report qra for skangass lng plant - ferry bunkering...

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.

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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

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DNV Rep. No.: 2013-4091

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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:

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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.

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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.

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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:

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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.

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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.

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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

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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/

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Figure 2 Risk contours today: LNG Base Load Plant (Train 1) without ferry bunkering

installation

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Figure 3 Risk contours today: LNG Base Load Plant (Train 1) without ferry bunkering

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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.

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Figure 4 Risks contours (Train 1 and ferry bunkering system) between bunkering

operations

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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

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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.

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Figure 7 Risks contours combination of Train 1 and bunkering facility, average of both

bunkering and no bunkering phases.

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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)


year)


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


Ship deck (during loading

only) Ship loading


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Ship bridge (indoor fraction

0.75, during loading only) Ship loading


Skangass operators at the

ferry terminal jetty

Ferry loading


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


year)


year)


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).

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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


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)


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


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


Ship deck (during loading only) Ship loading


Ship bridge (indoor fraction 0.75, during

loading only) Ship loading


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.

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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

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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


(Train 1)


– no bunkering



– during bunkering


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

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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


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


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

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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

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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


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

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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.

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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


(Train 1)


– no bunkering


3. Ferry bunkering facility – during

bunkering


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


– 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

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Revision No.: 1

Date : 2013-06-11 Page 26 of 39

Individual Location


(Train 1)


– no bunkering


3. Ferry bunkering facility – during

bunkering


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

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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

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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


DNV inputs

3. Ferry bunkering

facility – during

bunkering


DNV and Skangass

inputs

3. Ferry bunkering

facility – during

bunkering

Added risk

contribution

Skangass Inputs

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Individual

risk

(per year)

ISR

(per year)

Individual

risk

(per year)

Individual

risk

(per year)

ISR

(per

year)

Individual

risk

(per year)


building (indoor) 2.00E-05 5.13E-07 1.99E-05 5.12E-07 1.98E-05 5.09E-07


Most exposed

process point 4.47E-05 4.50E-07 4.47E-05 4.50E-07 4.47E-05 4.50E-07

Control room


Total 1.30E-06 1.30E-06 0.00E+00


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



disconnection)1

Ship loading

terminal 9.93E-06 1.38E-07 9.93E-06 1.38E-07 9.93E-06 1.38E-07


only) Ship loading

terminal 1.33E-05 3.42E-07 1.33E-05 3.42E-07 1.33E-05 3.42E-07



terminal 1.33E-05 1.28E-07 1.33E-05 1.28E-07 1.33E-05 1.28E-07



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)




Most exposed

process point 4.94E-04 7.49E-06 4.94E-04 7.49E-06 4.69E-04 7.49E-06

Control room


Total 2.58E-05 2.58E-05 2.58E-05


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



disconnection)1

Ship loading

terminal 6.40E-05 8.91E-07 6.40E-05 8.91E-07 6.40E-05 8.91E-07


only) Ship loading

terminal 7.34E-05 4.95E-06 7.34E-05 4.95E-06 7.34E-05 4.95E-06



terminal 7.34E-05 2.48E-06 7.34E-05 2.48E-06 7.34E-05 2.48E-06



Ferry loading

terminal 1.32E-04 3.59E-06 1.30E-04 3.52E-06 7.82E-05 2.20E-06

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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




DNV inputs




DNV and Skangass inputs

3. Ferry bunkering facility –

during bunkering


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


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

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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

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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

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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


DNV inputs








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


– office workers

Energiveien

indoor Negl. Negl. Negl. Negl. Negl. Negl.



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


indoor 1.29E-04 6.12E-07 2.83E-05 6.05E-07 1.50E-05 2.91E-07

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Individual Location

3. Ferry bunkering

facility – during

bunkering


DNV inputs








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


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


– office workers

Energiveien

indoor 1.58E-09 3.25E-10 1.58E-09 3.25E-10 1.58E-09 3.25E-10



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


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

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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.

.

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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



MANAGING RISK


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



MANAGING RISK


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



MANAGING RISK


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:

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