NDE Requirements Of In-Service Inspection Codes

Size: px

Start display at page:

Download "NDE Requirements Of In-Service Inspection Codes"

Arleen Strickland
6 years ago
Views:

1 National Seminar & Exhibition on Non-Destructive Evaluation, NDE 2014, Pune, December 4-6, 2014 (NDE-India 2014) Vol.20 No.6 (June 2015) - The e-journal of Nondestructive Testing - ISSN NDE Requirements Of In-Service Inspection Codes Diwakar Joshi 1,a, Amit V. Deshpande 2,b, Hanuman Mane 3,c and Aditya Bhagwat 4,d 1, 2, 3,4 Insight Quality Services, Office No. 507/508, Siddharth Towers, Nr. Karishma Chowk, Kothrud , Pune, Maharashtra, India a diwakarj@gmail.com, b amit.deshpande@iqs-ndt.org, c hanuman.mane@iqs-ndt.org, d aditya.bhagwat@iqs-ndt.org Abstract Integrity assessment of ageing equipments becomes a very important aspect of remaining life calculations. The nondestructive evaluation techniques are playing an important role in in-service inspection. Non-destructive Examination (NDE) is the soul of in-service inspection. In-Service requirements for NDE are specified in different codes for pressure vessels (API 510), piping (API 570) and Storage tanks (API 653). Many methods and techniques of NDE are employed routinely. Codes specify the method of NDE. Visual testing is of great significance. In general, to cover detection of discontinuities throughout the cross section, surface and volumetric techniques are always specified. Some techniques have branched and evolved very well for in-service inspection for example, Ultrasonic testing of heat exchanger tube (bobbin probe), MFL of tank bottom. Many recently developed techniques, as compared to the classical techniques, have taken their place in codes, and are now used. In-service inspection requirements can vary. Methodology of inspection is service based. An industry may go for on-stream inspection rather than internal inspection. One may opt for risk based inspection which adopts a different methodology. Frequency of inspection is critical. Codes will provide recommendations on frequency. Personnel qualification requirement is strictly specified. Customer specified acceptance standards may be more stringent than those specified by code. Planning and executing NDE precisely is of importance. All such plans have to be time-based. Quality and completeness of NDE is of utmost importance. Results of in-service inspection are important and may lead to major decisions by the owner user. This paper is detailing the NDE methods applied for different equipments and evaluation / analysis methodology. Keywords: In-service inspection, Codes and their requirements, NDE and NDE methods, Methodology of inspection, Industry requirements, Owner/User, RBI Risk based Inspection, American Petroleum Institute (API)

2 Introduction Non-Destructive Examination (NDE) is widely used in in-service inspection; moreover NDE is the soul of in-service inspection. The word inspection spells out the following What is required? What is actual? What is the tolerance? Whether it is acceptable or not? And make a report. For finding out what is required, you must have knowledge to know the requirement. For knowing what is actual, you must have skill to measure the actual. Once you know actual values, you need to segregate them as Accepted or Rejected. This is the base for inspection. The Plant Inspections can be broadly divided as: 1) Inspection of new plant equipment and piping prior to placing them in service (during fabrication / installation) - i.e., to ascertain the fitness for proposed use 2) Periodic inspection of In-service plants - i.e., to ascertain the fitness for continued use Major Inspection Codes For Oil And Gas Industry Purpose Pressure Vessels Plant Piping Storage Tanks New Construction ASME Sec. VIII Div. 1 & 2 BPV Codes ASME B 31.3 API 650 In-Service Inspection API 510 API 570 API 653 Objective- New Construction Code V/S In-Service Code Inspection Codes for New Construction 1) Gives Rules for new construction using a) Right design b) Right material c) Right Manufacturing Process 2) Main Purpose is to find discontinuities arising during Design and Manufacturing Stage 3) Gives how to construct a vessel rightly before putting it into service In-Service Inspection Code 1) Focus is totally different. Does not give any rules of construction but gives methodology to deal with equipments put in service. 2) Main purpose is to find service-related degradations of Equipments (corrosion, erosion, fatigue, HIC, etc.) 3) Takes 3 R decisions based on results of NDT and Inspection: a) Run b) Repair c) Replace New construction equipments are inspected against drawing and specified requirements, whereas, the in-service inspection is carried out to assess the deterioration caused by different damage mechanisms and the status of equipment in comparison with the original status. The general damage mechanisms for pressure vessels, storage tanks and piping are listed in Table 1

3 Sr. No. Applicable Damage Mechanism Table 1 General Damage Mechanisms Prominent For Pressure Vessels, S torage Tanks And Piping [1] Pressure Vessels Piping Above Ground Storage Tank 1 Brittle Fracture 2 Thermal Fatigue Erosion/Erosion- Mechanical Failure Vibration- Induced Fatigue Galvanic Atmospheric Under Insulation (CUI) Cooling Water Boiler Water Condensate Microbiological Induced (MIC) - Applicable NDE Method [Note 1] Susceptible vessels should be inspected for pre-existing flaws/defects. No NDE Method applicable as it is a sudden failure. VT, MT, PT; SWUT for non-intrusive inspection of internal cracking; Specialized ultrasonic Techniques for heavy wall reactor internal attachment welds VT, UT, RT; IR Scans for refractory loss on stream PT, MT, SWUT for fatigue cracking; VT for small diameter piping - - VT, PT, MT - - VT, UT VT, UT Soil Caustic 14 Sulfidation - 15 Chloride Stress Cracking VT (Partial/Full Stripping); UT (Thickness); Real Time Profile X-ray (Small Pipe Boring); Neutron Backscatter Technique (Identify Wet Insulation); Deep Penetrating Eddy-Current Inspection; IR Thermography (Wet Insulation and Missing Insulation Under The Jacket); Guided Wave UT Ultrasonic Flow Meters (Check Flow Velocity); EC or IRIS Inspection of Tubes - WFMT (Deaerator cracking problems) - VT VT, Guided UT (Buried Or On-Grade Metallic Components) VT, UT thickness, UT, and RT UT thickness and Profile Radiography (Thinning) VT (Cracking); PT or Phase Analysis EC Technique; ECT; UT

4 (ClSCC) Fatigue - - Caustic Stress Cracking (Caustic Embrittlement) Hydrochloric Acid - Sour Water Sulphuric Acid Amine Stress - Cracking Wet H 2 S Damage (Blistering/HIC/ - SOHIC/SCC) High Temperature Hydrogen - Cracking (HTHA) [Note 1] VT Visual Testing RT Radiographic Testing UT Ultrasonic Testing PT Liquid Penetrant Testing MT Magnetic Particle Testing WFMT Wet Fluorescent Magnetic Particle Testing SWUT Shear Wave Ultrasonic Testing IR Infrared Testing ACFM Alternating Current Field Measurement UT and MT (Rotating Equipment); WFMT (Deaerators); UT/EMATS (Cycling Boiler) WFMT, EC, RT or ACFM (Cracks); AET (Crack Growth); UT including External SWUT (Crack Depth); No PT UT thickness or Profile Radiography (Thinning) UT thickness or Profile Radiography (Thinning) - - UT / RT VT, WFMT or ACFM Techniques; AET (Crack Growth); UT including External SWUT (Crack Depth) WFMT, EC, RT or ACFM (Cracks); AET (Crack Growth); UT including External SWUT (Crack Depth); No PT UT; VT; WFMT/RT (Advanced Stages Of Damage); AET Not Proven The application of the NDE Methods for different equipments is dependent on the type, location and orientation of the discontinuity and accessibility. The methods used for on-stream inspection and internal inspection may differ. A summary of the NDE carried out for pressure vessels, piping and tanks is described in Table 2

5 Table 2 Application of the widely used NDE Methods on Pressure Vessels, Piping and Above Ground Storage Tanks Sr. No. Component NDE Method Application Area / Extent (Acceptance Standard As Per Construction Code) 1 Pressure Vessel VT 1. External Inspection Ladders, Stairways, Platforms and Walkways 2. Foundation and Supports 3. Concrete foundation 4. Anchor Bolts 5. Concrete Supports 6. Steel Supports 7. Vessel Buckling and Bulging 8. Vessel Supports lugs 9. Fire-Proofing for support beams and guy wires 10. Grounding Connections 11. Auxiliary Equipments 12. Protective Coatings 13. External Supports 14. Soil 15. Leaks 16. Pitting 17. Cracking 18. Lamination 19.Blistering 20. Deformation 21. Metallic linings 22. Localised and uniform corrosion process side PT MT RT UT 1. Vessel Supports lugs 2. Nozzle Fillet Joints 3. External Supports (Fatigue Cracking) 1. Vessel Supports lugs 2. Nozzle Fillet Joints 3. External Supports (Fatigue Cracking) 4. Deaerator Cracking (WFMT) 1. Profile Radiography for Insulated Small Bore Pipes 2. Repair Welds 1. Thickness Measurement (High temperature probes for on-stream) 2. Anchor Bolts, if required 3. Thickness gauging for steel supports 4. Shear Wave for Vessel Supports Areas of concern The two eyes are not sufficient for visual inspection. A trained brain behind the two eyes will do this. The experienced inspector can see through the material and analyse the situation Right procedure, technique and equipments are essential Right procedure, technique and equipments are essential Interpretation API QUTE qualification is becoming popular for onstream

6 lugs 5. Nozzle Fillet Joints 6. Lamination 7. Erosion 8. Metallic Linings 9. Repair Weld ET 1. Heat Exchanger Tubes Thinning Baffle areas critical Miscellaneous 1. Neutron Backscatter for CUI 2. Metallic Lining Spark Test 3. Metallography (Replication) 4. Hammer Testing 2 Piping VT 1. Vibrating Piping 2.Internal Visual Inspection for Big Piping 3. External Visual Inspection For misalignment, vibrations and leakage 4. CUI 5. Valves 6. Flange Joints 7. Buried Pipes Holiday Survey 8. Hammer Testing PT 1. Surface Cracks 2. Pin Holes Experience required Experienced inspector is a must Procedure MT 1. Surface Cracks Procedure RT 1. CUI by Profile Radiography 2. Injection Point 3. Repair Welds UT 1. Thickness Measurement 2. CUI 3. Injection Point 4. CML Monitoring 5. Long Range UT 6. Shear Wave UT For ID Breaking Flaws 7. Repair Weld 8. Long Range UT Miscellaneous 1. AC Flux Leakage for surface breaking flaws 2. Replication for metallurgical changes 3. Leak Testing 4. PMI 5. Neutron Backscatter for CUI Qualified NDT operator Specialised Technique Special Training 3 Above Ground Storage Vessel VT 1. Welds 2. Cavities 3. Inside surfaces 4. Bottom to shell welds Experienced person

7 PT 1. Welds 2. Cavities 3. Back gouged surface of root pass (shell thickness > 1 in.) MT 1. Welds 2. Cavities 3. Back gouged surface of root pass (shell thickness > 1 in.) RT 1. Welds Vertical / Horizontal UT 1. Welds Vertical / Horizontal Miscellaneous A. Vacuum Box Testing for 1. Welds 2. Bottom plate leak paths B. Tracer Gas Testing for 1. New bottom welds, unless vacuum box tested C. Diesel Oil Test for 1. First pass of new shell-tobottom welds and final pass of new shell-to-bottom welds unless vacuum box tested 2. Floating roof deck seams and other joints required to be light/vapour tight D. Air Leak Testing 1. Welds 2. First pass of shell-tobottom welds and final pass of shell-to-bottom welds unless vacuum box tested E. Low Frequency ECT Procedure Procedure Technique Technique Experienced operator is a must As compared to the new equipments, the difficulties faced in in-service inspection are equipment specific, viz., high temperature, equipment accessibility, etc. Therefore, in-service inspection by NDE demands more knowledge and understanding for application of NDE. Calibrated machines, correct procedure and qualified personnel are the basic requisites for any NDE and in-service inspection is not an exception for that. Quality and completeness of NDE is of utmost importance. Generally, all the in-service inspection codes are referring the acceptance standard from the original construction codes. The procedures for NDE are in-line with original construction codes and in-turn it refers to ASME Section V. However, as the situation in which these NDE Techniques are to be employed, being different, one has to take special precautions while doing in-service NDE. High temperature probes are a common requirement. Alternatively, the temperature correction factor can be used. API is specifying special qualification Industry Qualified UT Shear Wave

8 Examination for inside surface breaking flaws detection. A lot of relevant information can be obtained from API website TOFD and PA are also used in some specific cases. High magnification boroscopes and fibrescopes are in use now. However, standard workmanship samples shall be used to avoid overrating the discontinuities. Measurement devices are available with these equipments. PT and MT are common techniques in in-service inspection. However, sulphur and chlorine content control for the chemicals used on Austenitic Stainless Steels, Titanium and Nickel become very important. Also, comparators shall be sued for sensitivity control. Calibration of MT equipments, lux meter calibration and maintaining light requirements on job is critical. radiographic technique is primary requirement; however, is a common problem too. We have to keep in mind that we need an OK joint and not an OK radiograph. On-site radiation safety is very important. Digital radiography is making its own place. In Eddy Current Testing, calibration with properly machined standard tube is very important to simulate the actual situation. Cleaning of the tubes is very important. Finally, it is worth mentioning that when NDE is carried out by service agencies, the competence of service agency needs to be established. The following ASTM standards are very useful for this purpose 1. E Standard Practice for Establishment and Maintenance of Quality Control Systems for Non-Destructive Testing Agencies 2. E Surveying Non-Destructive Testing Agencies Conclusion If we apply in-service inspection techniques intelligently and effectively, and if we ensure that NDE is carried out completely and correctly, the assessment of remaining life becomes more accurate. Hence, one has to understand the NDE requirements and methodology in a greater detail. Generally, in in-service inspection, we are focusing on the smallest discontinuity we can detect. However, we shall also think of the biggest discontinuity we can miss. This is an essential philosophy to end with a safe and reliable operation. References [1] API Damage Mechanisms Affecting Fixed Equipments in the Refining Industry

BODY OF KNOWLEDGE API-653 ABOVEGROUND STORAGE TANK INSPECTOR CERTIFICATION EXAMINATION

BODY OF KNOWLEDGE API-653 ABOVEGROUND STORAGE TANK INSPECTOR CERTIFICATION EXAMINATION October 2009 (Replaces November 2008) API Authorized Aboveground Storage Tank Inspectors must have a broad knowledge