Nebosh Oil and Gas Possible Exam Questions Question
A) Q (A) – Identify the hazardous properties of Liquid Petroleum Gas (LPG) A: Fire, explosion, asphyxiation, environmental harm, toxic, vaporisation can cool equipment
and cause cold burns, empty vessels can still be dangerous as vapours stay within the vessel, they are stored under great pressure, gas is heavier than air and will need gas detection Q (B) – outline the risks with Liquid Petroleum Gas (LPG)?
A: Odourless and colourless so difficult to detect, heavier than air so does not float into atmosphere, any leaks will cause environmental damage, will cause severe cold burns, asphyxiate, formation of hydrates (ice plugs) if draining out water from pressurised tanks, possible BLEVE if flames impede of LPG sphere Question
Safety cases / reports provide documented evidence that an oil and gas installation is safe Outline the typical contents of these types of documents A) A: Scope of works, System de scription, System requirements, Major hazard assessment Risk Assessment, Controls Controls for risk reduction / elimination, Safety analysis / testing, Name and address of the installation operators, Major accident prevention policy (MAPP), Safety management system, Description and layout of the installation, Types of operations carried out, Identification of major hazards, Major hazard scenarios, Performance standards of safety critical equipment , Emergency response procedures (ERP Documentation), The offsite plan (onshore) Question 3
An employee was seriously injured at work within an oil and gas installation Identify the documented information that might be used by the investigation team to determine the causes of this accident. A) A: Witness statements, plans, diagrams of plant, safe systems of works, photographs, previous accident records, technical guidance, manufacturers information , training records, toolbox talks, risk assessments, permit to work records, CCTV Coverage, health issues of injured party, instrument readouts, information form safety meetings Question
Give the meaning of the following terms: Q: Upper flammable limit (UFL) A: Upper flammable limit (UFL) – the maximum percentage of air bey ond which is not flammable Q : Lower flammable limit A: Lower flammable limit – minimum percentage of air, lower is not flammable Q : Flashpoint A: The lowest temperature at which the liquid produces a vapour and f orms ignitable mixture with
air Q : Highly flammable liquids A: A liquid that has a flashpoint of less than 21c
Question
Outline four types of works activity within an oil platform that may require a permit to works and give reasons in each case for the requirement. A: hot works permit where heat is used or generated ( welding, flame cutting, grinding) Reason: to ensure work is planned and controlled to minimise minimise the risk of fire A: Works that will involve the breaking of containment of a flammable / toxic substance or pressure
system. Reason: To ensure the works are planned and controlled, isolated and test to prevent harm from
hazardous substances. A: Work on h igh voltage electrical equipment Reason: To ensure work is controlled and planned and isolated accordingly A: Entry into tanks and sto4rage vessels Reason: To ensure confined space works are planned, escape procedures in place including
emergency action plan A: Working at Height Reason: to ensure works planned and controlled and fall prevent measures in place, works are
segregated A: Works on emergency systems s ystems Reason: To be controlled and planned making sure making sure alternative emergency action plan in
place when main system off line Question
Outline operational control measures that could minimize the risk of p lant damage or injury during start up or shut-down process Answer • • • • • • • • • • • •
The use of trained competent persons Working from approved process operator guides and procedures Ensure all safety systems are in place a nd online Ensure all instrumentation is working in control room Tell everyone on the installation what is about to happen Clear all production decks until plant is online Make sure there is line of communication between outside operators and control room Walk the lines for any items that may be out of place Use interlocking systems to ensure correct opening of valve systems Ensure standby equipment is in place Start the plant up in small levels of pressure to highlight and leaks. Increase pressures gradually
Question Q : Identify hazards associated with the sludge A: Absorption through skin, Inhalation from dust of fumes, Ingestion through poor hygiene,
Radiation, Carcinogenic – cancerous, Environmental pollutant Q : Outline four controls measure to reduce the risk to workers A: Training and awareness, good housekeeping, use of RPE, use equipment to control and handle the
sludge instead of hands on approach, dilute using water, employ health surveillance. surveillance. Q : Identify two other forms of equipment where sludge may be found A: Inside pipeworks, on the drilling stand, inside filters, in coolers, inside coalesces Question A work has requested a permit to works in order to replace damaged thermal insulation in an overhead pipe rack that runs between two plants.
Q(A): Identify three hazards associated with this activity Answer Working at height, heat form the process pipework, manual handling, falling objects Q(b): Outline the control measures that should be in place to reduce the risk to the worker. Answer: • Safe access (certified) to gain access to the height • The task may need the system to be closed down while the works are carried out • Area barriered off the restrict access below the task through falling objects • Risk assessment to identify the hazards associated with the task ( to be carried out with the operative(s)) Breathing zone monitoring and RPE if r equired • • Communication Communication between both plants for permit to w work ork to be eff ective • Adequate supervision • Manual handling assessments carried out • Trained and competent people carrying the works out • Correct isolations • Correct PPE Use of MEWPS • • Fall arrest protection
Question An outgoing operator is handing over to an incoming operator at the end of a shift. Q (a) Explain the key principles of a safe han dover Answer • • •
• • •
Be regarded as high priority Face to face Be two way communications with both parties taking joint responsibility responsibility for the exchange of accurate information Verbal and written means of communication Be given adequate time, no distractions and given as much resource as needed Not to be rushed and involve all shift members
Q (b) Outline to main operational issues communicated at shift ha ndover Answer • • • • • • • •
Permits to work in place that are still effective Future nominations Maintenance issues, current and up and coming Plant issues, overrides and breakdowns Abnormal events Shutdowns planned and unplanned New personnel to the shift Faults with any safety critical equipment
Question Q: Outline the following failure modes that may lead to loss of hydrocarbon containment from
storage tanks / vessels or pipelines A: Creep – this is a form of plastic deformation that takes place place in steel held for long periods of time
at high temperature and may over time fail. B: Stress corrosion cracking cracking – is a failure f ailure that requires the paring of materials suited to the product
being used, some chemicals react with certain metals and should be carefully researched. C: Thermal Shock – this is where the rapid change in temperature can have an impact on the
integrity of the pipe or vessel being used and can cause the material to crack and burst. D: Brittle Fracture – this is the rapid failure of a material already under stress, this could be through
welding defects or fatigue crack Question A: Identify two ways in which vapour clouds can generate? •
Rapid depressurisation in a vessel containing pressurised product such as LPG
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Rupture of a vessel containing pressurised product su ch as LPG
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Loss of containment of a product from a leaking valve or gland.
B: Outline how a vapour cloud explosion can be generated?
These can be confined (CVCE) or unconfined (UCVCE), both involve a leak which makes the product vaporise to form a cloud. If that cloud reaches an ignition source then the cloud will explode. These clouds can travel a fair distance to find an ignition source. C: Identify the physical consequences of vapour cloud explosions?
These will include fire, materials and property damage as well as subsonic flame propagation Question Q: An operator is draining a flammable liquid from process pipework to a metal container. The
supervisor is concerned about the possibility of electro static charge forming and stops the operation until a risk assessment is undertaken. A: Identify the factors that influence the generation of the electrostatic charge •
The flow of proud t through pipes can generate charge, this will include flow rate, speed of the product and design of the p ipework (size and shape).
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Turbulence / splashing of the product through filling operations or mixing process.
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Particles present in the product with the inclusion of poorly conducted liquids
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Equipment not bonded can cause the sparking between equipment
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Static charge can be created through some clothes.
B: Outline the practical ways of minimising the formation of an electrostatic charge •
Keep liquids at a low velocity
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Ensure piping design parameters are not breached; recommended product speed is 15 feet per second
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Limit the free fall of liquids and fill from the bottom with pipes submerged
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Adequate bonding and grounding to be in place with all connected equipment
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The adding of anti-static additives to limit the creation of static charge
Question Q: petroleum storage tanks fires have been reduced substantially by using floating roofs, but a fire
risk may still exist A: Outline how a fire may still exist with floating roof tanks
Fire would still be a risk of the seal around the edge of the tank was damaged and letting out vapour into the ullage space, not only would the vapour escape and find an ignition source, the natural air could impede into the storage tanks and create its own risk of fire by creating and flammable atmosphere. B: Identify two examples of fire protection systems used on floating roof tanks
A foam deluge systems around the top of the tank Fixed oscillating monitors and firefighting capabilities around the perimeter of the tanks bunded area, with, firefighting detection systems and hazardous area classification zone in place.
Question Q: During an inspection an external fuel storage tank is found without a bu nd wall A: Identify the environmental impact if a tanks failure occurred •
Contamination of the ground area
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Contamination of the water course should the spill reach drains and sewers
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Impacts on wildlife
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Evaporating fuel could have an effect on the ozone layer
B: Outline the features which should be in cluded in the design of a tank bun d wall •
The bund should be constructed from impermeable materials
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Should be able to cope with 100% of the contents of the tank
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Incompatible chemicals should have their own bunded area
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No drains free flowing out of the bund, must lead to separator
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Nothing should penetrate the bund and go over it, this includes vehicle and foot traffic
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High level alarm linked to the control room
Question Q: knowledge of failure modes is vital during the initial plant design, safe operation procedure
development and process operation. A: Identify three types of failure mode Creep – is slow movements under stress made made more severe with heat for long periods of of time with
an increase in temperature approaching melting point Brittle Fracture – rapid run of cracks through stressed material which has little plastic deformation
before failure occurs. Stress Corrosion Cracking – this is where alloys are under constant pressure and tensile stress made
worse in a corrosive environment, more so at high temperatures. B: Identify factors or conditions that may in fluence the likelihood of failure modes •
Incorrect materials used
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Excessive stresses stresses built into the material material EG poor welding
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Rapid changes in temperatures
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Starting system up too quickly
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Steam plant creating water hammer or thermal shock
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Materials subjected to long periods of excessive heating EG flame impingement
Question Q: Outline the physical design features of an oil and g as installation that would minimise minimise the risk to
operating staff in the event of a major incident? A: •
separation of the temporary refuge, control room and emergency control and command centre from the main produ ction operation, if not possible to use jacket separation protection, these can be protected with fire and blast walls, fireproofing, positive air pressure inside any building, assessment of hazards for occupied building, protected escape routes
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Emergency shutdown systems installed independent from regular fire and gas detection.
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Safety critical elements with high integrity level, HIPPS pipelines protection system
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Reduce the amount of overrides and inhibits in the system
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Fire proof emergency shutdown valves for protection
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Deluge skid operating around the escape route
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Automatic doors on accommodation
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Fire compartmentation compartmentation
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Install VESDA system for early de tection
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Minimise stocks stocks held on site
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Open up areas to allow added airflow for gas clearing should it escape.
Question Q: Outline the factors that should be considered when providing means of escape in an oil and gas
installation to enable all workers to reach reach a place of s afety in the event of a fire? A: •
All escape routes protected with deluge system and fire walls,
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No congested area within the escape routes
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Route clearly marked to the point of evacuation
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Fire compartments to reduce fire spread
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More than one access route from each area
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More means of communication
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Fireproofing to at least H120 (1150c) in most areas
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Increase number of alarms including flashing beacons
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Other means of escape (Skyscape, rope ladders)
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PPE, fire protective clothing, breathing apparatus
Question
An oil installation contains a vessel that requires protection from exposure to f ire in the form of active or passive fire protection Q: Identify two examples of passive fire protection to protect the vessels A: Mortar based materials or intumescent paints, Fire walls to particular areas Q: Outline why the metal legs of the vessel should be protected? A: The metal legs of the structure should be protected protected to prevent the steel from buckling to ensure
the vessel remain support as not the release further contents thus heating the fire further Q: Outline how a fixed water deluge system could provide fire protection? protection? A: This would be automatic detection for each area protection and deliver large amounts of water
thus cooling the fire, mist systems produce more water which can remove the oxygen from the fire aiding in putting it out. Q: Identify two addition examples of active fire protection
A: CO2 inert gas protection removing the oxygen and foam systems for helipad and rim seal on storage tanks.
