The Egyptian Natural Gas Company
Prepared by:
Nubaria-Metnama
Natural Gas Pipeline,
Egypt
E2818 v7
QUANTITATIVE RISK ASSESSMENT
June 2011
Final Report
Nubaria-Metnama Pipeline QRA
EXECUTIVE SUMMARY
The Nubaria-Metnama Natural Gas pipeline starts from Al-Nubaria power station passing
by North Giza power station and ends at Metnama area. This pipe line is used to feed this
area with Natural Gas for power plants to be used in the production of electricity.
EcoConServ was assigned to prepare a Quantitative Risk Assessment (QRA) study for the
proposed Nubaria-Metnama Natural Gas pipeline, on behalf of the The Egyptian Natural
Gas Company (GASCO). This report is the main deliverable of this assignment.
This document sets out the Nubaria-Metnama Natural Gas pipeline QRA in order to identify
the key hazards and risks associated with the new pipeline. The study focuses on the major,
worst-case hazards, essentially in order to prioritize the potential impacts to the public.
RISK CRITERIA
Individual risks are the key measure of risk acceptability for this type of study, where it is
proposed that:

Risks to the public can be considered to be broadly acceptable if below 10-6 per year.
Although risks of up to 10-4 per year may be considered acceptable if shown to be
ALARP.

Risk in the range of 10-6 to 5 x 10-7 may cause injury to persons who could not find a
shelter within 30 seconds.
RISK RESULTS – PUBLIC
From the day of construction and until 20 years of operation, only two villages will be
affected by the 5 x 10-7 risk of injury contour which are Izbt Masjid Ar-Rahman and AlBaradah villages, with no real risk for the residents of the villages.
After 20 and until 30 years of operation, five villages will be affected, but again only by the
5 x 10-7, which means that they are no real risk too.
After 30 years, the 1x10-6 risk appears but does not reach any villages except Al-Baradah
village; also the 5 x 10-7 reaches 7 villages with no real risk to the residents.
Concerning Al-Baradah village, GASCO ensures that they performed a field visit and that the
exact placement of the pipeline will be based on real conditions according to real ground
situation. This will decrease the risk at Al-Baradah village to a high extent. Furthermore, all
villages which may be affected in the future will be repeatedly visited by the GASCO team to
ensure that populations are not exposed to unacceptable risk. Special attention will be paid
to the village of Al-Baradah.
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Nubaria-Metnama Pipeline QRA
RECOMMENDATIONS
The results of this QRA report show that the 1 x 10-6 risk contour (which is the risk of
fatality to the public) does not appear except after 30 years of operation and even then has
a negligible effect. However the 5x10-7 risk of injury contour appears but with a limited
effect and it is acceptable for population to exist within its vicinity.
GASCO will take all possible actions to organize building construction and encroachment
around both banks of the pipeline. Also, they are committed to coordinate with local
authorities about any new projects to be constructed in the area of the project. This will
limit the effect of any accident to a great extent.
The emphasis on risk reduction should be on preventative measures, i.e. to minimize the
potential for leaks to occur. This would chiefly be achieved through appropriate design (to
recognized standards) and through effective inspection, testing and maintenance plans /
procedures. All of these measures are already included in the pipeline design and
mitigation measures to be followed strictly by GASCO.
Rapid isolation of significant leaks will not eliminate the risks but will help to further
minimize the hazards and, particularly, the ignition probability (by limiting the total mass
of flammable gas released). For isolation to be effective first requires detection to occur.
Close monitoring and rapid shutdown of the pipeline in case of an emergency are
important to limiting the effects of leaks.
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Nubaria-Metnama Pipeline QRA
CONTENTS
EXECUTIVE SUMMARY ........................................................................................................................................... 1
RISK CRITERIA ...............................................................................................................................................................1
RISK RESULTS – PUBLIC ...................................................................................................................................................1
RECOMMENDATIONS ......................................................................................................................................................1
ABBREVIATIONS .................................................................................................................................................... 8
1
INTRODUCTION ............................................................................................................................................ 9
1.1
1.2
1.3
2
SITE DESCRIPTION ....................................................................................................................................... 11
2.1
2.2
2.3
2.4
3
RISK ASSESSMENT FRAMEWORK .......................................................................................................................19
INDIVIDUAL RISK CRITERIA ...............................................................................................................................20
SOCIETAL RISK CRITERIA..................................................................................................................................21
METHODOLOGY .......................................................................................................................................... 22
5.1
5.2
5.3
5.4
5.5
5.6
6
PIPELINE DESCRIPTION....................................................................................................................................17
PIPELINE SPECIFICATIONS ................................................................................................................................17
MITIGATIONS FOR CONSTRUCTION AND PIPELINE OPERATION ................................................................................17
RISK ACCEPTANCE CRITERIA ....................................................................................................................... 19
4.1
4.2
4.3
5
LOCATION ....................................................................................................................................................11
LAND USE ....................................................................................................................................................11
LOCATION OF VALVE ROOMS ...........................................................................................................................12
METEOROLOGICAL CONDITIONS .......................................................................................................................15
PROJECT DESCRIPTION ............................................................................................................................... 17
3.1
3.2
3.3
4
BACKGROUND .................................................................................................................................................9
OBJECTIVES AND SCOPE ....................................................................................................................................9
LAYOUT OF STUDY ...........................................................................................................................................9
DATA COLLECTION .........................................................................................................................................22
HAZARD IDENTIFICATION (HAZID) ...................................................................................................................23
FREQUENCY ANALYSIS ....................................................................................................................................23
CONSEQUENCE ANALYSIS ................................................................................................................................23
RISK CALCULATIONS .......................................................................................................................................23
RISK SOFTWARE TOOLS...................................................................................................................................24
FREQUENCY ANALYSIS ................................................................................................................................ 25
6.1
6.2
6.3
6.3.1
6.3.2
6.3.3
6.4
GENERAL .....................................................................................................................................................25
BASIC FAILURE FREQUENCIES ...........................................................................................................................26
EXTERNAL INTERFERENCE FACTORS ADJUSTMENTS ...............................................................................................27
Marker Tape ........................................................................................................................................27
Depth of Cover .....................................................................................................................................27
Wall Thickness .....................................................................................................................................28
GROUND MOVEMENT FACTORS ADJUSTMENTS ...................................................................................................28
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Nubaria-Metnama Pipeline QRA
6.5
6.6
7
ASSUMPTIONS ............................................................................................................................................ 31
7.1
7.2
7.2.1
7.2.2
7.2.3
7.3
7.4
7.4.1
7.4.2
7.4.3
7.5
7.5.1
7.5.2
8
ADJUSTED FAILURE FREQUENCIES .....................................................................................................................29
PROBABILITY OF PIPELINE IGNITION ...................................................................................................................30
INTRODUCTION .............................................................................................................................................31
BACKGROUND ASSUMPTIONS ..........................................................................................................................31
Weather Categories .............................................................................................................................31
Wind Direction .....................................................................................................................................32
Atmospheric Parameters .....................................................................................................................32
VULNERABILITY/ IMPACT CRITERIA ASSUMPTION FOR JET FIRE ...............................................................................33
FAILURE CASE DEFINITION ASSUMPTIONS...........................................................................................................33
Failure Cases - Definition .....................................................................................................................33
Failure Cases - Parameters...................................................................................................................34
Failure Cases - Release Types ...............................................................................................................34
CONSEQUENCE ANALYSIS ASSUMPTIONS ............................................................................................................35
General ................................................................................................................................................35
Fire Modeling .......................................................................................................................................35
HAZARD IDENTIFICATION ........................................................................................................................... 36
8.1
GENERAL HAZARDS ........................................................................................................................................36
8.2
HAZARDOUS PROPERTIES OF NATURAL GAS ........................................................................................................39
8.3
DETAILED HAZARDS IDENTIFICATION .................................................................................................................39
8.3.1
Natural Gas Line ..................................................................................................................................39
9
FAILURE CASE DEFINITIONS ........................................................................................................................ 42
9.1
9.2
10
CONSEQUENCE ASSESSMENT ..................................................................................................................... 44
10.1
11
CONSEQUENCE OF JET FIRE ACCIDENTS ..............................................................................................................44
RISK ASSESSMENT ...................................................................................................................................... 45
11.1
12
INTRODUCTION .............................................................................................................................................42
METHODOLOGY ............................................................................................................................................42
CALCULATED RISK DUE TO JET FIRE....................................................................................................................45
RISK RESULTS .............................................................................................................................................. 47
12.1
12.2
12.3
12.4
FREQUENCY ESTIMATION ................................................................................................................................47
INDIVIDUAL RISK CONTOURS ............................................................................................................................48
RISKS TO THE PUBLIC ......................................................................................................................................49
RECOMMENDATIONS......................................................................................................................................50
13
BIBLIOGRAPHY............................................................................................................................................ 68
A1
RISK ACCEPTANCE CRITERIA ....................................................................................................................... 70
A1.1
INTRODUCTION .............................................................................................................................................70
A1.2
BASIS FOR CRITERIA .......................................................................................................................................70
A1.2.1
Need for Criteria ..............................................................................................................................70
A1.2.2
Principles for Setting Risk Criteria ...................................................................................................70
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Nubaria-Metnama Pipeline QRA
A1.2.3
Framework ......................................................................................................................................71
A1.3
PROPOSED RISK CRITERIA ................................................................................................................................73
A1.3.1
Individual Risk .................................................................................................................................73
A1.3.2
Societal Risk.....................................................................................................................................75
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Nubaria-Metnama Pipeline QRA
LIST OF FIGURES
FIGURE 2-1: A GOOGLE EARTH IMAGE SHOWING THE NUBARIA–METNAMA PIPELINE WITH VALVE ROOMS LOCATIONS AND POWER PLANTS
ON THE LINE ........................................................................................................................................................... 14
FIGURE 5-1: QRA METHODOLOGY ......................................................................................................................................22
FIGURE 6-1: AVERAGE CONTRIBUTION OF INCIDENT CAUSES FOR ALL CATEGORIES OF PIPELINES .......................................................25
FIGURE 6-2: GENERAL CONTRIBUTION OF FAILURE CAUSES IN CASE OF FULL-BORE RAPTURE .........................................................26
FIGURE 7-1: WIND ROSE (PROBABILITY OF WIND DIRECTION) ..................................................................................................32
FIGURE 10-1: ALOHA JET FIRE OUTPUT AT 70 BAR ................................................................................................................44
FIGURE 11-1: RISK AT 70 BAR PRESSURES AS AFUNCTION OF DISTANCE FROM CENTER OF PIPELINE AT 1.2 M DEPTH OF COVER ..............46
FIGURE 12-1: PIPELINE PATH GENERAL VIEW SHOWING THE FOURTEEN VILLAGES AROUND THE PIPELINE ............................................52
FIGURE 12-2: LESS THAN 20 YEARS INDIVIDUAL RISK CONTOURS AT IZBT MASJID AR-RAHMAN (10-6 RISK CONTOUR DOES NOT APPEAR)53
FIGURE 12-3: LESS THAN 20 YEARS INDIVIDUAL RISK CONTOURS AT AL-BARADAH VILLAGE (10-6 RISK CONTOUR DOES NOT APPEAR) .....54
FIGURE 12-4: 20 – 30 YEARS INDIVIDUAL RISK CONTOURS AT IZBT MASJID AR-RAHMAN VILLAGE (10-6 RISK CONTOUR DOES NOT APPEAR)
...........................................................................................................................................................................55
FIGURE 12-5: 20 – 30 YEARS INDIVIDUAL RISK CONTOURS AT IZBT SIDI IBRAHIM(10-6 RISK CONTOUR DOES NOT APPEAR) ...................56
FIGURE 12-6: 20 -30 YEARS INDIVIDUAL RISK CONTOURS AT IZBT JAMAL AL-FRANSAWI (10-6 RISK CONTOUR DOES NOT APPEAR).........57
FIGURE 12-7:20 - 30 YEARS INDIVIDUAL RISK CONTOURS AT KAFR MANSOUR VILLAGE (10-6 RISK CONTOUR DOES NOT APPEAR) ..........58
FIGURE 12-8: 20 – 30 YEARS INDIVIDUAL RISK CONTOURS AT AL-BARADAH VILLAGE (10-6 RISK CONTOUR DOES NOT APPEAR).............59
FIGURE 12-9: 30 -40 YEARS INDIVIDUAL RISK CONTOURS AT IZBT AS-SUKHNA AL-JADIDA.............................................................60
FIGURE 12-10: 30 – 40 YEARS INDIVIDUAL RISK CONTOURS AT IZBT MASJID AR-RAHMAN ............................................................61
FIGURE 12-11: 30 – 40 YEARS INDIVIDUAL RISK CONTOURS AT IZBT SIDI IBRAHIM .......................................................................62
FIGURE 12-12: 30 – 40 YEARS INDIVIDUAL RISK CONTOURS AT IZBT JAMAL AL-FRANSAWI ............................................................63
FIGURE 12-13: 30 – 40 YEARS INDIVIDUAL RISK CONTOURS AT KAFR MANSOUR .........................................................................64
FIGURE 12-14: 30 – 40 YEARS INDIVIDUAL RISK CONTOURS AT DARAWA VILLAGE .......................................................................65
FIGURE 12-15: 30-40 YEARS INDIVIDUAL RISK CONTOURS AT AL-BARADAH VILLAGE ...................................................................66
FIGURE 12-16: F-N CURVE MARKING THE ALARP ZONE AND THE FREQUENCY FOR LESS THAN AND GREATER THAN 20 YEARS OF
OPERATION ............................................................................................................................................................ 67
FIGURE A- 1: "ALARP" FRAMEWORK FOR RISK CRITERIA ........................................................................................................73
FIGURE A- 2: AN INTERPRETATION OF UK HSE SOCIETAL RISK CRITERIA (F-N CURVE)...................................................................76
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Nubaria-Metnama Pipeline QRA
LIST OF TABLES
TABLE 2-1: LOCATION OF VALVE ROOMS ..............................................................................................................................12
TABLE 2-2: TEMPERATURE AND HUMIDITY FOR NORTH GIZA AREA .............................................................................................15
TABLE 6-1: BASE FREQUENCIES FOR PIPELINE RELEASE ............................................................................................................26
TABLE 6-2: BASE FREQUENCY FOR PIPELINES IN THE DIAMETER CATEGORY OF 29” – 35” ...............................................................27
TABLE 6-3: REDUCTION FACTOR RELATED TO THE DEPTH OF COVER...........................................................................................28
TABLE 6-4: FREQUENCY REDUCTION FACTOR RELATED TO WALL THICKNESS ................................................................................28
TABLE 6-5: SUB CAUSES OF GROUND MOVEMENT AND THEIR CONTRIBUTIONS ............................................................................28
TABLE 6-6: FINAL FREQUENCY AFTER ADJUSTMENTS FOR THREE YEARS CATEGORIES ......................................................................29
TABLE 6-7: PROBABILITY OF IGNITION FOLLOWING A RELEASE FROM PIPE ...................................................................................30
TABLE 7-1: ATMOSPHERIC PARAMETERS...............................................................................................................................32
TABLE 7-2: SUMMARY OF IGNITED RELEASE OUTCOMES, OR HAZARD TYPES................................................................................35
TABLE 8-1: HAZARD CAUSES, CONSEQUENCES AND PROPOSED OR INHERENT SAFEGUARDS ..............................................................37
TABLE 12-1 : FREQUENCIES USED FOR ALL THE CASES AT THE THREE OPERATION YEARS CATEGORIES .................................................47
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Nubaria-Metnama Pipeline QRA
ABBREVIATIONS
AIChE
ALARP
ALOHA
API
BP
CCPA
CCTV
CIA
DNV
EGIG
EGPC
EPA
ESD
F/N
FM200
FRED
GASCO
HAZID
HCRD
HRSG
HSE
HVAC
IP
LFL
LP
MAOP
NFPA
NG
NOAA
OEM
QRA
UK
American Institute of Chemical Engineers
As Low As Reasonably Practicable
Areal Locations of Hazardous Atmospheres
American Petroleum Institute
British Petroleum
Center for Chemical Process Safety
Closed Circuit Television
Central Intelligence Agency
Det Norske Veritas
European Gas Pipeline Incident Data Group
Egyptian General Petroleum Company
Environmental Protection Agency
Electrostatic Discharge
Frequency – Number of Fatalities Curve
Dupont waterless fire suppression system
Fire, Release, Explosion and Dispersion
Egyptian Natural Gas Company
Hazard Identification
Hydrocarbon Release Database
Heat Recovery Steam Generator
Health and Safety Executive
Heating, Ventilation and Air Conditioning
Intermediate Pressure
Lower Flammability Limit
Low Pressure
Maximum Allowable Operating Pressure
National Fire Protection Association
Natural Gas
National Oceanic and Atmospheric Administration
Office of Emergency Management
Quantitative Risk Assessment
United Kingdom
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Nubaria-Metnama Pipeline QRA
1 INTRODUCTION
1.1 BACKGROUND
Nubaria-Metnama Natural Gas pipeline is planned to be constructed between Nubaria
Power Station and Metnama area for the transfer of natural gas through the West of the
Nile Delta area. The design of the project is performed by the Egyptian Natural Gas
Company (GASCO).
EcoConServ was assigned to prepare a Quantitative Risk Assessment (QRA) study for the
proposed Nubaria-Metnama Natural Gas pipeline, on behalf of GASCO. This report is the
main deliverable of this assignment.
1.2 OBJECTIVES AND SCOPE
The main objectives of this QRA study are:

To identify and quantify the major hazards associated with the proposed pipeline

Assess the acceptability of the risks to people (any nearby residential areas), against
internationally recognized criteria.
The scope covered is for a QRA, which is focused on the worst-case hazards, and associated
risks, in order to assess the key risks.
1.3 LAYOUT OF STUDY
The layout of the remainder of this document consists of the following sections:

Section 2 and Section 3 describe the site of the pipeline and the give details about the
project, and the mitigation measures adopted by GASCO.

Section 4 sets out the risk criteria proposed for this study, on which the
determination of acceptability will be based. This is covered in detail by Appendix
A1.

Section 5 clarifies the methodology adopted while carrying out the risk assessment
and the tools used for the study.

Section 6 describes the frequency analysis and the effect of the preservative
measures on the frequency

Section 7 summarizes the assumptions undertaken in this study in detail (detailed
assumptions / failure case definition).
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Nubaria-Metnama Pipeline QRA

Section 8 and Section 9 summarize the outcome of the Hazard Identification step and
enumerate the failure cases.

Section 10 describes the Consequence Assessment steps and presents its results.

Section 11 describes the Risk Assessment steps and presents its basic results.

Section 12 details the final risk results, which are primarily based around the
individual risk contours. These are discussed with respect to the potential risks to
the public. It also presents the Conclusions and Recommendations of the analysis.
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Nubaria-Metnama Pipeline QRA
2 SITE DESCRIPTION
2.1 LOCATION
The Nubaria-Metnama Natural Gas pipeline starts from Al-Nubaria power station passing
through several villages and agricultural land in the West of the Delta, near its end it passes
by North Giza power station and ends at Metnama area. The pipeline is 104 Km long and
passes through the Bhaira, Menofia, Giza and Qalyubiyah Governorates. Figure 2-1 shows
the Google earth image for the pipeline showing the valve rooms locations and numbers,
Al-Nubaria power station as the starting point of the line, and North Giza power station that
benefits from the pipeline.
2.2 LAND USE
The pipeline passes through agricultural land, and moves adjacent to the agricultural area
border where possible. First part of the pipeline is located to the West bank of Al-Rayyah
An-Nasiri canal, after valve-room 7 the line crosses the canal to North Giza power plant.
After this, the pipeline crosses the Rashid Branch, the Damietta Branch of the Nile and
several other canals.
It is memorable to note that the detailed maps on which the pipeline was placed are old
dating back to 1992, on the other hand the Google earth images are based on the satellite
photos taken within 2010. During this time some villages extended and the pipeline now
passes through one of them, namely Al-Baradah village (see Figure 12-1).
GASCO ensures that they have done a physical survey of the entire route and that they will
not construct a pipeline passing through villages, only through agricultural land, and that
the exact placement of the pipeline will be based on real conditions according to real
ground situation. Limited accuracy due to drawing the pipeline on the Google Earth image
or during measuring distances from the actual maps may account for the difference than
the real case.
The pipeline passes beside several Villages; these Villages are listed from the North
(beginning of the line) and moving South then East with the line. The villages are:

Al-Iman – ‫قرية اإليمان‬

Salah Al-Din – ‫قرية صالح الدين‬

Badr - ‫بدر‬

Umar Makram–‫قرية عمر مكرم‬

Umar Shahin–‫قرية عمر شاهين‬
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Nubaria-Metnama Pipeline QRA

Izbt As-Sukhnah Al-Jadida–‫عزبة السخنة الجديدة‬

Izbt Masjid Ar-Rahman–‫عزبة مسجد الرحمن‬

Al-Khatatba - ‫الخطاطبة‬

Izbt Sidi Ibrahim–‫عزبة سيدي إبراهيم‬

Izbt Jamal Al-Fransawi–‫عزبة جمال الفرنساوي‬

Ar-Raml - ‫الرمل‬

Al-karadi - ‫الكرادي‬

Kafr Mansour–‫كفر منصور‬

Sheshaa - ‫شعشاع‬

Darawah - ‫داراوة‬

Kafr Ash-Shurfa Al-Gharbia–‫كفر الشرفة الغربية‬

Al-Baradah - ‫البرادعة‬

As-Sabah and Kafr ash-Shaheed – ‫الصباح وكفر الشهيد‬
2.3 LOCATION OF VALVE ROOMS
Table 2-1 shows the approximate location of each of the 12 valve rooms placed on the
pipeline according to Geographical coordinates from Google earth.
Table 2-1: Location of Valve Rooms
Location Name
North
East
Valve Room 1
Valve Room 2
Valve Room 3
Valve Room 4
Valve Room 5
Valve Room 6
Valve Room 7
Valve Room 8
Valve Room 9
Valve Room 10
Valve Room 11
30° 42’ 16.88”
30°35 38.02”
30° 32’ 29.54”
30° 29’ 43.12”
30° 25’ 34.84”
30° 20’ 17.17”
30° 14’ 55.05”
30° 14’ 48.49”
30° 12’ 12.10”
30° 14’ 09.06”
30° 14’ 08.57”
30° 12’ 42.76”
30° 40’ 12.77”
30° 42’ 49.77”
30° 45’ 58.70”
30° 48’ 15.81”
30° 48’ 56.89”
30° 48’ 17.59”
30° 55’ 07.53”
30° 56’ 33.74”
31° 00’ 25.64”
31° 05’ 51.72”
31° 11’ 08.57”
31° 16’ 00.60”
Valve Room 12
12
Distance to Valve Room (km
between valve rooms)
0
13
8
8
8
10
15
4
10
10
9
9
Nubaria-Metnama Pipeline QRA
13
Nubaria-Metnama Pipeline QRA
Room 1
Room 2
Al-Nubaria Power Station
Room 3
Room 4
Room 5
Room 6
North Giza Power Station
Room 7
Room 10
Room 8
Room 9
Room 11
Room 12
Figure 2-1: A Google Earth image showing the Nubaria–Metnama pipeline with valve rooms locations and power plants on the line
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Nubaria-Metnama Pipeline QRA
2.4 METEOROLOGICAL CONDITIONS
The meteorological conditions for the pipeline were taken as the meteorological data for
the of North Giza Power Plant site, as the pipeline feeds the plant and the meteorological
conditions of the area through which the pipeline pass is nearly constant. The
meteorological data for the North Giza Power Plant were obtained from the Giza
Meteorological Station, and cover the area of 50 km around the station.
Table 2-2shows the annual temperature and humidity variation around the site. The wind
rose for the area is shown in Figure 2-2. The wind rose shows that wind blows mainly from
the North and that the wind speed seldom increases over 10 knots.
Table 2-2: Temperature and humidity for North Giza area
Month
January
February
March
April
May
June
July
August
September
October
November
December
Annual-average
Av.
Daily Max.
19.8
21.2
24.1
28.7
32.5
34.8
35.3
34.8
33.0
30.6
25.7
21.1
28.46
Av. Temperature (oC)
Av.
Highest Daily
Daily Min.
Max.
6.9
7.6
9.8
13.1
16.7
19.8
21.5
21.6
19.6
17.0
12.7
8.6
14.58
15
31.5
36.2
39.0
43.5
48.0
48.0
45.5
42.9
44.0
44.5
38.8
36.3
Lowest Daily
Min.
3.3
2.0
1.2
3.5
7.9
11.9
15.0
15.3
11.9
8.9
3.4
-1.1
Relative
Humidity
(%)
66
61
59
51
48
51
58
62
61
62
67
68
59.5
Nubaria-Metnama Pipeline QRA
Figure 2-2: Wind rose of North Giza (wind speed in Knots)
16
Nubaria-Metnama Pipeline QRA
3 PROJECT DESCRIPTION
3.1 PIPELINE DESCRIPTION
The pipeline is 104 km long starting at Al-Nubaria power station and feeds the North Giza
power plant along its path. The line has 12 valve rooms to act as a safeguard for the
pipeline.
3.2 PIPELINE SPECIFICATIONS
The pipe diameter is 32 inch with a daily average flow-rate of 8 MMscmd, an inlet gas
pressure is in the range 60-70 bar. The pipeline will be buried at a depth of 1.2 m and has
marker tapes to indicate its path.
3.3 MITIGATIONS FOR CONSTRUCTION AND PIPELINE OPERATION
The following mitigation measures are followed by GASCO during the construction and
operation of the pipeline:

The Quality Control ISO 9001 is applied throughout the project,

International codes and criteria are used during the choice of the path and the
design of the pipeline,

Direct and accurate supervision on all the construction phases will be present
through the company’s engineers and technicians,

Engineering inspection will be done during all the project phases,

Pipelines must successfully pass the hydrostatic test at a pressure of 1.5 times the
maximum operating pressure before the starting to operate,

The gases being transmitted must not contain any corrosive materials,

The pipelines have corrosion resistant internal lining,

The pipelines are externally coated with three layers of polyethylene and checked
before the pipes are put down and buried,

Cathodic protection systems are applied as soon as the line is put in the ground,

The most up-to-date internal testing systems are applied to discover any defects and
address them early, if any. (On-Line Inspection technique).

The internal testing system is repeated periodically and the results are compared
against the previous test results.
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Nubaria-Metnama Pipeline QRA

The SCADA system, available at the National Control Center (NATA), will be used to
control and isolate the areas at risk immediately in case of emergencies in order to
ensure a speedy control and minimize the damage,

The choice of the main pipelines paths to be outside the residential areas,

The thickness of the pipeline is chosen to match the population class near the highly
populated areas,

The valve rooms are distributed on the pipeline in a way that decreases the amount
of confined gas and enables easy discharge in case of emergency.

Coordination with the local authorities and the concerned authorities about the
pipeline path and maps to be taken into consideration when approving any new
projects or constructions,

Increasing the awareness about the pipeline in the nearby communities through the
patrol squads.
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Nubaria-Metnama Pipeline QRA
4 RISK ACCEPTANCE CRITERIA
In the absence of Egyptian legislation setting definite limits for acceptable risk, the risks
evaluated within this study were referenced against internationally accepted criteria, in
order to determine the acceptability of the risks and any need for risk reduction measures
to be implemented within the design process. The EGPC does have its own standards for
risk acceptance, but it was considered more conservative in this case to apply the
internationally accepted criteria.
The risk criteria proposed to be used are drawn from the widely used framework set out by
the UK’s HSE, using the As Low As Reasonably Practicable (ALARP) principle, and proposes
risk acceptance criteria to be used as guidance for this study.
4.1 RISK ASSESSMENT FRAMEWORK
The following measures of acceptability should be evaluated in assessing the risks from any
hazardous activity:

Individual risk criteria should be used to limit risks to members of the public.

Cost-benefit analysis should be used to ensure that, once the above criteria are
satisfied, an optimum level of safety measures is chosen for the activity, taking
costs as well as risks into account. (Note that this is outside the scope of this
study.)
The simplest framework for risk criteria is a single risk level which divides tolerable risks
from intolerable ones. Such criteria give attractively simple results, but they need to be
used very carefully, because they do not reflect the uncertainties both in estimating risks
and in assessing what is tolerable. For instance, if applied rigidly, they could indicate that
an activity which just exceeded the criteria would become acceptable as a result of some
minor remedial measure which in fact scarcely changed the risk levels.
A more flexible framework specifies a level, usually known as the maximum tolerable
criterion, above which the risk is regarded as intolerable whatever the benefit may be, and
must be reduced. Below this level, the risks should also be made As Low As Reasonably
Practicable (ALARP). This means that when deciding whether or not to implement risk
reduction measures, their cost may be taken into account, using cost-benefit analysis. In
this region, the higher the risks, the more it is worth spending to reduce them. If the risks
are low enough, it may not be worth spending anything, and the risks are then regarded as
negligible.
This approach can be interpreted as dividing risks into three tiers (as is illustrated in
Appendix A1):
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
An upper band where risks are intolerable whatever the benefit the activity may
bring. Risk reduction measures or design changes are considered essential.

A middle band (or ALARP region) where the risk is considered to be tolerable
only when it has been made ALARP. This requires risk reduction measures to be
implemented if they are reasonably practicable, as evaluated by cost-benefit
analysis.

A negligible region where the risks are negligible and no risk reduction
measures are needed.
4.2 INDIVIDUAL RISK CRITERIA
Individual risk is widely defined as the risk of fatality (or serious injury) experienced by an
individual, noting that the acceptability of individual risks should be based on that
experienced by the most exposed (i.e. ‘worst-case’) individual.
The most widely-used criteria for individual risks are the ones proposed by the UK HSE,
noting that these have also been interpreted for projects in Egypt.
These criteria are:

The acceptable criterion, for the public, corresponding to the level below which
individual risks can be treated as effectively negligible, is 10-6 per year (i.e. 1 in
1,000,000 years)

If the risk calculated from heat radiation at residential areas exceeds 5 x 10-7per
year, this will cause injury after 30 seconds of direct exposure to the heat. The
risk of injury in this case is 5 x 10-7 (i.e. 5injuries in 10,000,000 years), which
may considered negligible.
In terms of the acceptability of individual risks, it should be noted that:

Individual risks are typically presented as contours that correspond to the risk
experienced by a person continuously present, outdoors, at each location.

While people are unlikely to remain “continuously present, outdoors” at a given
point, the individual risk levels used to assess residential developments are not
modified to account for any presence factor or the proportion of time spent
indoors. That is, it should be conservatively assumed that dwellings are occupied
at all times and that domestic properties offer no real protection against the
potential hazards.
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
It should also be noted that lower criteria are often adopted with respect to
vulnerable populations, such that schools and hospitals, for example, should be
located such that the individual risks are well below 10-6 per year.
4.3 SOCIETAL RISK CRITERIA
A proposed criterion for Societal Risk is set out in Appendix A1in the form of an F-N curve,
which gives the cumulative frequency (F) of exceeding a number of fatalities (N).
It is, however, important to note that the acceptability of societal risks can be subjective
and depends on a number of factors (such as the benefits versus the risks that a facility
provides). There is not a single established indicator in terms of societal risk.
The proposed societal (F-N) criteria are considered to provide useful guidance on the
acceptability of the societal risk, although it should be emphasized that the criteria are not
as widely accepted as individual risk and should be used as guidance only.
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5 METHODOLOGY
QRA is a well-established methodology to assess the risks of industrial activities and to
compare them with risks of normal activities. The QRA methodology used is shown in
Figure 5-1.
Figure 5-1: QRA Methodology
5.1 DATA COLLECTION
This study is based on information sent to EcoConServ by email in addition to the general
pipeline path map and detailed terrain maps, which were obtained from (GASCO).
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5.2 HAZARD IDENTIFICATION (HAZID)
The hazard identification process is important for any risk analysis. A HAZID was been
performed in the course of preparing the QRA depending on historical data for gas
transportation accidents. The HAZID study for the pipeline has enabled us to identify and
enumerate the failure cases that require further analysis.
5.3 FREQUENCY ANALYSIS
Failure frequencies were determined for each event in order to perform a probabilistic risk
assessment. Generally, a number of techniques are available to determine such frequencies.
The approach relies on generic data. This provides failure frequencies for equipment items
where data has been obtained from failure reports from a range of facilities. Frequency
assumptions are detailed in Chapter 7.
5.4 CONSEQUENCE ANALYSIS
For each identified hazard scenario, consequence analysis tools were used to determine
consequence effect zones for each hazard. In general the different possible outcomes could
be:
•
Dispersing of Hydrocarbon Vapor Cloud
•
Explosion
•
Flash Fire
•
Jet Fire
The particular outcomes modeled depend on source terms (conditions like fluid,
temperature, pressure etc.) and release phenomenology. The current understanding of the
mechanisms occurring during and after the release is included in our consequence analysis
models and tools. These models and tools are explained in Section 5.6.
5.5 RISK CALCULATIONS
The outcome of the risk analysis is risk terms presented in form of risk curves, where the
location of specific individual risk measurements is displayed.
The individual risk is the risk for a hypothetical individual assumed to be continuously
present at a specific location. The individual at that particular location is expected to
sustain a given level of harm from the realization of specified hazards. It is usually
expressed in risk of death per year. Individual risk is presented in form of risk contours.
Risk contours were generated using the tools described in Section 5.6
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5.6 RISK SOFTWARE TOOLS
A collection of freely available software and in-house developed programs were used to
estimate the risk in this study. This approach has enables a deep understanding of the risk
calculations methodology. The use of this risk software tools enables the users to have
control over the modeling and hence the majority of the assumptions are covered in the
inputs to, rather than within, the software.
Consequence modeling is done using ALOHA, a tool developed by EPA’s Office of
Emergency Management (OEM) and the National Oceanic and Atmospheric Administration
Office of Response and Restoration (NOAA), to assist front-line chemical emergency
planners and responders. ALOHA is an atmospheric dispersion model used for evaluating
releases of hazardous chemical vapors. ALOHA allows the user to estimate the downwind
dispersion of a chemical cloud based on the toxicological/physical characteristics of the
released chemical, atmospheric conditions, and specific circumstances of the release.
ALOHA can estimate threat zones associated with several types of hazardous chemical
releases, including toxic gas clouds, fires, and explosions. The input to ALOHA is mainly the
conditions at the release source, and the output is a graph showing the release effect at the
specified standard radiation levels or overpressure according to the type of release. The
graphs from ALOHA are then turned into a digital format in the form of a table showing the
distances in all directions at each radiation level.
The general principles of consequence identification are:

Dispersion results are drawn in from ALOHA software, taking flammable and toxic
hazard ranges separately. These are used for delayed ignition hazards, such as toxic
impacts and flash fires.
Similarly, the way the risks are calculated, via event trees, is part of the user-defined input.
The risk assessment software is written using a programming language that takes the
digitized graphs from ALOHA as an input, taking into consideration the frequency of
occurrence and the probability of ignition of each type of release. The inputs are
consequences in the form specified above, where each will have an event frequency
together with an immediate ignition probability or a background delayed ignition
probability. The probability of weather category and wind direction is determined as per
Assumptions of Chapter 7, as are the ignition and explosion probabilities (as discussed
further in Chapter 7). All other variations on the outcome frequency are defined before
input, e.g. the probability of isolation failure or variation in release orientation. The risk
from all different releases is then added to give the final total risk contours graph, which is
presented on a Google Earth image for the pipelines.
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6 FREQUENCY ANALYSIS
6.1 GENERAL
The failure data of release are derived from the European Gas Pipeline Incident Data Group
(EGIG, 2008). The European data is derived based on a significant exposure experience in
terms of kilometer years experienced from 1970 – 2007 in fifteen European countries,
which is a statistically significant base for estimating release frequencies. The general
statistical data is averaged on all the fifteen countries without taking the regional
differences, such as population density and geological conditions, into consideration, which
makes the data more reliable for use. The frequency also takes into consideration a number
of variable factors such as: wall thickness, depth of cover, probability of ignition, etc.
The operating conditions of the pipeline that will be constructed by GASCO between the
Nubaria and Metnama are covered well in the statistical data used in the report of EGIG
about pipelines, these conditions are the operating pressure, pipe diameter, wall thickness,
depth of cover and coating material.
The analysis of the main incident causes for all categories of pipelines (different diameters,
thicknesses, pressures, etc.) shows that the main cause of incidents is through external
interference followed by construction defect / Material Failure then corrosion as can be
seen in Figure 6-1.
Figure 6-1: Average contribution of incident causes for all categories of pipelines
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6.2 BASIC FAILURE FREQUENCIES
The average data derived from EGIG for all pipelines are shown in Table 6-1, where they are
categorized by the cause of the incident and gives the frequency of each cause. For more
specification, only the data for pipes of diameters greater than 29” will be used during the
calculations of the frequency. Also the frequency of material defects will be calculated
according to the year of construction as more advanced measure. Figure 6-2 shows the
contribution of failure causes in case of full-bore rupture before the specific measures
applied for this case.
Figure 6-2: General Contribution of Failure Causes In Case of Full-Bore Rapture
Table 6-1: Base Frequencies for Pipeline Release
Cause
Pipeline General Base frequency by Cause and Hole Size
(Per 1000 km-year)
Hole
Full-Bore Rupture
(10 mm < d < 50 mm)
External Interference
0.1
0.03
Construction/Material Defect
0.015
0.01
Corrosion
0.0025
0
Ground Movement
0.008
0.009
Other/Unknown
0.003
0
Total
0.1285
0.049
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The failure data indicate that for pipelines with a diameter from 29” to 35”, only full
rupture can occur at this diameter with the frequency shown in Table 6-2. Table 6-2 also
shows the change in the construction defect/ material failure based on the number of years
that passed since the construction, for this study three categories are adopted, the first is
since the construction till 20 years, the second is the period of 20-30 years since
construction and the third is 30-40 years since construction. More measures will be applied
later to account for all the mitigation measures taken by GASCO and the difference between
the Egyptian and European geographical terrain.
Table 6-2: Base Frequency for pipelines in the diameter category of 29” – 35”
Pipeline Full Bore Rupture Base frequency for 29” – 35” Diameter Class
(Per 1000 km-year)
Years since
Less than 20 years
20 – 30 years
30 – 40 years
construction
Cause
External Interference
0.0048
0.0048
0.0048
Construction/Material
0
0.0029
0.0039
Defect
Corrosion
0
0
0
Ground Movement
0.009
0.009
0.009
Other/Unknown
0
0
0
Total
0.0138
0.0167
0.0177
6.3 EXTERNAL INTERFERENCE FACTORS ADJUSTMENTS
The base frequencies in Table 6-2 are adjusted to account for the additional preservative
measures taken for each pipeline, such as: Pipeline depth, wall thickness and the presence
of Marker Tape. These measures will result in decreasing the likelihood of external
interference; therefore it is the main factor that is going to be affected.
6.3.1 MARKER TAPE
Corder (Corder, 1995) has reported that a damage reduction factor of 1.67 was achieved
when marker tape is provided above pipelines based on experimental data derived from
testing undertaken by British Gas. This factor will be used in this study to reduce the
frequency of impacts resulting from external interference for sensitivity cases with marker
tape.
6.3.2 DEPTH OF COVER
The depth of cover presents the depth at which the pipeline will be buried, as the depth of
cover increase the reduction factor decrease and so the frequency decrease. The depth of
1.11 m has no reduction factor where for depths below this value the frequency increases
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Nubaria-Metnama Pipeline QRA
and above it the frequency decrease. These data were originally available to the depth of
1.4 m, which were extrapolated to reach a value of 2.0 m and are shown in Table 6-3.
Table 6-3: Reduction Factor Related to the Depth of Cover
Depth of Cover (m)
Reduction Factor
0.8
1.30
1.0
1.11
1.2
0.92
1.4
0.73
1.6
0.54
1.8
0.35
2.0
0.157
Thus a reduction factor of 0.92 (for 1.2 m depth) will be used in this study.
6.3.3 WALL THICKNESS
The (EGIG, 2008) database summarizes pipeline failure frequencies by wall thickness.
Based on the data, the factors in Table 6-4 are used for pipes with varying wall thicknesses.
Table 6-4: Frequency Reduction Factor related to Wall Thickness
Pipe Wall
Thickness (mm)
Puncture
(Hole)
Rupture
(Full-Bore)
2.5 (0-5 mm)
7.5 (5-10 mm)
12.5 (10-15 mm)
2.4
1.0
0.5
5.8
1.0
0.5
Note that GASCO uses an additional conservative measure which is increasing the pipe
thickness from the usual 0.5” (12.7 mm) to 0.625” (16 mm) near the areas with low
population and to 0.75” (19 mm) near the highly populated areas, all the road and river
crossings. Therefore, it is convenient to assume a wall thickness higher than 15 mm for
population areas near the pipeline and roads and rivers which decreases the corrosion
probability to its minimum.
6.4 GROUND MOVEMENT FACTORS ADJUSTMENTS
The factors that compromise the ground movement frequency are not all experienced in
Egypt due to the difference in the geographical terrain, although Europe is near enough;
therefore these factors are either removed or reduced to match the earthquake categories
of Egypt versus Europe. Table 6-5 shows the factors that contribute in the base ground
movement frequency.
Table 6-5: Sub causes of Ground Movement and their Contributions
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Sub-Causes of Ground Movement
Percent Contribution
Land Slide
55%
Flood
19%
River
6%
Mining
5%
Dike break
1%
Lightning
3%
Other
2%
Unknown
9%
The factors that were removed are flood, mining, dike break and lightning while the land
slide factor was reduced to the third of its value to take into consideration that the delta
areas is far enough from the tectonic plates boundaries, which are the main earthquakes
reason, unlike some of the contributing countries in the EGIG data like Italy and Spain.
6.5 ADJUSTED FAILURE FREQUENCIES
The effect of release from a hole in the pipe was found to be negligible compared to the
release from full-bore rupture; as the pipe diameter class indicates according to the
statistical data from EGIG. Also the preservative mitigation measures taken by GASCO, such
as the polyethylene coating, the cathodic protection and the hydrostatic test on the pipe at
1.5 its maximum operating pressure, eliminate the possibility of corrosion which is the
main reason for hole rupture. Therefore, the effect of hole-release is not carried forward.
The frequency of full-bore rupture after taking into account the marker tape and depth of
cover in the external interference factor and adjusting the ground movement factor is
shown in Table 6-6.
Table 6-6: Final Frequency after Adjustments for three years Categories
Pipeline Full Bore Rupture Base frequency for 29” – 35” Diameter Class
(Per 1000 km-year)
Years since construction
Less than 20 years
20 – 30 years
30 – 40 years
Cause
External Interference
0.0026
0.0026
0.0026
Construction/Material Defect
Corrosion
Ground Movement
Other/Unknown
0
0
0.002
0
0.0029
0
0.002
0
0.0039
0
0.002
0
Total
0.0138
0.0167
0.0177
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It is important to note that the construction/ material defect factor will not appear as a
considerable factor except after 20 years since the pipeline was built and will only slightly
increase after 10 more years. Therefore three calculations were made to take into
consideration the change in this factor.
6.6 PROBABILITY OF PIPELINE IGNITION
The probability of ignition of holes and ruptures used in the frequency assessment was
based on the (EGIG, 2008) Report Section 3.4.3, summarized in Table 6-7. The probability
differs in case of rupture according to the pipe diameter.
Table 6-7: Probability of Ignition Following a Release from Pipe
Hole size
Hole (50 mm)
Rupture (d <406 mm)
Rupture (d> 406 mm)
Ignition Probability
2%
10%
33%
Possible sources of ignition include but are not limited to: direct heat (Smoking, cooking,
etc.), electrical current (lights, irrigation pumps, tractors, cars, etc.), lightning, etc.
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7 ASSUMPTIONS
7.1 INTRODUCTION
The basic aim of this Assumptions chapter is to document the details underpinning this
QRA study.
Background data:
The site-specific aspects that apply (or potentially apply) to each of the release scenarios
(failure cases) modeled are referred to as ‘background data’. This covers the meteorological
conditions and the potential ignition sources that are specific to the site, and the potentially
exposed populations.
General assumptions:
The basic methodology adopted for studies of this kind is set out in the following sections,
in order to describe the basis for the defined scenarios and modeling approach. It should be
emphasized that elements of these sections are generic and are intended to define the
broad approach only.
7.2 BACKGROUND ASSUMPTIONS
7.2.1 WEATHER CATEGORIES
As well as the wind direction, the actual weather conditions, in terms of the wind speed and
the stability (a measure of atmospheric turbulence), determine how quickly the flammable
plume disperses to lower non-hazardous concentrations.
In the absence of detailed meteorological data (i.e. covering the stability categories), two
representative weather conditions are applied to model the dispersion of each release
scenario. These are D5 and F2 conditions, which are widely adopted (such as by NFPA and
the UK HSE) as broadly representative of ‘typical’ and ‘worst-case’ dispersion conditions,
respectively:

D5 – neutral stability (D) and 5 m/s wind speed.

F2 – stable (F) conditions and 2 m/s wind speed.
UK HSE guidance suggests that good practice for QRA studies is to assume that D5
conditions apply for 80% of the time and F2 for the remaining 20% - again, in the absence
of detailed data only.
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Although based on the experience of conducting QRA worldwide suggests that this
provides a reasonably representative (and slightly conservative) basis when compared
against local weather conditions.
7.2.2 WIND DIRECTION
The wind rose for the region where the pipeline will be constructed is given below.
Figure 7-1: Wind Rose (Probability of Wind Direction)
Please note that the above figure is based on the True North. The data provided is based on
annual averages and, hence, is applied to the risk model as being the same for all time
periods (e.g. day and night).
7.2.3 ATMOSPHERIC PARAMETERS
The representative atmospheric parameters that are applied to the consequence modeling
are summarized in Table 7-1, below.
Table 7-1: Atmospheric Parameters
Parameter
Value
Unit
Notes
Air temperature
22
°C
The range of min/max temperatures is 2 to 41 °C, where 20 °C is taken as a
representative base value in case of absence of representative data.
Surface
temperature
22
°C
Taken as the same as air temperature, above.
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Relative
humidity
60
%
Assumed. Note that its influence on dispersion / consequences is minor.
Surface
roughness
1
m
Representative parameter for regular large obstacles based on TNO Purple
Book guidance.
Solar radiation
1
kW/m2
Assumed. Note that its influence on dispersion / consequences is negligible.
1.013
bar
Atmospheric
pressure
Negligible influence on dispersion /consequences.
As indicated in the above table, assumptions such as surface roughness can significantly
affect the hazard ranges predicted for the worst-case release scenarios. However, the
influence on most releases is minor and the purpose of the risk study is to determine the
frequency of the most representative outcomes. Hence, the overall risks will be reasonable
robust to the above assumptions.
7.3 VULNERABILITY/ IMPACT CRITERIA ASSUMPTION FOR JET FIRE
The basis for the jet fire impact levels and criteria is summarized below.

The levels at which impairment from fires occurs are defined for three radiation
levels, of greater than 37.5 kW/m2, 12.5 kW/m2 and 4.7 kW/m2which are
referenced within the risk model as ‘flame’, ‘radiation’ and ‘Injury’ impacts,
respectively.

A fatality rate of 100% is assumed at radiation levels of 37.5 kW/m2 or greater and
50% for 12.5 kW/m2 or greater for personnel outdoors that are exposed to
radiation effects from jet fires. These values involve a degree of judgment, but are
consistent with standard practice (and slightly conservative).

For the 4.7 kW/m2 radiation level the risk of injury assigned is 50 chances in million
years.
7.4 FAILURE CASE DEFINITION ASSUMPTIONS
7.4.1 FAILURE CASES - DEFINITION
The key factors in selection of the representative sections (i.e. the generic failure cases)
are:
•
Gas released.
•
Flow conditions (temperature and pressure).
•
Release location (the area in which the release occurs, including the height).
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•
Isolation.
For each of the pipe sections, up to five representative release sizes are considered:
•
Full-bore rupture (where the hole diameter is larger than the diameter of the
pipeline, based on the most representative line size within each section)
•
Large leaks (e.g. due to connection failures) - 75 mm (3”) equivalent diameter
•
Medium, Small and Very Small leaks (e.g. due to corrosion, impact and other
such cases) – 25, 12 and 2 mm (1”, ½” and 1/10”) equivalent diameter leaks
respectively.
7.4.2 FAILURE CASES - PARAMETERS
For each of the release scenarios to be modeled, the key inputs to the derivation of release
parameters are the flow conditions, flow-rate and location, where the parameters are
derived as follows:
•
Flow conditions (temperature and pressure) were obtained through GASCO as
mentioned in section 3.2, where the pressure drops through the whole pipeline
from about 70 bar to about 30 bar. However, according to GASCO’s request, the
pressure in the pipe is taken to be 70 bar along the pipeline, representing noflow conditions, as a conservative measure.
•
Release location: The release location selected is necessarily representative as it
is taken to be at any point along the pipeline. The release is modeled at a depth
of 1.2 m from the surface of the ground, which is the depth of cover of the
pipeline, also the presence of marker tape is taken into account as stated by
GASCO.
7.4.3 FAILURE CASES - RELEASE TYPES
The outcome, and hence the way in which the discharge and subsequent dispersion
parameters are modeled are listed below:
•
In case of immediate ignition after the release the result is jet fire.
•
If the release is not followed by immediate ignition, it will result in a flash fire.
The flash fire consequence is negligible compared to the jet fire consequence and
is not carried forward for further assessment.
•
Toxicity. Natural gas has no known toxic or chronic physiological effects (that is,
it is not poisonous). Exposure to a moderate concentration may result in a
headache or similar symptoms due to oxygen deprivation but it is likely that the
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Nubaria-Metnama Pipeline QRA
sound accompanying the release would be heard well in advance of
concentrations being high enough for this to occur.
7.5 CONSEQUENCE ANALYSIS ASSUMPTIONS
7.5.1 GENERAL
For each release event defined, dispersion modeling and fire size calculations are
conducted within ALOHA modeling software tool. These consequence results are used
directly by the risk modeling software.
The consequences are input to the risk model in groups of hazard type, which depend upon
the type of release and when ignition occurs, as summarized Table 7-2 below. Note that this
table addresses flammable impacts only; toxic impacts will also apply for unignited
releases depending on the composition.
Table 7-2: Summary of Ignited Release Outcomes, or Hazard Types
Release Type
Gas release
Hazard Type (Consequence)
Immediate Ignition
Delayed Ignition
Jet fire (or fireball for short Flash fire/explosion
duration release)
7.5.2 FIRE MODELING
Based on the derivation of the release parameters, the determination of the initial fire
effects is handled by the ALOHA as follows.

All immediately ignited releases are modeled as jet fires.

All delayed ignition events are modeled as flash fires or VCEs (not applicable for this
study).

Flash fires are based on the LFL (Lower Flammability Level) distance (not
applicable for this study).
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8 HAZARD IDENTIFICATION
8.1 GENERAL HAZARDS
The first step in any risk assessment is to identify all hazards. The merits of including the
hazard for further investigation are subsequently determined by its significance, normally
using a cut-off or threshold quantity.
Once a hazard has been identified, it is necessary to evaluate it in terms of the risk it
presents to the neighboring community. In principle, both probability and consequence
should be considered, but there are occasions where if either the probability or the
consequence can be shown to be sufficiently low or sufficiently high, decisions can be made
on just one factor.
Table 8-1 shows the general hazards that were found for the N.G. pipeline, along with
possible causes, expected consequences and proposed or inherent safeguards.
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Table 8-1: Hazard causes, consequences and proposed or inherent safeguards
Site Area
Hazard Cause
Hazard Consequence
Pipeline
External interference
Leak/rupture, ignition,
jet fire, flash
Pipeline
Construction error
Leak/rupture, ignition,
jet fire, flash
Pipeline
Corrosion
Leak/rupture, ignition,
jet fire, flash
37
Proposed / Inherent Safeguard
 pipeline marker signs to be installed at regular intervals
 The national control center (NATA) will be used to control
and isolate the areas at risk immediately in case of
emergencies
 The choice of the main pipelines paths to be outside the
residential areas
 Increasing the awareness about the pipeline in the nearby
communities through patrol squads
 Coordination with the local authorities and the concerned
authorities about the pipeline path and maps to be taken
into consideration when approving any new projects or
constructions
 The thickness of the pipeline is chosen to match the
population class near the highly populated areas
 hydrostatic test at a pressure of 1.5 times the maximum
operating pressure before operating
 The most up-to-date internal testing systems are applied to
discover any defects and fix them early
 The internal testing system is repeated periodically and the
results are compared against the previous test results
 External coating system corrosion protection
 Corrosion resistant internal lining
 Gases transmitted must not contain any corrosive materials
 Cathodic protection systems are applied
Nubaria-Metnama Pipeline QRA
Site Area
Hazard Cause
Hazard Consequence
Pipeline
Ground Movement,
Earthquake
Leak/rupture, ignition,
jet fire, flash
NG Valve rooms
Equipment failure
causing leaks due to
corrosion or defects
Gas release
Jet fire if ignited
Flash fire if ignition is
delayed
38
Proposed / Inherent Safeguard
 land is flat with no subsidence potential
 Use of Horizontal Directional Drilling as a construction
method for water way crossings
 Use of steel pipes which are flexible enough to take the
shape of the ground beneath it
 Inherent flexibility and strength of gas transmission
pipelines and equipment
 Closed rooms for security
 QA, welding inspection
 Hydrostatic testing of equipment
 Radiography of circumferential welds – ultrasonic on pipes
 Maintenance/inspection
Nubaria-Metnama Pipeline QRA
8.2 HAZARDOUS PROPERTIES OF NATURAL GAS
The inherent hazards of the fitting line arise from the flammability of the natural gas, and
the pressure at which it is transmitted and processed in the station. The types of hazardous
incident which may occur, in theory at least, would all require a leak in the fitting line or
associated equipment (e.g. valves, meters, flanges, etc.). They are: Jet fire and flash fire.
It is noted that natural gas is lighter than air (i.e. a buoyant gas) and if released tends to rise
and disperse rather than accumulate forming a flammable cloud thus it is not possible for
Vapor Cloud Explosion to occur.
8.3 DETAILED HAZARDS IDENTIFICATION
The following section constitutes detailed qualitative hazard identification for those
incidents listed in Table 8-1.
8.3.1 NATURAL GAS LINE
The following fitting line design and operational details, below, were used:

Inlet Pressure – 70 bar

Outlet Pressure – 70 bar

Length – 104 km

Diameter – 32 inch (8128 mm); and

Wall thickness – varying according to the population density in each area (from
0.5” to 0.75” (12.7mm -19mm)), therefore, taken as above 15mm.
There is historical evidence of gas transmission pipeline failure. Historical evidence (Bolt &
Horalek, 2004)indicates that there are a number of factors that can lead to fitting line leak
and subsequent release of gas. The details below summarize those incidents that have
historically led to fitting line failure and gas release:

External Interference – external interference accounts for the majority of release
incidents in gas transmission fitting lines (Bolt & Horalek, 2004).

Flood Damage – this may occur where the fitting line traverses river beds or water
courses. The potential for fast running water could lead to scouring above the fitting
line exposing the pipe to potential impact from rocks and debris moving in the
water stream. In addition, surface flooding could lead to the fitting line floating from
the trench, leading to fitting line damage. A review of the fitting line route indicates
that the fitting line will be laid away from flood areas. Additionally, Horizontal
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Directional Drilling will be used as a construction method for waterway crossings.
Hence, this hazard has not been carried forward for further analysis.

Subsidence Damage – where fitting lines are installed near or in banks and levees,
wash away may expose the fitting line and uneven weight could cause severe fitting
line damage. However, the fitting line is not installed in a bank or levee and
therefore, incidents resulting from subsidence have not been carried forward for
further analysis

External Corrosion Damage – many soils are acidic and fitting lines installed
without external protection are susceptible to corrosion and eventual failure
(leaks). The fitting line is installed underground and hence is exposed to acidic soils
increasing the potential for external corrosion. Therefore, polyethylene coating is
applied for protection as well as cathodic protection. Incidents involving external
corrosion (excluding impact) have not been carried forward for further analysis.

Internal Corrosion Damage – the introduction of corrosive gas to the fitting line
could result in accelerated corrosion or moisture in the gas could lead to corrosion
impact on the pipe internal surface. However, gas fed is dry and non-corrosive,
having passed many kilometers through this line, also internal lining is used to
protect the pipe. Hence, the likelihood of corrosion from this source is considered
negligible. Incidents as a result of corrosion have therefore not been carried forward
for further analysis.

Faulty Material – the use of faulty materials, such as fitting line with manufacturing
defects, could lead to premature fitting line failure resulting in rupture. However,
pipe material will be purchased from a quality assured organization (i.e. ISO9001),
which minimizes the potential for faulty materials. Further, the fitting line will be
fully tested in accordance with the appropriate requirements, including a pressure
test to prove fitting line will operate safely and without failure at maximum
allowable operating pressure (MAOP). The quality assurance testing regime
minimizes the potential for fitting line failure as a result of material defects. These
measure are strictly followed, therefore the faulty material frequency will not start
to affect the flow except after 20 years of operation, which could be minimized
through regular check of the pipeline.

Faulty Construction – like the faulty materials incidents detailed above, faulty
construction can also lead to failure of the fitting line. For example, faulty welding
can lead to premature failure and gas release. However, fitting line welds will be
subjected to X-Ray inspection minimizing the potential for failure from this source.
Further, the fitting line will be subjected to a testing regime, further minimizing the
40
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potential for faulty construction failure. Additional construction problems, such as
poor support or alignment in the pipe rack will be minimized by strictly following
the appropriate requirements. These measure are strictly followed, therefore the
faulty material frequency will not start to affect the flow except after 20 years of
operation, which could be minimized through regular check of the pipeline.

Ground Movement – this may occur where fitting lines are installed in an
earthquake zone. Earthquakes and excessive ground movement may lead to
damaged pipe racks and buckled pipework or, in the worst case, rupture. However,
the fitting line would not be installed in an earthquake zone. Delta area is relatively
stable and earthquakes of the magnitude that could result in fitting line rupture are
rare. The risk of ground movement is slightly taken into consideration in the
frequency of pipe rupture, as not all the ground movement factors are present for
the proposed pipeline.

“Hot Tap” by Error “– “hot tap” is the connection to a live gas line during operation.
When this is conducted by expert personnel the risk is negligible. However, failure
to identify a live gas fitting line and attempts, by error, to connect to this fitting line
could lead to fitting line breach and gas release. To identify gas fitting line, marker
signs will be installed on the fitting line in accordance with the appropriate
requirements. This incident therefore, has not been carried forward for further
analysis.
The above analysis is supported by the results of studies conducted by the European Gas
Pipeline Incident Data Base (Bolt & Horalek, 2004), which conducts research into gas
pipeline incidents both in Europe and overseas. The results of these studies indicate that
the majority of pipeline incidents 50% occur as a result of external interference, 17% due
to material defects and 15% due to corrosion.
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9 FAILURE CASE DEFINITIONS
9.1 INTRODUCTION
The basic aim of the Failure Case Definition stage is to identify the failure cases, or major
accident hazards, that will have the potential to result in risks to populations around the
pipeline path, and hence will be inputs to the risk modeling.
The basic approach adopted is summarized in Section 9.2.
Note that the failure case definition presented in this section is underpinned by the
methodology set out in Section 7.
9.2 METHODOLOGY
For the purposes of this risk assessment it is not necessary (or practical) to attempt to
model all of the potential hazards associated with all the points of the pipeline. The basic
approach adopted instead is summarized below.

70 bar pressure will be used over the whole pipeline as a conservative measure.

The scenario is carried out at the valve rooms and then extended over the whole
pipeline length

Two risk values were considered 1 x 10-6 and 5 x 10-7 per year, where the first value
represents the risk of fatality and the second represents the risk of injury.

These failure cases are then superimposed upon the image of the pipeline on Google
Earth to define the populated areas that are at risk from this line.
Note that the general methodology adopted in deriving the initial failure cases, and the
subsequent development of each, is detailed in Section 7 . Note also that the subsequent
modeling approach is also described in Section 7.
The failure cases derived for each unit are presented in the following section. The section
includes a basic description of the failure case, as well as the representative flow conditions
and the primary hazard outcome(s) of each release.
Due to the insignificance of the risk due to the hole compared to the full-bore rupture, as
detailed in Section 7, therefore the hole consequence is not carried forward for
investigation.
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10 CONSEQUENCE ASSESSMENT
The consequence of the failure cases were estimated using the methodology of Section5
and the assumptions detailed in Chapter7. Consequences presented here are jet fire
consequence as the flash fire consequence was found to be negligible compared to the jet
fire consequence.
10.1 CONSEQUENCE OF JET FIRE ACCIDENTS
The failure case which result in jet fire, has the following calculated data by ALOHA, where
the hole diameter is equal to the pipe diameter: The total amount burned in 1 hr is 237,173
kg and the flame length is 91 m.
A sample jet fire output is shown in Figure 10-1shows radiation contours of 37.5, 12.5 and
4.7 kW/m2 for 70 bar jet fire scenarios. Note that ALOHA figures assume that the wind
blows towards the positive x-axis
Figure 10-1: ALOHA jet fire Output at 70 bar
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11 RISK ASSESSMENT
The Risk assessment is based on the data presented in Section6. Before calculating the risk,
the rupture was first assumed to be at every point in the pipeline each representing a
separate case. Then during the risk assessment the risk for each heat radiation contour was
calculated, and the risks of all cases were added to reach the final result which shows the
risk as a function of the distance from the center of the pipeline.
11.1 CALCULATED RISK DUE TO JET FIRE
The collected Risk calculated for each section is shown as a function of the distance from
the center of the pipeline. Figure 11-1shows the calculated risk from the center of the
pipeline at 70 bar with distance for the time of construction of less than 20 years, then
between 20 - 30 years and after 30 – 40 years in operation.
The distance from the center of the pipe to the 1 x 10-6 and 5 x 10-7 risk contours (fatality
and injury) was obtained from the Risk – Distance curve (Figure 11-1). From the time of
construction and until 20 years the 1 x 10-6 risk contour does not appear and the distance
for the 5 x 10-7 risk contour is 80 m in average. Between 20 – 30 years of operation the 1 x
10-6 risk contour does not appear again and the distance for the 5 x 10-7 risk contour is 180
m in average. Between 30 - 40 years of operation the 1 x 10-6 risk contour has an average
distance of 35 m and 190 m for the 5 x 10-7 risk contour.
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Figure 11-1: Risk at 70 bar pressures as afunction of distance from center of pipeline at 1.2 m depth of cover
46
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12 RISK RESULTS
The risks were calculated from the results of the consequence analysis of the failure cases
and the estimation of the frequencies of those cases. The frequencies were estimated based
on the assumptions; data and practices explained in Sections 6&7 and are presented in
Section 12.1.
Individual risks are the key measure of risk acceptability for this type of study, where it is
proposed that:

Risks to the public can be considered to be broadly acceptable if below 10-6 per year,
although noting that societal risk factors should also be considered (including the
type of population potentially exposed). Although risks of up to 10-4 per year may be
considered acceptable if shown to be ALARP.
Individual risks are presented in Section 12.2, while risk to the public is presented in
Section.12.3
12.1 FREQUENCY ESTIMATION
Table 12-1 shows the frequencies calculated for each of the cases identified during the
hazards identification phase at the three operating years categories.
Table 12-1 : Frequencies used for all the cases at the three operation years categories
Years of
Operation
Less than 20
years
Fire accident
type
Basis for Frequency
Calculations
Frequency
of Fatality
Frequency of
Injury
Jet Fire
1.52 x 10-6 from Section 6x 1
probability of fatality for
37.5 kW/m2 and x 0.5
probability of fatality for
12.5 kW/m2
Frequency of injury is at 4.7
kW/m2
1.52 x 10-6
1.78 x 10-8
2.48 x 10-6
2.90 x 10-8
2.64 x 10-6
3.09 x 10-8
20 – 30 years
Jet Fire
30 – 40 years
Jet Fire
2.48 x 10-6 from Section 6x 1
probability of fatality for
37.5 kW/m2 and x 0.5
probability of fatality for
12.5 kW/m2
Frequency of injury is at 4.7
kW/m2
-6
7.2 x 10 from Section 6x 1
probability of fatality for
37.5 kW/m2 and x 0.5
probability of fatality for
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Years of
Operation
Fire accident
type
Basis for Frequency
Calculations
12.5 kW/m2
Frequency of injury is at 4.7
kW/m2
Frequency
of Fatality
Frequency of
Injury
12.2 INDIVIDUAL RISK CONTOURS
At this stage in the risk assessment the most useful measure of risk is individual risk, which
is presented in the form of contours. The individual risk contours for the risk assessment
are presented for each village at risk alone to emphasize the type of risk that will affect the
residents and to what extent. The individual risk contours give the risk of fatality (or
serious injury) experienced by a person continuously present, outdoors and the risk of
injury that can be experienced by a person if he did not find a shelter within 30 seconds.
Figure 12-1 shows the villages that are present around the pipeline with their positions as a
reference, these villages are:

Al-Iman

Badr

Umar Makram

Umar Shahin

Izbt As-Sukhna Al-Jadida

Izbt Masjid Ar-Rahman

Izbt Sidi Ibrahim

Izbt Jamal Al-Faransawi

Izbt Ar-Raml

Kafr Mansour

Sheshaa

Darawah

Al-Shurfa Al-Gharbia

Al-Baradah
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At 1.2 m depth of cover and in the operating time till 20 years, Figure 12-2 and Figure 12-3
represent the two affected villages which are Izbt Masjid Ar-Rahman and Al-Baradah
consecutively, these villages are affected by the 5x10-7 risk of injury contour only.
Between 20 – 30 years of operation, 5 villages are expected to be affected, also by the 5x107 risk of injury contour only. These villages are shown in Figure 12-4 to Figure 12-8, and in
order they are: Izbt Masjid Ar-Rahman, Izbt Sidi Ibrahim, Izbt Jamal Al-Faransawi, Kafr
Mansour and Al-Baradah.
The expected villages to be affected between 30-40 years of operation are 7 villages as
shown in Figure 12-9 to Figure 12-15. These 7 villages are mainly affected by the 5x10-7 risk
contour, and the 1x 10-6 although appearing does not affect any villages except Al-Baradah.
The seven villages are: Izbt As-Sukhna Al-Jadida, Izbt Masjid Ar-Rahman, Izbt Sidi Ibrahim,
Izbt Jamal Al-Faransawi, Kafr Mansour, Darawa and Al-Baradah
12.3 RISKS TO THE PUBLIC
As discussed above, Figure 12-2 and Figure 12-3are focused on the villages that fall within
the risk contours at the first 20 years of operation, where it can be seen that:

The 10-6 individual risk contour does not exist

The 5 x 10-7 touches Izbt Masjid Ar-Rahman and covers small part of Al-Baradah
village
Figure 12-4 to Figure 12-8 are focused on the villages that fall within the risk contours after
20 years of operation and until 30 years, where it can be seen that:

The 10-6 individual risk contour does not exist

The 5 x 10-7 passes through Izbt Masjid Ar-Rahman, Izbt Sidi Ibrahim, Izbt Jamal AlFaransawi, Kafr Mansour and Al-Baradah villages.
Figure 12-9 to Figure 12-15 are focused on the villages that fall within the risk contours after
30 years of operation and until 40 years, where it can be seen that:

The 10-6 individual risk contour just barely exists and does not affect any nearby
villages except Al-Baradah village (see note below regarding this village)

The 5 x 10-7 passes through Izbt As-Sukhna Al-Jadida, Izbt Masjid Ar-Rahman, Izbt
Sidi Ibrahim, Izbt Jamal Al-Faransawi, Kafr Mansour, Darawa and Al-Baradah
villages.
Concerning Al-Baradah village, GASCO ensures that they performed a field visit and that the
exact placement of the pipeline will be based on real conditions according to real ground
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situation. This will decrease the risk at Al-Baradah village to a high extent. Furthermore, all
villages which may be affected in the future will be repeatedly visited by the GASCO team to
ensure that populations are not exposed to unacceptable risk. Special attention will be paid
to the village of Al-Baradah.
From the above results it is apparent that the 1x10-6 risk of fatality contour will not appear
except after more than 30 years of operation, and even then, its effect will be negligible and
is expected not to reach any of the nearby villages. However, it is recommended to put this
risk in consideration for future expansion of the areas adjacent to the pipeline.
The F-N curve, Figure 12-16, gives the cumulative frequency (F) of exceeding a number of
fatalities (N). In the region between the red and the green lines the risks are acceptable
only if demonstrated to be As Low As Reasonably Practicable (ALARP).
The maximum frequency is marked by a black line for the operating periods: less than and
greater than 20 years. The figure indicates that the number of fatalities is the number of
individuals present outdoors in the fire area with no barrier separating them from the
accident source. The Figure shows that:

For the first 20 years of operation: the risk is considered to be negligible if less than
65 individuals are present outdoors near the accident source, while the risk is
considered to be ALARP if 6500 individuals are present outdoors near the accident
source.

After 20 years of operation: the risk is considered to be negligible if less than 40
individuals are present outdoors near the accident source, while the risk is
considered to be ALARP if 4000 individuals are present outdoors near the accident
source.
Based on the low population density along the path of the pipeline, and the small affected
area by the 10-6 contour, it is to be concluded that the risk will never exceeds the ALARP
border for the whole lifetime of the pipeline, resulting in an acceptable level of risk.
12.4 RECOMMENDATIONS
The results of this QRA report show that the 1 x 10-6 risk contour (which is the risk of
fatality to the public) does not appear except after 30 years of operation and even then has
a negligible effect. However the 5x10-7 risk of injury contour appears but with a limited
effect and it is acceptable for population to exist within its vicinity.
GASCO will take all possible actions to organize building construction and encroachment
around both banks of the pipeline. Also, they are committed to coordinate with local
authorities about any new projects to be constructed in the area of the project. This will
limit the effect of any accident to a great extent.
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The emphasis on risk reduction should be on preventative measures, i.e. to minimize the
potential for leaks to occur. This would chiefly be achieved through appropriate design (to
recognized standards) and through effective inspection, testing and maintenance plans /
procedures. All of these measures are already included in the pipeline design and
mitigation measures to be followed strictly by GASCO.
Rapid isolation of significant leaks will not eliminate the risks but will help to further
minimize the hazards and, particularly, the ignition probability (by limiting the total mass
of flammable gas released). For isolation to be effective first requires detection to occur.
Close monitoring and rapid shutdown of the pipeline in case of an emergency are
important to limiting the effects of leaks.
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Nubaria-Metnama Pipeline QRA
Al-Iman
Umar Makram
Umar Shahin
Izbt As-Sukhna Al-Jadida
Badr
Izbt Masjid Ar-Rahman
Izbt Sidi Ibrahim
Izbt Jamal Al-Faransawi
Sheshaa
Kafr Mansur
Al-Shurfa Al-Gharbia
Al-Baradah
Izbt Ar-Raml
Darawah
Figure 12-1: Pipeline path general view showing the fourteen villages around the pipeline
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Izbt Masjid Ar-Rahman
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-2: Less than 20 years Individual Risk Contours at Izbt Masjid Ar-Rahman (10-6 risk contour does not appear)
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NG Pipeline
Al-Baradah Village
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-3: Less than 20 years Individual Risk Contours at Al-Baradah Village (10-6 risk contour does not appear)
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Izbt Masjid Ar-Rahman
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-4: 20 – 30 years Individual Risk Contours at Izbt Masjid Ar-Rahman Village (10-6 risk contour does not appear)
55
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Izbt Sidi Ibrahim
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-5: 20 – 30 years Individual Risk Contours at Izbt Sidi Ibrahim(10-6 risk contour does not appear)
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Izbt Jamal Al-Fransawi
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-6: 20 -30 years Individual Risk Contours at Izbt Jamal Al-Fransawi (10-6 risk contour does not appear)
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Kafr Mansur
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-7:20 - 30 years Individual Risk Contours at Kafr Mansour Village (10-6 risk contour does not appear)
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NG Pipeline
Al-Baradah
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-8: 20 – 30 years Individual Risk Contours at Al-Baradah Village (10-6 risk contour does not appear)
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Nubaria-Metnama Pipeline QRA
Izbt As-Sukhna Al-Jadida
A
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-9: 30 -40 years Individual Risk Contours at Izbt As-Sukhna Al-Jadida
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Izbt Masjid Ar-Rahman
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-10: 30 – 40 years Individual Risk Contours at Izbt Masjid Ar-Rahman
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Izbt Sidi Ibrahim
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-11: 30 – 40 years Individual Risk Contours at Izbt Sidi Ibrahim
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Izbt Jamal Al-Fransawi
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-12: 30 – 40 years Individual Risk Contours at Izbt Jamal Al-Fransawi
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Kafr Mansour
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-13: 30 – 40 years Individual Risk Contours at Kafr Mansour
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Darawa Village
NG Pipeline
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-14: 30 – 40 years Individual Risk Contours at Darawa Village
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NG Pipeline
Al-Baradah
1 x 10-6 Risk Level
5 x 10-7 Risk Level
Figure 12-15: 30-40 years Individual Risk Contours at Al-Baradah Village
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Figure 12-16: F-N curve marking the ALARP zone and the frequency for less than and greater than 20 years of operation
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13 BIBLIOGRAPHY
Abdul Rosyid, O. (2006). System-analytic Safety Evaluation of the Hydrogen Cycle for
Energetic Utilization. Otto-von-Guericke-University.
Alcock, J. (2001). Compilation of existing safety data on hydrogen and comparative. EIHP2
Report.
API. (1995). Management of Hazards Associated With Location of Process Plant Buildings
(First Edition ed.). API Recommended Practice 752.
Bolt, R., & Horalek, V. (2004). European Gas pipeline Incident Data Group Pipeline Incident
Database. 13th Colloquium Reliability of HP Steel Pipes. Prague, Czech Republic.
CCPS, A. (1999). Guidelines of Consequence Analysis of Chemical Releases. New York:
American Institute of Chemical Engineers.
Corder, I. (1995). "The Application of Risk Techniques to the design and operations of
pipelines". IMechE.
Eggen, J. (1995). GAME: development of guidance for the application of the Multi-Energy
Model. TNO Report PML.
EGIG, E. G. (2008). 7th EGIG Report 1970 - 2007, Gas Pipeline Incidents Data Group (EGIG).
Report Number EGIG08.TV-B.0502.
HSE, U. (1999). Offshore Hydrocarbon Release Statistics. Offshore Technology Report. UK
HSE.
LASTFIRE. (1997). Large Atmospheric Storage Tank Fire Project – LASTFIRE. Technical
Working Group.
Technica. (1990). Atmospheric Storage Tank Study for Oil and Petrochemical Industries
Technical and Safety Committee. Singapore.
TNO. (1997). Methods for the calculation of physical effects, (3 ed., Vol. 2). The Hague:
Committee for the Prevention of Disasters.
Witlox, H., & Bowen, P. (2001). Flashing liquid jets and two-phase dispersion – A review. HSE.
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APPENDICES
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A1 RISK ACCEPTANCE CRITERIA
A1.1 INTRODUCTION
This appendix introduces the concept of risk acceptance criteria and the As Low As
Reasonably Practicable (ALARP) principle, and proposes risk acceptance criteria to be used
as guidance for this study. It should be emphasized that the selection of criteria is open to
interpretation, in the absence of any formal local regulations, but where the intention of
this study is to use criteria that are consistent with internationally accepted practice.

Section A1.2 describes the basis for the risk criteria, introducing the widely accepted
As Low As Reasonably Practicable (ALARP) concept.

Section A1.3sets out the criteria that are proposed for this study, covering both
individual and societal risk criteria.
A1.2 BASIS FOR CRITERIA
A1.2.1 NEED FOR CRITERIA
A risk analysis provides measures of the risk resulting from a particular facility or activity.
However, the assessment of the acceptability (or otherwise) of that risk is left to the
judgment and experience of the people undertaking and/or using the risk analysis work.
The normal approach adopted is to relate the risk measures obtained to acceptable risk
criteria.
A quantitative risk analysis produces only numbers, which in themselves provide no
inherent use. It is the assessment of those numbers that allows conclusions to be drawn
and recommendations to be developed. The assessment phase of a study is therefore of
prime importance in providing value from a risk assessment study.
A1.2.2 PRINCIPLES FOR SETTING RISK CRITERIA
Given that society accepts hazardous activities in principle, and does not have limitless
resources to devote to their safety, the following set of principles is considered by some to
be appropriate when making decisions about their acceptability in specific cases:
1. The activity should not impose any risks which can reasonably be avoided.
2. The risks should not be disproportionate to the benefits (in terms of jobs, tax
revenues and finished products) which the activity produces.
3. The risks should be equitably distributed throughout the society in proportion to
the benefits received.
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4. The risks should be revealed in minor accidents which the emergency services can
cope with, rather than in catastrophes.
In reality, principles such as these are impossible to achieve. In fact, when resources are
limited, such principles may be in conflict with each other. For example, reducing
catastrophic risks may require expenditure that could have saved more lives from lowfatality accidents.
The following approach is proposed for assessing the risks from any hazardous activity,
being the nearest practical approach to the ideal situation:

Individual risk criteria should be used to limit risks to individual workers and
members of the public. These address the equity requirement (3) above insofar as it
applies to individuals.

Societal risk criteria should be used to limit risks to the affected population as a
whole. These attempt to address requirement (2) above, although in a necessarily
crude fashion since the benefits of hazardous activities are even more difficult to
quantify than their risks. They also address the equity requirement (3) above
insofar as it applies to communities. By expressing societal risk criteria on a
frequency-fatality (FN) curve, they can also address the catastrophe risk in
requirement (4) above.

Cost-benefit analysis should be used to ensure that, once the above criteria are
satisfied, an optimum level of safety measures is chosen for the activity, taking costs
as well as risks into account. This addresses requirement (1) above.
An activity is said to have tolerable risks if it satisfies all three aspects of this approach, and
intolerable risks if it fails to meet any of them.
Leaving aside other inputs to the decision, an activity with tolerable risks would generally
be regarded as acceptable to the company, the regulatory authority and the public, while an
activity with intolerable risks would generally be regarded as unacceptable.
A1.2.3 FRAMEWORK
The simplest framework for risk criteria is a single risk level which divides tolerable risks
from intolerable ones (i.e. acceptable activities from unacceptable ones). Such criteria give
attractively simple results, but they need to be used very carefully, because they do not
reflect the uncertainties both in estimating risks and in assessing what is tolerable. For
instance, if applied rigidly, they could indicate that an activity which just exceeded the
criteria would become acceptable as a result of some minor remedial measure which in fact
scarcely changed the risk levels.
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A more flexible framework specifies a level, usually known as the maximum tolerable
criterion, above which the risk is regarded as intolerable whatever the benefit may be, and
must be reduced. Below this level, the risks should also be made as low as reasonably
practicable (ALARP). This means that when deciding whether or not to implement risk
reduction measures, their cost may be taken into account, using cost-benefit analysis. In
this region, the higher the risks, the more it is worth spending to reduce them. If the risks
are low enough, it may not be worth spending anything, and the risks are then regarded as
negligible.
This approach can be interpreted as dividing risks into three tiers as is illustrated in Figure
A- 1.

An upper band where risks are intolerable whatever the benefit the activity may
bring. Risk reduction measures or design changes are considered essential.

A middle band (or ALARP region) where the risk is considered to be tolerable only
when it has been made ALARP. This requires risk reduction measures to be
implemented if they are reasonably practicable, as evaluated by cost-benefit
analysis.

A negligible region where the risks are negligible and no risk reduction measures
are needed.
There is some consensus on this three-band approach, and versions are used by the UK,
Dutch, Swiss and US Santa Barbara criteria.
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Figure A- 1: "ALARP" Framework for Risk Criteria
A1.3 PROPOSED RISK CRITERIA
A1.3.1 INDIVIDUAL RISK
Individual risk is widely defined as the risk of fatality (or serious injury) experienced by an
individual, noting that the acceptability of individual risks should be based on that
experienced by the most exposed (i.e. ‘worst-case’) individual.
The most widely-used criteria for individual risks are the ones proposed by the UK HSE
(Reference 1), noting that these can also be used for projects in Egypt.
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These criteria are:

The maximum tolerable individual risk for workers is taken as 10-3 per year (i.e.
1 in 1,000years).

The maximum tolerable individual risk for members of the public is 10-4 per year
(i.e. 1 in10,000 years).

The acceptable criterion, for both workers and public, corresponding to the level
below which individual risks can be treated as effectively negligible, is 10-6 per
year (i.e. 1 in1,000,000 years)

Between these criteria the risks are in the ‘ALARP’ or tolerability region. In this
region the risks are acceptable only if demonstrated to be As Low As Reasonably
Practicable (ALARP).
In terms of the acceptability of individual risks, it should be noted that:

Individual risks are typically presented as contours that correspond to the risk
experienced by a person continuously present, outdoors, at each location.

While people are unlikely to remain “continuously present, outdoors” at a given
point, the individual risk levels used to assess residential developments are not
modified to account for any presence factor or the proportion of time spent
indoors. That is, it should be conservatively assumed that dwellings are occupied
at all times and that domestic properties offer no real protection against the
potential hazards. Hence, the individual risks contours can be used directly with
respect to the public, while for workers it is more appropriate to consider the
most exposed individual (accounting for the time they spend in different areas,
indoors, away from the hazards, etc).

The individual risk criteria proposed for the public correspond to an individual
having a chance of death or serious injury (due to the hazards assessed) of
between 1 in 10,000and 1,000,000 years. To put these risks into context, note
that the risk of death in the UK due to road accidents is just over 1 in 10,000
years, while the risk of an individual being struck by lightning is widely quoted
as being 1 in 10,000,000 years.

For risks approaching the maximum tolerable individual risk level for the public
of 10-4peryear (1 in 10,000 years) to be considered to be acceptable, it should be
demonstrated that all reasonably practicable measures to minimize the risks
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have been, or will be, taken. The same applies for risks closer to the acceptable
criterion of 10-6per year, but where the degree of effort (and expenditure) that
would be considered to be practicable would be less.
It should be emphasized that a variety of individual risk criteria are used worldwide, as
shown by selected examples given below:
For risks to the public a lower / tolerable criterion of 10-6per year is widely accepted.
However, lower values are adopted by some companies and legislators. For example,
Statoil have a lower criterion of 10-7 per year and where for new facilities the Dutch
authorities use 10-6 per year as the upper / maximum criterion.
It should also be noted that lower criteria are often adopted with respect to vulnerable
populations, such that schools and hospitals, for example, should be located such that the
individual risks are well below 10-6 per year.
The maximum criterion for the public varies between 10-3 and 10-5 per year (or lower in
some cases – as indicated above). The UK HSE value of 10-4 per year is maintained in this
study as a representative maximum. However, it should be emphasized that this is a
maximum value and it would be extremely rare for this level to be considered acceptable
for a new facility / development. That is, there is unlikely to be sufficient justification that
there are no practicable methods of reducing this level of risk. In fact, it is considered to be
best practice to treat 10-6 per year as the target criterion, while risks of up to 10-5 per year
would require strong justification and risks above 10-5 per year should be avoided with
respect to the public.
It should, in any case, be emphasized that risks above 10-6 per year are acceptable only if
shown to be ALARP.
In summary, it is proposed that:

Risks to the public can be considered to be broadly acceptable if below 10 -6 per
year, although noting that societal risk factors should also be considered
(including the type of population potentially exposed). Although risks of up to
10-4 per year may be considered acceptable if shown to be ALARP, it is
recommended that 10-5 per year is adopted for this study as the maximum
tolerable criterion.
A1.3.2 SOCIETAL RISK
A proposed criterion for Societal Risk is set out in Figure A- 2 in the form of an F-N curve,
which gives the cumulative frequency (F) of exceeding a number of fatalities (N).
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It is important to note that the acceptability of societal risks can be subjective and depends
on a number of factors (such as the benefits versus the risks that a facility provides). There
is not a single established indicator in terms of societal risk. For example, the UK HSE does
not apply specific societal risk criteria in general, although they are applied to particular
sites such as ports. Instead, the emphasis is placed on demonstrating that the risks are
ALARP, where judgment on the ultimate acceptability of the risks is determined on a case
by case basis.
However, the UK HSE do quote a single point risk criterion which has been interpreted to
form an F-N criterion, as shown in Figure A- 2. The maximum tolerable risk line is based on
a standard 1:1 slope through the UK HSE’s quoted intolerable societal risk level of “50 or
more fatalities occurring with a frequency of 1 in 5000 years” (N=50 and F=2 x 10 -4 per
year). The minimum (broadly acceptable) risk line is simply assumed to be two orders of
magnitude lower.
This is considered to provide a useful guidance on the acceptability of societal risk,
although it should be emphasized that the criteria are not as widely accepted as individual
risk and should be used as guidance only.
Figure A- 2: An interpretation of UK HSE Societal Risk Criteria (F-N Curve)
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