Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Development of NDT Inspection Techniques For Heavy Wall Stainless Steel Piping Presented by: Larry Bartley - Canspec Group Inc. Plant Services Coordinator Presented to National Pressure Equipment Conference February 9 – 11, 2005

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Acknowledgements Brian Beresford Canspec Group Inc. David Mackintosh Canspec Group Inc. Wayne Smith Oxy Vinyls, Canada Hang Zheng Canspec Group Inc. Gary Kroner Carbon Steel Inspection

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Overview Introduction Detection method Probe development Test standard Inspection of the test pipes Analysis technique Conclusions

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Introduction Canspec developed a nondestructive examination method for SA-312 TP 316L SS pipes: –NPS 3 in. diameter (0.121 in. wall thickness) and –NPS 6 in. diameter (0.146 in. wall thickness). Examine pipes while in operation Pipes in horizontal position Pipes had been used to carry liquid vinyl chloride monomer (VCM) at 150 psig and approximately 17  C since Pipes were known to have corrosion pits on the internal surface.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Corrosion mechanism Water condensates containing chlorides tended to gather at the bottom of the pipe, causing pitting on the internal surface. Inside the pits, water and high concentrations of chloride ions collected. Corrosion rate inside pits increased, eventually caused a large cavity inside the pipe wall.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Sample NPS 3 in. diameter test piece

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Choice of NDE Method Factors in decision: material, size of pipes, type of defects Eddy current was considered to be the best choice. Eddy current has good sensitivity to corrosion pits on the pipe internal surface while scanning from the outside. Eddy current allows a fast and efficient inspection of the pipes while the plant is in operation.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Probe Development Probe consisted of a differential coil embedded in a hand-held housing. Two stainless steel bars maintained constant clearance between the coils and the pipe surface and provided wear resistance Probe is hand-held for easy scanning along the pipe surface.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Test Standard A section of the test pipe (NPS 3 in.) was longitudinally split in half and one half was made to be a test standard piece. Defects: four 3 / 64 in. (0.047 in.) diameter drilled holes of depths 100%, 75%, 50% and 20% wall. Natural corrosion pit about 0.05 in. diameter, in. deep (26% wall loss) Tests indicated good sensitivity to the shallowest hole (20% wall loss). The calibrated test system could detect and size the natural pit.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis View of Test Standard

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Permeability variation A simulated permeability variation was also added to the test standard piece. Objective: to set the system to differentiate irrelevant indications due to permeability variations.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Inspection Results — Flaws detected: 1)Through-wall pinhole 2)Inside diameter indication, 90% wall-loss pit. 3)Inside diameter indication, 20% wall-loss pit. (All above defects located at the bottom of the pipe.)

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Eddy Current Data from the 90% pit

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Visual Verification Pipe was longitudinally split in half, and internal surface was cleaned by wire brush. Small diameter pits could be seen at locations predicted by eddy current examination.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Results from the Pit Called at 90% Metallographic examination revealed a 1 mm diameter opening on the pipe internal surface. Inside the pipe wall, the pit broadened to an area of 3.5 × 5 mm. Wall loss was physically measured to be 90%.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis View of the 90% pit from the internal surface

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Scanning electron microscope (SEM) image of the cross section of the 90% pit.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Scanning electron microscope (SEM) image of the 90% pit.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Diameter 0.04 in., depth in. (17% wall loss). Results verified that the system met the required sensitivity to 25% wall loss. Results from the Shallow Pit

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Inspection of the Test Pipes (cont’d) The second indication was a 0.04 in. diameter, in. deep pit which accounted for a 17% wall loss. More importantly, the system could detect a pit where the wall loss was as small as 17%, which met the required 25% wall loss criteria. View of the 20% pit from the internal surface

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Analysis Technique An inspection and analysis procedure was developed specifically for the pipes to be inspected. The procedure detailed the equipment required, the calibration standard, the operation parameters and procedure. Methods of identifying irrelevant indications were specifically addressed. Data Analysis

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Analysis Technique (Cont’d) ASME standard 100% 60% 20%

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Analysis Technique (Cont’d) Permeability Mix 100% Standard Perm Test Pipe

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Analysis Technique (Cont’d) Defect in test pipe 17% wall loss

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Continued NDE Inspection of another NPS 3 in.-diameter pipe in the plant showed an indication different from pit- like indication. Subsequent metallographic examination of this area revealed longitudinally-oriented crack-like defects associated with corrosion. The defects were up in. deep inside the pipe, which accounted for a 20% wall loss.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Analysis Technique (cont’d)

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Conclusions  Pitting was caused by chloride corrosion as a result of moisture in the liquid VCM in the pipe.  The wall loss measured from the cross section of the pit was 90%, which confirmed the eddy current inspection results.  The inspection system can detect pits larger than 20% wall loss, which meets the 25% wall loss criteria required by the customer.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Conclusions  The system can give a reasonably good estimation of the amount of wall loss and the size of a pit within its resolution ranges.  The system can also detect crack-like defects associated with corrosion.  The system has the ability to eliminate false indications caused by permeability variations.

Engineering NDT Advanced NDE Pressure Equipment Integrity Management Lab Analysis Thank You (