Pressurised Pipeline Repair or Modification Enabled by Double Block And Bleed Isolation Tools

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Paul Holland
8 years ago
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1 STATS GROUP Process & Pipeline Integrity Solutions Pressurised Pipeline Repair or Modification Enabled by Double Block And Bleed Isolation Tools Dale Millward Director EPRS & Subsea Services

2 Presentation Reasons for pipeline repair or modification RISK level - ALARP Double Block Isolation Tools Piggable and non Piggable Repair or Modification Scenarios Valve Replacement/Installation Pipeline Tie Ins Retrospective installation of pigging facilities Dead leg Removal Recent Case Study pipeline tie in. Short Animation Q&A

3 Reasons for Repair or Modification Valve replacement or installation 36 ESDV Replacement 36 SSIV Installation

4 Reasons for Repair or Modification Making pipelines piggable / Removing unpiggable features Retrofitting pigging facilities

5 Reasons for Repair or Modification Tie-in of new pipeline to existing

6 Reasons for Repair or Modification Removal of dead legs - due to accelerated corrosion rates in stagnant piping Replacement of a damaged section

7 So, what's the safest way? Initially, it may be considered that the safest way to repair or modify a pipeline is to depressurise it and remove all hydrocarbon content, prior to doing the work; i.e. It has a risk level that is As Low as Possible. However, this may not be the safest method, or the way that has a residual risk level that is As Low As Reasonably Practicable (ALARP). The risks associated with ceasing production, depressurising, hydrocarbon removal, dewatering and starting up again need to be properly assessed. The following factors should also be assessed: Discharge to the environment Risks associated with decommissioning and recommissioning work scopes Stopping downstream production Flow assurance issues Out of service time Following a proper risk assessment it could be decided that depressurising the entire pipeline is not the safest overall way of doing the work or it does not have residual risk that is ALARP.

8 ALARP - Isolation If it turns out that it is not reasonably practicable to depressurise and hydrocarbon free the pipeline then it may be necessary to break containment while the pipeline is pressurised and contains production inventory; If the system has insufficient existing methods of isolation, then a temporary, fail safe, pressure capable, isolation tool, complying with industry isolation standards and recommended practices will be required - typically a double block tool, where both barriers are fully proven in situ (in the isolation position). Double Block Isolation Tool The next section of this presentation will introduce isolation tools that provide the required level of isolation and explain how they can be assessed to provide an isolation barrier that is deemed to reduce the risk to As Low As Reasonably Practicable.

9 Isolation Guidance Industry isolation guidance specifies: A proved DBB Isolation exists where the sealing integrity of two separate isolation barriers are proven before the isolation is relied upon. Each part of the isolation should be proved separately. BOTH isolation seals must be proven using full isolated pressure in the correct direction. This level of isolation ensures that no single isolation barrier failure will endanger the worksite.

10 Type Approved Double Block Isolation tools BISEP (Branch Installed Self Energised Plug) Tecno Plug DNV GL TYPE APPROVAL for Pipeline Isolation Plugs Type Designations BISEP and Tecno Plug Complying with DNV-OS-F101, DNV-RP-F113 & ASME VIII div. 2 Slide: 10

11 Proved Double Block Isolation In Situ Test Sequence Secondary Seal Integrity Test Pressure locked in the annulus Pressure behind vented, Secondary seal tested with: Full differential pressure in correct direction Tecno Plug BISEP Page. 11

12 Proved Double Block Isolation In Situ Test Sequence Primary Seal Integrity Test Pipeline pressure in front Annulus pressure vented Primary seal tested with: Full differential pressure in correct direction Tecno Plug BISEP Page. 12

13 Self Energisation, Failsafe Feature Self-energisation feature maintains safe isolation while differential pressure (above the verified minimum pressure) exists across the tool The Isolation plug has two separate activation mechanisms Dual Redundant Activation The Isolation tool is activated and held in place by internal hydraulics and it is energised and mechanically locked in by differential pressure Both separate activation mechanisms need to be removed to unset the plug Tecno Plug Self Energisation

14 PASSIVE UNSET Fail-Safe Unset and Recovery Feature In the unlikely the event of control system failure or possibly flat batteries, the Passive Unset feature ensures the Tecno Plug is always recoverable upon job completion. Passive unset is achieved by raising the tail pressure to equalise with the head pressure. This de-latches the locked in hydraulic pressure; it is open circuited to return. Equalising the pressure removes self energisation force. Once equalised the plug will then passively unset without any active control input NOTES: Isolation cannot be unset until the breaking containment operation is completed and the pressure behind the plug is raised to pipeline isolated pressure. If the pressure is equalised, the plug will become unset unless it is actively commanded not to unset. The passive unset is done in a safe and controlled manner only when the pressure is equalised across the tool.

15 Scenarios Valve Replacement BISEP and Tecno Plug used together to replace receiver and kicker line valves without affecting production Tecno Plug Isolation of 36 gas export pipeline for SDV replacement Slide: 15

16 Pipeline Tie In 24 pipelines tied into existing 36 trunk lines Slide: 16

17 Removing Un-piggable features Retrofitting Pigging Facilities Slide: 17

18 Removing Dead Legs With the isolation tools installed and tested. Dead legs were removed. Flange were welded on so new valves could be installed. Repeated at 12 similar locations Slide: 18

19 Case Study Subsea pipeline tie in Following animation will run through how this was achieved Slide: 19

SAFETY - LIFE SAVING RULES MECHANICAL ISOLATION CAT A-1 SOP #3

SAFETY - LIFE SAVING RULES MECHANICAL ISOLATION CAT A-1 SOP #3 SUNCOR ENERGY PRODUCTS DISTRIBUTION TERMINAL OPERATING MANUAL STANDARD OPERATING PROCEDURE SAFETY - LIFE SAVING RULES Verify isolations of hazardous energy before any work begins. Date Issued: February