The Chad Risk Assessment

Abo Homos-Nubaria Pipeline QRA

Project Description

Pipeline Route

The Abo Homos-Nubaria gas pipeline starts from the outlet of a gas collection unit at

Abo Homos, and extends to the southwest for 400 m. It then turns to the southeast and runs parallel to the ring road to Basnatawy for 2.5 km, and then extends toward the south, intersecting El-Mahmoudiya canal, Cairo-Alexandria railway, and CairoAlexandria road near the El-Azmaly estate. It follows the eastern side of El-Khadra canal, and then follows the Damanhour canal eastward for 2.5 km until turning south for

1 km to cross the Abdel Hamid canal and continue along it briefly for 500 m. The pipeline turns southeast and again follows the Damanhour canal at the east side of the Sharawa estate. The pipeline crosses the road to Hosh Issa, and then runs parallel to the Khairy drain along the western side for about 15 km, until it nears a transformer station at El-Nagareen estate. The path crosses the Ferhash canal and continues eastward alongside it, then turns south with the Abo Shousha canal. It crosses El-

Hagar canal and runs along its southern side for 11.5 km, and then crosses back to the northern side before El-Haddayn estate. The pipeline passes north of El-Ashraf, then turns south to cross the Nubaria canal and continue along it for 3 km, then once again turns south, crossing the Alexandria-Embaba railway, and finally reaching the Nubaria power station.

Pipeline Design Criteria

At the minimum, the pipeline will be built, operated, and maintained to the standards of

ASME B31.8, which dictates the use of good engineering practices for public safety in all conditions and local regulations as a minimum, along with any additional local regulations. as well as other relevant high standards for pipeline routing with consideration for nearby settlements.

Settled areas along the pipeline are classified by population density, which is used to determine the Location Class, as defined in Table 4-1. Location Classes are used to determine the design criteria appropriate for different sections of the pipeline. They are also used in determining the amount of surveillance activity to be conducted.

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Abo Homos-Nubaria Pipeline QRA

Table 4-1: Determination of Location Class

Generally a zone 200m wide is considered on either side of the route of the pipeline. To include a maximum number of buildings for human occupancy, the pipeline route is also divided lengthwise into sections of 1 mile. Within a multiple dwelling unit, each separate dwelling unit is counted as a separate building. However, ASME B31.8 does not provide restrictions on the proximity of a pipeline to a building or group of buildings, which can lead to pipelines being constructed close to buildings (and vice versa).

The following proximity limits should be applied to all pipeline design and to new buildings developed close to existing pipelines.

•No pipeline operating at a pressure greater than 7 bar must can be within 3m of a building in residential areas, and 6m desert areas.

•Any pipeline closer than 25 m to a normally occupied building should operate at a pressure that is 40% of the material yield strength or less, and have a wall thickness of at least 0.375".

•Any pipeline closer than 12.5m to a normally occupied building should operate at a pressure that is 40% of the material yield strength or less, and be laid with greater than or equal to 0.5" wall thickness.

Wall thickness is also increased at road crossings, and impact protection measures

(cast in site or pre - cast concrete slab) shall be provided on all pipeline crossings.

Warning tape is placed above and below such impact protection.

Valve Room Locations

Eight (8) valve rooms will be constructed along the pipeline, in the following locations:

•valve room (1) at zero km (Abo Homos collection station)

•valve room (2) at 7 km

•valve room (3) at 10 km

•valve room (4) at 24 km

•valve room (5) at 43 km

•valve room (6) at 54.5 km

•valve room (7) at 59.5 km

•valve room (8) at 65 km (Nubaria power station)

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Abo Homos-Nubaria Pipeline QRA

Major Crossings

There are many crossing that the proposed pipeline route encounters. Some of them will be crossed using an open trench, but major crossings and waterways will be crossed using the Horizontal Directional Drilling (HDD) technique. The following crossings will be encountered:

•Mahmoudiya Canal – 5.3 km

•Cairo-Alexandria Agricultural Road and Railway – 8.5 km

•El-Khadra Canal – 9.2 km

•Hosh Issa Road – 15.8 km

•El-Zamarana Canal – 23.1 km

•Ferhash Road – 39.3 km

•El-Hagar Canal – 43.9 km

•Zohor El-omra Canal – 54 km

•Nubaria Canal – 63 km

Design Gas Composition and Flow Rate

The main stream of natural gas will come from the national network once the pipeline has been filtered. The pipeline is designed to transport the gas at a maximum inlet pressure of 70 bar. The compositions of the gas coming from the national network are indicated in the table below.

Table 4-2: National Network Gas Composition [Reference: GASCO]

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Gas delivered will be commercially free of materials and dust or other solid or liquid matter which may interfere with the operation of lines.

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Abo Homos-Nubaria Pipeline QRA

Assessment of Risks

This part of the study would address the identification, analysis and subsequent assessment of major hazards associated with the relevant onshore pipeline.

They are categorised, and makes judgement on the tolerability of risks to personnel associated with these hazards. The international criteria for risk tolerability are used to base such judgements.

Scenarios that could result in major hazards will be identified and evaluated using Quantified Risk Assessment ‘QRA’. This technique is used to establish the expected frequency of such incidents occurring on each facility and their consequences.

This section will be linked to the rest of the proposed study in order to tie together the logic of the arguments and bring the findings into better context. It will encompass:

o Policy, Standards and Criteria,

o The sources of hazards,

o Hazardous substances, and their inventories,

o Events which are capable to cause major accidents,

o Analysis of the consequences and their effects on employees, third parties and the public,

o Evaluation of individual and societal risks, using International Risk Tolerability Criterion,

o Measures to prevent, control or minimise likely consequences,

o Emergency procedures and emergency systems, derived from consideration of the above issues.

From these studies, risk reduction measures are identified, and improvements to the hardware and the management systems are considered.

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Abo Homos-Nubaria Pipeline QRA

Methodology

The proposed QRA methodology is shown in Figure 6.1.

Scenario

Development

Impact Assessment

Estimate/

Measure Risks

Verify

Decide Risk

Mitigation Measures

FIGURE 6.1 QRA Risk Assessment Frame-work

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Abo Homos-Nubaria Pipeline QRA

The QRA Criteria for risk tolerability is shown in Figure 6.2.

1 in 10,000

1 in 1 million

FIGURE 6.2 International Gas Criteria for the QRA Risk Tolerability

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Abo Homos-Nubaria Pipeline QRA

Plan of Work

The plan of work includes the following:

o Review the relevant facilities documentation.

o Carry out a physical survey of the pipeline route in order to identify the potential hot spot. o Identify the prevailing weather conditions.

o Set the QRA methodology.

o Investigate generic and specific release scenarios. o Define the impairment criteria.

o Perform flammability assessment.

o Select the appropriate consequence modelling software to be used. o Perform sensitivity analysis.

o Define ignited release scenarios.

o Define the consequence modelling analysis input data.

o Perform consequence modelling analysis using the selected modelling software. o Define failure frequencies (frequency assessment).

o Perform risk assessment.

o Risk evaluation with respect to international risk acceptance criterion.

o Investigate risk reduction measures and corrective actions (as applicable).

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Abo Homos-Nubaria Pipeline QRA

Operation of the Pipeline

The pipeline is provided with an automatic shutdown valve (ESDV) at the pipeline start. This ESDV is included within the inlet station facilities at the pipeline start.

Also, another automatic shutdown valve (ESDV) shall be installed at the pipeline end. This ESDV shall be included within the receiving station facilities at the pipeline end.

Other inline sectionalizing valves are manual isolation valves installed on different intervals on the pipeline route in order to minimize leaks and potential failures.

Flow measurements are provided for the pipeline to facilitate flow measurement and leakage indication.

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Abo Homos-Nubaria Pipeline QRA

Emergency Plan

Emergencies in Stations:

There is an emergency plan for the existing pipelines.

Actions in response to the emergency cases are generally restricted to the isolation of valves, reporting the incident and follow up with relevant authorities.

Gas Pipeline:

The Company has an emergency booklet that covers the main gas transmission line and customers.

There is also an emergency room dedicated for such emergencies. Emergencies are prioritised at different levels, and include the following:

o Gas leaks (instrumentation and equipment),

o Gas explosion,

o Natural events to include earthquakes, heavy rain and external events.

Response to these emergencies focus on isolation and reporting for actions.

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