RECENT ULTRASONIC TESTING TECHNOLOGY DEVELOPMENTS IN DOOSAN BABCOCK

Transcription

1 RECENT ULTRASONIC TESTING TECHNOLOGY DEVELOPMENTS IN DOOSAN BABCOCK Qualification of new techniques Colin Bird Consultant, NDT Department

2 Paper Objectives Demonstrate how new inspection technologies can improve plant efficiency by reducing down time. Show that new technologies can be introduced where there are no appropriate standards. Demonstrate the challenge and some solutions to novel technique qualification via two case studies.

3 Small Bore Pipe Inspection and Qualification Drivers for Change Cost Reduction Phased Array Technique 30 welds per shift per team Radiography 15 welds per shift per team. PA team 2 operators per team, Radiography 4 man team. Outage Time Reduction No radiographic exclusion zones. Multiple phased array teams Work in parallel with welding teams Proven outage time compression of 10% to 30%. Safety Improvement No radiographic hazard. 11 to 13mm gap between tubes

4 Small Bore Pipe InspectionTechnique Inspection Technique Pipe Diameters 25mm to 90mm diameter Wall Thickness 3mm to 12mm Material Currently ferritic tubing Developing austenitic capability Focused Phased Array Probes 10MHz 32 element Scanner Bi direction bracelet scanner

5 Inspection Standards 1995 ASME Code case 2235 Subject to proving trials Codes require detection of pores, worm holes, slag and planar flaws. Why! UT is inherently less sensitive to pores than radiography. Radiography is less sensitive to planar flaws. Planar flaws cause catastrophic failure pores may leak if the pipe becomes thin due to corrosion or erosion. Do we require manufacturing QA or Fitness for service.

6 Small Bore Pipe Inspection Technique High inspection sensitivity to detect small pores requires a flaw discrimination method. 3.9mm 3.1mm 2.8mm 6dB drop off sizing for smooth planar defects Maximum amplitude sizing for echodynamic pattern 1 3 and 4 defect responses. 14 September

7 Inspection Development Doosan commenced development in 2009 in collaboration with RWE. Comprehensive practical trials Range of representative samples containing about 70 real defects*. Tube butt welds 4-9mm thick. Theoretical coverage modelling Live qualification dossier. 14 September

8 Inspection Qualification GENSIP (2014) (Generator Safety Improvement Program) Consortium of UK power generators plus China Light & Power. EDF France (2014) Qualification via ENIQ process. Technical Justification involving defect detection modelling and trials.

9 Inspection Qualification - Modelling Comparison of amplitude with small variations in target position

10 GENSIP Qualification Trials Collaborative Trial administered by E.ON. 10 companies performed blind trials using phased array UT techniques. 50 welds 10 flaw types 90 flaws 2 Days to complete trial including reporting Radiography used as a control under open trial conditions. 14 September

11 GENSIP Qualification Trial Results Doosan Babcock Radiography 14 September

12 Conclusions from GENSIP Qualification Trials Training of the inspection personnel with the procedure is necessary. Reliability is not achieved by solely procuring the correct equipment. There are weaknesses in radiography and phased array UT but the weaknesses in phased array UT can be mitigated with training. 14 September

13 HDPE Pipe Inspection and Qualification Drivers for HDPE Pipe Usage and Inspection Corrosion resistance Longer life Less time lost due to maintenance programmes Erosion resistance Longer life Lower coefficient of friction Smaller diameter for a given flow rate but usually lower operating pressures. Weld fusion line. Weld flash. Location of defects.

14 HDPE Pipe Inspection and Qualification Inspection Technique Top and bottom arcs from planar defect Pipe bore weld flash

15 HDPE Pipe Inspection Drivers and Hurdles for Usage Drivers Corrosion resistance Longer life Less time lost due to maintenance programmes Erosion resistance Longer life Lower coefficient of friction Hurdles Smaller diameter for a given flow rate but usually lower operating pressures. No defect acceptance standards No volumetric inspection standards Weld fusion line. Weld flash. Location of defects.

16 HDPE Pipe Inspection Qualification No standards Zero tolerance agreed with EDF Test Piece Manufacture Simulating LOF Implanting ultrasonic targets Back fill? Within welding process? Target material Stainless steel chosen Target location and accuracy Location confirmation with x-ray Target Shape w.r.t. inspection method Target shape, round, linear, oval Undergoing Independent Qualification

17 HDPE Pipe Inspection Application Experience Pipes from 350mm diameter to 1200mm diameter Pipe thickness from 35mm to 68mm Single sided inspection Temperature range 5 to 40 C Procedure Adapted to accommodate variable site temperature and conditions. Proven from many pipe system inspections.

18 Conclusions Robustly qualified, ultrasonic inspection techniques, applied in lieu of radiography, can add value to utility power companies. Small Bore pipe inspection and HDPE pipe inspections techniques have been developed to a point where they can be applied to plant in highly regulated environments. To demonstrate that newly developed inspection techniques are reliable extensive trials need to be performed under blind and semi-blind conditions to the satisfaction of the utilities and their third party inspection bodies. Extreme care must be taken when designing technique trials for new situations and materials to ensure that a meaningful result is achieved.

19 Thin Wall Stainless Steel Pipe Inspection Stainless Steel Compressive stress Decrease ultrasonic reflection Variable ultrasonic reflection One sided access Spigot Customer Requirement 100% defect detection Sizing accuracy ± 0.25mm 98% confidence Mean remaining ligament for weld Tight defect tip WCNDT

20 Thin Wall Stainless Steel Defect Sizing WCNDT Accuracy of defect sizing - Crack tip and root response positioning - Not amplitude based - pattern analysis -

21 Stainless Steel Grain Structure Weld root Grain back scattered energy Assurance of defect detection - Not amplitude based - Detection of weld volume - Very high inspection sensitivity WCNDT