D
ET
N
ORSKE
V
ERITAS
Report on
QRA for POL IRDs/ depots
BHARATPUR
For
Hindusthan Petroleum Corporation Limited
Mumbai – 400 001
Maharashtra, India
QRA for POL IRDs/ depots – Bharatpur
DET NORKSE VERITAS AS
EMGGEN CHAMBERS, 10C.S.TROAD,VIDHYANAGARI, SANTACRUZ (E),KALINA
MUMBAI 400098 TEL:+912226676400
FAX: +912226653380
http://www.dnv.com
For:
Hindusthan Petroleum Corporation Limited Gresham Assurance Building, Sir P.M. Road, Post Box No. 198, Fort,
Mumbai – 400 001 Maharashtra, India Account Ref.:
K Somashekhar Rao, Sr. Manager – HSE-O&D [email protected]
Date of First Issue: 2013-05-29 Project No. PP046380
Report No.: 12QR1P2-27 Organisation Unit: Maritime & Oil and Gas, India
Revision No.: 02 Subject Group: SHE
Summary:
DNV conducted Quantitative Risk Assessment (QRA) for HPCL POL IRDs/ depots. This QRA Study aims to identify Individual and Societal Risk associated with the Bharatpur location. This report presents the DNV’s findings and conclusion from the study.
Prepared by: Vishalakshi Daine
Consultant Signature
Verified by Anil Bhat Avvari
Consultant Signature
Approved by: Salian Varadaraja
Project Sponsor Signature
No distribution without permission from the client or responsible organisational unit (however, free distribution for internal use
within DNV after 3 years) Indexing Terms
No distribution without permission from the client or responsible organisational unit Key Words QRA
Strictly confidential Service Area SHE Risk Management
Unrestricted distribution Market Segment Oil & Gas
Rev. No. / Date: Reason for Issue: Prepared by: Verified by Approved by: 02/30-07-2013 Draft report issued to HPCL
for comments
VDAI AVAB VASAL
All rights reserved. This publication or parts thereof may not be reproduced or transmitted in any form or by any means, including photocopying or recording, without the prior written consent of Det Norske Veritas AS.
Executive Summary
Det Norske Veritas (DNV) conducted a Quantitative Risk Assessment (QRA) study covering the entire HPCL POL IRDs/ depots. The presentation of results is in line with UK HSE guidelines. This report presents the DNV’s study findings and conclusion from the study for the Bharatpur.
The overall objective of the QRA study is to quantify the level of individual fatality risks associated with the Bharatpur; and to demonstrate that the level of risks is in compliance with the UK HSE guidelines
Based on the QRA study for the Bharatpur, the following conclusions and recommendations can be drawn:
Area under Study Major Hazard Recommended Control /Mitigation
Tank Farm
Pool fire and Tank fire are major events in the Tank farm area, leading to the escalation of the fire from one tank to the another
Ensure availability of water spray system in the tank farm area for protecting the tank from the external fire Ensure regular
maintenance procedure to reduce likelihood of failure of the valves, flanges and pipes
Pump House Area
Release of pressurized
inventories from the pump house may cause severe
damage in the Depot
premises
Consider providing HC detectors in Pump house area
Gantry Operations
Fire due to Leak during TT loading operations. Major events of pool fire due to leak or spillage, flash fire are observed. Hazardous radiation levels of 12.5 kw/m2 and 37.5 kW/m2 are observed close to gantry.
As the gantry area is a high risk
and high consequence zone, ensure minimum activity of trucks and personnel in this area.
Ensure emergency escape route
is provided and informed to all
Area under Study Major Hazard Recommended Control /Mitigation
gantry and TT crew.
Consider provision of HC detectors for early detection of hazardous leaks. Ensure training, SOP, emergency procedures established and implemented for all personnel at gantry. Ensure PPE usage by all personnel.
Ensure that the loaded trucks spend minimum time near the gantry after the loading operations
Office Building
Fire radiation due to leak from the loaded tanker trucks.
Ensure that the loaded trucks spend minimum time near the gantry after the loading operations
Even though the Individual and societal risk levels of the Bharatpur has been found to be in ALARP region in assessing with HSE UK risk criteria, In order to maintain the level of risk at this level, cost effective risk mitigation measures should be implemented to mitigate the risks to a level that is As Low As Reasonably Practicable (ALARP).
GLOSSARY
ALARP: As Low As Reasonable Practical
HSE : Health Safety Environment
IR : Individual Risk
JF : Jet Fire
kW/m2 : Kilo Watt per Square Metre, a measure of heat flux or radiant heat
LFL : Lower Flammable Limit
LOC : Loss of containment
LSIR : Location Specific Individual Fatality Risk per year P&ID : Piping and Instrumentation Diagram
PLL : Potential Loss of Life
QRA : Quantitative Risk Assessment
UFL : Upper Flammable Limit
UK HSE: UK Health and safety Executive
TABLE OF CONTENTS
Executive Summary ... III
1 INTRODUCTION ... 1 1.1 Background ... 1 1.2 Objectives ... 1 1.3 Scope of Study ... 1 1.4 Report Structure ... 2 1.5 Facility Description ... 3 1.6 Input Data ... 5 1.6.1 Material Inventory ... 5 1.6.2 Process Conditions ... 5 1.6.3 Material Composition ... 5 1.6.4 Weather ... 5 1.6.5 Ignition Sources ... 5 1.6.6 Population ... 5
2 RISK ASSESSMENT CRITERIA ... 6
2.1 UK HSE criteria ... 6
2.2 Individual Risk Criteria ... 7
2.3 Societal Risk Criteria ... 8
3 RISK RESULTS ... 9
3.1 Individual Risk ... 9
3.2 Societal Risk ... 11
3.2.1 FN Curve ... 11
4 CONCLUSIONS AND RECOMMENDATIONS ... 13
List of Tables
Table 2-1: Societal Risk Criteria – Onsite ... 8
Table 3-1: LSIR ... 9
List of Figures
Figure 1-1: Bharatpur Layout ... 3Figure 1-2: Bharatpur Layout ... 4
Figure 2-1: ALARP Principle ... 6
Figure 2-2: FN Curve and Criterion Line ... 7
Figure 3-1: Individual Risk Contours for Bharatpur ... 10
Figure 3-2: FN Curve Onsite ... 11
1
INTRODUCTION
1.1
Background
Det Norske Veritas (DNV) conducted a Quantitative Risk Assessment (QRA) study covering the entire HPCL POL IRDs/ depots. The presentation of results is in line with UK HSE guidelines. This report presents the DNV’s study findings and conclusion from the study for the Bharatpur.
1.2
Objectives
The overall objective of the QRA study is to
- Quantify the level of individual fatality risks associated with the Bharatpur; and
- Demonstrate that the level of risks is in compliance with the UK HSE guidelines
1.3
Scope of Study
DNV has performed the work in accordance to the UK HSE guidelines. Following are the important aspects of this study:
- Verify the individual and societal risk levels in accordance with UK HSE criteria
- Tabulation of the consequences in terms of:
Distances to radiation levels, Lower Flammability Limit (LFL) and explosion overpressure for different weather classes according to specific criteria classes.
1.4
Report Structure
This report presents:Section 1 Introduction
This section provides a general introduction of the project, the main objectives of the QRA study, the scope of study, and the structure of this report.
Section 2 Risk Assessment Criteria
This action outlines the risk criteria applied in this QRA study.
Section 3 Risk Results
This section provides the risk results due to process hazard
Section 4 Conclusions and Recommendation
This section outlines the overall conclusions of the study and provides the recommendation to be implemented in order to ensure ALARP performance in the operation.
Section 5 Reference
This section details the reference used in this QRA.
Annexe 1 QRA Methodology
This appendix explains the QRA methodology applied in this QRA.
Annexe 2 Assumptions Register
The assumptions presented are applied in the modelling and preparation of the reports/technical notes.
Annexe 3 Failure case and frequency analysis
This appendix defines the failure cases selected for analysis, as well as the corresponding frequencies.
Annexe 4 Consequence Analysis
This appendix presents outcome of an event in terms of toxic, fire and explosion.
1.5
Facility Description
The Bharatpur layout is shown in the figure below.
Report No.: 12QR1P2-27
s
1.6
Input Data
1.6.1
Material Inventory
Material required for the QRA study is taken from the Mass and Energy balance sheet provided by the client. The static and dynamic inventory is calculated based on the flow rate and equipment dimension provided by the client. The inventory details with respect to vessel and pipelines is given at Annexe 3 - Failure case and frequency analysis.
1.6.2
Process Conditions
The process conditions like temperature and pressure required for the QRA study is taken from the Mass and Energy balance sheet and Process flow diagram provided by the client. The details are placed in a table at Annexe 3 - Failure case and frequency analysis.
1.6.3
Material Composition
Material required for the QRA study is taken from the Mass and Energy balance sheet provided by the client for most of the cases. If the data is not available suitable representative material is considered as per DNV – Technical note 13 and international standard. This is explained in Assumption Register (Annexe 2) in detail.
1.6.4
Weather
Meteorological data are required at two stages of the QRA. First, various parts of the consequence modelling require specification of wind speed and atmospheric stability. Second, the impact (risk) calculations require wind-rose frequencies for each combination of wind speed and stability class used.
1.6.5
Ignition Sources
In order to calculate the risk from flammable materials, information on the ignition sources (which are present in the area over which a flammable cloud may drift) is required.
1.6.6
Population
All the population details are provided to the study and the presence factor is explained with respect to the unit is given in details in Assumption Register (Annexe 2).
s
2
RISK ASSESSMENT CRITERIA
In order to determine acceptability, the risk results are assessed against a set of risk criteria as per UK HSE criteria.
2.1
UK HSE criteria
Following points details the UK HSE guidelines:
- An individual risk below 1 x 10-6 fatalities per year is considered as acceptable for both plant workers and public. An individual risk above 1 x 10-4 fatalities per year for public is considered as unacceptable and an individual risk above 1 x 10-3 fatalities per year for workers is considered unacceptable. Between these limits the risk is considered as ALARP (As Low as Reasonably Practicable). An indication of this is shown in the below figure
Figure 2-1: ALARP Principle
- Societal risk can be represented by FN curves, which are plots of the cumulative frequency (F) of various accident scenarios against the number (N) of casualties associated with the modeled incidents. The plot is cumulative in the sense that, for each frequency, N is the number of casualties that could be equaled or exceeded.
s
Often ‘casualties’ are defined in a risk assessment as fatal injuries, in which case N is the number of people that could be killed by the incidents.
Figure 2-2: FN Curve and Criterion Line
2.2
Individual Risk Criteria
The UK HSE Individual Risk Criteria was considered to assess the risk for HPCL POL IRDs/ depots. Individual risk above 10-3 per annum for any person shall be considered intolerable and fundamental risk reduction improvements are required.
Risk criteria for Individual Risk for on-site are as follows:
- Individual risk levels above 1 x 10-3 per year will be considered unacceptable and
will be reduced, irrespective of cost
- Individual risk levels below 1 x 10-6 per year will be broadly acceptable
- Risk levels between 1 x 10-3 and 1 x 10-6 per year will be reduced to levels as low as reasonably practicable (ALARP). That is the risk within this region is tolerable only of further risk reduction is considered impracticable because the cost required to reduce the risk is grossly disproportionate to the improved gained
s
2.3
Societal Risk Criteria
When considering the risk associated with a major hazard facility, the risk to an individual is not always an adequate measure of total risks; the number of the individuals at risk is also important. Catastrophic incidents with the potential multiple fatalities have a little influence on the level of risk but have a disproportionate effect on the response of society and impact of company reputation.
The concept of societal risk is much more than that for individual risk. A number of factors are involved which make it difficult to determine single value criteria for application to a number of different situations. These factors include;
- The hazard, the consequential risks and the consequential benefits
- The nature of assessment
- Factors of importance to the company, government, regulators and authorities, public attitudes and perception and aversion to major accident
Societal risk is the relationship between frequency of an event and the number of people affected. Societal risk from a major hazard facility can thus be expressed as the relationship between the number of potential fatalities N following a major accident and frequency F at which N fatalities are predicated to occur. The relationship between F and N, and the corresponding relationship involving F, the cumulative frequency of events causing N or more fatalities, are usually presented graphically on log-log axis.
DNV has used following societal risk criteria. Societal risk should not be confused as being the risk to society or the risk as being perceived by society. The word “societal” is merely used to indicate a group of people and societal risk refers to the frequency of multiple fatality incidents, which includes workers and the public. Societal risk is usually represented by an FN (Frequency – Number of Fatality) curve.
Table 2-1: Societal Risk Criteria – Onsite
Maximum Tolerable Intercept With N=1
Negligible Intercept With N=1
s
3
RISK RESULTS
3.1
Individual Risk
Location specific individual risk (LSIR) is used to indicate the risk at a particular location. It is the risk for a hypothetical individual who is positioned there for 24 hours per day, 365 days per year. It is a standard output from a QRA. In onshore studies, the geographical variation of LSIR may be represented by iso-risk contour plots and used for land-use planning. In offshore studies, an LSIR value is normally computed for each separate module on the installation. Since in reality people do not remain continually at one location, this is not a realistic risk measure.
Table 2.1 presents the LSIR
Table 3-1: LSIR
S.No Location LSIR Remarks
1 D.G Control room 5.62E-07 Acceptable
2 Gantry 7.38E-07 Acceptable
3 Office Building 3.60E-06 Acceptable
4 Workers change room 3.34E-06 Acceptable
Table 3-2: Major Risk Contributors to office building
S.No Location Risk/yr %
1 Large Leak from MS Tanker 8.42E-07 23.40
2 Large Leak from SKO Tanker 7.22E-07 20.08
3 Large Leak from HSD Tanker 6.25E-07 17.39
4 Medium leak from MS Tanker 3.91E-07 10.88
Report No.: 12QR1P2-27
3.2
Societal Risk
3.2.1
FN Curve
FN curve defines the societal risk. It represents the relationship between the frequency and the number of people suffering a given level of harm from the realisation of specified hazards. It is usually taken to refer to the risk of death and usually, expressed as a risk per year.
The following figure presents the onsite societal risk FN Curve for Bharatpur. The “blue line” represents the upper limit of risk and the “green line” represents the lower level of risk. The region between this two represents the risk in the ALARP (AS LOW AS REASONABLY PRACTICABLE) region. The region beyond the blue line indicates the unacceptable region and the region below blue line represents the broadly acceptable region. The “red line” represents the level of societal risk that has been realised around Bharatpur.
Figure 3-2: FN Curve Onsite
- Compared to the UK HSE risk criteria, the FN Curve shows that societal risk is within the Acceptable region and does not exceed the unacceptable criteria.
FN Curve Offsite
4
CONCLUSIONS AND RECOMMENDATIONS
Area under Study Major Hazard Recommended Control /Mitigation
Tank Farm
Pool fire and Tank fire are major events in the Tank farm area, leading to the escalation of the fire from one tank to the another
Consider providing water spray system in the tank farm area for protecting the tank from the external fire
Ensure regular
maintenance procedure to reduce likelihood of failure of the valves, flanges and pipes
Pump House Area
Release of pressurized
inventories from the pump house may cause severe
damage in the Depot
premises
Consider providing HC detectors in Pump house area
Dyke should be provided to the pumps to limit pool formation of the release inventory
Gantry Operations
Fire due to Leak during TT loading operations. Major events of pool fire due to leak or spillage, flash fire are observed. Hazardous radiation levels of 12.5 kw/m2 and 37.5 kW/m2 are observed close to gantry.
As the gantry area is a high risk
and high consequence zone, ensure minimum activity of trucks and personnel in this area.
Ensure emergency escape route
is provided and informed to all
gantry and TT crew. Consider provision of HC detectors for early detection of hazardous leaks.
Area under Study Major Hazard Recommended Control /Mitigation
Ensure training, SOP, emergency procedures established and implemented for all personnel at gantry. Ensure PPE usage by all personnel.
Ensure that the loaded trucks spend minimum time near the gantry after the loading operations
Office Building
Fire radiation due to leak from the loaded tanker trucks.
Ensure that the loaded trucks spend minimum time near the gantry after the loading operations
5
REFERENCES
- “Methods for the calculation of physical effects – due to releases of hazardous materials (liquids and gases)” TNO Yellow Book, CPR – 14E, 2005
- A Flack / B Bain / T Lindberg / J R Spouge “Process Equipment Failure Frequencies” Rev. 04, October 2009 for Process Pipes, Pumps, Atmospheric Storage Tank
- CCPS, Guidelines for Consequence Analysis of Chemical Releases, American Institute of Chemical Engineers, 1999.
- Lees, F. P., Loss Prevention in the Process Industries, Butterworth-Heinemann, 1996
- Oil Industry Safety Directorate (OISD), First Edition, August 2007.
- Robin Pitblado, Andreas Flack, Phil Crosthwaite, David Worthington, “Consequence Handbook”, Report no.:70037714, August 2008
Det Norske Veritas (DNV) is a leading, independent provider of services for managing risk with a global presence and a network of 300 offices in 100 different countries. DNV’s objective is to safeguard life, property and the environment.
DNV assists its customers in managing risk by providing three categories of service: classification, certification and consultancy. Since establishment as an independent foundation in 1864, DNV has become an internationally recognised provider of technical and managerial consultancy services and one of the world’s leading classification societies. This means continuously developing new approaches to health, safety, quality and environmental management, so businesses can run smoothly in a world full of surprises.
Global impact for a safe and sustainable future:
Annexe 1
Table of Contents
1 QRA METHODOLOGY ... 1
1.1 Introduction to Risk Assessment ... 1 1.2 What is QRA? ... 2 1.3 Key Components in QRA ... 2 2 QRA APPROACH ... 5
2.1.1 Hazard Identification ... 5 2.2 Consequence Modelling/Phast Software ... 6 2.3 Frequency Analysis ... 7 2.4 Risk Calculation/PHASTRISK Software ... 7 2.4.1 Built-In Event Trees ... 7 2.4.2 Atmospheric Condition ... 10 2.4.3 Risk Presentation: ... 10 3 QRA SOFTWARE TOOL ... 12
List of Tables
Table 2-1: Explosion Overpressure Effects ... 6 Table 2-2: Effects of Thermal Radiation ... 7 Table 3-1 PHAST RISK Default Vulnerability Parameters ... 17
List of Figures
Figure 1-1: QRA methodology ... 3 Figure 1-2: ALARP Principle ... 4 Figure 2-1 : Event Tree 1 – Continuous Vapour Release ... 8 Figure 2-2: Event Tree 2 – Continuous Release with Rainout ... 8 Figure 2-3: Event Tree 3 – Instantaneous Vapour Release ... 9 Figure 2-4: Event Tree 4 – Instantaneous Release with Rainout ... 9
1
QRA METHODOLOGY
1.1
Introduction to Risk Assessment
This section is presented to assist the reader who is not familiar with the terms used in this document and for those who are familiar to confirm DNV understanding of the terms and their application in the context of this document. An oil & gas facility has the potential to cause harm such as:
- Sickness, injury or death of workers and people in the surrounding community
- Damage to property and investments
- Degradation of the physical and biological environment
- Interruption to production and disruption of business
A state or condition having the potential to cause a deviation from uniform or intended behaviour which, in turn, may result in damage to property, people or environment, is known as hazard. Thus a scraper trap is a hazard because it has the potential to cause a fire; processes such gas compression is a hazardous activity because it has the potential to cause fires and explosions. The word “hazard” does not express a view on the magnitude of the consequences or how likely it is that the harm will actually occur. A “major hazard” is associated with Loss of Containment and has the potential to cause significant damage or multiple fatalities. Again, the term does not imply that such events are likely. Incidents are the actual realization of a hazard, i.e. an event or chain of events, which has caused or could have caused personal injury, damage to property or environment. They are sudden unintended departures from normal conditions in which some degree of harm is caused. They range from minor incidents such as a small gas leak to major accidents such as Flixborough, Mexico City, Bhopal, Pasadena, Texas City, etc. Sometimes, the more neutral term “event” is used in place of the more colloquial term “incident”. For flammable incidents, ignition has to take place for a hazard to be realized.
Risk is the combination of the likelihood and the consequences of such incidents. More scientifically, it is defined as the likelihood of a hazard occurrence resulting in an undesirable event. The likelihood may be expressed either as a frequency (i.e. the rate of events per unit time) or a probability (i.e. the chance of the event occurring in specified circumstances). The consequence is defined as an event or chain of events that result from the release of a hazard. The impact or effect is the degree of harm caused by the event. Safety is the inverse of risk. The higher the risk for an occupation or installation, the lower is its safety. The popular understanding of safety sometimes appears to be “zero risk”, but this is impossible in an intrinsically hazardous activity such as oil and gas production.
1.2
What is QRA?
Quantitative risk assessment (QRA) is a means of making a systematic analysis of the risks from hazardous activities, and forming a rational evaluation of their significance, in order to provide input to a decision-making process.
QRA is sometimes called ‘probabilistic risk assessment’ term originally used in the nuclear industry. The term ‘Quantified Risk Assessment’ is synonymous with QRA as used here. The term ‘quantitative risk analysis’ is widely used, but strictly this refers to the purely numerical analysis of risks without any evaluation of their significance.
QRA is probably the most sophisticated technique available to engineers to predict the risks of accidents and give guidance on appropriate means of minimizing them. Nevertheless, while it uses scientific methods and verifiable data, QRA is a rather immature and highly judgmental technique, and its results have a large degree of uncertainty. Despite this, many branches of engineering have found that QRA can give useful guidance. However, QRA should not be the only input to decision-making about safety, as other techniques based on experience and judgment may be appropriate as well.
1.3
Key Components in QRA
The study is based on the premises of a traditional Quantitative Risk Assessment. The key components of QRA are explained below, and illustrated in Figure 1-1.
The first stage in a QRA is defined as system definition where the potential hazards associated with a facility or activities are to be analyzed. The scope of work for a QRA should be to define the boundaries for the study, identifying which activities are to be included and which are excluded, and which phases of the facility’s life are to be assessed. The hazard identification consists of a qualitative review of possible accidents that may occur, based on previous accident experience or judgment where necessary. There are several formal techniques for this, which are useful in their own right to give a qualitative appreciation of the range and magnitude of hazards and indicate appropriate mitigation measures. This qualitative evaluation is described in this guide as “hazard assessment”.
In a QRA, hazard identification uses similar techniques, but has a more precise purpose – defining the boundaries of a study in terms of materials to be modelled, release conditions to be modelled, impact criteria to be used, and identifying and selecting a list of failure cases that will fully capture the hazard potential of the facilities to be studied. Failure cases are usually derived by breaking the process system down into a larger number of sub- systems, where failure of any component in the sub-system would cause similar consequences. In pipeline case, this can be performed by breaking the line into sections depending on availability of isolation valves along the line.
Figure 1-1: QRA methodology
Once the potential hazards have been identified, the frequency analysis estimates how likely it is for the accidents to occur, based on the type and number of equipment components included in the defined failure cases. The component failure frequencies to be used are usually derived from an analysis of historical accident experience, or by some form of theoretical modelling.
In parallel with the frequency analysis, consequence modelling evaluates the resulting effects if the accidents occur, and their impact on people, equipment and structures, the environment or business, depending on the defined scope of the QRA study. Estimation of the consequences of each possible event often requires some form of computer modelling. Consequence analysis requires the modelling of a number of distinctive phases, i.e. discharge, dispersion, fires and explosions (for flammable materials).
Closely liaised with the consequence assessment is the impact assessment, i.e. how does the fire, explosion or toxic cloud affect human beings. When the frequencies and consequences / impact of each modelled event have been estimated, they can be combined to produce risk results. Various forms of risk presentation may be used, commonly grouped as follows:
- Individual risk - the risk experienced by an individual person
- Group/Societal risk - the risk experienced by a group of people exposed to the hazard
The next stage is to introduce criteria, which are yardsticks to indicate whether the risks are acceptable, or to make some other judgment about their significance. Risk assessment is the process of comparing the level of risk against a set of criteria as well as the identification of major risk contributors. The purpose of risk assessment is to develop mitigation measures for unacceptable generators of risk, as well as to reduce the overall level of risk to As Low as Reasonably Practical (Figure 1-2).
Figure 1-2: ALARP Principle
High Risk Low Risk ALARP Region Unacceptable Region Broadly Acceptable Region Given immediate attention and a response developed commensurate with the scale of the threat
Broadly acceptable only if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement gained
Necessary to maintain assurance that risk remains at this level High Risk Low Risk ALARP Region Unacceptable Region Broadly Acceptable Region Given immediate attention and a response developed commensurate with the scale of the threat
Broadly acceptable only if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement gained
Necessary to maintain assurance that risk remains at this level
2
QRA APPROACH
2.1.1
Hazard Identification
Hazard identification is the structured study of a plant in order to produce a list of foreseeable, potentially hazardous releases. In a plant, there is a wide range of substances that, if released, could cause injury or fatality. The hazards applicable for the plant have been identified through:
- Knowledge transfer from other risk assessments for boosting station plants carried out by DNV within the applicable confidentiality constraints
- Site specific parameters
- The selection of appropriate hazards considered a range of issues, including: Nature of potential hazards
Position of plant in relation to the surrounding community Complexity of the process
DNV has concentrated on the flammable hazards.
A list of the main process streams is defined from the Process Flow Schemes (PFS). Of these, some were considered to be non-hazardous (e.g., water streams) or only likely to give a local hazard (e.g., small pool fires), and were not analyzed further. The streams identified to be hazardous were further analyzed in the QRA.
The range of possible releases for a given stream covers a wide spectrum, from a pinhole leak up to a catastrophic rupture (of a vessel) or full bore rupture (of a pipe). It is both time-consuming and unnecessary to consider every part of the range; instead, a finite number of failure cases are generated to characterize each unit. The number of specific cases and the distribution of the cases in terms of the size which are analyzed quantitatively take into account the potential consequences and the format of the frequency data that are being used.
2.2
Consequence Modelling/Phast Software
The consequence analysis is performed using DNV proprietary software PHAST. PHAST is a consequence and impact assessment module integrated within DNV risk calculation software PHASTRisk. PHAST calculates wide range of possible consequences from the LOC events, including:
- Jet Fire, causing thermal radiation impact
- Pool Fire, causing thermal radiation impact
- Flash Fire, causing thermal radiation impact within the flammable cloud envelope
- Explosion, causing overpressure impact
Various factors affecting the extent of consequence are also considered within the PHAST model which includes:
- Atmospheric conditions, including solar radiation flux, ambient temperature, humidity and wind speed/direction as well as weather stability
- Release location
- Release orientation
Detailed findings of the consequence analysis for selected failure cases are presented in Section 6. The qualitative levels of explosion and heat radiation effects are described in Table 2-1 and
Table 2-2 respectively are used to assess the likelihood of harm to people or the likelihood of further loss of containment and / escalation as per DNV’ Technical note.
Table 2-1: Explosion Overpressure Effects
Overpressure (bar) Effects Within Zone
0.02 10% window glass broken
0.05 Window glass damage causing injury
0.1 Repairable damage to buildings and house facades 0.2 Structural damage to buildings
Table 2-2: Effects of Thermal Radiation
Radiation Intensity
(kW/m2) Observed Effect
37.5 Sufficient to cause damage to process equipment
25 Minimum energy required to ignite wood at indefinitely long exposures (non piloted)
12.5 Minimum energy required for piloted ignition of wood, melting plastic tubing
9.5 Pain threshold reached after 8 sec, second degree burns after 20 sec
4
Sufficient to cause pain to personnel if unable to reach cover within 20 s, however blistering of the skin (second degree burns) is likely; 0% lethality
1.6 Will cause no discomfort for long exposure
2.3
Frequency Analysis
The failure frequencies for the scenarios developed are obtained from DNV’s Technical Notes (TN 14).
2.4
Risk Calculation/PHASTRISK Software
As mentioned earlier, DNV proprietary software PHASTRisk is used for the main risk calculation in the study. PHASTRisk combines consequence results from the PHAST module with a range of risk-related information in order to produce risk results.
2.4.1
Built-In Event Trees
PHASTRisk has 4 built-in consequence outcome event trees, i.e. continuous vapour release, continuous release with rain-out1, instantaneous vapour release,
release with rain-out. These event trees are presented in to
. It is noted that ‘No Ignition’ event leads to ‘No Effect’ for ‘flammable-only’ material release.
2
Figure 2-1 : Event Tree 1 – Continuous Vapour Release
Figure 2-3: Event Tree 3 – Instantaneous Vapour Release
Figure 2-4: Event Tree 4 – Instantaneous Release with Rainout
PHAST RISK also accounts for a short-duration continuous release, an event where a continuous release lasts for relatively short duration and hence gives effects similar to an instantaneous release. Release duration of 20 seconds is used as the cut-off time to consider continuous release giving instantaneous effects.
Further, in the event of an instantaneous vapour release, PHASTRisk models the event as a pure fireball, in which the thermal radiation impact defines the level of human fatality, discounting the overpressure wave which may accompany the event.
Various probability factors which will determine the route of event within the event trees are also determined in the PHASTRisk model. These include:
Immediate Ignition: This is directly specified and will be different depending on the size
of the release.
Delayed ignition: This is a calculated value within PHASTRisk, unique to each release
case and release direction. The calculation is based on the strength, location and presence factor of all ignition sources specified, and the extent and duration of dispersing flammable vapour clouds being exposed to those sources. Delayed ignition sources can be modelled as point sources (e.g. ground flares), line sources (roads, power lines) or area sources (e.g. to cater for “background” sources posed by a variety of human activity). Fireball / flash fire / explosion probability in the event of immediate ignition of instantaneous release. This is directly specified in PHASTRisk. Flash fire/explosion probability in the event of delayed ignition. This is also directly specified in PHASTRisk. Entire Complex has been considered as Ignition source with ignition probability 0.09 and operating probability 1 as per DNV Technical Note.
2.4.2
Atmospheric Condition
Variation in wind direction defines the apparent orientation of consequences. PHASTRisk accounts for the different wind directions from the wind distribution probability input and combine the values into the risk calculation. Atmospheric conditions, which include temperature and humidity, are also addressed.
2.4.3
Risk Presentation:
Risk would be presented in terms of Individual and Societal (group).
Individual Risk per Annum (IRPA) is the annual frequency that any individual in a
specific worker group becomes a fatality. Individual risk criteria are intended to ensure that individual workers are not exposed to excessive risk levels on an installation. They are largely independent of the number of workers exposed, and hence in principle may be applied to different situations.
Location specific individual risk (LSIR) is used to indicate the risk at a particular
location. It is the risk for a hypothetical individual who is positioned there for 24 hours per day, 365 days per year. It is a standard output from a QRA. In onshore studies, the geographical variation of LSIR may be represented by iso-risk contour plots and used for
separate module on the installation. Since in reality people do not remain continually at one location, this is not a realistic risk measure.
IRPA = ∑ LSIR x presence factor
Risk is defined as the product of the consequences (here measured as harm to people) and the likelihood of occurrence (i.e. an expected rate of occurrence per year). Societal (or group) risk measures the risk of an operation to the company, the industry or a community. There are several ways of presenting societal risk, but the measure, which is found to be most useful for offshore installations, is the Potential Loss of Life (PLL). PLL is defined as the long term average number of fatalities per year due to a specific cause and can be expressed mathematically as:
PLL = ∑ f . N
Where:
∑= sum for all outcomes
f = frequency of an outcome (per year)
N = number of fatalities caused by the outcome
Potential Loss of Life (PLL) is the measure of the average number of statistical fatalities that may be expected within a given time period. "PLL per year" is another term for annual fatality rate. Potential loss of life (PLL) is a societal or group risk measure and is typically used in cost benefit analysis for assessing remedial measures, or for comparing alternatives during the design stages of any project. There is no acceptance criterion for PLL.
3
QRA SOFTWARE TOOL
The basis for this QRA study is DNV’s proprietary risk modelling software, PHAST RISK software version 6.7.
The PHAST RISK software has been in existence since the 1970s, and has been under continual development and improvement ever since, which is managed by DNV’s London-based software development division.
An electronic database of approximately 1400 materials is available to the PHAST RISK software, with the material properties regularly reviewed and if required re-adjusted, based on the latest available data. The PHAST RISK consequence modelling results (for each material) are regularly reviewed and where required re-calibrated, based on the latest available accident and test data.
The PHATS RISK software will calculate dispersion and consequence modelling results for all specified weather classes and wind speeds with the failure case specified release frequency data, specified weather class, wind speed, wind directional probability data, specified immediate ignition probability data, software calculated delayed ignition probability data, built-in event tree alternate consequence outcome branch probability data, fatal impact probability data for each alternate consequence outcome (e.g. jet fire, flash fire, explosion), based on the specified consequence impact criteria levels, and specified population data by location, to produce individual and societal risk results, as required.
This PHAST RISK modelling software requires the following inputs to be able to produce risk results:
- Import an electronic map of the study area, on which individual fatality risk contour results may be produced.
- The electronic map may be programmed in PHAST RISK to:
- Superimpose all on-site and off-site populations within the study area by location, and specifying the day / night number of people for each location.
- Superimpose all potential ignition sources within the study area, which may cause delayed ignition of a flammable release.
Delayed ignition sources may be specified as point sources (e.g. flares, fired heaters, diesel-generators, and transformers), area sources (e.g. welding work shops) or line sources (e.g. roads, railway lines, and overhead power lines). Each ignition source carries additional specification in terms of presence factor and ignition source strength (probability of ignition per unit time, when in contact with a flammable vapour cloud between LFL and UFL). The actual delayed ignition probability of any release is calculated by PHAST RISK, based on the dispersion modelling results and event duration.
The immediate ignition probability associated with each flammable failure case is a risk analyst programmed value, based on historical ignition data, which varies with leak size and release phase (Gas / Liquid / 2-Phase) (the larger the leak vapour flow rate, the higher the ignition probability, typically varying from 1% to 30%, unless above auto ignition, then 100%).
Prepare and import weather class, wind speed and wind direction probability data for the study area. Normally separate day / night, weather class, wind speed, wind directional probability files are entered into PHAST RISK, most often broken down into 16 wind directions.
Enter all identified failure cases, which are defined in terms of: Location, Material released, Quantity released (or release duration), Temperature, Pressure, Leak size, Leak direction (e.g. horizontal, vertical), Leak elevation, Leak frequency and Immediate ignition probability.
Each failure case calculation in PHAST RISK starts with discharge modelling. Based on release duration and release phase (gas, liquid, 2-phase), PHAST RISK directs the dispersion and consequence calculations to one of 4 alternate, built-in consequence outcome event trees (continuous vapour release, continuous release with rain-out, instantaneous vapour release, instantaneous release with rain-out), where each event tree branch probability carries default values, which may be re-programmed by the risk analyst.
PHAST RISK will then calculate all alternate consequence outcomes (e.g. jet fire, explosion) of the event tree selected, in terms of hazard range and event duration (where applicable), for each weather class / wind speed combination.
So far the calculations performed in PHAST RISK only relate to the alternate consequence outcomes and the consequence hazard ranges, for each specified failure case. To produce risk results, PHAST RISK will perform impact frequency calculations, using the failure case specified leak frequency as starting point. Frequency aspects of the risk calculations relate to the:
Risk analyst defined failure case leak frequency.
Weather class, wind speed and wind directional probability, for each of the 16 wind directions.
Specified immediate ignition probability and PHAST RISK calculated delayed ignition probability. The delayed ignition probability calculation is based on the strength and location of all specified ignition sources and the failure case dispersion hazard range, combined with vapour cloud persistence (duration). PHAST RISK selected event tree and branch probabilities, for each alternate consequence out come.
Fatal Impact probability for each alternate consequence outcome. This is based on the PHAST RISK calculated magnitude of each consequence and the PHAST RISK default impact probability criteria or risk analyst specified impact criteria for that type of consequence.
Location and number of people (or equipment) within hazard area for societal risk results, with separate calculations for day and night, indoors and outdoors.
PHAST RISK performs its individual and societal risk calculations based on a 200 x 200 grids (40,000 points), with the grid point spacing automatically varied, based on the consequence hazard range results.
For each release case, PHAST RISK takes the failure case release frequency as initial input, multiplies this by the first weather class / wind speed probability, for the first of 16 wind directions.
PHAST RISK takes this result and multiplies it by the immediate ignition probability, while also separately multiplying this result by the PHAST RISK calculated delayed ignition probability.
These 2 results are multiplied by the first of the event tree consequence branch probabilities, relating to immediate or delayed ignition branch path.
PHAST RISK takes the calculated consequence hazard range and verifies which grid points are within the consequence hazard area. For each grid point within range PHAST RISK then calculates the magnitude of the consequence at each grid point (e.g. explosion overpressure at a particular grid point may be 3psi).
The calculated consequence magnitude at each grid point is then compared to the PHAST RISK programmed impact criteria level, and the likelihood of fatality or damage calculated, based on the impact probability criteria specified in PHAST RISK, for the type of consequence and the magnitude of the consequence.
This calculation is repeated for each event tree alternate consequence outcome at each grid point, for that weather class / wind speed and wind direction, and the result added to the previous risk level, at each grid point.
The above calculations are then repeated for each of the 16 wind directions, cumulatively adding to the risk level at each grid point.
The above calculations are repeated for all day / night weather classes, wind speeds and wind directions, cumulatively adding these risk results at each grid point.
Once all risk calculations at these grid points have been completed for the first failure case, the next failure case will be calculated, again adding all results cumulatively at each grid point. This is repeated until all failure cases have been calculated, while PHAST RISK also tracks the risk contribution made by each failure case at each grid point.
Once completed, PHAST RISK produces individual risk contour results by linking points of equal risk, based on the pre-specified levels of individual fatality risk (or equipment damage) to be plotted, and using linear interpolation between relevant grid points. The risk contour results are super imposed on the electronic site map, entered in the PHAST RISK software.
PHAST RISK can also produce societal risk results by comparing the calculated level of individual risk at all 40,000 grid points, and combining this with the number of people indoors and outdoors, entered by the risk analyst by location.
The above discussion demonstrates that the meteorological data, ignition data and population data entered into the PHAST RISK software are critical to the risk results.
Note that with default settings the risk modelling within PHAST RISK aims to produce conservative offsite fatality risk results. This is in line with the intention of performing a QRA as per the “Guidelines for QRA Study (Revision April 2008)” for a purpose of land-use planning. This is achieved by the build-in but programmable parameter settings, which include:
Indoor & outdoor people fatality impact criteria levels, for each alternate consequence outcome. For flammable releases the alternate consequences would
be spill fires, fire balls, jet fires, flash fires and vapour cloud explosions (VCEs), each with predefined values for the impact levels that will affect people. For jet fires, pool fires and fire balls the varying percentage fatalities (with distance) is calculated based on the Eisenberg Probit equation. For flash fires the LFL envelope is used and for VCE overpressure two impact criteria levels are used, 1.5 psi (0.1 barg) and 5 psi (0.34 barg).
For jet fires, pool fires and fire balls the varying percentage fatalities (with distance) is calculated based on the Eisenberg Probit equation. For flash fires the LFL envelope is used and for VCE overpressure two impact criteria levels are used, 0.5(0.034) psi, 1.0 psi (0.068 barg) and 5 psi (0.34 barg).
4 built-in event trees (Continuous No Rain Out; Continuous With Rain Out;
Instantaneous No Rain Out; Instantaneous With Rain Out) that are automatically selected based on the type of material and the release conditions. Each event-tree assigns a ‘split’ between alternate consequence outcomes (spill fires, fire balls, jet fires, flash fires, VCEs and no hazard), based on the immediate ignition, delayed ignition and no ignition probabilities.
People vulnerability criteria, which pre-determines the fraction of fatalities
resulting indoor & outdoor from being exposed to specific consequence outcomes for a specified duration, or to one or more specified criteria levels. The normal default people fatal fraction impact criteria used in PHAST RISK are shown in the below table.
Annexe 2
Table of Contents
1 RISK CALCULATION TOOL ... 1 2 METEOROLOGICAL DATA ... 2
2.1 Day Weather Class... 2 2.2 Night Weather Class ... 2
3 IGNITION ... 4
3.1.1 Identification of Ignition Sources ... 5
4 POPULATION ... 5 5 MATERIAL COMPOSITION ... 5 6 IMPACT CRITERIA... 6
6.1 Jet fire, pool fire and fireball ... 6 6.2 Flash fire ... 6 6.3 Explosion ... 6
1
RISK CALCULATION TOOL
The risk analysis within this study is conducted using DNV Software’s Phast Risk program Version 6.7, which is an industry standard method for carrying out QRA of onshore process and pipelines (chemical and petrochemical) facilities.
- Phast Risk allows efficient identification of major risk contributors, so that time and effort can then be directed to mitigating these highest risk activities.
- Phast Risk analyses complex consequences from accident scenarios, taking account of local population, land usage and weather conditions, to quantify the risk associated with the release of hazardous materials.
- Phast Risk incorporates the industry standard consequence modeling of Phast.
Phast Risk is intended as a set of models for risk analysts to enable them to provide timely, accurate and appropriate advice on safety related issues. It models all stages of a release from outflow through a hole or from a pipe end, through atmospheric dispersion, rain-out and re-evaporation of liquid, to thermal radiation from fires, explosion overpressures and toxic lethality. PhastRisk combines recognized and validated models for the various physical phenomena, automatically selecting the appropriate model depending on the circumstances of the release. It provides an experienced risk analyst with a tool that allows them to focus their attention and experience on the real problem areas rather than the administration of large quantities of data.
2
METEOROLOGICAL DATA
Data on the wind speed and stability category have been obtained from the client and this will be used for this particular QRA study. There are two different weather classes for Day and Night which are listed below:
2.1
Day Weather Class
- D11 : D stability (neutral) and 11 m/s wind speed.
- B2 : B stability (Unstable) and 2 m/s wind speed.
2.2
Night Weather Class
- D11 : D stability (neutral) and 11 m/s wind speed.
- F3 : F stability (very stable) and 3 m/s wind speed.
This distribution is combined with the wind rose information to generate likelihood for the wind to be from a particular direction and of a specified speed and stability.
Table 2-1: Wind Speed Distribution (Day)
Wind Direction Weather Categories 3B 5D N 0.042958904 0.00460274 NE 0.042958904 0.00460274 E 0.104328767 0.011178082 SE 0.024547945 0.002630137 S 0.006136986 0.000657534 SW 0.018410959 0.001972603 W 0.085917808 0.009205479 NW 0.110465753 0.011835616 Calm 0.177972603 0.019068493
Table 2-2: Wind Speed Distribution (Night) Wind Direction Weather Categories 3B 5D N 0.060931507 0.005041096 NE 0.038082192 0.003150685 E 0.060931507 0.005041096 SE 0.038082192 0.003150685 S 0.022849315 0.001890411 SW 0.060931507 0.005041096 W 0.167561644 0.013863014 NW 0.190410959 0.015753425 Calm 0.121863014 0.010082192
Referring to the same study, the following meteorological parameters will be applied:
An average ambient condition as follow is used in the study:
- Atmospheric temperature : 15-25°C
- Surface temperature : 15-25°C
- Humidity : 70%
3
IGNITION
In order to calculate the risk from flammable materials, information on the ignition sources (which are present in the area over which a flammable cloud may drift) is required. For each ignition source considered, the following factors need to be specified:
- Presence Factor
- This is the probability that an ignition source is active at a particular location.
- Ignition Factor
- This defines the “strength” of an ignition source. It is derived from the probability that a source will ignite a cloud if the cloud is present over the source for a particular length of time.
- Location
The location of each ignition source must be specified on the site layout. This allows the position of the source relative to the location of each release to be calculated. The results of the dispersion calculations for each flammable release are then used to determine the size and mass of the cloud when it reaches the source of ignition.
If these factors are known for each source of ignition considered, then the probability of a flammable cloud being ignited as it moves downwind over the sources can be calculated. The data is entered into the risk quantification software, namely PHAST RISK, for each source (as that used for population data). The PHAST RISK software then calculates equivalent combined ignition factors and presence factors for all sources based on its location on the map.
Ignition sources in a QRA study may be of 3 types:
Point sources Known specific sources such as flares, workshops, etc. Line sources Roads, railways, electrical transmission lines.
Area sources Population, industrial sites where location of specific ignition sources is unknown.
3.1.1
Identification of Ignition Sources
The ignition sources identified for the proposed expansion project are near-by Industrial plants and onsite ignition sources like hot machinery surfaces, electrical sources. No specific field survey is performed for the neighbouring industrial plants in this risk study; however, generally a process petro-chemical plant has various types of ignition sources on-site, e.g. hot work, hot surface, flare, turbine, compressor and vehicles movement etc.
In summary, the ignition sources considered in this QRA study are listed below:
- It is assumed that stringent ignition control is maintained, as is the standard prevailing in the HPCL Bharatpur
- Entire Complex has been considered as Ignition source with ignition probability 0.9 and operating probability 0.1 as per DNV Technical Note.
4
POPULATION
A representative estimate of the exposed populations is sufficient to determine the acceptability of societal risks by determining the order of magnitude of potential fatalities within a population group.
The basis of the population assigned to the facility will be based on the data given by HPCL Bharatpur. Further analysis of the population will be conducted in order to define various factors associated with the population presence, e.g. day/night variation, fraction of time spent indoor etc.
5
MATERIAL COMPOSITION
6
IMPACT CRITERIA
The following impact criteria are used.
6.1
Jet fire, pool fire and fireball
Two sets of criteria are used to determine impact from combination of these events. Areas exposed to radiation levels of 37.5 kW/m2 are assumed to give 100% fatality level. The fatality levels in areas exposed to lower radiation levels are determined using the following Probit function.
Pr = -36.38 + 2.56 ln(I1.333 . t) Where:
Pr : Probit
I : thermal radiation level in W/m2 t : exposure duration in second
The maximum exposure duration for these events is set to 20 seconds. This is assumed as the time that someone will remain within the radiation envelope before attempting to escape.
6.2
Flash fire
The area within the LFL envelope of flammable vapor cloud is used as single value criteria and it is assumed that this area gives 100% fatality level.
6.3
Explosion
The study applies the TNT Correlation Model which utilizes two fixed coefficients to establish ranges to specified damage levels (these coefficients are 0.03 for heavy damage to buildings and 0.06 for repairable damage to buildings). These damage levels are not explicitly associated with overpressure levels but are generally considered to be equivalent to 0.3 and 0.1 bar for heavy and repairable damage, respectively. The damage levels are used as single criteria to establish the human fatality rate.
Fatality modification factors are also applied and are combined with the above impact criteria to produce the final fatality rate resulted from each type of consequence. Separate factors are used for people being outdoors at the time of the event and for people inside a building. The parameters considered for Explosion are following:
- Explosion location criterion: Cloud Centroid
7
RELEASE SIZES
The following representative leak sizes have been applied:
Release Sizes:
- Small release through 5 mm equivalent hole, representative of 3 to 10 mm hole sizes.
- Medium release through 25 mm hole, representative of 10 to 50 mm hole sizes.
- Large release through 100 mm hole, representative of 50 to 100 mm hole sizes.
- Catastrophic Rupture at vessel diameter/ Full bore release at pipeline diameter, representative of releases larger than 150mm.
Annexe 3
Table of Contents
1 HAZARD IDENTIFICATION ... 3
1.1 Failure case scenarios ... 3 1.2 Continuous Releases ... 5 1.3 Instantaneous Releases ... 5 1.4 Events which could lead to a Release ... 5 1.5 Failure Cases ... 6 1.6 Release duration ... 8
2 FREQUENCY DISCUSSION ... 8
List of Tables
Table 1-1 : Failure case scenarios ... 3 Table 1-2 : List of Failure Cases ... 6 Table 2-1 : Failure frequencies of the identified scenarios ... 9
1
HAZARD IDENTIFICATION
1.1
Failure case scenarios
Following scenarios have been identified for the Bharatpur Table 1-1 : Failure case scenarios
Sr. No Failure Case
Material
Handled Temp Pressure
1 TK-1 HSD ambient atmospheric
2 TK-2 HSD ambient atmospheric
3 TK-3 SKO ambient atmospheric
4 TK-4 SKO ambient atmospheric
5 TK-5 MS ambient atmospheric
6 TK-6 MS ambient atmospheric
7 TK-7/UG MS ambient atmospheric
8 TK-8/UG MS ambient atmospheric
9 TK-9/UG HSD ambient atmospheric
10 TK-10 WATER ambient atmospheric
11 TK-11 WATER ambient atmospheric
12 TK-12 HSD ambient atmospheric 13 TK-13 HSD ambient atmospheric 14 TK-14 MS ambient atmospheric 15 TK-15 MS ambient atmospheric 16 TK-16 MS ambient atmospheric 17 TK-17 HSD ambient atmospheric 18 TK-18 HSD ambient atmospheric
19 HSD Pump_2400 LPM HSD ambient 2.5bar
20 SKD Pump_1200 LPM SKO ambient 2.5bar
21 MS Pump 2400 LPM MS ambient 2.5bar
22 Receipt Pipeline to Tank MS MS ambient 2.5bar
23 Receipt Pipeline to Tank HSD HSD ambient 2.5bar
24 Receipt Pipeline to Tank SKO SKO ambient 2.5bar
25 pl from tank to pump house_MS MS ambient 2.5bar
26
PL from tank to pump
house_HSD HSD ambient 2.5bar
Sr. No Failure Case
Material
Handled Temp Pressure 28
PL from pump house to
gantry_MS MS ambient 2.5bar
29
PL from pump house to
gantry_SKO SKO ambient 2.5bar
30
PLfrom pump house to
1.2
Continuous Releases
If ignited immediately, a continuous release will form a jet fire. If ignition is delayed, a flammable cloud would be formed and drifted with the wind. In such situation, if the cloud is ignited (after some delays), a flash fire or Vapour Cloud Explosion (VCE) may result, depending upon the degree of congestion within area and energy strength of the ignition source.
1.3
Instantaneous Releases
An instantaneous release would result from catastrophic rupture of a storage vessel (such as the storage cylinders, the trailers etc.) or reactors. If ignition is immediate, a fireball may be formed depending on the nature of the material. If ignition occurs after some delay similar to continuous release, a flash fire or VCE may be the consequence.
1.4
Events which could lead to a Release
Releases can be caused by:
- Impact event;
- Natural event (e.g. tide, waves, tsunamis, strong winds);
- Failure or leak from other equipment, pipe-work or fittings;
- Internal explosion in ship;
- Incorrect operation;
- Release occasioned from other operations or maintenance;
1.5
Failure Cases
The failure cases with the hole sizes considered for each of the release is as follows Table 1-2 : List of Failure Cases
Sr. No Failure Case Hole Size (mm)
Small Medium Large Cata/ FBR
Tank Fire 1 TK-1 5mm NA 100 mm catastrophic Rupture Tank Fire 2 TK-2 5mm NA 100 mm catastrophic Rupture Tank Fire 3 TK-3 5mm NA 100 mm catastrophic Rupture Tank Fire 4 TK-4 5mm NA 100 mm catastrophic Rupture Tank Fire 5 TK-5 5mm NA 100 mm catastrophic Rupture Tank Fire 6 TK-6 5mm NA 100 mm catastrophic Rupture Tank Fire 7 TK-7/UG 5mm NA NA catastrophic Rupture NA 8 TK-8/UG 5mm NA NA catastrophic Rupture NA 9 TK-9/UG 5mm NA NA catastrophic Rupture NA 10 TK-10 5mm NA 100 mm catastrophic Rupture Tank Fire 11 TK-11 5mm NA 100 mm catastrophic Rupture Tank Fire 12 TK-12 5mm NA 100 mm catastrophic Rupture Tank Fire 13 TK-13 5mm NA 100 mm catastrophic Rupture Tank Fire 14 TK-14 5mm NA 100 mm catastrophic Rupture Tank Fire catastrophic Tank
Sr. No Failure Case Hole Size (mm)
Small Medium Large Cata/ FBR
Tank Fire 16 TK-16 5mm NA 100 mm catastrophic Rupture Tank Fire 17 TK-17 5mm NA 100 mm catastrophic Rupture Tank Fire 18 TK-18 5mm NA 100 mm catastrophic Rupture Tank Fire 19 HSD Pump_2400 LPM NA NA NA FBR NA 20 SKD Pump_1200 LPM NA NA NA FBR NA 21 MS Pump 2400 LPM NA NA NA FBR NA 22 Receipt Pipeline to Tank MS 5mm 25mm 100 mm FBR NA 23 Receipt Pipeline to Tank HSD 5mm 25mm 100 mm FBR NA 24 Receipt Pipeline to Tank SKO 5mm 25mm 100 mm FBR NA 25
pl from tank to pump
house_MS 5mm 25mm 100 mm FBR NA
26
PL from tank to pump
house_HSD 5mm 25mm 100 mm FBR NA
27
PL from tank to pump
house_SKO 5mm 25mm 100 mm FBR NA
28
PL from pump house to
gantry_MS 5mm 25mm 100 mm FBR NA
29
PL from pump house to
gantry_SKO 5mm 25mm 100 mm FBR NA
30
PLfrom pump house to
gantry_HSD 5mm 25mm 100 mm FBR NA