AC-100-A4Z-0-61593 Rev 2

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ABU DHABI GAS LIQUEFACTION COMPANY (ADGAS)

FEED for Power Generation andAssociated facilities at Das Island forNASR FFD Loads

Process Philosophy

Project No. 021/57083

Document No. AC-100-A4Z-0-61593 Rev 2

Date: 29 September 2013

Power

13th Floor, Al Dhafir TowerNajda St.PO Box 44169, Abu Dhabi,UAETelephone: +971 2 495 1100Facsimile: +971 2 676 6429www.worleyparsons.com

Copyright 2013 WorleyParsons

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FEED FOR POWER GENERATION AND ASSOCIATED FACILITIES AT DAS ISLAND FOR NASR FFD

LOADS

PROCESS PHILOSOPHY

PROJECT 021/57083 - FEED FOR POWER GENERATION AND ASSOCIATED FACILITIES AT DASISLAND FOR NASR FFD LOADS

REV DESCRIPTION ORIG REVIEW WORLEY-PARSONSAPPROVAL

DATE CLIENTAPPROVAL

DATE

2 Issued for Design

SABA VENK BUKA/MEEJ

29-Sep2013

1 Issued for Approval

SABA VENK/JADK BUKA/MEEJ

23 July2013

0 Issued for Client

Comments SABA VENK BUKA/MEEJ

16-June-

2013

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Page 2 of 22 021/57083 : AC-100-A4Z-0-61593 Rev 2 : 29 September 2013

SYNOPSIS

This document presents the Process Philosophy for the FEED for Power Generat ion and

As soc iated faci l i t ies at Das Island for NASR FFD Loads.

Disclaimer

This report has been prepared on behalf of and for the exclusive use of ABU DHABI GAS

LIQUEFACTION COMPANY (ADGAS), and is subject to and issued in accordance with the

agreement between ABU DHABI GAS LIQUEFACTION COMPANY (ADGAS) and

WorleyParsons. WorleyParsons accepts no liability or responsibility whatsoever for it in respect of

any use of or reliance upon this report by any third party.

Copying this report without the permission of ABU DHABI GAS LIQUEFACTION COMPANY

(ADGAS) or WorleyParsons is not permitted.

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CONTENTS

1 INTRODUCTION ................................................................................................................ 4

1.1 Project Background............................................................................................................. 4

1.2 Purpose ............................................................................................................................... 4

1.3

Definitions / abbreviations ................................................................................................... 5

2 PROJECT FACILITY .......................................................................................................... 6

3 PROCESS DESCRIPTION ................................................................................................. 8

4 OPERATING AND CONTROL PHILOSOPHY ................................................................. 10

5 ESD PHILOSOPHY .......................................................................................................... 12

5.1 Safeguarding System for GTG Package .......................................................................... 13

6 TIE-IN PHILOSOPHY ....................................................................................................... 14

6.1 Preliminary Tie-in Summary List identified during FEED: ................................................. 14

7

FLARE RELIEF AND BLOWDOWN PHILOSOPHY ........................................................ 15

7.1

Overpressure .................................................................................................................... 15

7.2 Emergency Depressurisation ............................................................................................ 15

8 VENT AND DRAIN PHILOSOPHY ................................................................................... 17

9 ISOLATION PHILOSOPHY .............................................................................................. 19

9.2 Spectacle Blind/RSP ......................................................................................................... 20

9.3 Pump Isolation .................................................................................................................. 20

9.4

Equipment/Vessel Isolation .............................................................................................. 20

9.5 Instrument Isolation........................................................................................................... 20

9.6

Control Valve Isolation ...................................................................................................... 21

9.7

Train Isolation ................................................................................................................... 21

9.8 Diesel System Isolation .................................................................................................... 21

10 REFERENCES ................................................................................................................. 22

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1 INTRODUCTION

1.1 Project Background

Abu Dhabi Gas Liquefaction Company Limited (herein after called ADGAS) operates an LNG Plant

on Das Island, U.A.E. The Plant consists of two identical trains with associated utilities

commissioned in 1977 and a third train with associated utilities commissioned in 1994. Plantproducts are LNG, LPG, Pentane and molten Sulphur. These are exported through separate jetties;

one for LNG, LPG and Pentane and the other one for Sulphur.

Electrical Power is generated at Das Island by seven (7) nos of Power Generation units. ADGAS has

total four power generators; two steam turbine generating sets (LG1 and LG2) and two gas turbine

generating sets (LG5 & LG6). ADMA OPCO has three gas turbine generators (GT1, GT2 and GT3).

The two gas turbine generators, GT1 and GT3 are connected to 11 kV double bus bar switchboard in

ADMA OPCO power station. The two steam turbine generators, LG1 & LG2, are connected to new

ADGAS 11 kV Switchboard (substation L1). However, the other three gas turbine generators GT2,

LG5 and new LG6 are connected to ADGAS 33 kV switchboard. In addition to the above, ADGAS is

planning to install 8thPower Generator which will be connected to ADGAS 33 kV switchboard.

Due to the growth of the power demand from planned expansion projects at USSC and Al Nasr fields,

ADGAS launched the study and engineering requirement for 9thand 10

thGTGs. The two GTGs have

been planned based on estimated power demand of 38 MW for the ADMA-OPCO NASR FFD project

taking into consideration the current power generation capacity at Das Island.

ADGAS has appointed WorleyParsons as engineering consultant to perform Front End Engineering

Design (FEED), Project Definition Report (PDR), Engineering, Procurement and Construction (EPC)

tender package for this project, "Power Generation and Associated facilities at Das Island for NASR

FFD Loads of ADMA OPCO" on Das Island.

1.2 Purpose

The document provides the Process description and Process philosophies for GT4 (9th) and GT5

(10th) Power Generators on Das Island.

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1.3 Definitions / abbreviations

ADGAS Abu Dhabi Gas Liquefaction Company

ADMA OPCO Abu Dhabi Marine Operating Company

CCB Central Control Building

CCR Central Control Room

COMPANY Abu Dhabi Gas Liquefaction Company

CONTRACTORThe organization appointed by ADGAS to execute the job including its

subcontractors (if any)

DCS Distributed Control system

EPC Engineering, Procurement & Construction

FEED Front End Engineering Design

FG Fuel Gas

F&G Fire & Gas

FGTU Fuel Gas Treatment UnitGTG Gas Turbine Generator

HSE Health Safety & Environment

IA Instrument Air

LNG Liquefied Natural Gas

PDR Project Definition Report

PFD Process Flow Diagrams

P&ID Piping & Instrument Diagram

PMS Power Management SystemRSP Removable Spool Piece

SUPPLIER The organization selected to supply the equipments and services.

UCP Unit Control Panel

WP WorleyParsons Ltd

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2 PROJECT FACILITY

The project consists of installation of the GT4 (9th) & GT5 (10

th) Gas Turbine Generators and tie-ins

with the existing fuel gas and utility systems that is required in order to meet future load requirements.

Due to growth of the power demand for the planned expansion projects at Das Island, a study and

engineering requirement for LG8 (11th) and two future GTs are envisaged. The GTs planned for the

future have been proposed in the Granite and Costain Batch Mixing Plant Area which is at the

adjoining plot extending further from the GT4 (9 th) and GT5 (10th) location. Process and Utilityrequirements are provided catering for 5 no. GTs i.e. GT4, GT5, LG8 and two future GTs.

Accordingly, the Sour / Sweet Fuel gas, Diesel Fuel, Instrument Air, Nitrogen and Potable Water lines

from the tie-ins are sized for 5 no. of GTs i.e GT4, GT5, LG8 and two future GTs.

Installation shall be designed such that they are compatible with the existing facilities. Monitoring of

Electrical parameters associated with Generators is performed by Power Management System

(PMS). Process controls for instruments within the GT package are carried out by GT UCP & outside

GT Battery limit are controlled from DCS and ESD for control and shutdown actions. The instrument

and control equipment for the new generators shall be designed such that they are compatible with

the existing GTGs.

The project covers the following facilities:

2 Nos. of new Gas Turbine Generators (GTGs) with its auxiliaries.

Independent Fuel Gas conditioning skid for each Generator. The Fuel Gas conditioning skid

consists of Gas Filter Separator, Electric Gas heater and associated pipes, instrumentation &

fittings.

A closed drain system common for GT4, GT5, LG8 and two future GTs shall be provided to

collect hydrocarbon drains and vents. The closed drain system consists of a drain drum and

transfer pump.

The existing diesel transfer Pumps of 90 m3

/h is not adequate to supply diesel to all eight (8) GTs.Hence, it is proposed to replace the existing diesel pumps with new pumps of higher capacity.

Following tie-ins are required for the above facilities:

Two sources of Sour Fuel Gas have been identified for supply to GTs. One tie-in is from 780#

header in the ADGAS LNG Train-2 area and the other alternative supply is from 780# header in

the ADMA LNG manifold area. The Sour Fuel gas supply to GT4, GT5, LG8 and two future GT's

shall be at around 50.8 barg.

Sweet gas supply to GT4, GT5, LG8 and two future GT's shall be from the downstream of the

FGTU, which shall be in future. Currently, no sweet gas supply is available for new and future

GTs. The sweet gas supply to GT4, GT5, LG8 and two future GT's shall be at 49 barg.

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The hydrocarbon drains from the new closed drain system shall be pumped to the existing

hydrocarbon drain header in the existing ADMA power station which is further routed to the inlet

of spheroids located in the ADMA-OPCO process area.

The hydrocarbon vents from the new closed drain system shall be routed to the tie-ins identified

at the existing Flare header in ADMA-OPCO process area.

Instrument air tie-in from Instrument air header identified in the Boiler area near ADMA-OPCO

power plant (GT1/GT2/GT3).

Potable water tie-in identified in the Boiler area near ADMA-OPCO power plant (GT1/GT2/GT3).

Nitrogen tie-in from the Nitrogen header identified in the 60 Atmospheric Manifold area near

ADGAS Booster Compressor House.

Diesel fuel tie-in will be from the new Diesel Fuel Transfer pumps.

Service Air is not available at this area. Service Air required for maintenance in GT4, GT5, LG8

and two future GTs shall be supplied from mobile Air Compressor.

Refer Site visit Report, Doc. No. AC-100-4AZ-0-61629 for Tie-in locations.

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3 PROCESS DESCRIPTION

The GT4 (9th) and GT5 (10

th) Power Generators are considered to be dual fuel (Fuel gas and Liquid

Fuel) type. Sour Fuel Gas / Diesel shall be used for power generation in GTs.

Fuel Gas System:

Two sources of Sour Fuel Gas have been identified for supply to GTs. One tie -in is from 780# header

in the ADGAS LNG Train-2 area and the other alternative supply is from 780# header in the ADMA

LNG manifold area. The Sour Fuel gas supply to GT4, GT5, LG8 and two future GT's shall be at

around 50.8 barg.

Sweet gas supply to GT4, GT5, LG8 and two future GTs shall be taken from downstream of the

FGTU, which shall come in future. Currently, no sweet gas supply is available for new and future GTs.

The sweet gas supply to GT4, GT5, LG8 and two future GT's shall be at 49 barg.

The sour fuel gas is passed through the Gas Filter Separator which is part of the Fuel Gas

Conditioning Package to remove any hydrocarbon condensate formed in the gas supply line and to

meet the fuel gas specification required by GTG Package. This Gas Filter Separator comprises of

necessary control and instrumentation including a level control valve which shall operate based on

level in the Gas Filter Separator.

The gas from the Gas Filter separator is routed to the fuel gas heater. The fuel gas heater is

employed with continuous temperature control to superheat the fuel gas to GTG specification

requirement of 75 C. A clean, dry fuel gas from the unit is fed to the gas turbine.

Diesel Fuel System:

Distillate fuel is stored in a storage tank 80-D-701 at the east side of the ADMA power station. The

diesel required for all eight GTs is 103 m3/h. The existing diesel pump of capacity 90 m

3/hr is not

adequate to supply diesel to all eight (8) GTs. Hence, new diesel transfer pumps of higher capacity

i.e. 110 m3/h (1 operating + 1 standby) are provided to supply diesel to all 8 no of GTs i.e GT1, GT2,

GT3, LG7, GT4, GT5 and future GTs LG8 & LG9.

New Diesel transfer pumps shall start automatically when any GT is to be run with diesel oil. For

existing GT1, GT2 and GT3 diesel pumps start automatically if fuel gas pressure on any of the GT

falls below 11.90 barg or 170 psig. The automatically initiated change over occurs only when the

transfer is from gas to diesel oil operation. The change over from diesel oil to fuel gas when the fuel

gas pressure is stabilized is to be done manually. The operating conditions of Diesel Fuel required for

GT4 & GT5 are as follows:

Operating Pressure : 3.55.0 barg

Operating Temperature: 40 C

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Drain and Vent System:

The drain and vent from the Fuel Gas Conditioning Package and the GTG package is connected to a

new common Closed Drain System for GT4, GT5, LG8 and two future GTs. The Closed Drain drum

shall be located inside a pit with relevant Fire and Gas detectors. The operational hydrocarbon drain

from the Gas Filter Separator shall automatically discharge into the drain header (at pump discharge)

through level control valve, whereas the drain from the separator and heater during maintenance shall

be manually drained into the Closed Drain drum.

The Closed Drain drum will be equipped with a vertical sump pump to transfer the liquid to the

existing hydrocarbon drain header in the ADMA power station which is further routed to the inlet of

Spheroids located in the ADMA-OPCO process area.

Manual vents / PSV / BDV discharge from the Fuel Gas Conditioning Package of GT4 & GT5 are also

routed to the Closed Drain drum. The gas from the drum shall be routed to the existing flare header in

ADMA-OPCO process area.

GT4 and GT5:

Power generation package consists of one dual fuel turbine, which will run either on fuel gas or diesel

fuel. The principal components comprise an Axial-flow compressor, Fuel and combustion system and

Power turbine. The generator rotor is coupled to the turbine through a speed reducing load gearbox.

As part of this project, two (2) new dual fuel (Gas and Diesel) turbo Generators (GT4 & GT5) are

envisaged. The estimated rating of each generator is 38 MW at site conditions.

Atmospheric air is drawn through air intake filters into the axial-flow compressor where it passes

through multiple stages of compression and is discharged to the combustion chamber. The fuel is

supplied by fuel gas or diesel fuel (for start-up and limited time of operation) system. Combustion of

fuel takes place in combustion chamber. The resulting high temperature and high pressure

combustion gas is then expanded through the turbine, which drives the axial flow compressor and the

generator.

After passing through the turbine the exhaust gas passes out to the exhaust stack to atmosphere. A

dedicated lubricating oil console supplies cool, clean and pressurized oil for the unit.

Closed circuit cooling water system is considered for cooling of turbine assembly. Potable Water

supply is envisaged for make-up in the Closed circuit cooling water system of GT4, GT5, LG8 and

two future GTs. Gas turbine will be started by electric motor. An emergency diesel generator will be

installed to provide essential power supply in the event of a blackout situation.

Detailed description / operation of turbines lube oil system, fuel change over, machine functionality to

be addressed during detailed engineering phase of the project once vendor information is available.

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4 OPERATING AND CONTROL PHILOSOPHY

The Operating Philosophy relies on the active involvement of operations personnel in the design

phase of the Project.

The basic operational philosophy under this project is to operate safely, effectively, and efficiently with

high environmental standards that maximize value from the installed asset over their full life cycle

against agreed performance targets.

This philosophy shall be reviewed and further developed during detailed engineering phase of the

project in accordance with Project Documents and Standards, International Standards and best

practices and will be achieved through:

Providing a safe and healthy operating environment by inherent design, maintenance and

operation.

Embracing Company environmental expectations.

Progressive improvement of environmental and operating performance.

Employing competent and well trained teams.

Operating experience with similar equipment and/or facilities.

Reliability requirements by the Company.

The sour fuel gas from the headers identified in the ADMA LNG manifold area and ADGAS LNG

Train-2 area is routed to the Fuel Gas Conditioning Package of GT4 & GT5 to meet the GTG

specification before sending the fuel for combustion.

Provision for sweet gas supply in future is identified when FGTU in ADGAS area is installed. Each

GTG is isolated with a shutdown valve from the source and the pressure is controlled with a pressure

control valve (from 50 bar g to 30 bar g) to meet the GTG pressure requirement. The pressure

control valves are designed for 2 x 100% capacity, but operate in parallel at 2 x 50% capacity.

The required Fuel Gas temperature at the inlet of GTG package is maintained by online electrical

heater at Fuel Gas Conditioning Package. Electrical heater will trip on high high outlet temperature.

The level in Gas-Filter separator is automatically controlled with the level control valve. High high

level in Gas-Filter Separator shall close gas inlet and outlet shutdown valves. Low low liquid level in

Gas Filter Separator shall close liquid outlet shutdown valves. Alarms are activated on high high and

low low liquid levels.

In addition to Fuel Gas Conditioning Package, GTG is also equipped with diesel connection to start

upon diesel mode automatically when the fuel gas supply pressure goes low. Refer Section 3 for

details.

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Automatic start of new diesel transfer pumps shall be done by individual GT Unit Control Panel (UCP)

in case of changeover from fuel gas to diesel fuel when fuel gas pressure is low.

Details on Operating and Control philosophy of GTG within vendor package shall be developed

during detailed engineering phase based on Fuel gas and turbine generator vendor information.

The following sequence is envisaged for changeover from fuel gas to diesel liquid.

Auto-start of new Diesel transfer pumps.

Initiation of automatic change over sequence from fuel gas to diesel without interruption in power.

o Open the individual XVs on diesel supply line for GT4 & GT5.

o Close the individual SDVs on sour fuel gas / sweet fuel gas supply line for GT4 & GT5.

Stop the Fuel gas supply to GTG package.

Detailed changeover philosophy from Fuel gas to Diesel liquid shall be developed during detailed

engineering based on vendor information.

The change over from Diesel fuel to Fuel gas when the fuel gas pressure is stabilized is to be done

manually.

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5 ESD PHILOSOPHY

Emergency Shutdown (ESD) System shall be Safety Programmable Logic Based System, designed

to bring the facilities into a safe predetermined shutdown condition during hazardous condition which

reduces potential consequences of that hazard.

For this project, three levels of shutdown are envisaged. ESD 1, ESD 2 & ESD 3 described as below.

ESD 1: Both GTG Train / Package shutdown with emergency depressurisation of the process.

ESD 1A: Both GTG Train / Package shutdown with emergency depressurisation of the process

ESD 2: Both GTG Train / Package shutdown and isolation of GTG Train / Package

ESD 3: Shut down of individual process and equipment.

The following emergency causes are envisaged as part of this project, that is executed through ESD

PLC.

ESD 1:

Confirmed Fire and Gas detection.

ESD 1A:

Confirmed Fire and Gas Detection in Fuel Gas piping/Tie-in along with Fuel Gas Pressure Low

Low

ESD 2:

Instrument Air Low Low Pressure

ESD 3:

Fuel Gas Pressure Low Low

High High Level in Fuel Gas Separator.

High High Temperature at outlet of Heater.

Low Low Level in Fuel Gas Separator

Low Low Level in Closed Drain Drum

Low Low Pressure at Diesel Pump suction

Gas Turbine & Generator Safeguarding system

- Over speed of turbine

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- High Vibration of Turbine

- GTG Bearing Temperature High High

- GTG exhaust Temperature High High

- Lube Oil Header Pressure Low Low

- Lube Oil Supply Temperature High High

- Lube Oil Return Temperature High High

- Generator Vibration High High

- Generator Winding Temperature High High

Note:

Causes related to FG supply package are also listed here. However, it is to be confirmed during

detailed design based on vendor information.

For details on actions, refer to Project Cause and Effect Diagram, Document No. - AC-80-A3A-0-

61623.

5.1 Safeguarding System for GTG Package

The safeguarding system of Power turbine shall include those required for normal startup and

shutdown protection and their associated permissive logic and those systems required for prevention

of damage to the turbine due to mal-operation or abnormal/emergency conditions.

The turbine protection/safeguarding system includes:

Fuel gas supply low low pressure

Over speed protection

Over temperature protection

Vibration detection and protection

Flame detection and protection system

Detailed Safeguarding/Shutdown philosophy shall be addressed during detailed engineering phase of

the project based on package vendorsinformation.

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6 TIE-IN PHILOSOPHY

The main objective and requirement of the Tie-in and shutdown philosophy are summarised below:

The number of shutdowns and their duration shall be minimized.

Maximise the use of the planned facility shutdown following most optimum sequence for

completion of works.

Ensure safe isolation and subsequent depressurisation is achieved for any piping tie in work.

Ensure compatibility of "old" and "new" piping specifications.

Identify the requirement for any early tie-in.

Due consideration shall be given to installation and "constructability" for each tie-in.

All the construction work shall be completed before the shutdown.

Detailed Tie-in & Shutdown plan shall be prepared prior to implementation of tie-ins. All shutdown

activities shall be subjected to permit to work requirement.

Tie-ins are considered for the following fluid services:

1. Sour fuel gas

2. Sweet fuel gas

3. Diesel

4. Instrument Air, Nitrogen, potable water

For sour fuel gas, two tie-in points are considered. Sour and sweet fuel gas tie-in points along with

Double Block and Bleed arrangement shall be provided under FGTU project. No hot tapping is

envisaged in this project.

EPC Contractor shall further develop this tie-in philosophy during the detailed engineering and

produce a detailed tie-in package. Integrity of the existing system shall be critically reviewed by EPC

contractor prior to finalization of this document.

6.1 Preliminary Tie-in Summary List identified during FEED:

For details of tie-in points and locations, refer to the Project P&IDs, Piping General Arrangement

drawings and Tie-in Schedule.

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7 FLARE RELIEF AND BLOWDOWN PHILOSOPHY

The Flare, Relief and Blowdown system is a closed network of PSVs, Flare headers and KO drum

which shall be provided to allow safe disposal of hydrocarbons in the event of system overpressure,

emergency depressurisation and during operational flaring of the facilities.

7.1 Overpressure

Overpressure Protection shall be provided throughout the facility in order to prevent mechanical

failure of vessel and pipe work due to overpressure scenarios. All equipment shall be provided with

protection devices sized for respective relief contingencies. Pressure relief may consist of one PSV or

two PSVs. Process facilities shall be designed to minimise the possibility of over pressurising of

equipment.

Relief devices:

The following type of pressure relieving device shall be used in the facility:

Conventional spring-load type relief valves

The safety relief valve shall meet the requirements of API STD 526.

1. Conventional relief valves shall be used when there is no back pressure or when back

pressure is less than 10 % of the set pressure.

The fuel gas conditioning package will be fully rated for 600#. Relief valve in the package will be

designed for Fire scenario. During fire, the calculated relief load from PSVs to flare is 220 kg/h. This

shall be verified / confirmed during detail engineering by Fuel Gas Conditioning Package vendor.

Fuel Gas Separator liquid line is connected to Closed Drain Pump discharge 150# header. PSV is

considered on 150# header as an overpressure protection during the event of gas blow by from fuel

gas separator. During gas blow by the calculated relief load from PSVs to flare is 1320 kg/h.

7.2 Emergency Depressurisation

Emergency depressurisation (blowdown) shall be provided for hydrocarbon processing equipment to

protect pressure vessels from rupture under external fire conditions and to minimise uncontrolled

release of hydrocarbon inventory and the associated potential for escalation in a fire emergency. The

blowdown valve shall be located at the high point in the piping with the inlet line falling back to the

source vessel without pockets and the outlet line falling on the flare header without pockets. This

feature is to eliminate the potential for a condensate/water slug to accumulate upstream or

downstream of the blowdown valve and thereby avoid resulting excessive pipe stresses when the

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blowdown valve opens. Depressurizing will be carried out via dedicated depressurization valves to the

flare.

Emergency Depressurisation shall be required for the following scenarios:

Fire exposure:

Emergency depressurising for fire scenario shall be considered for large equipment operating at a

gauge pressure of 1700 KPa (approx. 250 psi) or higher in accordance with the stipulations of API

521. Additionally, when hydrocarbon content in the vessel can create a highly flammable atmosphereby flashing during fire, depressurisation will be required. High inventory hydrocarbon will also be

required to depressurise. Based on BP guidelines (GP 44-80 Relief Disposal and Depressurisation

Systems), depressurisation shall be designed to reduce vessel or process system internal pressure to

6.9 bar g (100 psig) or 50% vessel of the design pressure whichever is lower within 15 minutes.

The effects of initiating depressurisation shall be:

Immediately isolate relevant depressurisation inventory through closure of associated SDVs

and shutdown of relevant equipment and packages.

Open the relevant blowdown valve after a timed delay.

For the Fuel Gas Conditioning Package, during emergency depressurisation, the calculated flow rate

through the blowdown valve to bring down the pressure from 58 bar g to 6.8 bar g in 15 minutes is

641 kg/h for vessel thickness of 15 mm. This shall be verified / confirmed during detail engineering by

Fuel Gas Conditioning Package vendor.

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8 VENT AND DRAIN PHILOSOPHY

This philosophy applies to the use of vents and drains for all equipment and piping in all

hydrocarbons, toxic, chemical and non-hazardous services for the facilities that are planned to be

installed. It is necessary to be able to vent and drain sections of plant, items of equipment and

individual lines, in order to facilitate start-up, shut down for maintenance, inspection, tie-ins, and loss

prevention. Collection systems for vent and drain fluids depend upon the condition and nature of the

fluid to be handled during the stages of vent and draining operation. This vent and drain philosophy

will primarily describe the vent and drains from process vessels, process equipment, low point piping

etc.

The philosophy is based on the following considerations:

When the use of vents and drains is unavoidable they should be safe in compliance with HSE

policy on the project.

Venting/draining of hydrocarbons, toxic and chemical fluids directly to atmosphere is not

allowed from any equipment or piping irrespective of size or volume contained within the

equipment or pipe work. This includes any equipment or piping system that may be

contaminated with hydrocarbons or toxic or chemical fluids during abnormal operations.

Wherever possible, an equipment or pipe work or instrumentation to be drained shall have its

inventory reduced to the minimum safe practically attainable level by transfer to other parts of

process/systems, depressurized to flare or other suitable location depending on the process

fluid and then connected to the appropriate drain system for recovering the remaining contents

within the system. This will allow for recovery of hydrocarbons and chemicals to the maximum

extent possible.

All process vents and drains in hydrocarbon service and other toxic services, shall discharge into

closed vent/relief and drain systems. The design of all piping shall seek to minimise high point

pockets in liquid lines, and low point pockets in vapour/condensate lines. The P&IDs shall indicate thelocation and the type and size of the vents and drains required for process and operating purposes.

In general, vents and drains for equipment and piping shall be provided with 2 valves (unless

otherwise shown). Vent and drain valves that are not hard piped to suitable collection system shall be

fitted with a blind flange.

Closed Drains:

The closed drain (CD) system collects liquids from normally pressurized and hazardous equipment

prior to their maintenance. All closed drains will be hard piped from the equipment item to the closed

drain header keeping the hazardous fluid out of contact with the atmosphere. The closed drain

system will be isolated from individual items of equipment during normal operation.

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The closed drain header and lateral sub-headers should slope towards the Closed Drain Drum to

allow gravity flow. The Closed Drain Drum will be located at low level. A vertical pump will be used to

pump the liquid back to process. No sparing is considered for drain pump as the operation is

intermittent. The discharge of the pump will be connected to existing 2 header via RSP. RSP will be

in dropped condition when pump is not in operation and the pump discharge will be end blinded.

During operation of pump, the RSP will be installed at discharge.

The closed drain drum will be connected to the existing flare header. Hydrocarbon vapors from drum

will be safely disposed to the flare system.

The closed drain drum sizing is based on the liquid collected from Gas Filter Separators, Heaters and

piping from five GTs (i.e. GT-4, GT-5, LG-8 and two future GTs)

Open Drains:

Atmospheric drains collecting the surface waste liquid which are either contaminated such as drip

trays, base plate etc or non-contaminated shall be disposed off manually. Any waste water spillage

during maintenance of equipment shall be diverted to local Oily water sumps and the disposal shall

be contracted to third party (vacuum truck).

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9 ISOLATION PHILOSOPHY

The maintenance/inspection work should be implemented only on plant, units or systems which have

been shutdown, depressurised to atmospheric pressure, cooled, and drained, purged free of

flammable or toxic gases and isolated.

The method of isolation is dependent on such factors as type of maintenance and/or inspection work

involved, i.e. of a major, routine or minor nature, the properties of the process fluid in the live plantconnected to the equipment being maintained and the pressure and temperature of those fluids.

These factors determine whether isolation should consist of single or double block valves, together

with bleeds and inserted spades or closed spectacle blinds.

Inserted spades or closed spectacle blinds should always be used during maintenance, since they

provide the most positive means of isolation.

The isolation philosophy which shall be adopted for the project is described below:

9.1 Double Block & Bleed (DBB)

Double block and bleed will be provided for isolation of equipment. Integral double block and bleed

will be considered for isolation of instruments in all hydrocarbon gas/liquid (including fuel gas)

systems having operating pressure more than 150 psig, which may require maintenance/inspection

activities. For systems having operating pressure lower than 150 psig will be provided with single

isolation valve.

The following table summarises the minimum isolation categories that shall be followed:

(Reference: BP GP 44-40, Isolation of equipment for maintenance and emergency)

Fluid TypeMaximum Operating Pressure

150 psig >150 psig and

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Note:

V - Valving required to allow the installation of the blank flanges and Spades (Positive isolation)

I - Valving required to allow performing intrusive maintenance without Positive isolation (If positive

Isolation presents a greater risk)

SVI - Single Valve Isolation

DBB - Double Block and Bleed

The above table excludes isolations necessary for confined space entry which will be always a

positive isolation.

Pipework, including instrument lines DN 20 (NPS ) nominal bore and smaller, the isolation depends

on the pressure rating of the piping.

Automatic shutdown valve in combination with another manual isolation valve and a bleed can be

considered as a double block and bleed system.

9.2 Spectacle Blind/RSP

Use of spectacle blind / RSP shall be provided for positive isolation purpose where the equipment or

piping can be disconnected and taken out for maintenance for a longer duration or where a vessel

entry is expected.

9.3 Pump Isolation

Pump is not spared. Positive isolation for the Pump shall be achieved by placing a RSP at pump

upstream (i.e. Closed Drain Drum inlet) and at pump outlet. During Maintenance, RSP shall be

dropped for positive isolation.

9.4 Equipment/Vessel Isolation

As the vessels and GTG train are not spared and is integral part of the process, a complete shutdown

is necessary for vessel and GTG train for inspection/maintenance purpose. Isolation type is dictated

as mentioned in section 9.1. Positive isolation should be achieved by inserting spectacle blinds / RSP

as applicable for vessel entry.

9.5 Instrument Isolation

In hydrocarbon service wherever applicable, all new pressure, flow and level instruments will be

provided with a double block & bleed valve arrangement to isolate the instruments from the process

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fluid. For all non-hydrocarbon services, a single block valve will be provided for isolation of

instruments.

9.6 Control Valve Isolation

Double block and bleed valve arrangement shall be provided to allow isolation of individual control

valve at downstream and upstream.

9.7 Train Isolation

Double block and bleed valve arrangement shall be provided at upstream/inlet of each Train to allow

isolation from other Train.

9.8 Diesel System Isolation

Single isolation valve shall be provided to isolate the Diesel system.

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10 REFERENCES

1. AC-100-A4Z-0-61590 Rev. 2Process Basis of Design

2. AC-80-A3A-0-61627 Rev 3PFD for GT-4

3. AC-80-A3A-0-61628 Rev 3PFD for GT-5

4. AC-80-A3A-0-61603 Rev 3P&ID for GT-4

5. AC-80-A3A-0-61604 Rev 3P&ID for GT-5

6. AC-80-A3A-0-61605 Rev 1P&IDClosed Drain System

7. AC-80-A3A-0-61620 Rev 1Diesel Fuel Transfer Pumps

AC-100-A4Z-0-61593 Rev 2

Documents

Transcript of AC-100-A4Z-0-61593 Rev 2