report qra for skangass lng plant - ferry bunkering...
TRANSCRIPT
DET NORSKE VERITASTM
REPORT NO./DNV REG NO.: 2013-4091 / 17TLT29-7
REV.1 , 2013-06-11
Report
QRA FOR SKANGASS LNG PLANT -
FERRY BUNKERING PROJECT
SKANGASS AS
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Reg. No.: 17TLT29-7 Revision No.: 1
Date : 2013-06-11 Page iii of iv
Rev. No.
Date Reason for Issue Prepared by Verified by Approved by
A 2013-06-03 Draft issue signed and
verified
BERTHOM RISVIK ELLING
© Reference to part of this report which may lead to misinterpretation is not permissible.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Reg. No.: 17TLT29-7 Revision No.: 1
Date : 2013-06-11 Page iv of iv
Table of Contents Page
EXECUTIVE SUMMARY .........................................................................................................................1
1 INTRODUCTION ...............................................................................................................................3
2 FACILITY AND OPERATION DESCRIPTION ...............................................................................4 2.1 Facility description ..................................................................................................................... 4 2.2 Facility operation........................................................................................................................ 4
3 QUALITATIVE COMPARISON WITH CONVENTIONAL BUNKERING SYSTEMS ................6
4 COMPARISON OF RIGID LNG LOADING ARMS AND FLEXIBLE LOADING HOSES ..........7
5 RISK RESULTS ..................................................................................................................................8 5.1 Risk contours .............................................................................................................................. 8
5.1.1 Introduction ......................................................................................................................... 8
5.1.2 Risk contours generated by the Train 1 .............................................................................. 8
5.1.3 Risks contours generated according to the bunkering facility operational phases ........... 11 5.1.4 Risk contours generated by the plant with the bunkering facility .................................... 14
5.2 Individual Risk 1st
party and 2nd
party ...................................................................................... 16
5.2.1 Introduction ....................................................................................................................... 16 5.2.2 Hours of presence ............................................................................................................. 16
5.2.3 Risk Results ...................................................................................................................... 17 5.3 Societal and Individual Risks 3
rd party .................................................................................... 21
5.3.1 Societal Risk for 3rd
party ................................................................................................. 21
5.3.2 Hours of presence ............................................................................................................. 22 5.3.3 Individual Risk for 3
rd party .............................................................................................. 23
6 SENSITIVITIES ................................................................................................................................28 6.1 Individual Risk 1
st party and 2
nd party ..................................................................................... 28
6.2 Societal and Individual risk 3rd
party ....................................................................................... 31
6.2.1 Societal risk ....................................................................................................................... 31 6.2.2 Individual risk ................................................................................................................... 33
6.3 Sensitivities discussion ............................................................................................................. 35
7 SHIP MANIFOLD LOCATION .......................................................................................................36
8 CONCLUSIONS AND RECOMMENDATIONS ............................................................................37
9 REFERENCES ..................................................................................................................................39
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 1 of 39
EXECUTIVE SUMMARY
Skangass is in the process to install an LNG bunkering station at the Fjordline ferry terminal
in Risavika, located adjacent to Skangass’ LNG Base Load Plant. Skangass would like to take
benefit of the close proximity to ferry terminal (approximately 600 m), by feeding LNG
directly from the plant, through an underground pipeline.
The Skangass ferry bunkering project is currently in the detailed engineering phase. In order
to provide to the reader and the decision maker a risk overview as close as possible to the
reality, some of the assumptions have been reviewed, such as, for example, differentiation of
risk criteria for ferry terminal workers (2nd
party). All the assumptions are available in the
Appendix A of this report.
The main objective of this QRA is to:
Assess the combined risk for the ferry terminal area, taking into consideration both the
new LNG bunkering station and the updated risk results for the Base Load Plant,
Compare the risks with the risk acceptance criteria.
Based on experience in LNG bunkering, DNV assesses that the time of detection is likely to
be close to 90s in total (60s for detection and initiation, 30s for completion (time to close the
valve)). While Skangass estimates, based on its experience, that the total time can be reduced
down to 36s (30s for detection and initiation, 6s for completion). Even if a closing time of 6
seconds could be possible if Skangass documents that the facility uses a valve in compliance
with this requirement, DNV’s experience shows that time to detect and initiate the ESV is
often extended to 60 seconds.
Therefore this report contains three sets of risk results:
- The risk picture based on DNV recommendation corresponding to ESD total time of
90s, presented in section 5.
- Two sets of sensitivities, presented in section 6:
o Risk picture based on a mixed inputs from DNV recommendation and
Skangass input, 66s ESD total time,
o Risk picture based on Skangass estimation, 36s ESD total time.
DNV considers the risk results based on the first alternative (total ESD time of 90s) as the
valid results. The two sensitivities are there to help the reader to understand the impact of a
shorter duration of ESD completion
Risk calculated for the planned LNG bunkering station and LNG Base Load Plant (Train 1),
combined, is presented in the report:
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 2 of 39
The 1st/2
nd party individual risk is found to be within the ALARP region for all
personnel categories.
The calculated 3rd
party societal risk is acceptable or within the ALARP area for all
events.
3rd
party Individual Specific Risk is acceptable or in the ALARP area for all
individuals except.
The passengers on board the ferry are at lower risk than the passengers at the terminal.
As a consequence of this boarding of most of passengers is planned to take place
before bunkering, ref. Skangass’ Design Basis /4/. Late-comers will be able to board
once the bunkering operations are completed. According to the same reference, no
passengers are allowed in the passenger tube during bunkering and only late-comers
will board through the tube after bunkering.
The sensitivities show a reduction in the risk picture for 1st party (only for the group
“Skangass operators at the ferry terminal jetty”), 2nd
party and 3rd
party. However, the
risk results remain in the same order of magnitude.
The detailed engineering of Risavika ferry station is regarded as safer than standard practice.
As the calculated risk is in ALARP area, Skangass should consider taking measures to reduce
the risk as the one presented below as example. Indeed, ALARP stands for “As Low As
Reasonably Practicable”, meaning that the risk is tolerable if risk reduction is impracticable or
if its cost is grossly disproportionate to the improvement.
Recommendations for risk mitigation provided in the plant’s QRA /1/ are valid also for the
bunkering station:
Focus on ignition source control to reduce the ignition probability
In general, reduction of LNG volume in the bunkering pipeline (e.g. either by
segmentation or by depressurizing part of the pipelines in between bunkering
operation), would reduce the fire and explosion risk.
Liquid bunds/trays around the LNG loading arm where an LNG leak could occur
would help limiting the pool size in the event of an LNG leak.
DNV recommends that ESD equipment is qualified for compliance with the
requirements to short response time (from gas detection to isolation) assumed in the
sensitivities in this analysis.
DNV recommends to apply all the points for manual local supervision as presented in
section 8.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 3 of 39
1 INTRODUCTION
Fjordline is converting ferries for use of natural gas (LNG) instead of conventional fuels. In
light of this, Skangass is evaluating to install an LNG bunkering station at the Fjordline ferry
terminal in Risavika, located adjacent to Skangass’ LNG Base Load Plant. Skangass would
like to take benefit of the close proximity to ferry terminal (approximately 600 m), by feeding
LNG directly from the plant, through an underground pipeline.
The objective of this QRA is to:
Calculate the risk for the ferry terminal area, taking into consideration both the new
LNG bunkering station and the updated risk results for the Base Load Plant,
Compare the risks with the risk acceptance criteria, described in appendix C.
Risk levels are reported in terms of:
Individual risk for on-site manning (1st/2
nd party)
Societal risk for off-site population (3rd
party)
Report Structure
The main part of this report presents background, objectives, risk acceptance criteria and
results of the analysis. Mitigating measures are provided as recommendations. The content of
the 5 appendices is described below:
Appendix Description
Appendix A Assumptions Includes all major assumptions for the analysis.
Appendix B HAZID HAZID review of the ferry bunkering station in
Risavika.
Appendix C Risk in hazardous
activities and risk criteria
Risk definition and criteria for the 1st party, 2
nd
party personnel, and 3rd
party population.
Appendix D Leak frequency
calculation
Basis and results from LEAK.
Appendix E PHAST RISK software
package
General description of the software used to
estimate the Individual Risk and risk to 3rd
party.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 4 of 39
2 FACILITY AND OPERATION DESCRIPTION
2.1 Facility description
The bunkering facility is designed to complete bunkering of Fjordline ferries in about 1 hour
with vapour return. Furthermore the system is designed with no need for cooling down of the
bunkering line prior to bunkering operation.
The LNG Bunkering facility will consist of the following major equipment components:
LNG Bunkering Pump located in the LNG plant
Fiscal metering located in the LNG plant
8’’ LNG Pipeline
4’’ Vapour Return Line
LNG Loading arm
If needed, the details of equipment for the LNG bunkering facility are available in the
appendix D of this report.
The LNG bunkering pump and fiscal metering package will be located inside the Skangass
LNG plant, and the loading arm will be located at the bunkering jetty. LNG transfer pipeline
between the LNG plant and the bunkering station will be vacuum insulated and installed
below ground to protect it from external damage, ref. Figure 1.
2.2 Facility operation
As mentioned above, the bunkering facility is designed to be completed in 1 hour. During the
operation, at least two operators will be present at the ferry terminal jetty respectively on the
shore side and on the ship side to supervise locally the operation. Beside the fact that the
operators help the operation to get going, the operators will be special trained to take actions
in case of detection of any type of leak. This continuous local supervision will come in
addition to the automatic fire & Gas detection and will help to initiate the ESD system as soon
as possible and reduced the leak inventory.
Based on experience in LNG bunkering, DNV assesses that the time of detection is likely to
be close to 90s in total (60s for detection and initiation, 30s for completion (time to close the
valve)). While Skangass estimates on its experience, that the total time can be reduced down
to 36s (30s for detection and initiation, 6s for completion). Even if a closing time of 6 seconds
could be possible if Skangass documents that the facility uses a valve in compliance with this
requirement, DNV’s experience shows time to detect and initiate the ESV is often extended to
60 seconds.
Therefore this report contains three sets of risk results:
- The risk picture based on DNV recommendation corresponding to ESD total time of
90s, presented in section 5.
- Two sets of sensitivities, presented in section 6:
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 5 of 39
o Risk picture based on a mixed inputs from DNV recommendation and
Skangass input, 66s ESD total time,
o Risk picture based on Skangass estimation, 36s ESD total time.
DNV considers the risk results based on the first alternative (total ESD time of 90s) as the
valid results. The two sensitivities are there to help the reader to understand the impact of a
shorter duration of ESD completion.
-
Figure 1 LNG Base Load Plant and Fjordline ferry terminal area. LNG pipeline route
(indicative) as red line.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 6 of 39
3 QUALITATIVE COMPARISON WITH CONVENTIONAL
BUNKERING SYSTEMS
Skangass’ intention with its current design is to provide an LNG bunkering system for ferries
which is safer than conventional systems, e.g. by truck-to-ship, ship-to-ship or terminal-to-
ship. By ‘conventional’ is meant the small scale LNG filling stations in Norway, which is
found acceptable to DSB and the Norwegian Maritime Authority (Sjøfartsdirektoratet), and
therefore may be regarded as ‘standard practice’. Naturally, these stations vary in technical
features but are typically characterized by
Flexible filling hose
Bolted flange connections requiring manual disconnection
Manual operation (e.g. truck driver, ship crew)
Ventilation lines / relief to atmosphere
No automatic/instrumented shut down upon gas detection
Reasons for stating that Skangass’ proposed design is safer are basically due to the simplicity
of the bunkering terminal due to the benefit of the close proximity to the Skangass LNG Plant
and selection of equipment with low leak frequency. Some examples are:
Simpler – fewer possible leak sources:
o No ventilation lines or pressure safety relief valves to atmosphere
o All equipment components are selected based on low leak frequency (LNG
bunkering pump, LNG bunkering arm, vacuum insulated piping, etc.)
Reduced LNG inventory in the proximity of the bunkering system:
o No LNG buffer tank
o Pipeline in underground tunnel
Use of best available equipment:
o Loading arm instead of hose
o ESD link between ship/shore according to the SIGTTO standard
o Stainless steel, double wall, vacuum insulated piping – gas detection between
the walls – instead of PUR piping outside the plant
o Can pump without external seals instead of a centrifugal pump
Automatic, in addition to manual, ESD system
F&G detection and alarm system triggering automatic shutdown of the bunkering
system located on shore side and ship side.
Bunkering operation always manned with at least two operators. One on shore side
and one on ship side.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 7 of 39
A thorough assessment of the actual improvement of Skangass’ design as opposed to
‘conventional’ bunkering systems goes beyond the scope of this report, as this would require
a detailed assessment of each of the points above. The following is however noted: Each of
the points in the list above does not implicitly represent an improvement compared to
conventional design, in terms of safety, but as a whole, the technical design of Risavika
bunkering station is regarded as safer than standard practice.
4 COMPARISON OF RIGID LNG LOADING ARMS AND FLEXIBLE
LOADING HOSES
The memo developed by DNV /5/ presents a qualitative assessment of the difference between
rigid LNG loading arms and flexible hoses used in the truck-to-ship operations for instance.
Prior to this assessment, Skangass have decided upon rigid LNG loading arms as a base case
solution for LNG bunkering at Risavika. In case of maintenance or failure of these loading arms,
Skangass are considering using flexible LNG loading hoses as a backup solution for their Ferry
Bunkering Station at Risavika. The conclusion presented below summarizes the assessment done. All the details leading to this
conclusion can be found in the memo /5/:
“DNV agree with Skangass’ prioritization on using rigid loading arms as the base case for the
LNG bunkering operations at Risavika. If hoses shall be used as a backup solution, stringent
operation and maintenance procedures need to be in place to control risk for loss of containment.
DNV suggest to further analyze the risk picture of bunkering operations with flexible hoses.
However the available data are not sufficient and consistent enough to develop a possible
acknowledged failure frequency for flexible LNG hoses at this stage. This will only be possible
after a qualification program, such as the program TNO1 initiated last year”.
1 Dutch Organization for Applied Scientific Research (TNO), who has an independent position that allows to give objective
scientifically founded judgments and acknowledged as valid source of information for technical safety subjects, have recently
focused on the lack of sufficient qualification programs and proven track records for flexible LNG hoses
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 8 of 39
5 RISK RESULTS
5.1 Risk contours
5.1.1 Introduction
The risk contours show location specific risk result. This is the risk for a hypothetical
individual assumed to be continuously present at the specific location. “Continuously present”
correspond to an exposition of 8760 hours or one year period. For instance, to be exposed to
the risk level at the ferry terminal presented in Figure 6, an individual must live there 24
hours/7 days during one year.
Normally, individuals will not be continuously present throughout the year, therefore more
realistic estimate of the risk for an individual is provided by the individual-specific risk
figures, taking the actual exposure time into account, presented in section 5.2 and section 5.3.
The ISR is compared against the risk criteria presented in the Appendix C of this report.
Note that the risk contours shown are valid for 1st, 2
nd and 3
rd parties.
Below, risk contours are presented for different configurations as follows:
- Risk contours generated by the Train 1 of the plant or as it is today in section 5.1.2 ;
- Risk contours generated by Train 1 and bunkering facility or as it could be in section
5.1.4.
To help the reader to differentiate the risk due to the different operations phase of the
bunkering facility, the risk contours generated by the plant and the bunkering facility for the
two operational phases are presented in section 5.1.3. But note that these are considered as
snapshots and are only valid during the two specific periods:
- Risk contours generated by Train 1 and bunkering facility between the bunkering
operations (23 hours per day);
- Risk contours generated by Train 1 and bunkering facility during the bunkering
operations (assumed taking place 1 hour per day);
5.1.2 Risk contours generated by the Train 1
Figure 2 and Figure 3 show risk contours for the peninsula today due to the existing LNG
Base Load Plant (Train 1). The highest risk contour identified is 4E-4 per year covering the
northwest part of the LNG plant. The risk contours are comparable as the ones in the update
of the 2009 QRA, ref. /1/
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 9 of 39
Figure 2 Risk contours today: LNG Base Load Plant (Train 1) without ferry bunkering
installation
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 10 of 39
Figure 3 Risk contours today: LNG Base Load Plant (Train 1) without ferry bunkering
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 11 of 39
5.1.3 Risks contours generated according to the bunkering facility operational
phases
The risk contours generated by the LNG Base Load Plant (Train 1) and the ferry bunkering
facility presented below in the Figure 4 and Figure 5 are there to represent the risk variation
between the two different phases system – during bunkering and between bunkering
operations.
Note that theses risk contours are only valid during the two specific operational phases and do
not represent the risk contours a hypothetical individual continuously present in the area.
5.1.3.1 Risk contours between bunkering operations
Figure 4 shows risk contours. Note that these risk contours represent the case when no LNG
bunkering is taking place. I.e. the figure is a “snapshot” showing the risk a person, present at
any point outdoors, is exposed to between bunkering operations.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 12 of 39
Figure 4 Risks contours (Train 1 and ferry bunkering system) between bunkering
operations
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 13 of 39
5.1.3.2 Risk contours during bunkering operations
Figure 5 shows risk contours for the peninsula due to the LNG Base Load Plant (Train 1),
with the ferry bunkering facility installed. These risk contours however are valid during
bunkering of LNG. I.e. the figure is a “snapshot” showing the risk a person, present at any
point outdoors, is exposed to during bunkering operations.
Comparison with Figure 4 shows that the 1E-4 and 1E-5 risk contours are drifted slightly
southwards, due to the activity at the jetty during the bunkering. However, according to
Figure 5 the risk for passengers outdoors at the ferry terminal is slightly increasing, but
remains in the same order of magnitude.
Figure 5 Risk contours (Train and ferry bunkering system) during bunkering
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 14 of 39
5.1.4 Risk contours generated by the plant with the bunkering facility
Figure 6 and Figure 7 show risk contours for the peninsula due to the LNG Base Load Plant
(Train 1) with the ferry bunkering system installed. The contours show individual risk, for a
person present at any point outdoors, continuously exposed 8 760 hours per year, at any time
of the day, an average of both bunkering and no bunkering phases. Therefore, these figures
are the most appropriate for comparing with today’s risk picture, i.e. Figure 2 and Figure 3.
The presence of the underground pipeline increases the overall risk level. The additional
pipeline raises the risk around the main pipe rack located at the south of the plant; the areas
covered by 2E-4 and 1E-4risk contours appear to be extended southwards. Apart for this
increase, the new installation does not change the coverage of risks contours 4E-4, 3E-4 as
shown in Figure 2. Concerning the 1E-5 risk contour; it now covers a greater part of the
peninsula including the ferry terminal and its surroundings.
Figure 6 Risks Contours for the combination of Train 1 and bunkering facility, average
of both bunkering and no bunkering phases.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 15 of 39
Figure 7 Risks contours combination of Train 1 and bunkering facility, average of both
bunkering and no bunkering phases.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 16 of 39
5.2 Individual Risk 1st
party and 2nd
party
5.2.1 Introduction
This chapter presents the calculated individual risk for 1st and 2
nd parties. For better seeing
what contributes to the risk, the results are presented in the following way:
1. Risk for the area today, due to the existing LNG Base Load Plant (Train 1). The
calculated values are compared with the acceptance criteria, ref. Appendix C.
2. The added risk contribution due to the planned ferry bunkering facility, when no LNG
bunkering is taking place. I.e. with 7 barg in the pipeline upstream the ESV at the
loading arm, 23 hours a day. The calculated values thus do not represent total risk
during this operational phase, and cannot be compared with the acceptance
criteria.
3. The added risk contribution due to the planned bunkering facility, during bunkering.
I.e. 10 barg operating pressure for 1 hour a day. The calculated values thus do not
represent total risk during this operational phase, and cannot be compared with
the acceptance criteria.
4. Risk for the area after installation of the ferry bunkering facility, equals to the sum of
1-3 above. The calculated values are compared with the acceptance criteria, ref.
Appendix C.
5.2.2 Hours of presence
To calculate the different specific exposure to the risks expressed in ISR in Table 3 and Table
2, the different hours of presence per group has been assumed as presented in Table 1.
Conservatively it has been assessed that the each group is present to all the bunkering taking
place during their working days assumed to be 225 days per year.
Table 1 Hours of presence per year of 1st party personnel
Individual Location
1. LNG Base Load
Plant (Train 1)
2. Ferry bunkering
facility – no
bunkering
3. Ferry bunkering
facility – during
bunkering
Hours of presence (per
year)
Hours of presence (per
year)
Hours of presence (per
year)
Control room building Control room
building (indoor) 1800 1800 225
Operator/Maintenance
Most exposed
process point 360 360 225
Control room
building (indoor) 1440 1440 225
Total 1800 1800 225
Truck loading (1 person per
truck per 1.2h)
Truck loading
terminal 438 438 225
Ship loading (jetty – only
during connection and
disconnection)
Ship loading
terminal 122 122 122
Ship deck (during loading
only) Ship loading
terminal 671 671 225
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 17 of 39
Ship bridge (indoor fraction
0.75, during loading only) Ship loading
terminal 671 671 225
Skangass operators at the
ferry terminal jetty
Ferry loading
terminal 450 450 225
Table 2 Hours of presence per year of 2nd party personnel
Individual Location
1. LNG Base Load
Plant (Train 1)
2. Ferry bunkering
facility – no
bunkering
3. Ferry bunkering
facility – during
bunkering
Hours of presence (per
year)
Hours of presence (per
year)
Hours of presence (per
year)
Ferry terminal – office
workers
Ferry terminal
indoor 1800 1800 225
Ferry terminal – industry
workers Ferry terminal
outdoor 1800 1800 225
5.2.3 Risk Results
Table 3 presents calculated Individual Specific Risk (ISR) per working group at the Skangass
LNG Base Load plant and ferry bunkering facility (1st party). During bunkering, 2 Skangass
personnel are assumed to be at the jetty inside the bunkering station area, and are therefore
included as 1st party. :
- ISR for all groups in all locations is according to Table 1 within the ALARP area or
acceptable. No values exceed the maximum risk criterion of 1E-03 per year.
Operators, who are assumed spending 20% of their working time in the process plant
and 80% of their time in the control room building, have the highest individual risk of
2.58E-5 per year.
- Adding the ferry bunkering system to the plant involves a slight augmentation of each
ISR, especially for the personnel around the loading bay (loading truck area), closest
location to the future pipeline’s location.
Table 5 presents calculated Individual Specific Risk (ISR) per working group at the Ferry
terminal (2nd
Party):
- ISR for all groups in all locations is according to Table 5 within the ALARP area. No
values exceed the maximum criterion of 1E-04.
- Adding the ferry bunkering system to the plant involves a net augmentation of both 2nd
party ISR. However, when comparing the contribution to the risk according to the
activities running, the phase “no bunkering” is contributing with about 80%. This is
due to the high fraction of time (23/24) for this phase compared to the fraction of time
bunkering is taking place (1/24).
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 18 of 39
Table 3 Individual specific risks for most exposed persons (1st party). Note that ISRs in column pairs 2. and 3. are additional risk
contributions, i.e. they do not represent total risk during this operational phase, and cannot be compared with the acceptance criteria,
ref. appendix C.
Individual Location
1. LNG Base Load Plant
(Train 1)
2. Ferry bunkering facility
– no bunkering
Added risk contribution
3. Ferry bunkering facility –
during bunkering
Added risk contribution
4. Combined Risk
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual
risk y
(per year)
ISR
(per year)
Control room building Control room
building (indoor) 1.18E-05 2.42E-06 1.04E-05 2.14E-06 2.00E-05 5.13E-07 4.22E-05 5.07E-06
Operator/Maintenance
Most exposed
process point 4.16E-04 6.50E-06 7.97E-06 5.38E-07 4.47E-05 4.50E-07 4.94E-04 7.49E-06
Control room
building (indoor) 1.18E-05 1.52E-05 1.04E-06 2.47E-06 2.00E-05 8.48E-07 4.22E-05 1.83E-05
Total 2.17E-05 3.01E-06 1.30E-06 2.58E-05
Truck loading (1 person per truck per
1.2h)
Truck loading
terminal 1.36E-04 6.80E-06 8.00E-05 4.00E-06 9.38E-05 2.41E-06 3.10E-04 1.32E-05
Ship loading (jetty – only during
connection and disconnection)1 Ship loading
terminal 4.45E-05 6.20E-07 9.53E-06 1.33E-07 9.93E-06 1.38E-07 6.40E-05 8.91E-07
Ship deck (during loading only) Ship loading
terminal 4.92E-05 3.77E-06 1.09E-05 8.35E-07 1.33E-05 3.42E-07 7.34E-05 4.95E-06
Ship bridge (indoor fraction 0.75, during
loading only) Ship loading
terminal 4.92E-05 2.05E-06 1.09E-05 2.99E-07 1.33E-05 1.28E-07 7.34E-05 2.48E-06
Skangass operators at the ferry terminal
jetty
Ferry loading
terminal 4.45E-05 3.80E-07 * 9.53E-06 4.32E-07 1.08E-04 2.78E-06 1.32E-04 3.59E-06
*Represent risk level for 2 hours of exposure to the LNG Load Base plant when operators are at the ferry terminal jetty.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 19 of 39
In Table 4 the AIR is calculated based on the Individual Specific Risk (ISR) for each working
group and the percentage of the total number of people each group constitutes.
The AIR is calculated from the formula
personnel ofNumber
)personnel ofNumber (ISRAIR
As shown in Table 4 AIR is still in the ALARP area, compared with the Skangass acceptance
criterion (ref. Appendix C), after installation of the ferry bunkering facility.
Table 4 Average ISR for 1st/2
nd party
Criteria
Total number
of exposed
individuals
LNG Base Load Plant (Train 1) LNG Base Load Plant (Train 1)
+ ferry bunkering facility
AIR 1st/2
nd party (per year) 59 4.56E-06 6.83E-06
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 20 of 39
Table 5 Individual specific risks for most exposed persons (2nd
party). Note that ISRs in column pairs 2. and 3. are additional risk
contributions, i.e. they do not represent total risk during this operational phase, and cannot be compared with the acceptance criteria,
ref. appendix C.
Individual Location
1. LNG Base Load Plant
(Train 1)
2. Ferry bunkering facility
– no bunkering
Added risk contribution
3. Ferry bunkering facility
– during bunkering
Added risk contribution
4. Combined risk
Individual risk
(per year)
ISR
(per
year)
Individual risk
(per year)
ISR
(per
year)
Individual risk
(per year)
ISR
(per
year)
Individual risk
y
(per year)
ISR
(per
year)
Ferry terminal – office
workers
Ferry terminal
indoor 1.02E-06 1.7E-07 1.68E-05 8.20E-07 2.32E-05 5.96E-07 2.82E-05 1.63E-06
Ferry terminal – industry
workers Ferry terminal
outdoor 7.39E-06 1.2E-06 3.99E-06 3.45E-06 1.08E-04 2.77E-06 1.32E-04 7.74E-06
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 21 of 39
5.3 Societal and Individual Risks 3rd
party
5.3.1 Societal Risk for 3rd
party
Figure 8 presents the calculated societal risk for 3rd
party, in terms of F-N curve, before and
after having installed the ferry bunkering facility. For better seeing what contributes to the
risk, the results are presented in a similar manner as in the previous chapter:
1. Risk due to the existing LNG Base Load Plant (Train 1) is shown as the light blue,
fully drawn line. The curve may be compared with the acceptance criteria, shown as
green and red straight lines, ref. Appendix C.
2. The added risk contribution due to the planned ferry bunkering facility, no LNG
bunkering, is shown as the violet, dotted line. The curve may not be compared to
the acceptance criteria.
3. The added risk contribution due to the planned bunkering facility, during bunkering, is
shown as the red, dotted line. The curve may not be compared to the acceptance
criteria.
4. Risk for the area after installation of the ferry bunkering facility, equal to the sum of 1-
3 above, is shown as the dark blue, fully drawn line. The curve may be compared with
the acceptance criteria.
As can be seen from the figure, the societal risk is still within the ALARP or acceptable area
after having installed the ferry bunkering facility.
Figure 8 F-N curves for societal risk 3
rd party, DNV inputs
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 22 of 39
5.3.2 Hours of presence
To calculate the different specific exposure to the risks expressed in ISR inTable 7, the
different hours of presence per group has been assessed as presented in Table 6.
Conservatively it has been assessed that the groups Energiveien+Risavika both, Container
area both, Rest companies both are present to the entire bunkering operation duration of 2
hours happening during their working days assumed to be 225 days per year , cf. Appendix A
of this report.
Also, conservatively it has been assumed that the groups Peninsula and Hiking track are
present during the bunkering operation and therefore exposed to the risk.
In addition, it has been assessed that the passengers on the ferry or boarding the ferry can be
present only during 30% of the bunkering operations, as they cannot be present each evening
(cf. Appendix A of this report).
Table 6 Hours of presence per year for 3rd party
Individual Location
1. LNG Base
Load Plant
(Train 1)
2. Ferry
bunkering
facility – no
bunkering
3. Ferry
bunkering
facility –
during
bunkering
Hours of presence
(per year)
Hours of presence
(per year)
Hours of presence
(per year)
Peninsula Peninsula 280 280 280
Hiking track Hiking track 70 70 70
Ferry Terminal – passengers Ferry terminal indoor 219 110 110
Energiveien+Risavika – office workers Energiveien indoor 1800 225 225
Energiveien+Risavika – industry
workers Energiveien outdoor 1800 225 225
Container area – office workers Container area indoor 1800 225 225
Container area – industry workers Container area outdoor 1800 225 225
Rest companies – office workers Rest indoor 1800 225 225
Rest companies – industry workers Rest outdoor 1800 225 225
Living quarters
(indoor fraction of 0.75) Rest indoor 8760 365 365
Tananger population
(indoor fraction of 0.75)
Tananger indoor /
Tananger outdoor 8760 365 365
Ferry deck Passengers indoor 219 109.5 109.5
Parking area - passengers Passengers outdoor 219 109.5 109.5
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 23 of 39
5.3.3 Individual Risk for 3rd
party
Table 7 shows the calculated Individual Specific Risk for 3rd
party, presented similarly as in
Table 3.
For better seeing what contributes to the risk, the results are presented in the following way:
1. Risk for the area today, due to the existing LNG Base Load Plant (Train 1). The
calculated values are compared with the acceptance criteria, ref. Appendix C.
2. The added risk contribution due to the planned ferry bunkering facility, when no LNG
bunkering is taking place. I.e. with 7 barg in the pipeline upstream the ESV at the
loading arm, 23 hours a day. The calculated values thus do not represent total risk
during this operational phase, and cannot be compared with the acceptance
criteria.
3. The added risk contribution due to the planned bunkering facility, during bunkering.
I.e. 10 barg operating pressure for 1 hour a day. The calculated values thus do not
represent total risk during this operational phase, and cannot be compared with
the acceptance criteria.
4. Risk for the area after installation of the ferry bunkering facility, equals to the sum of
1-3 above. The calculated values are compared with the acceptance criteria, ref.
Appendix C.
The highest combined risk is calculated for people present at the North West of the plant
(peninsula and hiking track) and in the ferry terminal. However note that all the risk values
are within the ALARP area. The combined risk values for people on the peninsula, at the
hiking track, in the parking area, passengers inside the ferry and the ferry terminal are within
the ALARP area. The rest of the categories are in the acceptable area.
It must be noted that the main contributor to the risk for each population is the duration of
their presence. Indeed the risk picture for the different categories except the passengers has
been assessed with the conservative assumption made that the same people will be present to
each bunkering operations all over the year during their working days (225 working days over
a year). It is more likely that the different groups will work based on a shift and therefore
could work in the morning instead and not be exposed to the risk due to the bunkering
activity.
It appears that the risk is higher between the bunkering operations than during the bunkering
operations for the location parking area, Rest companies, Living quarters. The reasons are
twofold:
- In an event of a leak between the bunkering operations, the total inventory of the
system has been assumed to be released. No leak control such as ESD system is taken
into account.
- Also, the ignition sources are more present between the bunkering operations in the
vicinity of this location. For example, between the bunkering operations, the
passengers will have to board the ferry with their cars. Therefore, contribution to the
ignition probability from the traffic on the parking and for passengers boarding have
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 24 of 39
been taken into account. Thus the ignition probability is higher, generating a greater
risk of fire event.
For the Tananger population, the ISR increase, due to the additional ferry bunkering activity,
is not significant.
The ISR related to the passengers are in the ALARP area but vary according to their location.
The passengers on board the ferry are exposed of a lower risk than the passengers at the
terminal. As a consequence DNV recommends to keep the boarding of passengers before the
bunkering is taking place as suggested in the ref. Skangass’ Design Basis /4/. According to
the same reference, no passengers are allowed in the passenger tube during bunkering and
only late-comers will board through the tube after bunkering.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 25 of 39
Table 7 Individual Risk for 3rd
party, Base Load Plant and ferry bunkering station combined. Note that ISRs in column pairs 2. and 3. are
additional risk contributions, i.e. they do not represent total risk during this operational phase, and cannot be compared with the acceptance criteria, ref.
appendix C.
Individual Location
1. LNG Base Load Plant
(Train 1)
2. Ferry bunkering facility
– no bunkering
Added risk contribution
3. Ferry bunkering facility – during
bunkering
Added risk contribution
4. Combined risk
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual risk
(per year)
ISR
(per year)
Individual
risk y
(per year)
ISR
(per
year)
Peninsula Peninsula 3.48E-05 1.11E-06 2.61E-06 8.34E-08 3.30E-06 1.06E-07 4.07E-05 1.30E-06
Hiking track Hiking
track 1.95E-04 1.56E-06 3.06E-05 2.45E-07 4.32E-05 3.45E-07 2.69E-04 2.15E-06
Ferry Terminal –
passengers
Ferry
terminal
indoor
1.02E-06 6.53E-08 3.99E-06 8.98E-08 2.32E-05 5.55E-07 2.82E-05 7.10E-07
Energiveien+Risavika
– office workers
Energiveien
indoor Negl. Negl. 8.26E-10 1.70E-10 Negl. Negl. 1.58E-09 3.25E-10
Energiveien+Risavika
– industry workers
Energiveien
outdoor 7.55E-09 1.55E-09 8.26E-09 1.70E-09 Negl. Negl. 1.58E-08 3.25E-09
Container area –
office workers
Container
area indoor 1.03E-08 2.12E-09 2.04E-08 4.19E-09 1.58E-07 4.07E-09 1.89E-07 1.04E-08
Container area –
industry workers
Container
area
outdoor
1.03E-07 2.12E-08 1.16E-07 2.38E-08 1.11E-06 2.86E-08 1.33E-06 7.36E-08
Rest companies –
office workers Rest indoor 2.33E-09 4.79E-10 3.98E-10 Negl. Negl. Negl. 2.80E-09 5.62E-10
Rest companies –
industry workers
Rest
outdoor 2.32E-08 4.77E-09 3.98E-09 8.18E-10 7.41E-10 Negl. 2.79E-08 5.60E-09
Living quarters
(indoor fraction of
0.75)
Rest indoor 2.33E-09 7.55E-09 3.98E-10 1.29E-09 Negl. Negl. 2.80E-09 8.85E-09
Tananger population
(indoor fraction of
0.75)
Tananger
indoor /
Tananger
outdoor
1.78E-08
(indoor) /
1.78E-07
(outdoor)
5.80E-08
2.25E-09
(indoor) /
2.25E-08
(outdoor)
7.31E-09 1.97E-09 (indoor) /
1.97E-08 (outdoor) Negl.
2.21E-08
(indoor) /
2.21E-07
(outdoor)
6.55E-08
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091
Revision No.: 1
Date : 2013-06-11 Page 26 of 39
Individual Location
1. LNG Base Load Plant
(Train 1)
2. Ferry bunkering facility
– no bunkering
Added risk contribution
3. Ferry bunkering facility – during
bunkering
Added risk contribution
4. Combined risk
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual risk
(per year)
ISR
(per year)
Individual
risk y
(per year)
ISR
(per
year)
Ferry deck Passengers
indoor 4.00E-07 2.18E-08 2.51E-06 5.16E-08 1.29E-04 6.12E-07 3.19E-05 6.85E-07
Parking area –
passengers
Passengers
outdoor 2.38E-06 5.95E-08 3.54E-06 4.43E-08 1.89E-06 2.37E-08 7.81E-06 1.27E-07
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 27 of 39
In Table 4 the AIR is calculated based on the Individual Specific Risk (ISR) for each working group
and the percentage of the total number of people each group constitutes.
The AIR is calculated from the formula:
personnel ofNumber
)personnel ofNumber (ISRAIR
As shown in Table 8 AIR is up from acceptable to ALARP area, compared with the Skangass
acceptance criterion (ref. Appendix C), after installation of the ferry bunkering facility.
Table 8 Average Individual specific risk 3rd
party ferry bunkering station (per year)
Criteria
Total number of
exposed individuals
LNG Base Load Plant
(Train 1)
LNG Base Load Plant
(Train 1)+ ferry
bunkering system
AIR 3rd
party (per year) 10 531 4.67E-08 1.37E-07
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 28 of 39
6 SENSITIVITIES
The results provided in section 5 are based on DNV recommendation corresponding to a total duration
of 90 seconds (60s to detect and initiate ESD and 30s for the ESD to close). However, Skangass
estimates that it is possible to activate the ESD system in a shorter time of 36s (30s to detect and
initiate ESD and 6s for the ESD valve to close).
Even if a closing time of 6 seconds could be possible if Skangass documents that the facility uses a
valve in compliance with this requirement, DNV’s experience shows that the detection, initiation time
of the ESV is often extended to 60 seconds.
Therefore two sensitivities have been developed to investigate the risk picture for:
- A duration of 66 seconds (60s to detect and initiate ESD, as recommended by DNV and 6s for
the ESD to close, as suggested by Skangass)
- A duration of 36 seconds as estimated by Skangass (30s to detect and initiate ESD and 6s for
the ESD to close)
For both cases it has been assumed that the consequences of a leak on the pipeline between the
bunkering operations will remain the same. Thus only the risk picture during the bunkering operation
will be impacted.
The results of these two sensitivities are compared against the risk results based on the time
recommended by DNV.
6.1 Individual Risk 1st party and 2
nd party
For 1st and 2
nd party the reduction in ESD time reduce the risk for the Skangass operators and terminal
workers at the ferry terminal,
For 1st party, Table 9 and Table 10 show the different individual risk according to the ESD time. The
individual risk for 2nd
party is presented in Table 11 and Table 12.
For the most exposed 1st party which are the Skangass operators at the ferry terminal, the individual
risk contribution from bunkering is reduced by 62% with initiation and closing time according to
Skangass inputs, and the overall LNG-related risk is reduced with 39%.
For the most exposed 2nd
party, which are the workers at the ferry terminal, the individual risk
contribution from bunkering is reduced by approximately 50% with initiation and closing time
according to Skangass inputs, and the overall LNG-related risk is reduced with 36% for outdoor
workers and 18% for indoor workers.
Table 9 Sensitivity, Individual specific risks for most exposed persons (1st party). Note that ISRs in
column 3.. are additional risk contributions, i.e. they do not represent total risk during this operational phase, and
cannot be compared with the acceptance criteria, ref. appendix C.
Individual Location
3. Ferry bunkering
facility – during
bunkering
Added risk contribution
DNV inputs
3. Ferry bunkering
facility – during
bunkering
Added risk contribution
DNV and Skangass
inputs
3. Ferry bunkering
facility – during
bunkering
Added risk
contribution
Skangass Inputs
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 29 of 39
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
Individual
risk
(per year)
ISR
(per
year)
Individual
risk
(per year)
Control room building Control room
building (indoor) 2.00E-05 5.13E-07 1.99E-05 5.12E-07 1.98E-05 5.09E-07
Operator/Maintenance
Most exposed
process point 4.47E-05 4.50E-07 4.47E-05 4.50E-07 4.47E-05 4.50E-07
Control room
building (indoor) 2.00E-05 8.48E-07 1.99E-05 8.46E-07 1.98E-05 8.37E-07
Total 1.30E-06 1.30E-06 0.00E+00
Truck loading (1 person per
truck per 1.2h)
Truck loading
terminal 9.38E-05 2.41E-06 9.36E-05 2.40E-06 9.30E-05 2.39E-06
Ship loading (jetty – only
during connection and
disconnection)1
Ship loading
terminal 9.93E-06 1.38E-07 9.93E-06 1.38E-07 9.93E-06 1.38E-07
Ship deck (during loading
only) Ship loading
terminal 1.33E-05 3.42E-07 1.33E-05 3.42E-07 1.33E-05 3.42E-07
Ship bridge (indoor fraction
0.75, during loading only) Ship loading
terminal 1.33E-05 1.28E-07 1.33E-05 1.28E-07 1.33E-05 1.28E-07
Skangass operators at the
ferry terminal jetty
Ferry loading
terminal 1.08E-04 3.69E-05 1.05E-04 2.71E-06 5.40E-05 1.39E-06
Table 10 Sensitivity, Individual specific risks for most exposed persons (1st party). Base Load Plant
and ferry bunkering station combined.
Individual Location
4.Combined Risk
DNV inputs
4.Combined Risk
DNV and Skangass
inputs
4.Combined Risk
Skangass Inputs
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
Individual
risk
(per year)
ISR
(per
year)
Individual
risk
(per year)
Control room building Control room
building (indoor) 4.22E-05 5.07E-06 4.22E-05 5.07E-06 4.20E-05 5.07E-06
Operator/Maintenance
Most exposed
process point 4.94E-04 7.49E-06 4.94E-04 7.49E-06 4.69E-04 7.49E-06
Control room
building (indoor) 4.22E-05 1.83E-05 4.22E-05 1.83E-05 3.26E-05 1.83E-05
Total 2.58E-05 2.58E-05 2.58E-05
Truck loading (1 person per
truck per 1.2h)
Truck loading
terminal 3.10E-04 1.32E-05 3.10E-04 1.32E-05 3.09E-04 1.32E-05
Ship loading (jetty – only
during connection and
disconnection)1
Ship loading
terminal 6.40E-05 8.91E-07 6.40E-05 8.91E-07 6.40E-05 8.91E-07
Ship deck (during loading
only) Ship loading
terminal 7.34E-05 4.95E-06 7.34E-05 4.95E-06 7.34E-05 4.95E-06
Ship bridge (indoor fraction
0.75, during loading only) Ship loading
terminal 7.34E-05 2.48E-06 7.34E-05 2.48E-06 7.34E-05 2.48E-06
Skangass operators at the
ferry terminal jetty
Ferry loading
terminal 1.32E-04 3.59E-06 1.30E-04 3.52E-06 7.82E-05 2.20E-06
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 30 of 39
Table 11 Sensitivity, Individual specific risks for most exposed persons (2nd
party). Note that ISRs in
column pairs 2. and 3. is additional risk contributions, i.e. they do not represent total risk during this operational phase,
and cannot be compared with the acceptance criteria, ref. appendix C.
Individual Location
3. Ferry bunkering facility
– during bunkering
Added risk contribution
DNV inputs
3. Ferry bunkering facility
– during bunkering
Added risk contribution
DNV and Skangass inputs
3. Ferry bunkering facility –
during bunkering
Added risk contribution
Skangass Inputs
Individual
risk
(per year)
ISR
(per
year)
Individual
risk
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
Ferry terminal –
office workers
Ferry
terminal
indoor
2.32E-05 5.96E-07 2.26E-05 5.81E-07 1.19E-05 3.04E-07
Ferry terminal –
industry workers
Ferry
terminal
outdoor
1.08E-04 2.77E-06 1.05E04 2.70E-06 5.39E-05 1.38E-06
Table 12 Sensitivity, Individual specific risks for most exposed persons (2nd
party). Base Load Plant
and ferry bunkering station combined.
Individual Location
4.Combined Risk
DNV inputs
4.Combined Risk
DNV and Skangass inputs
4.Combined Risk
Skangass Inputs
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
Individua
l risk
(per year)
ISR
(per year)
Individual risk
(per year)
Ferry terminal –
office workers
Ferry terminal
indoor 2.82E-05 1.63E-06 2.76E-05 1.61E-06 1.69E-05 1.33E-06
Ferry terminal –
industry workers Ferry terminal
outdoor 1.32E-04 7.74E-06 1.29E-04 7.67E-06 7.81E-05 4.96E-06
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 31 of 39
6.2 Societal and Individual risk 3rd
party
6.2.1 Societal risk
Figure 9, Figure 10 and Figure 11 show the societal risk according to the different ESD time. If the
detection and closing time is reduced then the societal risk due to the bunkering operation is slightly
reduced. The limited reduction observed is because the LNG Base Load Plant, the bunkering facility
and the LNG pipeline to the jetty are the main contributors, and the risk change from the loading
operation itself is relatively small.
Figure 9 F-N curves for societal risk 3
rd party, DNV inputs
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 32 of 39
Figure 10 Sensitivity F-N curves for societal risk 3rd party, Mixed inputs
Figure 11 Sensitivity F-N curves for societal risk 3rd party, Skangass inputs
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 33 of 39
6.2.2 Individual risk
Table 13 and Table 14 show the different individual risk according to the different ESD total time. We
can see that the individual risk is reduced when the ESD initiation and closing time is reduced.
The different ISR remain in the same order of magnitude.
When comparing between the DNV recommendations (total time of 90s) and a shorter time for closing
the valve as in the mixed inputs, a reduction in risk level is observed.
Applying the Skangass data for initiation and closing, the total reduction in LNG related risk is 39%
for passengers inside the ferry terminal and about 47% for passengers on board the ferry. There is
hence a significant risk reduction potential in in actions to reduce the initiation of the ESD system by
for example designing a manifold location (cf. section 8) allowing an easy activation by the operators
supervising the operation. The reduction in the risk related to bunkering itself is reduced with app.
50% with the Skangass data for initiation and closing of ESD.
Table 13 Sensitivities - Individual Risk for 3rd
party, Note that ISRs in column 3. is additional risk
contributions, i.e. they do not represent total risk during this operational phase, and cannot be compared with the
acceptance criteria, ref. appendix C.
Individual Location
3. Ferry bunkering
facility – during
bunkering
Added risk contribution
DNV inputs
3. Ferry bunkering facility
– during bunkering
Added risk contribution
DNV and Skangass inputs
3. Ferry bunkering facility
– during bunkering
Added risk contribution
Skangass Inputs
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Peninsula Peninsula 3.30E-06 1.06E-07 3.30E-06 1.06E-07 3.30E-06 1.06E-07
Hiking track Hiking
track 4.32E-05 3.45E-07 4.32E-05 3.45E-07 4.32E-05 3.45E-07
Ferry Terminal –
passengers
Ferry
terminal
indoor
2.32E-05 5.55E-07 2.26E-05 5.41E-07 1.19E-05 2.80E-07
Energiveien+Risavika
– office workers
Energiveien
indoor Negl. Negl. Negl. Negl. Negl. Negl.
Energiveien+Risavika
– industry workers
Energiveien
outdoor Negl. Negl. Negl. Negl. Negl. Negl.
Container area –
office workers
Container
area indoor 1.58E-07 4.07E-09 1.10E-07 2.82E-09 1.65E-08 4.24E-10
Container area –
industry workers
Container
area
outdoor
1.11E-06 2.86E-08 8.70E-07 2.23E-08 1.27E-07 3.26E-09
Rest companies –
office workers Rest indoor Negl. Negl. Negl. Negl. Negl. Negl.
Rest companies –
industry workers
Rest
outdoor 7.41E-10 Negl. 2.26E-10 Negl. 2.25E-10 Negl.
Living quarters
(indoor fraction of
0.75)
Rest indoor Negl. Negl. Negl. Negl. Negl. Negl.
Tananger population
(indoor fraction of
0.75)
Tananger
indoor /
Tananger
outdoor
1.97E-09
(indoor) /
1.97E-08
(outdoor)
2.67E-10
1.97E-09
(indoor) /
1.97E-08
(outdoor)
2.67E-10
1.97E-09
(indoor) /
1.97E-08
(outdoor)
2.67E-10
Ferry deck Passengers
indoor 1.29E-04 6.12E-07 2.83E-05 6.05E-07 1.50E-05 2.91E-07
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 34 of 39
Individual Location
3. Ferry bunkering
facility – during
bunkering
Added risk contribution
DNV inputs
3. Ferry bunkering facility
– during bunkering
Added risk contribution
DNV and Skangass inputs
3. Ferry bunkering facility
– during bunkering
Added risk contribution
Skangass Inputs
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Parking area –
passengers
Passengers
outdoor 2.07E-06 2.59E-08 2.07E-06 2.59E-08 1.14E-06 1.42E-08
Table 14 Sensitivities - Individual Risk for 3rd
party, Base Load Plant and ferry bunkering station
combined.
Individual Location
4.Combined Risk
DNV inputs
4.Combined Risk
DNV and Skangass inputs
4.Combined Risk
Skangass Inputs
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Individual
risk
(per year)
ISR
(per year)
Peninsula Peninsula 4.07E-05 1.30E-06 4.07E-05 1.30E-06 4.07E-05 1.30E-06
Hiking track Hiking
track 2.69E-04 2.15E-06 2.69E-04 2.15E-06 2.69E-04 2.15E-06
Ferry Terminal –
passengers
Ferry
terminal
indoor
2.82E-05 7.10E-07 2.76E-05 6.96E-07 1.69E-05 4.35E-07
Energiveien+Risavika
– office workers
Energiveien
indoor 1.58E-09 3.25E-10 1.58E-09 3.25E-10 1.58E-09 3.25E-10
Energiveien+Risavika
– industry workers
Energiveien
outdoor 1.58E-08 3.25E-09 1.58E-08 3.25E-09 1.58E-08 3.25E-09
Container area –
office workers
Container
area indoor 1.89E-07 1.04E-08 1.40E-07 9.12E-09 4.72E-08 6.73E-09
Container area –
industry workers
Container
area
outdoor
1.33E-06 7.36E-08 1.09E-06 6.73E-08 3.46E-07 4.83E-08
Rest companies –
office workers Rest indoor 2.80E-09 5.62E-10 2.75E-09 5.61E-10 2.75E-09 5.61E-10
Rest companies –
industry workers
Rest
outdoor 2.79E-08 5.60E-09 2.74E-08 5.59E-09 2.74E-08 5.59E-09
Living quarters
(indoor fraction of
0.75)
Rest indoor 2.80E-09 8.85E-09 2.75E-09 8.84E-09 2.75E-09 8.84E-09
Tananger population
(indoor fraction of
0.75)
Tananger
indoor /
Tananger
outdoor
2.21E-08
(indoor) /
2.21E-07
(outdoor)
6.55E-08
2.21E-08
(indoor) /
2.21E-07
(outdoor)
6.55E-08
2.21E-08
(indoor) /
2.21E-07
(outdoor)
6.55E-08
Ferry deck Passengers
indoor 3.19E-05 6.85E-07 3.12E-05 6.78E-07 1.79E-05 3.65E07
Parking area –
passengers
Passengers
outdoor 7.99E-06 1.30E-07 7.99E-06 1.30E-07 7.06E-06 1.18E-07
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 35 of 39
6.3 Sensitivities discussion
As stated in section 6.2.2, the reduction in ESD involves a reduction of the risk level. This is most
notably observed for the terminal workers, both Skangass jetty operators and ferry terminal dedicated
workers, and the 3rd
party passengers on the ferry and at the terminal. The risk for these populations
are in the ALARP area, and risk reducing measures shall hence be evaluated a cost benefit perspective.
DNV therefore recommends taking action to reduce as much as practicable the ESD total initiation and
closing time to reduce the inventory released. And as presented in the section 8, Skangass will get
benefit if the ignition sources are controlled during the bunkering as it will reduce the ignition
probability of a drifting cloud and is likely to reduce the overall risk level.
It should be noted that risk level reduction is not linearly proportional to the ESD total time reduction,
which again is proportional to the volume of LNG released. Indeed, while the time is reduced by 60%,
the ISR of the passengers in the ferry terminal is reduced by 39%. Hence, the observed risk reduction
is smaller than the actual reduction in closing time for the ESD valve. This result is considered as
normal. The reasons are multiple.
- In order to ignite the gas cloud has to be within the Lower Flammability Limit (LFL) and Upper
Flammability Limit (UFL) when it is exposed to the ignition source. A larger gas cloud will also
represent a larger extension of the cloud which is above UFL and hence not ignitable. Hence, some of
the ignition sources that for a smaller cloud were exposed to concentration below UFL may now be
outside this envelope.
- If the larger gas cloud that is built up by longer initiation time and closing time does not expose
additional ignition sources, the increase in ignition probability will be less.
- The risk model is based on modelling of selected representative scenarios and a representative wind
direction and drifting patterns. If the wind direction and release scenarios result in gas dispersion that
have a tendency to expose areas with few strong ignition sources, a growth in gas cloud size will not
result in a proportionally equivalent increase in risk level.
.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 36 of 39
7 SHIP MANIFOLD LOCATION
The following comments were given in the previous QRA and remain the same for this version of the
report:
DNV has reviewed the interim location of the ship bunkering manifold and ventilation intakes, to
assess if there could be any non-conformity with respect to the DNV class rules.
The review is based on Skangass Design Basis, ref. /4/ and info from Fjordline:
Bunkering location is suggested to be on deck 3, # 106, port side.
Ventilation intakes are located on car deck, # 149-161, both port and starboard sides.
Initial comments, taken into consideration that the exact location is not set, are as follows:
Areas within the distance of 3 m from the gas fuel manifold valve are considered as hazardous
zone 1 (ref. IEC standard 60092-502, 4.2.2.7)
Areas of 1.5 m surrounding the hazardous zone 1 is considered as hazardous zone 2 (ref. IEC
standard 60092-502, 4.2.3.1)
Within the areas described above all electrical equipment need to be certified for the relevant
zone.
Air inlets for non-hazardous enclosed spaces shall be taken from non-hazardous areas at least
1.5 m from the boundaries of any hazardous area (ref. IEC standard 60092-502, 8.2.5).
Implicitly, this means that ventilation inlets to the accommodation or other gas safe spaces
need to be located at least 6 m from the gas manifold.
These are general comments which should be considered during the design phase. A bunker manifold
which is arranged in such a way that the above requirements are fulfilled will be considered acceptable
according to DNV class rules with respect to location.
Given that the manifold will be installed at the suggested location, the distance to the ventilation
intakes should be sufficient.
Detailed review of the entire gas bunkering system in order to verify compliance with DNV rules Pt.6
Ch. 13 “Gas Fuelled Engine Installation” will be carried out on a later stage based on final design.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 37 of 39
8 CONCLUSIONS AND RECOMMENDATIONS
Risk calculated for the planned LNG bunkering station and LNG Base Load Plant (Train 1), combined,
is presented in the report:
The 1st/2
nd individual risk is found to be within the ALARP region or acceptable for all
personnel categories.
The calculated 3rd
party societal risk, in terms of F-N curve, is within the ALARP or acceptable
area for all events.
3rd
party Individual Specific Risk is found acceptable or in the ALARP area for all individuals.
The passengers on board the ferry are at lower risk than the passengers at the terminal. As a
consequence of this boarding of passengers is planned to take place before bunkering, ref.
Skangass’ Design Basis /4/. According to the same reference, no passengers are allowed in the
passenger tube during bunkering and only late-comers will board through the tube after
bunkering.
The sensitivities shows a reduction in the risk picture for 1st party (only for the group
“Skangass operators at the ferry terminal jetty”), 2nd
party and 3rd
party. However the risk
results remain in the same order of magnitude.
The technical concept of Risavika ferry station is regarded as safer than ‘standard practice’.
As the calculated risk is in ALARP area, Skangass should consider taking measures to reduce the risk
as the one presented below. Indeed, ALARP stands for “As Low As Practible”, meaning that the risk is
tolerable if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement.
DNV recommends a high focus on ignition source control to reduce the ignition probability at the
Skangass LNG plant and ferry terminal. The traffic should be kept to a minimum. The public should
be made aware the potentially hazardous bunkering taking place on the jetty and explained about the
different safety procedures.
It should be noted that fiscal metring system and/or the direct monitoring of Skangass operators
shutting down the ignition sources in the event of a detected leak, are already taken into account in the
analysis. In addition, DNV recommends investigating the possibility of controlling the ignition sources
due to the car traffic in ferry terminal area. Also, the use of Ex proof equipment at the jetty, and
possibly on the ferry, should be considered.
It has been found that the groups working in the vicinity of the plant and the ferry terminal see their
risk increased. It has been assessed that the main contributor to the risk is the underground pipeline
between the bunkering operations that remained under 7 barg of pressure and filled with LNG to cool
down the line.
In general, reduction of LNG volume in the bunkering pipeline by segmentation part of the pipelines in
between bunkering operation would reduce the fire and explosion risk.
Also reduction of the standby pressure between the bunkering operations by depressurizing the whole
underground pipeline would reduce the fire and explosion risk. This study does not account for any
segmentation or depressurization of the loading line.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 38 of 39
The main contributors to the leak frequencies are small bore fittings and flanges. Thus, it should be
considered to evaluate the benefits of using as less as practically possible flanges and small bore
fittings in order to reduce further the leak frequency at the jetty.
Liquid bunds/trays around the LNG loading arm where an LNG leak could occur would help limiting
the pool size in the event of an LNG leak.
Short response and closing times recommended by DNV for ESD upon confirmed leak are used in the
analysis (60 s for leaks response and 30 s for closing). This is based on continuous local supervision by
operators during transfer helping to activate the ESD system manually. It appears that the reduction of
the total ESD time will reduce the risk level, however the times estimated by Skangass are shorter than
what it is experienced in the industry.
Also, DNV recommends that all of the following conditions have to be met in order to justify a short
reaction time:
From the start to the end of the loading operation the operators present at the ferry terminal
jetty has a view of the loading operation and the loading/unloading arm. In particular, the
operator is not sitting inside a building during the loading operation.
The presence of the operators on-site is guaranteed by means of a facility such as a deadman’s
handle or by a procedure in the safety management system and is checked during inspections.
The process of actuating the emergency stop device by the operators present in the event of a
leak during the loading operation is laid out in a procedure.
The operators present on-site is adequately trained and is also familiar with the applicable
procedures.
The emergency stop device is positioned according to the applicable standards, so that an
emergency button can be actuated within a short time irrespective of the direction of the
outflow.
It is also possible to close the ventilation system in the ferry terminal, from the Skangass LNG Plant,
upon gas detection. It is recommended to include possible leaks from the ferry bunkering facility in
this picture to ensure that the ventilation system closes also upon gas detection from the ferry
bunkering facility.
Det Norske Veritas
Report for Skangass AS
QRA for Skangass LNG Plant - Ferry bunkering project
MANAGING RISK
DNV Rep. No.: 2013-4091 Revision No.: 1
Date : 2013-06-11 Page 39 of 39
9 REFERENCES
/1/
QRA for Skangass LNG Plant, DNV, Report no.: 2009-0068, Rev 1, 08.05.2009
/2/
Skangass Memo, Risikovurdering ved Installering av Kontainere/Brakke på LNG
anlegget, 23.10.2010
/3/
Skangass Memo, QRA Oppdatering: Risikovurdering ved lossing/”tømming” av
tankbil til LNG tank 42-TR-101, doc. no. SG200-SG-S-RS-0001, 01.11.2011
/4/
Skangass Project Design Basis, LNG bunkering of Fjordline at Risavikahavn, rev 0
draft, 16.02.2012
/5/
Comparison of LNG loading hoses vs. Rigid loading arms, Memo No. 16DJTWB-
2/JASTEIN, DNV, 18.03.2013
Det Norske Veritas:
DNV is a global provider of knowledge for managing risk. Today, safe and responsible business conduct is both a license to operate and a competitive advantage. Our core competence is to identify, assess, and advise on risk management, and so turn risks into rewards for our customers. From our leading position in certification, classification, verification, and training, we develop and apply standards and best practices. This helps our customers to safely and responsibly improve their business performance. Our technology expertise, industry knowledge, and risk management approach, has been used to successfully manage numerous high-profile projects around the world. DNV is an independent organisation with dedicated risk professionals in more than 100 countries. Our purpose is to safeguard life, property and the environment. DNV serves a range of industries, with a special focus on the maritime and energy sectors. Since 1864, DNV has balanced the needs of business and society based on our independence and integrity. Today, we have a global presence with a network of 300 offices in 100 countries, with headquarters in Oslo, Norway.
Global impact for a safe and sustainable future:
Learn more on www.dnv.com