QRA – Vessel Collision and Grounding Study Engineering Service in Qatar

OBJECTIVE

The objective of the QRA (Quantitative Risk Analysis) study is to identify hazards, quantify individual risks for personnel, and determine the Level of concern (thermal radiation, explosion overpressures, and toxic exposure) associated with the project facilities

The QRA study will determine the following:

  • Risk levels in the project;
  • and That risks associated with the project facilities are tolerable and ALARP (As low as reasonably practicable) by demonstration, and where necessary, additional design safeguards (barriers) are specified to reduce the risks to ALARP.

Importance of QRA

  • Quantifies risks arising out of the project;
  • Compare the impacts with Risk acceptance criteria as stated in Philosophy for HSE Risk Management of Vessel Collision and Grounding Study.
  • Recommend risk reduction measures to ensure that the risks are within ALARP;
  • Highlight risk ranking of hazardous scenarios with proposed risk reduction measures.

Methodology of QRA

Key steps included in the QRA investigation are as follows:

  • Analyzing every incident involving hydrocarbons or hazardous materials
  • Calculating the Probability of Hydrocarbon and Toxic Material Events
  • Quantification of the consequences of hydrocarbon/ toxic material incidents,
  • Combining outcomes and probability to provide a risk profile for people and assets
  • Identification of the current levels of risk to the personnel within the facility
  • Identification of LSIR contours for the safe location of new facilities within the plant area.
  • Finding and evaluating risk-reduction strategies Evidence that the hazards have been brought down to ALARP or tolerable levels

QRA Methodology Flow Chart

The QRA methodology flowchart illustrates systematically identifies and assesses project hazards by defining the scope, identifying hazards, and selecting failure cases. It models consequences and analyzes the frequency of each case to evaluate the risks. Risks are then checked against criteria to determine if they are As Low As Reasonably Practicable (ALARP). If not, risk reduction measures are applied, feeding into risk management for mitigation planning.

Data Gathering considers familiarization with regard to items such as Plant design, function, location, capacity, and layout Environmental weather data Process engineering details e.g. composition, heat and mass balance, equipment items, process parameters – pressure and temperature regimes, inventories, flowschemes Plant operation e.g. operational and emergency procedures

Hazard Identification – Hazard Identification (HAZID) is defined as a systematic way of identifying accidental events that may lead to injuries and fatalities, and the control measures in place to prevent these accidents from occurring. Types of hazards considered in this QRA (Quantitative Risk Analysis) are as following:

Types of hazards

  • Process Hydrocarbon Hazards: The hazardous scenarios based on material properties and potential system hazards leading to containment loss event will be identified. The primary hazards from process facilities are uncontrolled releases of flammable materials, with causes and consequences which will be studied extensively. The consequence modelling will cover the process facilities including Diesel pumping from RLTO Tank Farm to LOTS facility and storage and dispensing of diesel within the facility.
  • Ship Collision Hazards: In Ship collision The risk arising from Vessel to Vessel collision and Vessel to Port Collision within an marine terminal is considered in two parts: collision frequency and collision consequences. The Frequency and consequence of the Collision mentioned in IOGP was used for this study. Ship grounding effect resulting in potential loss of containment was studied as part of ship collision hazard. The risk to the OSV crew was assessed qualitatively
  • Structural Hazards – Structural hazards are typically applicable for marine platforms and hence was not studied.
  • Occupational Hazards: Occupational Risk Fatalities due to all causes were included, including boat transportation incidents and air transport as well as being struck, explosion/burn, electrical, drowning, falls, and ‘caught between’. The occupational Fatal Accident Rates (FARs) for company employees and contractors for offshore provided in IOGP was applied for this QRA study.
  • Transportation Hazards: Potential impact of vehicle collision with the piping / storage was considered, if credible, based on layout review. The consequence / outcome of the vehicle collision was considered as loss of containment or catastrophic failure.

Consequence Modelling

The consequence analysis is based on several steps to establish a comprehensive overview of the accident scenario and to determine the resulting impact on the platform in terms of structural damage or fatalities to personnel. The following procedures are involved in consequence modeling

  • Release rates and duration;
  • Gas dispersion modelling;
  • Thermal radiation modelling;
  • Explosion overpressure modelling.

Frequency Analysis

The following will be performed in the frequency analysis:

  • Equipment parts count, including pipeline/pipework lengths, flanges, valves, instrument connections, and so forth.
  • Location assessment of the parts count.
  • Determination of the location-specific failure rate of each component with globally accepted failure rate data. OGP Risk Assessment Data Directory, was used for this project.

Definition of Risk Tolerability Criteria

Risk levels arrived at in the QRA was compared with the Risk Tolerability Criteria to determine whether risks are unacceptable, tolerable if ALARP or broadly acceptable. The following quantitative criteria were used in the decision-making:

LSIR for location of developments (Land use planning purposes); and Individual Risk levels.

We will evaluate societal risk (F-N curve), if appropriate.

Risk Assessment

 The risk levels are established by:

  • Calculation of the failure frequency for different holes sizes based on the parts count analysis and hole size distribution;
  • Evaluation of the hazardous zones for the various release scenarios;
  • Summation of all the various failure frequencies and hazardous zones to generate an overall risk profile for the site/ facility;
  • Evaluation of the individual risk level based on occupancy data;
  • Comparison of the risk levels calculated with the required risk acceptance criteria.
  • The output from the frequency analysis and the consequence analysis are used to calculate risk, in conjunction with: Fatality probabilities; Weather data; and Location.

Risk assessment is undertaken for the following:

Individual Risk (IR) and Location Specific Individual Risk (LSIR).

Using the results of the QRA, appropriate and workable Risk Reduction Measures were identified in order to lower the project’s risk to As Low As Reasonably Pragmatic (ALARP). The main risk assessment was evaluated to determine the overall risk to the worker groups based on major hydrocarbon, toxic material hazards and non-hydrocarbon hazard like dropped objects, structural failure, ship collision, transportation as this is an marine Terminal.

Risk Evaluation

The primary risk contributors to the total risk need were determined as a consequence of the preceding processes. The main risk contributors provide guidance as to which areas in the facility design need more attention to reduce overall risk to ALARP levels. The principle of ALARP is to demonstrate that the risk levels are in the tolerable region and that the practicality of incorporating any additional risk reduction measures or potential design changes is disproportionate to the benefit obtained.

An evaluation was made of the sensitivity of the results to changes in assumptions and estimated probabilities and physical effects. This is particularly important where data is considered to have wide confidence bands or its applicability has inaccuracies.

Risk Reduction Measures

Risk Reduction Measures are recommended to improve the design or operation of the facility in order to reduce risks to ALARP and enhance its functional and HSE performance. Technically feasible and practical measures are proposed to reduce the frequency of event occurrence and mitigate the consequence if the event does occur.

Cost Benefit Analysis (CBA)

Cost-benefit analysis, or CBA, is a method for weighing the advantages and disadvantages of adding more safety precautions by contrasting the measure’s benefits with its implementation costs, in terms of the risk factored cost of accidents it will avert. The purpose of CBA is to show whether the benefits of a measure outweigh its costs, and thus indicate whether it is appropriate to implement the measure

Software For Risk Modelling

The risk modelling was performed using DNV PHAST & SAFETI Software Package. The risk model was prepared based on the consequence analysis results and the other data. The output from PHAST Risk (LSIR contours) was then be used in combination with the assumptions on personnel distribution and occupancy to calculate the Individual Risk (IR) contribution from various options of the project.