6.18 Offshore Emergency Shutdown System Design Philosophy

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Kingsnorth CCS Demonstration Project

Offshore Emergency Shutdown System Design Philosophy

1 SCOPE AND FUNCTIONAL REQUIREMENTS

1.1 Scope of Document

This document has been produced to outline the philosophy for the emergency shutdown system which shall be installed to protect personnel, asset and the environment from hazards associated with the operation of the pipeline and offshore facility part of the Kingsnorth Carbon Capture & Storage Project. This will also involve any onshore pipeline emergency shutdown requirements.

1.2 Pipeline & Offshore Facility

The offshore project consists of a circa 270 km dry CO2 pipeline from

Kingsnorth Power Station on the Isle of Grain to a new Offshore Normally Unmanned Installation (NUI) to utilise the depleted Hewett gas reservoir.

Note: The offshore project boundary starts at the exit of the compressor and includes the onshore metering and pig launcher.

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The offshore project shall study two cases as follows:

The base case of a single platform, which is rated to handle the CO2 that

is flowing in the pipeline when in the gaseous phase of the CO2 phase

envelope and then is to be upgradeable to cope with the dense phase operation. This base case option has a well capacity for 4 wells (one spare) and has a CO2 handling capacity of 6600 tonnes/day equivalent to

what is produced when generating 400 MW (gross);

An alternative case with enough capacity to handle 12 wells and is able to cope with an additional dense phase processing module that is suitable to handle the CO2 produced from a 1600 MW (gross) onshore power plant

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2 ASSUMPTIONS

The offshore Emergency Shutdown (ESD) system architecture will be consistent with its Integrity Level classification. There is an opportunity to have an offshore integrated control and safety system. Integrated in terms of peripheral devices and supplied by one vendor with segregated safety and control hardware.

The ESD system manufacturer should be the same as for the onshore carbon capture part of the Project. This will offer continuity between onshore and offshore plant.

2.1 Hydraulic Actuated Valves

It is recommended offshore actuated spring return valves are supplied by hydraulic motive power. This will keep the actuator weight and size to a minimum. Valve closure times shall account for potential of water hammer in dense phase operation.

2.2 Emergency Electrical Equipment

Typical offshore emergency electrical equipment to remain operational during an emergency are as listed below:

Emergency/Escape/Helideck Lighting; Emergency Communications;

Platform Control System including Pipeline Integrity System; ESD System;

Fire and Gas System;

Public Address and General Alarm System; Navaids and markings;

Temporary Safe Refuge (TSR)/Equipment Room Ventilation (HVAC) Systems fed from the emergency switchboard.

Emergency electrical equipment will normally be supplied from the emergency generator. Selected items will have an Uninterruptible Power Supply.

2.3 Remote Operability

The NUI will require a remote trip from Kingsnorth Power Station and a local offshore trip used while the facility is manned.

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3 DESIGN REQUIREMENTS

3.1 Objectives of the ESD System

The objectives of the ESD system are to shutdown the pipeline and injection facilities to:

Protect the facility personnel; Protect the environment;

Protect the plant and equipment on the facility.

The ESD system objectives shall be met by:

Provision of self acting mechanical devices or systems where appropriate;

Automatically sensing an abnormal facility operational or equipment condition. Note – Safeguarding interfaces for - heater failure; power failure; inadvertent valve opening; blocked outlet and intertrips between onshore and offshore needs to be confirmed by a separate study;

Automatically reacting to these conditions by shutting down ESD valves, wellhead valves and/or isolating where appropriate. Note - automatic CO2

sectionalised depressurising onshore and offshore needs to be confirmed by a separate study;

Providing additional manual facilities for shutdown and/or isolation of the facility;

Intertrip from Fire & Gas system detecting potential sources of hazard such as toxic or flammable gas and eliminating potential sources of ignition. Note – Mitigation systems for – toxic CO2 gas release; fuel gas release

(alternative heating source);

Providing audible and visual shutdown status information to the operators both onshore and offshore and raise General Platform Alarm at all potentially manned offshore locations.

The system as a minimum will meet the objectives described above. The ESD system functionality shall be typically determined from the following preliminary reviews:

Hazardous Identification/Operability Studies; Cause and Effects diagrams;

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3.2 Shutdown Hierarchy - Offshore

The Shutdown Hierarchy shall be based on the following three generic levels of Shutdown; presented in descending order of priority:

3.2.1 Total Platform Shutdown (TPS)

TPS is defined as the total isolation of the platform from external sources of process gas and deactivation of all process and non-essential utility systems. It is only initiated manually from dedicated push-buttons locally or from onshore Kingsnorth Power Station.

3.2.2 Surface Process Shutdown (SPS)

SPS is defined as the shutdown of all process systems and initiation of emergency depressurising (EDP), but leaving utility systems, including power generation operational.

3.2.3 Process/Utility Unit Shutdown

Unit Shutdown is defined as the tripping of individual process or utility systems or subsystems, initiated automatically and through operator action.

3.3 Classification of Safety Instrumented Functions

To enable optimisation of loop design and testing strategy, each shutdown function should be classified using a risk-based approach. This is achieved by subjecting all required Safety Instrumented Functions (SIF‟s) to an integrity level classification, to analyse the consequences of failure of that particular function upon demand, in terms of risk to personnel safety, potential asset loss, and effect on the environment. From this classification, Safety Integrity Level (SIL), Environmental Integrity Level (EIL) and Commercial Integrity Level (CIL) should be assigned to each function. Design of the function should optimise the combination of hardware, software and test interval to achieve the Probability of Failure on Demand prescribed by the highest of the SIL, EIL or CIL.

For example, the integrity levels in BS EN 61508-1 “Functional safety of electrical/electronic/programmable electronic safety related systems” are classified as SIL 1, 2, 3 & 4. Following this standard will generally identify that a SIF does not need to be assigned a SIL rating or where it does it will fall into the category of SIL 1, 2, 3 or 4.

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classification. It is also equally important for it to be operated, maintained and modified in such a way as to continue to meet the safety intent whilst in service.

3.4 Implementation of Safety Instrumented Functions

The adoption of a failsafe principle „de-energise to trip‟ shall apply to all final actuating devices and the ESD system. Shutdowns shall de-energise solenoid valves, trip motors, heaters etc, resulting in closure of spring return ESD valves or de-energising of motor, thyristor circuits.

Dependent upon the choice of manufacturer, it may be possible to purchase an integrated control, ESD, and Fire & Gas system compatible with the onshore carbon capture systems.

The control, ESD, and Fire & Gas functionality will be segregated for reasons of independence and differing integrity requirements. An integrated system i.e. from one system vendor would give common peripheral components in the communications, reporting, logging, operator interface areas and one maintenance contract.

The ESD shall be provided with a reliable Uninterruptible Power Supply which will be available for the period required to manage the emergency.

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4 MANDATORY REFERENCES

UK Statutory Instruments, Codes and Standards

SI 2005/3117 Offshore Installations (Safety Case) Regulations.

SI 1995/743 The Prevention of Fire and Explosion and Emergency Response Regulations

(PFEER)

SI 1996/913 Offshore Installations and Wells (Design and Construction, etc) Regulations (DCR) BS EN 61508 Functional Safety of

Electrical/Electronic/Programmable Electronic Safety-Related Systems BS EN 61511 Functional Safety – Safety Instrumented

Systems for the Process Industry Sector API RP-14C Safety Systems for Offshore Production

Platforms

5 PROJECT REFERENCES

1. Genesis Report No. KCP-GNS-PCD-STU-0001 Rev 03 – Kingsnorth Carbon Capture & Storage Project – Basis Of Design For Studies – Phase 1A

2. Genesis Drawing No. KCP-GNS-PCD-PFD-0003 Rev 01 - Kingsnorth Carbon Capture & Storage Project – PFD Offshore & Transport System CO2 Process System Demo Phase (Base Case)

3. Genesis Drawing No. KCP-GNS-PCD-PFD-0004 Rev A1 - Kingsnorth Carbon Capture & Storage Project – PFD Offshore & Transport System CO2 Process System Full Flow Scenario