2. Dr. Ir. Slameto Wiryolukito (slameto@material.itb.ac.id)
3. Muhammad Abduh ( abduh@reksolindo.co.id)
* Print Version Published in PetroEnergy Magazine Edition Nov-Des 2007
V. Operation and Maintenance
Operation variables (mechanical load, temperature, fluid chemical, contaminant, environment, etc) should be kept in control. Any uncontrolled variable could lead to unexpected material under-perform and un-anticipated damage growth. We should highlight corrosion and material defect as these are the biggest damage contributor, Figure 5.
Maintenance in objective of equipments and structures integrity should consider aspects as follows:
- Materials Capacity
The capacity of materials must be within its performance to withstand all designed service load, detain the growth of finger-print defect, and defend against corrosion and corrosion growth. Service load and finger print defect is designed within the design code, whilst in service damage is kept within defect codification.
- Control of Operation Variable
Operation variables should be controlled, any deviation can be unfavorable for material performance (service temperature, pressure, flow rate, erosive contaminants, CO2/H2S gas concentration). Uncontrolled abrasive contaminants can lead to erosion corrosion and uncontrolled H2S lead to SCC.
- Control of Defect and Damage
Any possible defect and damage should be under safety criterion. Crack propagation, fatigue, and corrosion growth should be under predictive in range of time, mechanical load, and temperature.
Figure 5. Pipeline Accident Records
Damage assessment is the most critical part of integrity management. Many operator companies perform fitness for service assessment during design or manufacture, but the most economic way the FFS should be performed in time during service. Defect management and standardizations effort in oil and gas industry can be summarized as follows:
a. Defect Codification.
A consensus between NACE, ILIA, and ASME together create defect information standard12 which categorized 25 threats as follow:
- Time Dependent (corrosion, SCC)
- Stable (manufacturing defect, welding defect)
- Time independent (weather related, vandalism)
An in-house standard by Shell13 offer more schematic defect information. (nomenclature, geometry definition, and information structure)
b. Defect Information Gathering
Recent progress in non destructive testing both inline (MFL, UT) and stand- alone NDT inspection (phased-array UT, TOFD UT, long range UT), aboveground inspection (ACVG, DCVG, Pearson, C-Scan) can be utilized for getting the best information of material defect
c. Defect Assessment
Many document has published to provide the industry the procedure to assess defect in equipment and structure. Some of them are fitness for service assessment (API 579 and BS 7910), structural integrity assessment procedure (SINTAP), and DNV-F101 for corrosion.
d. Data Integration
The opportunity to develop an integrated information system for more effective and efficient internal corporate communication should take the advantage of GIS data programming, intelligent pigging, and risk management policy14,15, Figure 6. The output for this system can be inspection plan, risk level information, and further direct assessment plan.
Figure 6. Screenshot of an application for GIS-Risk Assessment Data Integration
VI. Engineering Risk Management
To avoid defect from manufacture output nearly impossible, as well as to avoid the defect initiation during service. But defect or damage is controllable. Engineering risk management dealing with defect assessment, defect mapping/inspection.
A typical risk management process is shown in Figure 7.
Figure 7. Typical Risk Management Process
Method for defect assessment was long time defined by researcher in Battelle in 1979, and developed further for NG-18 Equation which then become the basis for assessment method in ASME B31G and modified B31G (RSTRENG). In England, in 1981 Researcher at The Welding Institute characterized the fracture behavior of welds containing defects by means of crack tip opening displacement (CTOD), leading to the development of BS PD6493 for the assessment of flaws in fusion welded structures. These documents then emerged to become widely used defect assessment guideline API 579 RP - Fitness for Service in United States and BS 7910 Guide on Methods for Assessing the Acceptability of Flaws in Fusion Welded Structures in England. From current available procedures and techniques in fitness for service assessment the most widely used are BS 7910, ASME B31.G, R6, and API 57916, Figure 8.
Industrial driver for Fitness for Service as engineering toolbox, which based on TWI Survey on 2001 are as follow:
- Determining the residual life of damaged plant;
- Ensuring safe operation beyond design life;
- Down-rating damaged plant below design;
- Demonstrating tolerance to defects within a safety case;
- Extending inspection intervals; and
- Reducing duration of outage and shutdown.
Figure 8. Most widely used FFS Procedures in Europe and United States(EU Fitnet Survey)
From many procedures of assessment, we can learn simple decision flow to choose which procedure is best fit. In 2002, sponsored by fifteen international oil and gas companies (Advantica Technologies, BP, CSM, DNV, EMC, Gas de France, Health and Safety Executive UK, MOL, Petrobras, PII, SNAM, Rate Gas, Shell Global Solution, Staoil, Toho Gas, and Total Finaelf) a protocol document named Pipeline Defect Assessment Manual (PDAM) has been published17, Figure 9. Featured guideline documents in PDAM are:
- DNV F-101 (for corrosion defect)
- Modified B31G/RSTRENG (for corrosion defect)
- BS 7910 (for defect related with welding)
- API 579 (corrosion/metal loss, mechanical dent/gouge, welding defect)
- Kiefner Equation NG-18 (corrosion. mechanical defect/dent/gouge)
- Schulze Global Collapse Solution (leak and rupture modes in circumferentially orientated stress)
- Leis PAFC (Pipe Axial Flaw Failure Criteria, for mechanical dent, gouge)
- Kastner Local Collapse Solution (circumferentially orientated manufacturing defect)
- The EPRG Guidelines on the Assessment of Defects in Transmission Pipeline Girth Welds
Recent development of FFS procedures demand require more guidance to estimate residual stress, material and thermal history, loading history, and NDE information reliability.
Failure Analysis – Don’t make mistake twice!
Many equipment fail even in strict company quality standard because there always a deviation from the initial assumptions. Failure analysis is recommended action when there is a failure occurs in order to find out the root cause and to give feedback to operation set-up and material procurement.
Figure 9. Flow of work for fitness for service assessment in Pipeline Defect Assessment Manual
Failure is likely to occur in high pressure system, summarized root causes of failure from HSE UK studies18 are as follows:
- Inadequate design and/or material for the loading and operating the environment;
- Incorrect and/or defective manufacture;
- Un-anticipated in service damage;
- System error in operation;
- Malfunction of instrument
- Human errors;
- External Event (fire, impacts, etc)
Conclusion
Engineering integrity is one fundamental element in corridor of integrity management in oil and gas industry. Engineering integrity should be considered as a system where one element affect the other. Engineering integrity as a system ranges from material selection and ,pre-service testing/commissioning, during operation and maintenance, defect/damage related risk management, to damage mitigation.
Development of engineering integrity needs multidisciplinary contribution of expertise in material and manufacturing process and process specialist incorporated with the advance technology from inspection companies. Best Practice for Risk Based Inspection as a Part of Plant Integrity Management, TWI and Royal & SunAlliance Engineering for the Health and Safety Executive UK, 2001.
Reference
1. Why Choose CRAs for Flowlines ?, Liane Smith, Belgian Welding Institute Paper 017, Belgium October 2007
2. Corrosion Protection and Cost Reduction by Using Reinforced Thermoplastic Pipe, Dr. Bert Dalmolen and John Newbert, Petromin Pipeliner Magazine Feb-May 2007, Malaysia
3. Control of Corrosion in Oil and Gas Production Tubing, Liane Smith, British Corrosion Journal Volume 34 Number 4, 1999, England
4. Brittle-Like Cracking In Plastic Pipe For Gas Service, Special Investigation Report, National Transportation Safety Board US, Washington, 1998
5. Optimising Stainless Steel Piping Fabrication Practice, Liane Smtih, North Scottish Branch of the Welding & Joining Society, Scotland, 2005
6. Smart Pig Fingerprint Inspections Can Lead To Fitness For Purpose Assessments And Contractial Disputes, Roland Palmer, Phil Hopkins, Popi Navis, Gordon Whintle, International Pipeline Conference, Canada, 2002
7. Pressure Vessel Corrosion Damage Assesment, Ian Partridge, John Wintle, Julian Speck, Inspectioneering Journal Volume 11 Issue #6 England, 2005
8 . Inspection Engineers Require New FFS Competencies: Illustrations From A Pressure
Vessel Failure Assessments And Failure Investigations, Julian Speck and Bridget Hayes, Inspectioneering Journal, England, 2005
9 .Practical Guidelines For The Fabrication Of Duplex Stainless Steels, International Molybdenum Association, 2001
10. Pipeline Accident Effects for Hazardous Liquid Pipelines, Joshua Greenfield, Ph.D, L.S, et.Al, US Department of Transportation, Research and Special Programs Administration Office of Pipeline Safety USA, 1996
11. Onshore Gas Pipeline Incidents in Western Europe in 1970-1997, European Gas Pipeline Incident Data Group, 1997
12. ASME B31.8S Managing System Integrity of Gas Pipelines, USA, 2001
13. Specifications And Requirements For Intelligent Pig Inspection Of Pipelines Version 3.2. Shell International Exploration and Production B.V, Netherland, 2005
14. Data Integration Ensures Integrity, World Pipelines, 2003
15. Multi-Pipeline Geographical Information System Based on High Accuracy Inertial Surverys, International Pipeline Conference, Calgary, 2000
16 .Survey of Current Application and Future Requirements for European Fitness-for-
Service Technology Technical Report, FITNET, European Fitness-for-service Network, C. Filiou, N. Taylor, P. Lejuste, R. Houghton European Commission Joint Research Centre – Institute for Energy, 2003
17. The Pipeline Defect Assessment Manual , COSHAM, A., HOPKINS,P., IPC02-27067,Proceedings of IPC 2002, International Pipeline Conference, American Society of Mechanical Engineers, Calgary, Alberta, Canada, 2002
18. Best Practice for Risk Based Inspection as a Part of Plant Integrity Management, TWI and Royal & SunAlliance Engineering for the Health and Safety Executive UK, 2001
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