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Life Cycle Integrity: Plant Design and Operation
Ankur Agarwal, Siddharth Singh Pipeline infrastructure is crucial in meeting the worldwide energy demand, which is projected to increase more than 50 per cent by the year 2030. The infrastructure is expected to grow at 7 per cent per year through 2020, with 231,900 km of oil and gas pipelines already planned or under construction.

Life cycle integrity is set of activities carried out in order to maintain the integrity / reliability of an object / process plant throughout its life, from first stage i.e. feasibility stage to last stage i.e. decommissioning of plant. These activities relate with design and many other verifications, which ensure that our process achieves operational success and product as per specifications. These activities reduce hazardous / accidental risk, capital expenditure, operation expenditure and optimise the reliable operational life cycle of plant.

Different stages of Plant Design and Operations are:
1. Concept and Feasibility stage [PREFEED]:

It mainly focuses on the need or requirement of market as well as acceptable return on appropri a t e investment (Capital cost, operating cost, revenue). Acceptable return can vary based on different type of industries and owners. Other terms defined during this stage are capacity of plant, site selection etc. During this phase study of input (feed streams) also carried out. Integrity control is implemented by analysis of oil or gas (feed stream), intermittent components (possibly produces during operation) and final products. It will give general idea about type of material to be used (mainly for pipelines) whether CS (with or with out chemical cleaning) or SS etc.

2. Preliminary Engineering or Schematic Design Phase [FEED]: This stage emphasises on schematic design and functional requirement of any plant. Design capacity of plant, economic evaluations, review of technologies provided by different licensors can continue from feasibility stage to this stage for further optimisation. In this stage over all process flow diagrams, mechanical selection diagrams, and process datasheets of all equipments etc should be completed for intensive review and approved for further detail engineering. In preliminary engineering phase potential hazard need to be identified and quantified. Preliminary project execution plan need to be prepared and it should be acceptable for further changes during detailing phase. In this stage selected material is finalised using different applicable codes and standards. For maintaining integrity, detail study of fluid properties will be performed to identify the presence of CO2, H2S, Chlorides, Water composition etc. It will give an idea of requirement of online and offline instruments for monitoring / sampling and their location.

3. Detail Engineering Phase: Detail engineering phase consist fur ther development of approved preliminary schematic design and drawings into construction drawing. Detailing phase is mainly about incorporation of detail engineering developments and life cycle cost analysis into feed package, Material logistic plans, purchase order for long lead items, complete detail project execution plan etc. Detail engineering phase confirms the monitoring / injection / sampling requirement and exact location and orientation of instruments. Safety integrated systems and controls logics are also verified / defined thoroughly during detail engineering phase in order to maintain the integrity of plant.

4. Procurement Phase: Procurement phase can be performed along with preliminar y and detail engineering phase. Procurement activities must ensure the timely purchase and delivery of required items by placing order for all long lead items on time, identification of local contractors and material suppliers, complete the material logistic plan etc.

5. Construction Phase: Execution of construction phase followed by mechanical completion ensures that plant is defect free in materials and workmanship. As-built drawings are also finalised, marked with all the changes from original bid, summarisation of safety records, original budget and actual cost including changes, original schedule and actual schedule etc. Safety and quality norms should be properly followed during construction phase to insure integrity of plant.

6. Commissioning and Start-Up Phase: Pre commissioning phase occurs prior to the commissioning of plant in which all control valves, control logics etc are being checked / tested to ensure the proper functioning of plant. Pre commissioning is generally done with utilities (Cooling water, Steam, Nitrogen etc). Then commissioning is performed by running of plant with live feed and ensures that the product quantity and specification are as per requirement. Performance guarantee test is done prior to the final acceptance criteria, which is the certification of compliances.

7. Operation Phase: Longest phase of a plant is operation phase. Operation must be oriented towards defined quantity of specified product as estimated during feasibility stage. No unexpected event during whole life cycle of a plant signifies the integrity of plant. To ensure the integrity, proper instructions like maintenance routine, operation instructions etc should be issued and followed. Also monitoring and inspection activities must be defined. These activities mainly consists data collection, analysis, reporting, corrective actions, process monitoring, etc. Proper implementation of well-defined instructions and procedures ensures the life cycle integrity of plant. It is also necessary that operators are well trained in order to identify and reduce safety risks before they escalate.



8. Decommissioning / Dismantling Phase:
Decommissioning of plant majorly consist repair, replacement, re use, scrap of existing plant. Definite procedure should be followed for decommissioning of plant. These procedures / guidelines must be used based on codes and standards, previous experience or lessons learnt from decommissioning of other plants etc. Decommissioning signifies the life cycle completion of plant.

Prospective
Pipeline infrastructure is crucial in meeting the worldwide energy demand, which is projected to increase more than 50 per cent by the year 2030. The infrastructure is expected to grow at 7 per cent per year through 2020, with 231,900 km of oil and gas pipelines already planned or under construction. Meanwhile, the worldĘs 3.5 million km of existing oil and gas transmission pipelines must continue to operate, often beyond their original design lives. To meet expectations, the industry must ensure safer operations, extended asset life and a reliable energy supply. Two main failure modes related to the pipelineĘs containment / structural function are:
1. Loss of Containment - Leakage of full bore rupture.
2. Gross deformation of pipe cross-section resulting in either reduced static strength or fatigue strength.
Pipeline integrity is established during the concept, design and construction (fabrication and installation) phases. The choices that are taken in the early design, as selection of pipe materials (carbon steel, stainless steel, clad pipe etc), pigging, buried or non-buried pipelines, monitoring systems, inhibitor systems, quality of the design / construction / installation phases will be decisive for the inspection and monitoring programme developed and implemented in the operation phase. During operation threat prevention, regular monitoring and routine maintenance as well as regular repair and rehabilitation are required.

As pipelines age, the operators have several new challenges to consider when required to operate beyond the design life such as:
• Time dependent degradation mechanisms such as corrosion and fatigue or third party damages.
• Changes in infrastructure from the as built, e.g. increased construction activity in the surroundings.
• Changes in operational conditions, e.g. increased production rates, tie-in to other pipeline system

Reassessment of the system based on available information, current industry practice and available technology should determine whether it is acceptable to extend the lifetime of pipeline system.

If the lifetime extension is not feasible (even after modifications are considered), decommissioning / abandonment of pipelines system should be planned and prepared.

A systematic and managed approach enables
• Improved pipeline availability due to reduced system and equipment failures.
• The potential to extend operations safely beyond original design life.
• Reduced maintenance cost due to regular monitoring and inspections. (See Fig.1)

Conclusion
A multi disciplinary approach towards plant integrity will result in operational excellence and extending the life of plant. A properly designed and constructed system carries out its intended function and can be maintained in a cost efficient manner.




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