Paper PS4-6

PS4-6.1

SAKAI LNG TERMINAL: COMPACT MULTI-STRATEGY TERMINAL BASED ON QUANTITATIVE DISASTER

RISK ASSESSMENT

Hiroshi Kuwahara Deputy Manager

Toshimitsu Okano Engineering Center Fossil Power Division

Kansai Electric Power Co., Inc 3-22 Nakanoshima, Kita-ku

Osaka, Japan

Tetsu Shiota President

Sakai LNG Corporation 3-1-10 Chikko Shinmachi, Nishi-ku, Sakai-shi

Osaka, Japan

ABSTRACT

In January 2006, the Sakai LNG Terminal commenced operations as the second LNG receiving terminal of The Kansai Electric Power Co., Inc. It is a multi-strategy terminal that, in addition to piping fuel gas for power generation, supplies gas for industrial use to nearby factories, ships LNG by lorry and supplies LNG for hydrogen fuel production to the largest liquid hydrogen production plant in Japan located adjacent to the terminal. Furthermore, as an LNG receiving terminal, it is one of the few facilities in the world equipped to load large class LNG tankers, which improves the LNG supply and demand balancing capacity by fitting in perfectly with Japan’s power supply and demand structure and LNG procurement characteristics.

Moreover, two key features of the Sakai LNG Terminal are that it is extremely small and located on the outskirts of a large urban area. It has the capacity to hold 420,000 m3 of LNG and the hardware for diverse means of send-out, yet everything is neatly concentrated into an approximate 110,000 m2 site in an industrial zone on the outskirts of the central city area, hence it has the smallest footprint in the world for an LNG terminal.

Because of the suburban location, the accident potential of the LNG facilities were quantitatively assessed in the planning phase of the terminal and the results were released to show the permitting authorities and local residents how safe the facilities would be. This was the first such risk assessment ever conducted on LNG facilities anywhere in the world.

Paper PS4-6

PS4-6.2

1． BACKGROUND TO LNG TERMINAL CONSTRUCTION

Deregulation began in Japan’s energy markets in 2000 and, since that time, those markets have become very competitive as power companies are supplying gas, gas companies are supplying power and new players have entered both businesses. Moreover, gas markets have grown first and foremost with hydrogen gas for fuel cell-powered vehicles.

Affront this backdrop, The Kansai Electric Power Co., Inc. built a second LNG receiving terminal on the outskirts of an urban area of high demand density and commenced operations in January 2006 in order to ensure price competitiveness in the electric power market and expand its revenue base by making inroads into gas markets. The events in this backdrop are outlined here following.

1.1 Deregulation of Japan’s Energy Markets

After the Plaza Accord of 1985, the Japanese yen rapidly appreciated, while international pressure calling for deregulation and demands from domestic industries for a correction to the price difference between Japan and the rest of the world increased, which made Japan’s high cost structure and price correction topics of the energy industry.

In the electric power business, the Electricity Enterprises Law was twice amended in 1995 and 1999, which liberalized the retailing of electric power (about 26% of all electric power) in March 2000. This put genuine market principles to work in Japan’s electric power market and brought the number of competing Power Producers and Suppliers (PPS) to 23 by March 2006. Figure 1 shows the power wattage sold by PPS and their share of all sold electric power wattage. Since liberalization, figures have grown steadfast with PPS accounting for 2.2% (of that 4.6% for extra high voltage and 0.67% for high voltage) of all power sold in Japan as of September 2006. Also since liberalization, electricity rates have tended to decrease, showing an approximate 15% reduction in price. The scope of liberalization will reach about 60% of all electric power in April 2007 when new amendments to the Electricity Enterprises Law go into force.

Figure 1. PPS Share of Power Sales since Retail Liberalization

0

2000

4000

6000

8000

10000

12000

2000 2001 2002 2003 2004 2005

Fiscal year

Elec

trici

ty S

ales

by

PPS

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on k

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0.5

1.0

1.5

2.0

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PPS

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re (%

)

Extra high voltage powerHigh voltage powerShare of extra high voltage powerShare of high voltage power

Paper PS4-6

PS4-6.3

Like the electric power business, retailing in the gas business was liberalized as well in 1995 affront the growing needs for gas by industry, etc. The scope of liberalization was broadened in 1999 to cover approximately 50% of all piped gas supply. As of March 2006, there were 108 contracts being handled by 21 new entrants, such as electric power companies and trading houses, giving these new entrants about 7.6% of the supply volume of all large volume supply.

1.2 Increased Consumption of Diverse Gases

Some 96.3% of the natural gas consumed in Japan is imported from overseas as LNG. A large portion of that is used as fuel for power generation and city gas. In the ten years from 1995, the supply of natural gas has increased about 1.3 times (Fig.2). Moreover, looking at sales volume by use of city gas, industrial consumption grew markedly, or about 1.9 times, over the ten year period from 1995 because of the rapid increase in the introduction of natural gas by high demand users, technological progress made with gas utilization equipment in recent years and demands for action against global environmental problems.

Figure 2. Trends in Sales of Town Gas by Sector

Though most of the increased consumption in natural gas is fed with imports, Japan has for some time been producing air separated gases such as liquid nitrogen and liquid oxygen using the cold heat of LNG. Sales of these gases have steadily increased owing to the favorable situation in industrial fields where these gases are consumed. Moreover, the rapid progress of fuel cell technology in recent years is expected to spur large future increases in the use of hydrogen gas that is obtained in the reforming of LNG, particularly in and around vehicle applications (Table.1).

Table 1. Fuel Cell Development Targets in Japan

2010 2020 2030 Fuel cell vehicles

(Number) Approx. 50,000 Approx. 5 million Approx. 15 million

Estimated hydrogen demand (t/year) Approx. 36,000 Approx. 580,000 Approx. 1.51 million

0

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600

800

1,000

1,200

1,400

1965 1970 1975 1980 1985 1990 1995 2000

Fiscal Year

Tow

n G

as S

ales

（×1

015J）

OthersIndustrialCommercialResidential

Paper PS4-6

PS4-6.4

1.3 Activities of Kansai Electric Power

Figure 3 gives an overview of Kasai Electric Power. In preparation for the aforementioned liberalization of Japan’s energy markets, Kansai Electric Power launched activities to reduce costs in its electric utility business and built facilities at its Himeji LNG Terminal to start gas consignment and ship LNG by lorry in order to increase sales of its gas business (Fig.4).

The Sakai LNG Terminal introduced here was newly built affront a backdrop of big changes in the economic environment in order to strengthen the company’s cost competitiveness of the electric utility business and establish a strategic comprehensive energy base for getting into the gas business. It was located in the vicinity of two thermoelectric power plants in an industrial zone of high energy demand density on the outskirts of a large urban area, and was built not only to pipe gas to these power plants but also to provide diverse means of gas send-out, hence enabling multiple business strategies.

Figure 3. Overview of Kansai Electric Power

Figure 4. Gas Sales of Kansai Electric Power

The Kansai RegionThe Kansai RegionServices Area: 30,000kmServices Area: 30,000km22

Population: 20 millionPopulation: 20 million

JapanJapan

TokyoTokyo

OsakaOsaka

Kansai Electric Power (FY 2005)Kansai Electric Power (FY 2005)Installed Plant Capacity : 41,750 MWInstalled Plant Capacity : 41,750 MWPower Generation : 152.2 billion kWhPower Generation : 152.2 billion kWh

Nuclear46%

Fossil44% Hydro

10%LNG17%

Oil7%

IndonesiaIndonesia AustraliaAustralia MalaysiaMalaysia QatarQatar

Coal20%

4.45 million tons/year4.45 million tons/year(67% of all fossil fuels)(67% of all fossil fuels)

The Kansai RegionThe Kansai RegionServices Area: 30,000kmServices Area: 30,000km22

Population: 20 millionPopulation: 20 million

JapanJapan

TokyoTokyo

OsakaOsaka

Kansai Electric Power (FY 2005)Kansai Electric Power (FY 2005)Installed Plant Capacity : 41,750 MWInstalled Plant Capacity : 41,750 MWPower Generation : 152.2 billion kWhPower Generation : 152.2 billion kWh

Nuclear46%

Fossil44% Hydro

10%LNG17%

Oil7%

IndonesiaIndonesia AustraliaAustralia MalaysiaMalaysia QatarQatar

Coal20%

4.45 million tons/year4.45 million tons/year(67% of all fossil fuels)(67% of all fossil fuels)

2 7

180 210

400

530

0

100

200

300

400

500

600

2000 2001 2002 2003 2004 2005

Fiscal Year

Gas

Sal

es (1

,000

ton)

Paper PS4-6

PS4-6.5

2． OVERVIEW OF THE SAKAI LNG TERMINAL

The biggest features of the Sakai LNG Terminal is that it is a multi-strategy terminal capable of delivery to diverse customers and that it is a compact terminal located on the outskirts of a large urban area. The following overview of the terminal will rotate around these features.

2.1 Compact Suburban Terminal

The Sakai LNG Terminal is located in an industrial zone on the outskirts of Sakai City (approx. 830,000 population), about 3 km from residential areas (see Fig.5). It sits on an approximate 110,000 m2 site and has an approximate annual handling capacity of 2.7 million ton between its 3 storage tanks (140,000 m3 capacity each), vaporizers, pumps and BOG systems. It is the world smallest class of LNG terminal owing to the rational equipment layout that resulted from the quantitative risk assessments discussed later.

Figure 5. Map of Sakai LNG Terminal Area

2.1.1 Overview of Major Equipment. Table 2 gives specifications and quantities of major equipment at the Sakai LNG Terminal.

One of the big features is the adoption of aboveground prestressed concrete tanks for storing LNG in a way that most effective utilizes the available land. Most of the other equipment is standard for an LNG terminal.

Nanko Power Station600MW×3units

Sakai LNG Terminal

Sakaiko Power Station250MW×8units

Approx. 3 km

Nanko Power Station600MW×3units

Sakai LNG Terminal

Sakaiko Power Station250MW×8units

Approx. 3 km

Paper PS4-6

PS4-6.6

Table 2. Major Equipment of Sakai LNG Terminal

Equipment Specifications

LNG storage tanks Prestressed concrete above-ground type 140,000 m3 x 3

Vaporizers Open rack vaporizer, 135 t/h x 6

LNG pumps In-tank pump, 190 t/h x 6

Unloading arms 4,000 m3/h x 3 (for LNG) 27,000 m3N/h x 1 (for RG)

BOG compressors 9.4 t/h x 3

Return gas blowers 27,000 m3 N/h x 2

Flare stack 35 t/h x 1

Vent stack 47 t/h x 1

Berth 80,000 DWT

2.1.2 Layout. Figure 6 shows where the Sakai LNG Terminal is located with respect to its surroundings and Figure 7 shows the layout of the terminal. The LNG tanks are located from the northern end to the eastern side of the central area. The primary processing equipment such as LNG vaporizers and BOG compressors, and utility systems are in the southern end of the central area, while the management offices are on the western side. Moreover, the LNG berth is in the southwestern quadrant of the site sandwiched between the Sakai LNG Terminal and a public road. It is connected to the terminal via 1.7 km of pipe.

Figure 6. Map of Sakai LNG Terminal

LNG Berth

Sakai LNG Terminal

LNG Berth

Sakai LNG Terminal

Paper PS4-6

PS4-6.7

Figure 7. Sakai LNG Terminal Photo

In layout studies, legal requirements were first ensured, that is to say, required clearances between equipment, minimum distances to safety devices, etc. Equipment was sectioned into zones by function (storage, production, utilities, etc.) and connected by emergency roads. Risk assessment results verified that the effects of foreseeable accidents could be contained within the area of the site. Table 3 gives safety codes and the actual situation at the Sakai LNG Terminal.

Table 3. Safety Codes and Actual Distances at Sakai LNG Terminal

Criteria Code Actual condition

Minimum distance between LNG equipment and residential areas or perimeter of industrial sites

206 m Approx. 2,500 m

Minimum distance between LNG equipment and site boundary 20 m Approx. 30 m

Minimum distance between LNG tanks 39 m Approx. 40 m Minimum distance between LNG equipment and hazardous substance equipment

20 m Approx. 30 m

Lorry Loading Dock(Under construction)

LNG Vaporizers

Ground Area: 110,000m2Utility Facilities

BOG Compressors

Office Building

Lorry Loading Dock(Under construction)

LNG Vaporizers

Ground Area: 110,000m2Utility Facilities

BOG Compressors

Office Building

Paper PS4-6

PS4-6.8

2.2 Multi-Strategy LNG Terminal

While its main purpose is to supply natural gas as a fuel for power generation, the Sakai LNG Terminal has diverse supply capabilities as a multi-strategy terminal for dealing with liberalization in Japan’s energy markets and the diversification of LNG supply. Two big features are that the terminal supplies utilities to the largest liquid hydrogen production plant in Japan located nearby, and that it has large loading infrastructure for ocean-going ships. Here following is an introduction to the diverse send-out functions of the Sakai LNG Terminal.

2.2.1 Gas Supply to Power Plants. The Sakai LNG Terminal supplies natural gas as a fuel for power generation to two thermoelectric power plants (see Fig. 5). Together, the two plants produce about 4 million kW of power.

Of these, the Sakaiko Power Plant is scheduled for refurbishing to the latest in gas turbine combined cycle power generation system from April 2009 to October 2010. In time for this refurbishing, pressure of the gas supplied to the plant will be boosted from the current 1.7 MPa to about 4.5 MPa, therefore plans are to add booster pumps and gas flow control equipment. Once pressure is boosted, gas supply systems of the Sakai LNG Terminal will be divided into high pressure and low pressure systems.

2.2.2 Gas Supply to Nearby Plants and Lorry Shipping Facilities. The Sakai LNG Terminal is located in an existing industrial zone. It supplies several tens of tons of natural gas per hour to nearby chemical plants and oil refineries using an approximate 4 km pipeline to the Sakaiko Power Plant and directly branching from there. Moreover, the terminal has lorry loading facilities to supply LNG to customers in areas not covered by existing LNG lines. Since sales opened in March 2006, about 1,200 lorries have carried about 13,000 ton of LNG as of November 2006.

2.2.3 Cold/Heat Usage and Hydrogen Production. Adjacent to the Sakai LNG Terminal, Hydro Edge Company built air-separated gas production plants and the largest liquid hydrogen production plant in Japan. Sales operations started in April 2006. As shown in Figure 8, the Sakai LNG Terminal supplies these plants with natural gas as a raw material for producing hydrogen and LNG as a heat and cold source for producing air-separated gases (nitrogen, oxygen and argon). Table 4 gives specifications of major equipment operated by Hydro Edge Company.

Though other existing LNG terminals separate liquids and gases using the cold and heat of LNG, the big feature here is that the use of the cold and heat of LNG has been further expanded to produce air-separated gases, which are in turn supplied as refrigerant for the production of liquid hydrogen at the same site. We view the Sakai LNG Terminal and the nearby liquid hydrogen production plant as a model for future LNG receiving terminals.

Paper PS4-6

PS4-6.9

Figure 8. System Flows of Liquid Hydrogen and Air Separation Gas Plant

Table 4. Major Equipment at Hydro Edge Company

Equipment Type of gas Production capacity Liquid Hydrogen 3,000 L/h x 2 Liquid hydrogen

production system Compressed Hydrogen 600 m3N/h

Liquid Oxygen 4,000 m3N/h

Liquid Nitrogen 12,100 m3N/h Air separation gas production system

Liquid Argon 150 m3N/h

■Liquid Hydrogen Plant

■Air Separation Gas Plant

HeatExchangerAir

Liquid Nitrogen （-196℃）

Liquid Oxygen（-183℃）

Liquid Argon(-186℃）

LN2

LAr

LO2

LorryShipmentLiquid Air

RectifyingTower

0.64MPa-169℃

LNGHeat-Ex

Liquid Nitrogen

4,000kL

50kL

965kL

Compressor

Product Tank

Steam Reforming

PSA Unit(CO2,H2O removal)

Liquefier

N2 Gas

H2 Gas

CO2 Gas

Pure Water

LH2

Liquid Hydrogen(-253℃）

H2＋CO2

（CH4＋2H2O → 4H2＋CO2）2MPa

Room Temp 300kL

LN2

Compressor

LorryShipment

Product Tank

LNG

NG return

NG

Sakai LNG

■Liquid Hydrogen Plant

■Air Separation Gas Plant

HeatExchangerAir

Liquid Nitrogen （-196℃）

Liquid Oxygen（-183℃）

Liquid Argon(-186℃）

LN2

LAr

LO2

LorryShipmentLiquid Air

RectifyingTower

0.64MPa-169℃

LNGHeat-Ex

Liquid Nitrogen

4,000kL

50kL

965kL

Compressor

Product Tank

Steam Reforming

PSA Unit(CO2,H2O removal)

Liquefier

N2 Gas

H2 Gas

CO2 Gas

Pure Water

LH2

Liquid Hydrogen(-253℃）

H2＋CO2

（CH4＋2H2O → 4H2＋CO2）2MPa

Room Temp 300kL

LN2

Compressor

LorryShipment

Product Tank

LNG

NG return

NG

Sakai LNGSakai LNG

Paper PS4-6

PS4-6.10

2.2.4 Loading. Last to be explained are gas loading and its background, considered the most characteristic send-out method of the Sakai LNG Terminal. Smaller terminals capable of loading coastal LNG carrier have existed for some time, but the loading facilities of the Sakai LNG Terminal were designed and built for loading large LNG tankers.

a． Japan’s Electric Power Supply and Demand Structure and Positioning of LNG-Fired Thermoelectric Power Generation

Figure 9 shows the annual power consumption of Japan. Large peaks are seen in the summer months of July and August in comparison to other periods. Given this consumption pattern, it is necessary to carefully balance power sources so as to ensure supply stability in respect of economics, environmental conditions and operating conditions of individual power sources.

Figure 9. Annual Electric Power Consumption in Japan

Figure 10 shows the power source structure of Kansai Electric Power and electric power consumption in fiscal 2005. Because of its high power generation capacity, nuclear power is the best source in terms of fuel supply stability, economics and environmental load. After that come coal-fired power generation and LNG-fired power generation. Nuclear and coal-fired power generation are positioned to deliver about the same output throughout the year, while, because of its good environmental qualities and output balancing capability, LNG-fired power generation is positioned about the middle of the supply structure so as to absorb the fluctuations in electric power consumption.

million kW

FY 2001FY 2000

FY 1995

FY 1990

FY 1985

FY 1975

FY 1965

Month

million kW

FY 2001FY 2000

FY 1995

FY 1990

FY 1985

FY 1975

FY 1965

Month

Paper PS4-6

PS4-6.11

Figure 10. Plant Capacity and Power Generation by Energy Source of Kansai Electric Power

b． Improving Supply and Demand Balance of LNG

Demand for natural gas has risen worldwide in recent years, spurring increases in the supply of LNG. Japan, which is the world’s largest importer of LNG, procures LNG via long-term take or pay contracts and has gradually built a LNG procurement environment. In addition, because of the aforementioned seasonal fluctuations in LNG consumption for power generation and the need to make up for demand that other power sources cannot cover or in other words as a mean for hedging power source risks, particularly a company like Kansai Electric Power, which relies greatly on nuclear power generation for supply, must operate LNG-fired power generation more flexibly and improve the supply and demand balance of LNG. This balance was before achieved on the supply side by joint purchasing with other LNG buyers and spot procurements, but because the Sakai LNG Terminal has infrastructure for loading the largest class of ocean-going LNG tanker, it improves the supply and demand balance of LNG.

c． Loading Facilities

Loading is done by reversing the flow through unloading equipment. There are 6 purpose-specific pumps capable of delivering 320 t/h each. Therefore a 140,000 m3 class LNG tanker can be completely loaded in about 30 hours. It is believed that the Sakai LNG Terminal is the only one of its kind in the world with this scale of loading. Though presently there are no customers seeking LNG supply this way, this loading function will enable LNG supply inside and outside Japan and improve terminal use as LNG procurement practices diversify and change shape from the current long-term contracting to spot procurements.

1033

890

456

841

954

0

500

1000

1500

2000

2500

3000

3500

4000

4500Pl

ant C

apac

ity （

10,0

00kW

）

691

156

308

252

105

0

200

400

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1600

Pow

er G

ener

atio

n（10

0 m

illion

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h）

Oil/OthersLNGCoalHydroNuclear

Paper PS4-6

PS4-6.12

3． QUANTITATIVE DISASTER RISK ASSESSMENT

Because the Sakai LNG Terminal was to be located on the outskirts of an urban area, a risk assessment was done in the planning phase to quantitatively and logically analyze the accident potential of the LNG facilities and demonstrate the safety of the terminal to permitting authorities and local residents. Results were publicized and led to agreements with authorities and residents. These results were applied to the basic design of the safety systems and other aspects of the terminal. The adequacy of the aforementioned compact equipment layout was verified by this risk assessment.

Japan’s LNG terminals boast a solid safety record with no major accidents having occurred in the 30-odd years since LNG was first introduced. However, because there is not data on accidents, probability theories based on accident potential were an unfamiliar subject in the industry.

The authors closely examined accident databases for Japanese oil storage tanks and the like, as well as data from the Great Hanshin-Awaji Earthquake of 1995. This data was then looked at in consideration of the characteristics of LNG and LNG equipment, and applied to LNG terminal equipment to identify the potential risks of an LNG terminal never before seen in the world. Furthermore, an impact assessment was done based on these results in order to quantitatively and logically assess the greater accident risks of the LNG receiving terminal.

Here following is illustrated and reported the specific evaluation technique of the risk assessment, from the basic concepts to results, which was done at the terminal.

3.1 Basic Concepts

The risk assessment policy followed the “Risk Assessment Guidelines for Petrochemical Plants” set forth by the Fire and Disaster Management Agency. Those guidelines indicate as the basic concept the use of a dual axis risk matrix consisting of accident frequency and impact range parameters to assess the comprehensive dangers or risks and examine preventative measures suited for the potential impact of those risks (Fig. 11-1,2).

Figure 11-1. Basic Concept of Disaster Risk Assessment

Estimate of Probability

Estimate of Impact

Assess Comprehensive Risk

ExaminePreventative Measures

Estimate of Probability

Estimate of Impact

Assess Comprehensive Risk

ExaminePreventative Measures

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PS4-6.13

Figure 11-2. Risk Matrix

3.2 Risk Assessment

The basic procedure of the actual risk assessment was conducted according to “Risk Assessment Guidelines for Petrochemical Plants” set forth by the Fire and Disaster Management Agency.

3.2.1 Assessment Procedure. Table 5 gives the specific assessment steps and explanations thereof.

Table 5. Assessment Procedure

Step Explanation

1

Selection of target equipment to assess Select equipment of a relatively high degree of danger based on the quantity of hazards there are and their proximity to public infrastructure.

2

Extraction of accident factors and setting of initial event Set a thinkable cause of accident such as a natural disaster (i.e. earthquake, etc.) or accident that could occur any day. Set the initial events for each cause of accident based on past cases. If no cases exist, use FMEA.

3

Event Tree Analysis (ETA) Develop an event tree of the development process of an accident from the initial events, including whether emergency equipment works or fails, whether fire or gas spreads or is contained, etc. Estimate the final events of the accident by adding the probability rate of each event obtained from databases.

4 Estimation of impact range

Evaluate the impact range of gas dispersion, radiating heat, etc., for the events of relatively high probability obtained by ETA.

5 Comprehensive risk assessment

Assess the comprehensive risk using the risk matrix based on accident probability (frequency of occurrence) and impact range.

AA AA

AA

AB

ABC

ABCD

BCDD

Risk Level

AA

A

C

D

B

Priority of Preventative Measures

Top

High

Medium

Low

Unnecessary

Probability

Impact

Very High

High

Medium

Low

Very Low Low Probable High

AA AA

AA

AB

ABC

ABCD

BCDD

Risk Level

AA

A

C

D

B

Priority of Preventative Measures

Top

High

Medium

Low

Unnecessary

Probability

Impact

Very High

High

Medium

Low

Very Low Low Probable High

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PS4-6.14

3.2.2 Estimation of Accident Probability. The most important step of the risk assessment was to estimate the accident probability or frequency of occurrence. For this, the last 5 years of accident databases for the approximate 85,000 oil storage tanks in Japan were used. When there was not a case involving an LNG tank, the causes of accidents with oil storage tanks were examined. The characteristics of LNG (i.e., non-corrosive, etc.) and LNG equipment were taken into consideration to identify the accident probability of LNG tanks.

To estimate the probability of emergency equipment working or failing at a branch event of the event tree analysis, equipment reliability data was applied to a fault tree analysis of the individual equipment components.

Figure 12 shows a representative example of an event tree analysis.

Figure 12. Example ETA of Leak from LNG Tank Pipe Flange

Also, to estimate the accident probability in the event of an earthquake, accident data from the Hanshin-Awaji Earthquake was examined and used. The Great Hanshin-Awaji Earthquake was a shallow earthquake of 7.3 magnitude that struck in a heavily populated urban area in 1995. In the hardest hit areas, oil tanks leaked and LPG leaked from a pipe flange of a 20,000-ton capacity tank, forcing approximately 28,000 households and approximately 72,000 people to evacuate. In the risk assessment of the Sakai LNG Terminal, the accident probability in an earthquake was estimated using as parameters accidents that occurred with the roughly 1,000 oil tanks in and around Kobe City, which was directly hit by the violent tremors of the Great Hanshin-Awaji Earthquake.

3.2.3 Estimation of Impact Range. Using the results from the event tree analysis, the impact range of the accident was estimated for an accident frequency of 10-7 time/year for everyday accidents and 10-5 time/earthquake for earthquake-driven accidents. These frequency of occurrence values are given as reference in the “Risk Assessment Guidelines for Petrochemical Plants” set forth by the Fire and Disaster Management Agency.

P0 = 5×10-5

Notes. P0 is the initiating event probability, which is set based on accident data for hazardous substance facilities.P1, P2, P3 are branch event probabilities, which are set based on equipment reliability data.

P1=0.99998

P2=0.9999

1-P2=0.0001LNG Leak from Tank Pipe Flange

Initiating Event

1×10 ‐7

Success

Failure

Leak detection & Pump stopping Consequence

5×10 ‐5

5×10 ‐9

1×10 ‐11

Success

LNG collecting system(Pipe, Pan, Pond)

Water curtainsystem

1-P3=0.002

P3=0.998

Gas Dispersion

Partial Gas Dispersion

1-P3=0.002

P3=0.998

Gas Dispersion

Partial Gas Dispersion

Success

Success

Failure

Failure

P0 = 5×10-5

Notes. P0 is the initiating event probability, which is set based on accident data for hazardous substance facilities.P1, P2, P3 are branch event probabilities, which are set based on equipment reliability data.

P1=0.99998

P2=0.9999

1-P2=0.0001LNG Leak from Tank Pipe Flange

Initiating Event

1×10 ‐7

Success

Failure

Leak detection & Pump stopping Consequence

5×10 ‐5

5×10 ‐9

1×10 ‐11

Success

LNG collecting system(Pipe, Pan, Pond)

Water curtainsystem

1-P3=0.002

P3=0.998

Gas Dispersion

Partial Gas Dispersion

1-P3=0.002

P3=0.998

Gas Dispersion

Partial Gas Dispersion

Success

Success

Failure

Failure

Paper PS4-6

PS4-6.15

Table 6 gives the estimated impact range for the major events of the impact range analysis by the frequency of occurrence. And, Fig. 13 gives the estimated impact range of gas dispersion caused by a leak from a pipe flange of an LNG tank.

Gas dispersion was calculated using the Sakagami formula, which is the Gaussian Plume Model. The formula is introduced in the guidelines of the Fire and Disaster Management Agency. The model is simple and cannot do calculations with considerations for gas density, heat balance, etc., but conclusions are on the safe side when applied to gases that are lighter than air such as methane, the main constituent of LNG.

Table 6. Estimated Impact Range for Major Accidents by Frequency of Occurrence

No Equipment Category Event Probability Impact range

1 Everyday 5×10-5

/year

2 Seismic

Gas dispersion (Water curtain

working) 3×10-4

/earthquake

Area around affected

equipment

3

LNG tank pipe flange

Everyday Gas dispersion (Water curtain not working)

1×10-7 /earthquake

Area around affected

equipment

4 LNG pipe weld (Parallel to city road) Everyday Gas dispersion 5×10-7

/year Within plant

grounds

5 LNG pipe weld (Crossing city road) Everyday Gas dispersion 5×10-7

/year

Area around affected

equipment

6 Everyday 5×10-7

/year

7

Gas pipe flange (Parallel to city road)

Seismic Gas dispersion

3×10-4 /earthquake

Area around affected

equipment

8 Heavy oil tank pipe flange Everyday Fire 2×10-7

/year

Area around affected

equipment

Paper PS4-6

PS4-6.16

Figure 13. Estimated Impact Range of Gas Spread Caused by Leak from LNG Tank Pipe Flange

3.3 Assessment Results

Figure 14 shows the risk matrix of final results. As can be seen, emergency equipment and equipment layout keep the risk level sufficiently low for all events. These results indicated that the risk level of the Sakai LNG Terminal was low, therefore additional emergency hardware and layout changes were not needed. However, because the assessment contains elements of uncertainty, soft measures were examined and it was ultimately decided to ensure safety efficacy by establishing a quick response structure for emergencies within the facility and a similar cooperative structure with related outside organizations.

Figure 14. Risk Assessment Results Using Risk Matrix

LNG collecting pondsLNG collecting ponds

LFL/2（2.5%）contoursLFL/2（2.5%）contoursWater curtain do not work: 40m radiusWater curtain work : 30m radius

LNG collecting pondsLNG collecting ponds

LFL/2（2.5%）contoursLFL/2（2.5%）contoursWater curtain do not work: 40m radiusWater curtain work : 30m radius

LFL/2（2.5%）contoursLFL/2（2.5%）contoursWater curtain do not work: 40m radiusWater curtain work : 30m radius

◇Everyday ◆Seismic* Event No. in this matrix isthe same as in Table 6.

Probability

Impa

ct R

ange

Very High

High

Medium

Low

Very Low Low Probable High

Serious impactoutside of plant

Minor impactoutside of plant

Inside of plant

Area aroundaffected equipment

Everyday 10-7 10-6 10-5 10-4 / yearSeismic 10-5 10-4 10-3 10-2 / earthquake

12

3

4

5

7

8

6 ◇Everyday ◆Seismic* Event No. in this matrix isthe same as in Table 6.

Probability

Impa

ct R

ange

Very High

High

Medium

Low

Very Low Low Probable High

Serious impactoutside of plant

Minor impactoutside of plant

Inside of plant

Area aroundaffected equipment

Everyday 10-7 10-6 10-5 10-4 / yearSeismic 10-5 10-4 10-3 10-2 / earthquake

12

3

4

5

7

8

6

12

3

4

5

7

8

6

Paper PS4-6

PS4-6.17

4． SUMMARY

This paper explained the progress of liberalization of Japan’s energy markets since 2000 and the growth of gas markets related to LNG, and introduced the Sakai LNG Terminal that was built against this backdrop and has been in operation since January 2006. In particular, it explained the major equipment, equipment layout and business operations from the perspective of the “compact” and “multi-strategy” concepts that are featured in the terminal. Furthermore, it explained the risk assessment that was done in the design phase of the terminal, from basic concepts to results. This risk assessment was based on quantitative calculations using an estimated frequency of occurrence of potential accidents. It was one of the few comprehensive risk assessments in the world to address an entire LNG terminal.