Hellenic Gas Transmission System Operator

Transcription

1 7 th th EUROPEAN FORUM GAS 2009 Hellenic Gas Transmission System Operator Madrid, 18th and 19th June, 2009 Hellenic Natural Gas HP Transmission System Uprating Study

2 Uprating study deliverables Management procedure Identify DESFA s internal management requirements for control of uprating contracts Specification Identify DESFA s technical requirements for uprating studies, for issue to approved contractors Feasibility study Determine feasibility of uprating DESFA s Ano Liossia to Lavrion pipeline from 40bar to 45bar operating pressure

3 Technical assessment requirements and acceptance criteria Technical assessment requirements and acceptance criteria from: Principal i pipeline operating code Supporting pipeline engineering standards Oh Other relevant engineering i standards d

4 Uprating Specification Principal code for design & operation

5 Uprating Specification Supporting pipeline standards Standard Title ELOT EN Gas supply systems 1594 Pipelines for maximum operating pressure over 16 bar Functional requirements ELOT EN Eurocode 3 Design of steel 1993 structures, Part Pipelines ELOT EN Petroleum and natural gas ISO industries Pipeline transportation systems Reliability-based based limit state methods Content Basic principles for gas supply systems Structural design of pipelines Methods to predict safety of operational pipelines

6 Uprating Specification General assessment method FFP = Fitness For Purpose

7 Uprating Specification Pipeline assessments To demonstrate pipeline safety at uprated MAOP Identify design requirements for uprated MAOP Each Code issue assessed for uprated conditions Uprated MAOP acceptable if safety level is adequate Acceptable safety level demonstrated by either: COMPLIANCE with Code requirements OR Alternative fitness-for-purpose (FFP) assessment Compliance with Code is preferred method

8 Uprating Specification Fitness for Purpose (FFP) Pipeline issues which COMPLY with Code are Fit-for-Purpose (FFP) Pipeline issues which DO NOT COMPLY with Code require special FFP studies FFP study yq quantifies safety level Acceptable safety level can avoid need to upgrade pipeline p

9 Uprating Feasibility Purpose of study One pipeline for uprating feasibility study Not a full demonstration of pipeline fitness for uprate Identify whether practical to proceed to next stage Ano Liossia to Lavrion selected by DESFA Assess raising of MAOP from 40 bar to 45 bar

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11 Natural Gas Transmission i System of Greece Main Line Technical Data Design code: ASME B 31.8 Hydrotesting : pressure 1,5*DP Construction period : Tests after construction : intelligent pigging Main High Pressure Pipeline Length 511 km MOP 66,4 bar DP 70 bar Design factor 0,5 0,72 NOM DIA: 36", material API 5L X65 wall thk 11,1 15,9 mm length 98 km 30", material API 5L X65 wall thk 9,52 20,6 mm length 408 km 30", material API 5L X52 wall thk 9,52 15,9 mm length 5 km

12 Uprating Feasibility Ano Liossia to Lavrion pipeline ANO LIOSSIA ATHENS LAVRION

13 Natural Gas Transmission System of Greece Branch line Technical Data Diameter 762 mm Wall thk 9,52mm 20,60mm Pipe Grade (API 5L) X52- X65 Pipe length 99,37 km Pipe Manufacturer Europipe Ilva External coating Internal coating Radiography Ultrasonic Checks Magnetic Crack detection Cathodic Protection Precommissioning Hydrostatic Test Pressure 65,87 124,9 bar Precommissioning Hydrostatic Test Date: Jan July 1998 Design Code ASME B31.8 : 2003 Design Pressure 40 bar Maximum Allowable Operating Pressure 40 bar Contractor: Stroytransgaz Consortium

14 Uprating Feasibility Legend Feasibility findings Apparent major code infringement i Apparent code infringement and/or possible need for FFP assessment No apparent uprating difficulty Not applicable

15 Uprating Feasibility Findings Issue Pipeline records Design factor Fatigue Fracture toughness Issue Hydrostatic test Depth of Cover Seismic Structural reliability Issue Location Class Building proximity Traffic route crossings Pipeline condition

16 Uprating Feasibility Findings summary No major Code non-compliance Majority of issues appear Code Compliant Some Non-Compliance issues will require fitness-for-purpose studies

17 Uprating Feasibility Hydrostatic test Five test record sheets examined Test pressures calculated from detail on record sheets Nine individual tests Five tests fully acceptable for MAOP of 45 bar Four tests show marginal non-compliance (at high-elevations only) Non-compliant tests require study of additional records then possible fitness-for-purpose assessment IDENTIFIED NON-COMPLIANCE IS NOT SIGNIFICANT

18 Uprating Feasibility Structural Reliability Assessment (SRA) Not addressed by Code Structural reliability target levels given by ELOT EN based on historic reliability of pipelines Generic assessment shows: Increasing MAOP from 40 to 45 bar makes no significant change to existing structural reliability BUT Existing structural reliability levels are lower than target levels More accurate SRA requires recent pipeline specific ILI data and Location Class data ACCEPTANCE LEVELS NEED TO BE CONSISTENT FOR ENTIRE DESFA SYSTEM

19 Uprating Feasibility Building proximity Original safety study states 53 locations with buildings within 10 metres of pipeline 33 residential 1 school 3 commercial 16 unclassified Risk assessment was carried out and risk level accepted Uprated MAOP will increase risk FFP assessment using Quantified Risk Assessment (QRA) at uprated MAOP probably required CHANGE IN RISK NOT LIKELY SIGNIFICANT

20 Uprating Feasibility Pipeline condition No in-line inspection (ILI) carried out Condition of pipeline not certain Identify any damage by ILI Confirm damage as FFP or repair QUANTITY OF DAMAGE NOT LIKELY SIGNIFICANT

21 Hellenic Natural Gas HP Transmission System Uprating Study Thank you for attention gr