could be bells, sirens or verbal instructions over public addressing system. Consideration might be taken for zoning and a staged alarm system. Automatic Fire service calls out through auto dialer or similar techniques. b) Factors to be considered when developing a safe means of escape for the supermarket.  The possible number of employees and visitors to be evacuated  The type of person such as their sensory disabilities and physical disabilities and age (old age, child) etc. to be considered  Means of Alerting and evacuating people through Public address system  The distance of fire evacuation routes; and the numbers of such routes  Ensuring that the escape routes and assembly points are clear from any obstructions.  The provision of emergency lighting and appropriate sign ages for demarking the exit routes from super market and restaurants, being sufficiently separated to avoid confusion  Assembly points - Well defined, Displayed and communicated and always free from any obstructions  Liaison with emergency services – such as their access requirements; without obstructing assembly areas and access to the buildings  The Appointment of trained Fire Marshals who can ensure clear escape routes and trained in evacuating people in safe manner.  Providing door marshals to prevent entry or re-entry to the store.  Security considerations such as minimizing the opportunity for theft / vandalism/sabotage.  The procedure, once drawn up, would need to be summarized on prominently displayed fire notices and tested with regular fire drills. Jan, 2011 29-IC3-09 OUTLINE the design features of a building intended to control the spread of fire and smoke.  Fire resistance of materials: Design features to control the spread of fire should include escape route requirements such as o fire resistance of materials used in the construction of walls, floors and o Provision for Fire protection (insulation) for structural steel works – ERCO edible oil factory o The treatment of timbers such as fire rated / retardant ETA 24
  17. 17. 17  Protection against fire and smoke using fire doors in staircases and corridors o Fire resistance closures at stairways and lift shafts o Compartmentalization: would need to be considered, although difficult in common areas in an open plan store, and o Fitting doors with intumescent stripes  Protection of dust and voids: Also protection of ducts and voids (in roofs and ceilings) to minimize and content the spread of smoke; Fire dampers and breaks in ducting  Smoke extraction: through automatic roof vents and sprinklers and auto shut off of the ventilation system in the event of fire. 30-IC3-10 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 design factors to be considered in providing an adequate sprinkler system for the facility.  Arrangement for testing the system  The means of activating the system (frangible bulbs or detector activated);  Linking of the sprinkler to the fire alarms  The need for a voting system to reduce the likelihood of false activation  Protection of electrical system in the warehouse  The capacity of water required, ; - The existence of an adequate and assured water supply and  The provision of fire water runoff  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.  The area to be covered and the presence of other combustibles apart from the stationery;  The fire loading of the area to be protected  Fire stopping for sprinklers and pipeworks passing through compartmentalization  The spray pattern required; Will the system be dry or wet  The height of the storage racks and their distance from the sprinkler heads; ETA 26, Jan 2007N 31-IC3-11 As Health, Safety and Environment Manager at a hazardous installation you are responsible for emergency planning. The site is regulated under the International Labour Organisation (ILO) Code of Practice ‘Prevention of Major Industrial Accidents’ 1991. (a) In the event of an uncontrolled release OUTLINE the need for emergency response measures. Marks-4 (b) OUTLINE the general emergency planning measures that should be taken by the ‘competent authorities’ in association with the works management of the installation. Marks-6 The event of an uncontrolled release, there would be - a need for emergency planning to localise the release and if possible, contain it; and to minimise the harmful effects of the release on people, property and the environment both inside and outside the installation by the use of safety systems, alarm systems and the emergency services. - Clear and well defined plans should be made available for quick and effective use and - Where emergency equipment and manpower are limited, provision should be made for mutual assistance between neighboring industrial activities. July 2011 July, 2009
  18. 18. 18 General emergency planning measures that should be taken by the competent authorities include - The need: to establish arrangements for an on-site emergency plan which should be drawn up by the management of the installation; - To establish arrangements for an off-site emergency plan to be drawn up by the competent authority in conjunction with the installation’s management, which should be prepared following consultation with various bodies such as the fire and police authorities and the hospital and ambulance services and which should be consistent with the on-site emergency plan; - to ensure that regular rehearsals were carried out in order to keep the off-site plan in a state of readiness and also - to ensure that information on safety was provided to members of the general public. END OF UNIT 3
  19. 19. 19 Element IC4 Storage, handling and processing of dangerous substances 32-IC4-03 BBB As part of a water treatment system, a manufacturer is to install a plant suitable for the reception and storage of sulphuric acid and caustic soda, both of which will be delivered in road tankers. These substances are highly corrosive and can react violently together. SULB Water treatment plant OUTLINE the safety provisions required for:  The design; Marks-10 (b) The operation; Marks-6 (c) The maintenance of the proposed storage facility. Marks-4 During Design ( Technical Req)of proposed plant:  The need for the storage tanks and pipe work to be constructed of suitable chemical resistant material;  The design, positioning and marking of the delivery inlets to prevent connection being made to the wrong tank;  Bunding must be provided around the storage tanks – the bunds must be capable of holding the entire contents of the tanks plus 10%;  The erection of hazard warning signs clearly identifying the contents of the tanks and the colour coding of pipe work;  The fitting of level indicators and high level alarms to prevent overfilling;  The provision of good vehicle access including a hard standing for tankers with facilities for spill containment  Provision of earthing and bonding for the tanker, connection and hoses  Measures to avoid the tanker being driven away whilst still connected and During Operation( procedural req)of proposed plant:  The introduction of a safe system of work including emergency procedures to deal with spillages  The provision of drench showers and eyewash stations and a good standard of lighting.  The provision and maintenance of a contingency supply of neutralizing and absorbent materials and water;  Providing training for the personnel involved including tanker drivers in the risks associated with the operation and the control measures to be followed and  The provision of PPE such as chemical suits, chemical resistant gloves and full face protection. During Maintenance of proposed plant:  The arrangements for the examination and testing of safety critical plant; The use of permit to work systems;  The completion of the flushing out of tanks and pipe work and their isolation before the start of maintenance work;  Regular cleaning of the bunds and The provision of training to maintenance staff in emergency procedures July 2012 July 2009 Jan 2008 Jan 2008N Jan 2006N 33-IC4-R- SAQ3 32-IC4-11 BBB Same Q repeated IC8-03 A road tanker is to be filled with petroleum (gasoline) at an installation. (a) IDENTIFY FOUR hazards associated with this operation. Marks-4 (b) DESCRIBE how a vapor cloud explosion could be generated in this situation. Marks-4 (c) OUTLINE practical ways of minimizing the risk of an electrostatic charge. Marks-4 (d) OUTLINE control measures that could reduce risks with road tanker filling. Marks-8 Or, An extremely flammable liquid is being transferred from a road tanker to a bulk storage tank. a. OUTLINE the control measures which would reduce the risk of ignition of the associated vapour due to static electricity. Marks-10 Jan 2012 July 2008 July 2010
  20. 20. 20 Tanker drivers are routinely required to work on top of road tankers during transfer operations. b. OUTLINE the factors that should be considered when assessing the risk for work on top of the road tanker. Marks-10 Or, Identify the safety features needed to protect against ignition by static electricity of the vapour of an extremely flammable liquid while it is being transferred from a bulk storage tank to a road tanker. 10, JUL 2008, Jul 2010 a. Practical ways of minimising the risk of an electrostatic charge - The use of tankers and pipework with high conductivity; Earthing the pipework and tanker and bonding to the same electrical potential. ; Reducing the velocity of the filling or draining operation by controlling the pump rate - Reducing constrictions by the smoother pipe unrestricted by strainers - Avoid splash filling or water contamination in pipe; Increasing the relaxation time by using longer pipework - Add anti-static additives ; Nitrogen blanketing of the road tanker to minimise the risk of explosion - The uses of a vapour return system to improve containment.; The provision of instrumentation to detect earth leakage - Using antistatic clothing and footwear b. Control measures that could reduce risks with road tanker filling - Preparation of written procedure and instructions; The identification of specified entry and exit routes - High level of communication and cooperation between tanker’s driver and the site operator - The use of pumps, hoses and other equipment which are suitable for the purpose, properly installed and regularly maintained - Fitting devices such as a high level alarm to prevent overfilling - The erection of barriers or the use of bollards and warning cones to prevent a collision - Installing a system to prevent tanker driving away to prevent the tanker driving away if hoses are still connected - Ensuring the tankers are positioned correctly with wheel chokes and hand brake applied - Ensuring hoses are coupled without submitting them to abnormal stress and valves operated in accordance with lay down procedure - Switching off electrical equipment which was not required for filling such as mobile phone and bonding and equalizing the potential between the tanker and fixed installation - Using bottom loading tankers in preference to those which are top loaded but if this is not possible ensuring that the top loaded tankers have a fill pipe which touch the bottom of the tanker and handrails or fall arrest equipment is provided to prevent falls - Finally preparing procedure to be followed in the event of the emergency and ensuring that all workers are fully aware about
  21. 21. 21 34-IC4-R- SAQ1 BBB A chemical company is involved in the bulk storage and transport of concentrated solutions of sodium hydroxide. OUTLINE the technical and procedural requirements needed to ensure the safety of these activities. 10 marks Technical issues relate to Design of Tanks, The Filling Operation with the tanker whereas - The presence of corrosive alkali and therefore, the tank and tanker should be made of suitable chemical resistant material that will not be corroded, such as stainless steel. - Avoid incompatible substance such as ACID, the location of Alkali storage should not be adjacent to any incompatible substance (ACID). - Bunding must be provided around the storage tanks – the bunds must be capable of holding the entire contents of the tanks plus 10%; - Usage of double skinned tanks; The erection of hard standings for vehicles and anti-collision barriers around the tank. - The fitting of level indicators and high level alarms and possibly a trip system to prevent overfilling; - Installing a system to prevent tanker driving away to prevent the tanker driven away if hoses are still connected - The erection of hazard warning signs clearly identifying the contents of the tank and tankers and the colour coding of pipe work; Procedural Issues will include Emergency Procedure, Training, PPE and Maintenance. - Chemical analysis prior to re-stocking, to avoid filling with incompatible materials - There must emergency procedures to deal with spillages or other emergencies - The provision absorbent materials and water; - The provision of drench showers and eyewash stations and a good standard of lighting. - Providing training for the personnel involved including tanker drivers in the risks associated with the operation and the control measures to be followed - The provision of PPE such as chemical suits, chemical resistant gloves and full face protection. - Provision for maintenance of plant- PTW and isolation of stored energy, vehicles and flexible pipe works - Since materials are being transported by tanker, there would be a need for safety advisor for dangerous goods. 35-IC4-R- SAQ2 With the aid of fully labeled diagram, IDENTIFY the key safety features of a building to be used as a facility for the storage of highly flammable solvents in 200 litre drums. The storage facility - The building of the storage facility should be constructed of non-combustible and fire resistant materials - An impermeable / solid base to be constructed; - Bunding must be provided to contain spills; Facility for collection / disposal of spillage - Light weight roofs and blast panels / fire explosion vents to be ensured - High or low level ventilation ; - Adequate separation distance from other buildings
  22. 22. 22 - Adequate provision for access and egress, including emergency escape and ramps to facilitate handling - Door locks and security – to avoid arson ; suitable warning / hazard signs and instruction displayed - Indication of zone classification; Facility for external electrical isolation. Fire safety / precaution - Segregation of incompatible materials; Sprinkler system or provision of fire extinguishers - Flammable vapour monitoring system and alarm 36-IC4-05 OUTLINE the factors to consider with respect to the design, construction and use of store room that is to be used for the storage of bulk stocks of palletized containers of highly flammable paints and thinners. 20 As far as design and construction of storeroom were concerned the following factors such as – - The construction of storeroom on an impermeable / resistant base with fire resistant materials with a light weight roof or blast panels - The provision of buildings to retain any spilled liquid; The provision of high / low ventilation - The provision of adequate separation from occupied building ; Segregation from traffic / evacuation routes with the use of fire walls if separation was not possible - The stores should have at least two access points to allow a means of escape - Ensuring that electrical installations were suitable for a zoned area - The provision of fire / smoke detection system, sprinklers, fire extinguishers - Adequate spacing between racking to allow the movement of FLT and The provision for separate access for pedestrians and the trucks. Use of the store room: - The control of source of ignition such as the FLT and portable electrical equipment - The storing of paint and thinner in a fire resistant containers away from source of heat and sun light - Procedure for decanting which should be carried out outdoors or in a separate area - Procedure for spillages where immediate clean up required using spill kit - Ensuring a high standard of housekeeping for the FLT routes and pedestrian walk ways - Regular inspection and maintenance of the racking and pallets - Arranging the safe disposal of wastages; Providing information and trainings to workers on necessary precautionary measures to be taken - Controlling access to the stores by limiting it to authorized person only Jan 2011
  23. 23. 23 37-IC4-08 The physical and chemical properties of liquefied petroleum gas (LPG) dictate a number of precautions which should be taken in the storage of LPG in cylinders. a) Select four of these properties and explain how one of the precautions is related to each property. b) Give, with reasons, additional precautions for the safe storage of LPG in cylinders. a. The properties can be selected include: - LPG is a flammable gas at standard temp and pressure; - It is denser than air; Escape clouds cool and therefore are not buoyant on thermal diffusion; - Liquid releases float on water; The lower explosive limit (LEL) is reached with small concentrations of LPG; - It is slightly anesthetic and suffocating in high concentrations b. Precautions for the safe storage of LPG in cylinders include: - Preferably stored in the open air; Floors should be concreted; - Noncombustible or fire resistant and Ventilated with an explosimeter installed. - Minimise quantity; - Elimination of ignition sources: no smoking, Provision of signage with 'extremely flammable' warnings; - Intrinsically safe / flame proof electrical equipment; - Only electrical apparatus for use in Zone 2 area should be allowed in storage area or within separation distance; - Dry powder extinguishers at storage location; - Control of combustibles; Removal of vegetation around storage area (not sodium chlorate weed killers / other oxidizing agents); - Segregated from oxygen cylinders (3m); Empty cylinders stored separately from full with valves shut / cap; - Cylinders stored upright; Protective caps kept in place on valves; - Storage compound should be protected from vehicle impact; - Storage situation greater than 3m from - cellars, drains or excavations and protected from the elements; - If more than 400 Kg store must have 2m high mesh fence, 2 exits, with Cylinders at least 1.5m from fence; 38-IC4 -02 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. Marks-20 - Risk assessment to be carried out for - The activities involved by using paints & solvents with hazardous properties (normally by reference to safety datasheet). - The circumstances in which the work was carried out. - Possible ignition sources and likelihood that a fire or explosion could occur - The control measures - The workshop should be constructed of fire resistant materials; An impermeable / solid base to be constructed; - Possibilities to replace the paint with less flammable - An external fire resistant storeroom to be provided for the paints and solvents - A reduced quantities of paint and solvent to be maintained at the workshop Jan 2010 July 2008
  24. 24. 24 - The paint and solvent should be kept in non-spill containers with lids. - Procedures to made and followed for the containment and clean-up of spillages and for the cleaning of the spray guns - Provision for Local exhaust ventilation - Safe electrical equipment with provisions of flameproof switchboards. - Fire fighting equipment, means of escape route, emergency procedure to be drawn and communicated to the workforce - Instruction, training on the risks involved in the operation and the precautions to be observed 39-IC4-R- LAQ2 A road haulage company which is an established carrier of nonhazardous bulk liquid, has been invited to tender for a contract to transport significant quantities of bulk flammable materials in tank containers. Advise the hauler company on i. The requirements for driver training and for the appointment of safety advisor 6 ii. The main duties of safety advisors in relation to the transport of dangerous goods. 14 i. The drivers of the tank and tank container carrying dangerous goods should – - Attend a vocational course of instructions communicated for transportation of dangerous goods - Sit in an assessment examination organized externally in order to obtain a competency certificate which needs to be updated at specific intervals. The Safety Officer appointed – must hold a vocational qualification where he had been instruction about the type of the means of transportation such as water, road and train and the type of dangerous goods to be transported. ii. The safety officer should act as catalyst and advise on Health, Safety and Environment matters in term of handling and transporting dangerous goods to the management, other responsibilities includes – - Developing a procedure for compliance with local rules governing the identification of dangerous goods – such as HAZCHEM signs - Developing procedure for purchasing vehicles – Complying the requirements for transporting significant quantities of bulk flammable material in tank container. - Procedure for checking equipment - Procedure for conducting training and maintaining records of attendance - Emergency procedure; accountabilities of employees during emergency - Monitoring of compliance of all procedure through suitable techniques such as HSE audit - Investigating incidents, accidents and Nearmiss - Complying the control measures / preventive measures identified during investigation to avoid recurrence - Prequalification and competency evaluation for sub contractors - Ensuring the distribution of operational procedures among the employees - Ensuring that the vehicles are maintaining required documents and equipment - The implementation of verification / inspection procedure to ensure the compliance with legislation governing loading and unloading of dangerous goods - Preparing annual performance report to the employer
  25. 25. 25 40-IC4-R- LAQ3. IC04- 7 As the Health, Safety and Environment Manager to a group of manufacturing companies, you have recently discovered drums of a highly flammable solvent being stored on open land at the rear of one of the group's factories. a) Draft a memorandum to the Production Manager of the company concerned explaining why storage in this manner is inappropriate. b) Describe, with the aid of sketches, the main features of a storage facility that would be appropriate for the storage of such drums. OR, With the aid of fully labeled diagram, identify the key features of a building to be used as a facility for the storage of highly flammable solvents in 200 l drums. a. Memo to the production manager: I have recently discovered that the drums of highly flammable solvents are stored in an open area at the rear of one of our factory, which is potential to cause any eventuality at the factory leading harm and loss. I therefore, would like to bring the issue to your kind notice / attention and set out the below reasons , why storing highly flammable solvents are inappropriate in such manner – - The risk of ignition leading fire as the drums are stored under direct sun - over heating from sun, on site ignition source and malicious damage can be causes of such ignition. - There is also significant risk of leaks or spillage which could lead to soil contamination as well as water contamination. - The cost of cleanup could occur if the drums got damaged resulting in leakage and spillage - The solvents also presents health risks to anyone in the vicinity - Open area storage are inviting arsons, theft and vandalism - Risk of drum handling using FLT and associated reduced stability in such location - It is a non-compliance of local regulation concerning the storage of flammable materials, hazardous to health or environment. - Finally it is one of the major breaches of insurance condition and environmental accreditation. b. The storage facility - The building of the storage facility should be constructed of non-combustible and fire resistant materials - An impermeable / solid base to be constructed; Adequate separation distance from other buildings - The storage facility to contain the drums of highly flammable liquid should be provided with Bund to contain spills; - Facility for collection / disposal of spillage or accumulated rain water - Door locks, perimeter fencing and security – to avoid arson ; suitable warning / hazard signs and instruction displayed - High or low level ventilation ; Indication of zone classification; Facility for external electrical isolation. Fire safety / precaution - Segregation of incompatible materials from the solvents such as acids, oxidizing agents to kept separately ; - Sprinkler system or provision of fire extinguishers - Flammable vapour monitoring system and alarm - Adequate provision for access and egress, including emergency escape and truck ramps to facilitate and handling drums ETA 31, Jan 2007 N
  26. 26. 26 41-IC4-10 A petrol storage tank in a bund containing three other similar tanks is overfilled during a transfer operation resulting in a large spillage of petrol into the bund. The petrol vapor is ignited from a remote source causing a catastrophic explosion and fire involving the whole of the installation a. IDENTIFY the design and construction measures that could have prevented such an event 4 b. OUTLINE the range of measures that would be necessary to mitigate the effects of such an event 6 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 alarm - level detection and vapour detector monitoring systems fitted in the bund - the provision of remote shut down systems - good standards or earthing and bonding b. The measures that would be necessary to mitigate the effects of such an event - Provision of adequate fixed foam installations to spray the surface of pools in the bunded areas - The installation of foam monitors capable of reaching the tops of tanks July 2007
  27. 27. 27 - The erection of radiation walls between adjacent bunds to prevent other tanks being heated - An adequate supply of firefighting water - 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 minimize the environmental effects of fire water run off - Regular draining and cleaning to remove rain water from bunds 42-IC4-04 In 1988 a disaster occurred on the piper alpha platform in the united kingdom a. IDENTIFY mechanical failures that contributed to the initial explosion - 4 b. OUTLINE the systems failures associated with the permit to work system that contributed initial explosion - 6 a. The mechanical failures that contributed to the initial explosion- - The removal of PSV (pressure safety valve) for service and its replacement with a blank flange (Blind flange) - The blank flange was made of ordinary metal sheet (without any Lock or tag with switch of pump) - The blank flange was fitted incorrectly and was not leak tight - On the night A running (condensate) pump was tripped and a stand by pump associated with blanked flange was operated by night shift without knowing about incorrectly fitted blank flange. - The condensate and gas escaped from the blanked flange that resulted in gas explosion b. - There were two permits taken – one for two weeks maintenance in the pump and other for the work on pressure valve of the same pump. - The failure with the PTW which was in operation for the removal of the pressure valve.  No mention of the need to cross reference permits / or  No cross reference of the two permits to indicate the removal of pressure valve in the pump in each of the permit.  Failure in communication at the end of the working day with the suspended permit returned to the control room but not displayed and not communicated to night shift team  No place on the permit for the issuer to declare that the work had been left in a safe condition - Inadequate written procedures for the permit to work in that there was reference of locking off or tagging valves to prevent inadvertent operation - A failure to check that the blank valve was leak tight at the time before pressurizing it - A failure in communication at shift handover with the absence of any written procedure for this event - The absence of formal training for those with the responsibilities of issuing permits - No attention drawn to the potential dangers associated with the suspended of permits - Finally inadequate monitoring and auditing by management of the permit to work procedure. January 2010 43-IC4-01 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' also called thermal runaway and July 2011 Jan 2009 July 2007
  28. 28. 28 b) IDENTIFY the conditions that may give rise to such an event. c) DESCRIBE the design and operational features of chemical processes necessary to prevent such an event. 2+4+4=10, a) An uncontrolled exothermic reaction where the heat produced by the reaction exceeds the heat removed. The surplus heat raises the temperature of the reaction mass, which causes the rate of reaction to increase resulting in RUNAWAY REACTION. Thermal runaway occurs because, as the temperature increases, the rate at which heat is removed increases linearly but the rate at which heat is produced increases exponentially. b) the conditions that may give rise to such an event includes – - Presence of Strongly exothermic reaction; - Inadequate provision, or failure in cooling of the reaction, and - Presence of contaminant catalysis. - Excessive quantities of reactants present in the reactor - The lack of sensitive temperature detection and control - the insulation of the reaction vessel where solid residues have build up on the internal walls of the vessel and mixer failure with loss of agitation - Increase in pressure and temperature from reaction serve to accelerate the reaction in accord with Le Chatelier’s principle. c) Carrying out a hazard and operability study (HAZOP) on the reaction process would be appropriate in this scenario; this may then have led to the inclusion of design features such as: - High integrity temperature detection being linked to the cooling / reactant addition system; - Pressure rise detection linked to cooling / venting / auto shut-down; - Vessel protected by correctly sized bursting disc. - Fitting of an agitation failure alarm system Operational Features such as - Only high caliber of operator required for such processes was employed; - The decision making requirements by operators in response to adverse operating condition were minimized - Ensure that maintenance activities / raw material handling do not introduce potential catalysts into the reaction; - The rate of addition of reactants was limited and that inappropriate scale-up or fouling was avoided 44-IC4-01 A hot liquid was accidently and violently discharged from the feed port of reactor vessel following the addition of a chemical regent during a chemical manufacturing process; The investigation suggested that the cause was a runaway exothermic reaction. i. OUTLINE the factors that may have contributed to the event and explain the principle involved. 10 ii. DESCRIBE the measures that could be taken to prevent a recurrence 10 a) The factors that may have contributed to the event scenario - It is likely that the incident was a violent exothermic reaction, which caused a thermal runaway, with subsequent rapid increase in temperature and pressure causing the ejection of vessel contents. ETA 29
  29. 29. 29 - The system was based on wrong procedures or incorrect assumptions about the heat generation and dissipation from quantities of chemicals used for the procedure. - Equipment failure, for example automatic feed breakdown or a failure of critical component such as stirrer and mixers; - Incorrect operating procedures such as the speed of addition or the method of mixing was wrong - The vessel contents could have been incorrect or the wrong materials have been added. - Contamination or contact with other chemicals reagent acting as catalyst. - Design failure, commissioning failure if the plant was not build as per the recognized specification - Human error – unauthorized modification. b) Measures to prevent a recurrence include - The feed of material should be controlled adequately, either manually or automatically to ensure correct speed of delivery. - Any engineering controls provided for temperature, pressure, level, quantities should be properly designed and maintained and tested. - Pressure changes and other warnings and alarms and - Automatic process shutdown if the feed of the reagents or the reaction exceeds the pre-set parameters. - Designed emergency neutralization or discharge of the process reactants if feed or the reaction exceeds the preset parameter - To prevent contamination, Procedural control measures such as quality control of feedstock purity and specification of supplied materials should be closely monitored. Allied to this would be the requirement for - Adequate training, instruction and information for operators to reduce human error, - Close supervision for normal operation and emergency conditions. - The use of laboratory or pilot plant trials and - The use of hazard analysis techniques (hazop). END OF UNIT 4
  30. 30. 30 IC 5 : Work Equipment With the aid of labelled sketches, outline the characteristic features of, and factors that promote, the following types of materials failure: (a) Brittle Failure; Marks-5 (b) Ductile Failure. Marks-5 July 2012 Jan 2008 45-IC 05 - 11 Coal is delivered by train to a power station and is transported by belt 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. Marks-10 Jan 2012 Jan 2010 46-IC 05 – 08 Materials can fail through various modes. (a) OUTLINE the meaning of ‘Metal Fatigue’. Marks-6 (b) IDENTIFY TWO factors which can contribute to such a failure AND, for EACH factor, outline ONE circumstance in which it may occur. Marks-4 (c) OUTLINE: (i) The characteristics of electrolytic corrosion. Marks-5 (ii)Factors which cause electrolytic corrosion. Marks-5 Jan 2012 Jul 2008
  31. 31. 31 47-IC 05 – R- LAQ 1 “A” a) IDENTIFY the possible modes of structural failure of pressure vessels and, with reference to different types of pressure vessel, describe the factors and conditions that may influence the mode and likelihood. 14 b) Review the measures that may be needed to prevent the structural failure of pressure vessels. 6 a. The possible modes of failures are as below - Creep ; Corrosion ; Brittle failure; Ductile failure; Metal fatigue The factors and conditions that may influence the mode and likelihood of such failure include: - Temperature (Low)– is an important factor with brittle failure, more likely to occur at low temperature, for example in LPG vessels - Temperature (high) – Creep and ductile failure are more likely to happened at high temperature for example in steam boiler - Cyclical pressure variations are likely to promote metal fatigue - Residual manufacturing stress, choice of materials, poor repair, welding and heat treatment can influence the likely stress in the vessels. - The contents of the vessels will affect the probability, extent and the type of any corrosion - Weak components such as seems, welds and loose access plates may promote failure. - Contamination – oil / grease in air receiver; Environment is also an important factors – Corrosive / hot - Operating within design specifications: o Overheating – low water level / scale formation; Over pressure – Safety gauge / valve failure b. Measures that may be needed to prevent structural failure - Designed safety feature – relief valves, sight gauge, level sensor and choice of material used - Specified design standards – Quality control, proof testing - Regular checks and test – servicing, maintenance and inspections - Thorough examination by competent persons - NDT (Non Destructive test) to identify the potential failure modes - Operating procedures to keep within specified performance - Water treatment for boiler and filters to remove contaminations. 48-IC 05 -04 “A” With the aid of labeled sketches, OUTLINE the characteristics of, and factors that promote, the following type of material failure a) Brittle Failure; b)Ductile Failure a) Brittle Failure: A brittle fracture generally occurs without warning or prior evidence of distress. It is a crystalline structure failure with minimal plastic or elastic deformation. There are generally characteristics ‘chevron’ marks from the point of initiation and the failure is sudden from rapid stress loading. The factors promoting a brittle fracture are - High tensile stresses,; Residual or locked in stresses; Sudden loading which does not give the material time to deform plastically, - Case hardening; Low temperatures and The degree of brittleness of the material b) Ductile Failure A ductile fracture generally has a smooth fracture surface with plastic deformation of the material before final fracture. There is evidence of necking and the final fracture is often brittle because there is insufficient material left to sustain a load. July 2012 Jan 2008
  32. 32. 32 This type of failure generally occurs as the result of a single stress overload though other promoting factors including - High temperatures,; Cold work hardening and - The plasticity of the material 49-IC 05 – R SAQ 2 “A” Describe, with practical examples and sketches the characteristics features of and that factors that promote the following types of failures in metal. i) Fatigue 10 ii) Creep 10 (NEBOSH diploma syllabus: Seven modes of failures- Ductile, brittle, metal fatigue, buckling, corrosion, Wear and creep) i) Fatigue: Characteristics: o Cracks spreading – repeatedly stressed, newly failed smooth surface o Beachmark – 90 degree to crackdown o Final failure ductile / brittle – insufficient material to withstand the load Fatigue: Factors: o Area of high stress concentration – corners, threads, holes o Cyclical loading ; Temperature, pressure and forced vibration Fatigue: Example: Rotating; Reciprocating ; Vibrating parts ii) Creep: Characteristics: Yielding and extension; Continuously loaded materials; plastic deformation Creep: Factors: unequal relaxation of stresses; Excess temperature; Choice of materials (Low creep) Fatigue: Example: Pressurised pipework; high speed rotating blades 50-IC 05 – R – LAQ 2 “A” A report into the collapse of a passenger walkways at a ferry port concluded that the immediate physical cause of collapse was a fatigue failure of a weld securing a stub axle to the walk ways. The walkways , which was designed and installed by contractor, was attached to a floating pontoon at one end and was intended to accommodate the movement cause by the rise and fall of the tide i) Explain the mechanism of “Fatigue Failure” 5 ii) OUTLINE the design and maintenance procedure that could have helped in preventing incident 10 iii) OUTLINE the steps that the ferry port could have taken to ensure that the contractor was competent to design and install the walkways 5 i. The mechanism of fatigue failure such as - Microscopic progressive cracks (point of high stress, variable loadings, little deformation)  Initiated at stress concentration. These Extend under Fluctuating stress until the material fails - The final failure may be ductile or brittle (when there is insufficient material to sustain the load)  There is Little or no deformation but the failure surface shows characteristics conchoidal marks
  33. 33. 33 ii. Design and Maintenance procedure includes - Deputing the competent and experienced designer - A peer review of the design considering the service condition and loading - Tidal and the possibility of the corrosion should be considered - Stress concentration should be minimized; Material with suitable fatigue strength to be selected - Risk assessment should be carried out at the design stage - Provision for maintenance and inspections; Maintenance and inspection requirement should be specified - Implementation of documented inspection and maintenance routine - Training of personnel on maintenance requirements; Periodic thorough examination by the competent person iii. Steps for prequalifying / ensuring competency the contractors - Enquiries for experience in similar projects - Verifications from recent clients – they could have provided the information about the performance of the contractor - Details of design personnel (qualifications, Experience etc.) - Quality control techniques - The use of Risk assessments for design stages should be queried - The use of third party checks / inspection on design to be queried - Finally the contractors should prepare a detailed plan Outlining the construction safety and installation arrangements 51-IC 05-14 – R – LAQ 3 “A” 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) DESCRIBE the mechanism and characteristics of fatigue failure 6 b) List THREE factors which can contribute to such a failure and for each factor describe one circumstance in which it may occur 6 c) DESCRIBE the measures that could have been taken to minimize the likelihood of such a failure 8 a) The mechanism and characteristics of fatigue failure such as - Microscopic progressive cracks (point of high stress, variable loadings, little deformation)  Crack propagation from points of stress concentration,  Fluctuating stress environments and  The characteristic fracture pattern. - The final failure may be ductile or brittle when there is insufficient material to sustain the load  Failed surface shows conchoidal beachmarks , which Progress as narrow rings at low and extended at full load b) Factors which could give rise to fatigue failure in practice such as: (only 3 factor with 1 circumstance) - High Fluctuating stress – Use outside the design criteria, Relative to fatigue strength of material, - Stress concentration – sharp corners, threads, holes, defects / flaws / cracks / impurities - Temperature – heat induces stress, change of material properties - Residual stress – imposed during manufacture and assembly and induced bending stress, and ETA 38, Jan 2007 N
  34. 34. 34 - Corrosion – stress concentrations in corrosion pits c) Measures to minimize the likelihood of fatigue failures such as - Design, manufacture and installation o Minimize stress concentration; specifying materials / components to match the service condition o Quality assurance; Correct assembly - The maintenance, inspection and examination (with NDT) o Failure record ; Reliability data; Non Destructive test o Examination of critical components o Replacements at planned intervals o Maintenance o Statutory examination requirements - Provision of training and instruction for those involved in the use and - The keeping of service history records. 52-IC 05 -12 “A” 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 10 b) OUTLINE the items that could be included on a checklist when inspecting pipework after construction. 10 a. The inspection strategies that could prevent pipework failures: - A thorough inspection must be done on current basis, more detailed manner than previous one. - The use of NDT techniques such as dye penetrate for the detection of surface faults and - And NDT techniques such as ultrasonic or radiography to detect those that were more serious - The engagement 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 the construction has been completed and should be ongoing throughout the life of the plant. - Those carrying out inspections should preferably include a member from design team who will be able to detect departures from the design intentions and also a member of the startup team who suffer most from the results of construction defects. b. Checklist - Suitable material such as specified grade of steel to be chosen for the construction of the pipe work. - 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 standards joint exists - No screwed joints have been used and ; All joints have been leak tested JAN 2010 Jan 2008
  35. 35. 35 - 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 avoidable - 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 53-IC 05 – 15, R-SAQ 3 “B” a. EXPLAIN the purpose of non-destructive testing (NDT) on items of plant. 2 b. Other than visual inspection, OUTLINE the principles, advantages and disadvantages of TWO NDT techniques 8 IC 05 - 16 “B” (a) OUTLINE the purpose of non-destructive testing (NDT) on items of plant. Marks-2 (b) OUTLINE the principles, benefits and limitations of the following NDT techniques: (i) Dye penetrant; Marks-4 (ii) Radiography. Marks-4 July 2011 July 2009 “B” OUTLINE the principles, advantages and disadvantages of: (a) Dye penetrant; (b) Magnetic particle inspection; (c) Radiography; (d) Ultrasonics as methods of non-destructive testing on the welded joints of a safety critical vessel. Marks-20 July 2011 July 2007 ANS of all above 3 Questions 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. The main NDT techniques required are: Principle of NDT Techniques Advantages Disadvantages The use of a dye penetrant method makes cracks visible as dye penetrates into it. It uses the principle of brightly coloured or fluorescent liquid applied to the surface of the component, which penetrates into any surface cracks or cavities. Developer is then applied which draws out the penetrant, so indicating cracks etc, that are not normally detected It is relatively cheap and is a simple operation It detects surface faults, It is quick and easy to use on large surfaces, It is cost effective, allows complex geometries to be inspected and is a portable technique (e.g. spray aerosol cans of penetrant can be used) it does not detect sub-surface faults It is only suitable for non-porous materials, There must be direct access to the surface of the component, Surface finish and roughness can affect inspection sensitivity, It indicates the length of the defect but not the depth and There are health and safety considerations such as possible confined space and flammability. Additionally, the penetrant used may have toxic