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 description, System requirements, Major hazard
assessment Risk Assessment, 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 beyond 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 forms
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 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 high 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
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
plant 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 and 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.
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 required
•Communication between both plants for permit to work to be effective
•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.
(a) Explain the key principles of a safe handover
Answer
•Be regarded as high priority
•Face to face
•Be two way communications with both parties taking joint 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
(b) Outline the main operational issues communicated at shift handover
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
Answer
A:Creep – this is a form of plastic deformation that takes place in steel held for
long periods of time at high temperature and may over time fail.
B: Stress corrosion cracking – is a failure 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?
Answer
•Rapid depressurisation in a vessel containing pressurised product such as LPG
•Rupture of a vessel containing pressurised product such as LPG
•Loss of containment of a product from a leaking valve or gland.
B: Outline how a vapour cloud explosion can be generated?
Answer
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?
Answer
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 pipework (size and shape).
•Turbulence / splashing of the product through filling operations or mixing
process.
•Particles present in the product with the inclusion of poorly conducted liquids
•Equipment not bonded can cause the sparking between equipment
•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
•Ensure piping design parameters are not breached; recommended product speed is
15 feet per second
•Limit the free fall of liquids and fill from the bottom with pipes submerged
•Adequate bonding and grounding to be in place with all connected equipment
•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?
Answer
Fire would still be a risk of the seal around the edge of the tank if it 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
Answer
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 bund wall
A:Identify the environmental impact if a tanks failure occurred
Answer
•Contamination of the ground area
•Contamination of the water course should the spill reach drains and sewers
•Impacts on wildlife
•Evaporating fuel could have an effect on the ozone layer
B:Outline the features which should be included in the design of a tank bund wall
Answer
•The bund should be constructed from impermeable materials
•Should be able to cope with 100% of the contents of the tank
•Incompatible chemicals should have their own bunded area
•No drains free flowing out of the bund, must lead to separator
•Nothing should penetrate the bund and go over it, this includes vehicle and foot
traffic
•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 more severe with heat for long
periods 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 influence the likelihood of failure modes
Answer
•Incorrect materials used
•Excessive stresses built into the material EG poor welding
•Rapid changes in temperatures
•Starting system up too quickly
•Steam plant creating water hammer or thermal shock
•Materials subjected to long periods of excessive heating EG flame impingement
Question
Q:Outline the physical design features of an oil and gas installation that would
minimise the risk to operating staff in the event of a major incident?
Answer
•separation of the temporary refuge, control room and emergency control and
command centre from the main production 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
•Emergency shutdown systems installed independent from regular fire and gas
detection.
•Safety critical elements with high integrity level, HIPPS pipelines protection
system
•Reduce the amount of overrides and inhibits in the system
•Fire proof emergency shutdown valves for protection
•Deluge skid operating around the escape route
•Automatic doors on accommodation
•Fire compartmentation
•Install VESDA system for early detection
•Minimise stocks held on site
•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 a place of safety in the
event of a fire?
Answer
•All escape routes protected with deluge system and fire walls,
•No congested area within the escape routes
•Route clearly marked to the point of evacuation
•Fire compartments to reduce fire spread
•More than one access route from each area
•More means of communication
•Fireproofing to at least H120 (1150c) in most areas
•Increase number of alarms including flashing beacons
•Other means of escape (Skyscape, rope ladders)
•PPE, fire protective clothing, breathing apparatus
Question
An oil installation contains a vessel that requires protection from exposure to fire
in the form of active or passive fire protection
Q: Identify two examples of passive fire protection to protect the vessels
Answer: Mortar based materials or intumescent paints, Fire walls to particular
areas
Q: Outline why the metal legs of the vessel should be protected?
Answer: The metal legs of the structure should be 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?
Answer: 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.
Q1
Many serious accidents or incidents, including the Piper Alpha disaster in 1988,
involve root causes associated with shift handover. An outgoing operator is
handing over to an incoming operator at the end of a shift.(a)
Explain the Key principles of safe shift handover.
Information on specific operational issues is not required in part a.
(10)
ANS: The Key principles of safe shift handover are; good shift handover allows the
accurate and effective communication of vital information to incoming personnel
in order to allow the safe operation of process plant and equipment. There are
three elements which contribute to an effective shift handover"
• A period of time when the outgoing team prepares the information it will %e
conveying to the incoming team
• A period of time when both the outgoing and the incoming team communicate
with each other and exchange all relevant information.
• A period of time when the incoming team cross checks the information passed
onto it as it takes the responsibility for the ongoing operations. Management
should ensure that the facilities, the arrangements and infrastructure allow
for good shift handover practice. !his should"
•Provide all staff who are involved in the handover process with training and the
development of good communication skills.
•Provide written procedures for effective shift handover
•Emphasize the importance of effective shift handover
•ensure that both parties take joint responsibility for conducting an effective shift
handover.
•Emphasize the use of both written and verbal means of communication
•Ensure that any important information is written into a log or report form. !he
log or report form should be brought to the attention of personnel at handover.
•include all personnel from both the incoming and outgoing team in the handover
without exception.
•ensure that managers and supervisors are available at all times and ensure an
open door policy.
•should be treated as high priority.\
(b) Outline the main operational issues communicated at shift handover.
(10)
ANS: The main operational issues communicated at shift handover include"
•work permits- the status of existing permits and the status of work in progress.
•the updating of work permits
•Preparations for upcoming maintenance
•new personnel to the shift
• Any plant overrides- existing and planned
•information about any abnormal events
• Any existing or planned shutdowns
• Any change in plant parameters
• Any routine operations and existing parameters which may need to be carried
out by the personnel from the incoming shift
• Any breakdowns which may have occurred
• Any faults which have occurred with safety critical equipment
• inhibits to the fire and gas (F/G) and emergency shutdown systems
• Any completed work and equipment which have returned to service
SECTION 2
you are advised to spend about bone and a half hours on this section, which
contains TEN questions.
2 (a) Identify the hazardous properties of liquid Petroleum gas (LPG).G
(4)
ANS hazardous properties of 2luqid Petroleum gas – LPG




it is heavier than air
vaporization – cold
storage – leaks
fire/ explosion
(b) Outline the risks associated with liquid Petroleum gas (LPG).
(4)
 ANS Risk associated with liquid Petroleum gas LPG
 Asphyxiations burns (hot and cold)
 fire / explosion
3
Safety cases and safety reports provide documented evidence that an oil and gas
installation is safe.
Outline the typical content of these types of documents.
ANS
Identification of major accident hazards using risk assessments (Q, SQ QRA), bowtie diagrams, etc. The impacts of potential major accident hazards should be
analyzed and identify:
 Each hazard scenario.
 Threats to safety and what causes them.
 Barriers to prevent those threats, Consequences of each threat were it
realised.
 Recovery measures required.
 Factors that could escalate the hazard or its consequences.
•Evaluation of major accident risks and measures taken to control those risks,
using details of all existing "designed-in" precautionary and safety measures.
Existing risk controls should be evaluated to see if these are adequate or further
risk controls are required to demonstrate ALARP. This would include:

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

Identify each hazard/incident scenario. Assess frequency criteria.
Assess consequence criteria
Assess occupied and unoccupied locations as separate criteria.
Assess Evacuation, Escape and Rescue (EER) facilities and requirements.
For higher risks, assess individually.
Identify and assess the risk control measures proposed to achieve ALARP.
• Arrangements for audit and audit reports with a plan showing the type of audit
(internal, external), how often they will be carried, in what areas they will be
conducted, how recommendations will be dealt with and actioned, and who will
be responsible for completion.
•Having an adequate safety management system in place, including the
management of contractors and sub-contractors.
Major accident prevention policies -in the case of safety reports these would need
supporting information from the safety management system
•Identification of the safety critical elements that are in place to manage major
accident hazards (scenarios, possible causes, controls, recovery systems).
•Details of the emergency plan. This would include layout drawings of the
installation, showing locations of all safety and emergency equipment, control
points (e.g. control room, radio room, etc.), isolation and shut-off controls, safe
access routes and escape ladders, access to boats and manning and launch
procedures.
4 (a)
Identify three marine hazards associated with all types of floating Platform
storage offloading units (FPSO).
ANS
•Oil/gas leak arising from:- Blowouts/pipeline leaks/process leaks
•Non-process incident:- such as fire/chemical spill and leaks
•Marine events- such as Collision of supply, stand-by and support vessels/collision
with other vessel/capsize or grounding
• Extreme loadings due to wind or waves
• Structural failure due to; Fatigue/Design error
•failure of derricks, cranes or other equipment
•Dropped objects during- Construction/crane operation/cargo transfer/drilling
operation
•Helicopter crash or fire during refueling
•capsize of crew boats or accident to personnel during transfer,
Crew change, in-field transfer
•construction accident: onshore or offshore work/marine
installation/commissioning activities/pipe laying
• Diving accident
• slips and trips
• Extreme environmental conditions (weather, waves, sea currents/temperature,
ice, etc).
• Accelerated wear and corrosion -the stress of constant movement/buffeting
and aggressive salt spray mean that structures and equipment can quickly fail if
maintenance is neglected.
• Collisions with other vessels and structures, these may result in environmental
damage (oil spills). An inadequate/defective mooring, combined with extreme
weather may contribute to this.
•The intrinsic hazards of the substances – for example, LNG, H2S and drilling
fluids ('mud') and the potential for fire.
(b) Identify suitable controls that minimize risk when operating floating Platform
storage offloading units (FPSOs).
• ship should be securely moored
• The responsible people in charge of terminal and tanker, respectively, should
agree on loading/off-loading.
•The ship's doors, ports, windows, etc. which open onto the tank deck, should be
kept closed (to avoid ingress of flammable vapours and the risk of explosion in
accommodation areas).
• Ventilation systems may also have to be adjusted or disconnected so as not to
suck inflammable vapours or act as an ignition source.
• Cargo tank vents should be protected by flame arresters.
• Ship to terminal connections (such as via directly connecting hose or marine
loading arms/ metal cargo arms) can be fitted with an emergency release.
• Liquid loading lines and vapour emission control lines (vapour recovery) should
be clearly distinguished, to avoid misconnection.
• Hoses should be inspected for defects before use.
• The position of the hoses/loading arms should be adjusted, so as not to place
undue strain on the components (the hoses themselves, ship's manifold
connection, etc).
• The weather should be monitored before and during the operation -the
operation being suspended in cases where high winds or electrical storms are
expected.
• Crews should keep watch for leaks during the operation, being prepared to halt
if leaks are detected.
• Precautions against electrical discharge need to be observed for electrical
discharge between ship and terminal.
• Co-ordinate activities (or take precautions), for example, if hazardous activities
are being undertaken in adjacent tanker berths.
•Do not allow tugs, helicopters, etc. to approach too close during the operation
(or suspend operations if they must).
• There should be joint formal agreement between the master of the vessel and
the terminal authority on readiness to load/unload cargo.
• No transfer should take place before this. Both sides should monitor the
operation and communicate throughout.
An oil installation contains a vessel that requires protection from fire exposure in
the form of active or passive fire protection.
(a) Identify TWO examples of passive fire protection to protect vessels.
(2)
Answers
fire walls/fire doors/fire resistant coatings/ thermal insulation
(b) Outline why the metal legs of the vessel should be protected.
fires can cause thermal weakening of steelwork and result in the collapse of
structures, failure of equipment, and subsequent escalation of the initial event.(c)
(c ) Outline how a fixed water deluge system could provide fire protection.
(2)
A fixed water deluge system could provide protection for a distillation column by
extinguishing the fire, controlling the fire or by providing protection for the
adjacent distillation columns with the cooling effect
(d) Identify TWO additional examples of active fire protection.
(2)
foam systems
Water Mist systems
Outline the following failure modes that may lead to loss of hydrocarbon
containment from storage tanks, vessels or pipelines
(a) creep: is slow movement under stress, made more severe with heat for
long periods, especially with increases in temperature approaching melting
points.
(b) stress corrosion cracking: occurs under tensile stress and is worse in a
corrosive environment at elevated temperatures.
(c) ) thermal shock: cracking associated with rapid temperature change with
different parts of an object expanding by different amounts where the
stress overcomes the strength of the materials.
(d) Brittle fracture.: Rapid run of cracks through a stressed material with plastic
deformation before failure caused by such things as repetition of
inappropriate heating or pressurizing rates
Outline FOUR types of work activity associated with an oil platform that might
require a permit-to-work AND give a reason in each case for the requirement.
A large oil company is proposing to build a new oil and gas installation in the
North sea. the Process safety Management team is analysing past incidents and
database records from the oil and gas industry.
Excluding active and passive fire protection systems,
outline physical design features of the platform that would minimise risk to
operating personnel in the event of a major incident.
Physical design features of an offshore platform that would minimise risk to
operating personnel in the event of a major incident are
Plant separation
Compartmentalization
Protection of personnel/ equipment
Means of escape
blow out panels
temporary refuges with communications & control
.
9 (a) Identify TWO ways in which vapour clouds can be generated.
Sudden depressurization
Rupture of vessel
Loss of containment
Uncontrolled buildup of pressure
(b) Outline how a vapour cloud explosion can be generated.
Vapour cloud explosion can be generated by
Confined / unconfined generation
Vapour cloud explosions may arise from vaporization of a release of liquefied gas
from a ruptured vessel or pipeline
(c) Identify the physical consequences of vapour cloud explosions.
 Physical consequences of vapour cloud explosions
 Overpressure
 fire & explosion resulting debris as airborne missiles
10 An operator is draining a flammable liquid from process pipework to a metal
container. The supervisor is concerned about the possibility of an electrostatic
charge forming and stops this operation until a risk assessment is undertaken.
during this work activity
(a) Identify factors that influence the generation of the electrostatic charge
Factors that influences the generation of the electrostatic charge


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
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hot dry weather
flow rate,
overfilling
lack of earthling/grounding
liquid instability
splash filling
none conductivity of materials
Agitation
Filters
Pressure velocity
(b) Outline practical ways of minimising the formation of an electrostatic charge.
Practical ways of minimising the formation of an electrostatic charge

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


Humidification of the atmosphere
Antistatic additives
Reduce flow velocity
Intrinsically safe equipment
Bonding and grounding of equipment and containers
 Avoid splash filling by submerging the fill pipe below the liquid level in the
container
 Increasing the conductance of floors, footwear
11 An employee was seriously injured in an accident at work within an oil and gas
installation.
Identify the documented information that might be used by the investigating
team to determine the causes of this accident.
documented information that might be used by the investigating team to
determine the causes of an accident
PTW
Photographs
Cctv footage
witness statements
Previous health and safety Meeting Minutes
Risk Assessments/ JSAs
Method statements
control room data
internal incident report forms
Maintenance records
disciplinary records
safe systems of work
Audit/inspection reports
Safe operating procedures
DNA test results
12. identify the hazards associated with crude/unrefined oil during extraction,
storage and processing.
•the potential for fire due to a leak or release of crude from heaters in the crude
desalting unit. Low boiling point components of crude may also be released if a
leak occurs.
•inadequate desalting can cause fouling of heater tubes and heat exchangers
throughout the refinery. fouling restricts product flow and heat transfer and leads
to failures due to increased pressures and temperatures.
•cooling-tower water can be contaminated by process materials and by-products
including sulfur dioxide, hydrogen sulfide, and carbon dioxide, with resultant
exposures.
•Hazards such as those related to liquids and vapors when opening or draining
pumps, valves, and 6or lines, and during product sampling, inspection, and
maintenance activities
•
!he potential for fire e&ists should hydrocarbon storage tanks be overfilled or
develop leak that allow vapors to escape and reach sources of ignition.
•hazards related to product sampling, manual gauging, inspection, and
maintenance activities including confined space entry where applicable.
identify two types of risk assessment techniques. two types of risk assessment
techniques are"
3isk assessment +,
The qualitative method of risk assessment can generally be considered to not
involve equations based on numbers to evaluate risk. Using a qualitative
approach, a cable trailing in a walkway used by infirm older patients may
beevaluated as being a "high" risk, because it is felt that somebody is bound to
trip