NDT.net • Oct 2004 • Vol. 9 No.10

Recent Applications of Phased Array Inspection for Turbine Components and Welded Structures

P. Ciorau, D. Macgillivray, R. Hanson
Inspection and Maintenance Services - Ontario Power Generation Pickering, CANADA

Corresponding Author Contact:
Petru Ciorau, Email: peter.ciorau@opg.com


Abstract

The paper presents recent development and field applications of phased array technology for the following turbine components [low-pressure rotors]: ABB - GEC : rotor steeple, welded rotor, blade roots of 900 MW and 160 MW turbines; Siemens - Parson : rotor steeple, blade roots, disk bore, anti-rotating hole, for 580 MW turbines (nuclear and thermal design); GE : rotor disk rim attachment of 850 MW turbine and Westinghouse: blade roots of 1,250 MW turbine. Capability demonstration on EDM notches, service-induced cracks and "crack-like" 3-D EDM notches for different items is also discussed. The lab results contributed to a reliable detection and sizing capability for in-situ inspection. Practical aspects of field inspection are illustrated and commented. The paper also presents some examples of weld inspection of SG manway welds and pipe welds [lab samples], as an extension of phased array technology in weld inspection domain.

Introduction

Inspection and Maintenance Services - Ontario Power Generation [ISD-OPG], develop together with RD Tech and Imasonic phased array systems, scanners and a large variety of probes for in-situ manual and automatic examination of ABB/GEC Alstom low pressure turbine components (rotor steeple grooves and blade roots). Progressive results of this 5-year project were reported and published in (1-6). Field commissioning and new developments for turbine and weld inspection will be presented in the present paper. The following topics will be presented:
  • Field inspection of ABB/GEC Alstom turbine of 900 MW at Darlington Nuclear Station
  • Extension of manual phased array inspection to smaller ABB turbine for both steeple and blade root.
  • Practical aspects of phased array inspection of GE turbine of 850 MW, disk rim attachments
  • Recent application, including capability demo for Parson/Siemens turbine components of 580 MW
  • Examples of phased array inspection for defect assessment of welded rotor and boiler manway
  • ISD-OPG recent inspection of Westinghouse blade roots of 1,250 MW turbine
  • Other applications and projects to extend the phased array technology to pressure boundary components.

Field application on ABB/GEC Alstom Turbines

The first inspection with six systems and data analysis under network in real-time took place in May 2001 on unit 2. More than 700 objects were inspected in 7,500+ locations. Data management was based on spread sheets, and the analysis team was located near the turbine. Analysis layouts with Tomoview 1.4R6 were not customized, and the results were behind by 3 days (see Table 1). Field activities are presented in Figure 1and Figure 2. Starting 2002, data management was developed, including an automatic d-base for both acquisition and analysis. As a result, the analysis results were closer to acquisition time. A major crack was detected and repaired on L-0 steeple-hook 1 (see Figure 3). Some fretting on L-0 Blades were detected and sized (see Figure 4). In April 2003, on D4 inspection, ISD used some innovative features which reduced the inspection time by 1.5 day for acquisition and by 2 days for analysis:
  • used Tomoview 2.2R9 and TOMO III PA
  • use OMNISCAN portable PA - battery operated (see Table 2 and Figure 5)
  • use next-generation mock-ups and blocks (simplified)
  • use special layouts for analysis
  • use eddy current data transmission line T1 for remote data analysis of UT phased array files.
  • automatic d-base based on priorities and number of scans

Fig. 1: Field activities of PA inspection on ABB 900-MW turbine, LP2 - Darlington NGS in May 2001.

Fig. 2: Calibration and field inspection with 4-head L-1 steeple scanner.

Fig. 3: Detection of a SCC on hook 1 concave - L-0 steeple (a) and steeple after repair (b).

Table 1: Acquisition and Analysis Performance during 2001-2003 inspections.
Year / Unit Acquisition Crew Acquisition Time [days] Analysis Crew Analysis Time [days]
2001 - D 2 8 8 6 11
2002 - D 3 8 7 4 9
2003 - D 4 8 5.5 4 7

A comparison between 2001 and 2003 manual inspection on L-0 steeple outlet ends is presented in Figure 5.

Fig. 4: L-0 Blade with a linear defect on platform. Defect length = 30 mm; defect height = 0.8 mm.

Fig. 5: Manual phased array on L-0 steeple, outlet side: a) Focus 32/32 -2001; b) OMNISCAN 16/16 - 2003.

Table 2: Hardware/software used in three inspection campaigns from 2001-2003.
Year Hardware Software
2001 3 Focus 32/128
3 Focus 32/32
Tomoview 1.4R6
2002 1 TOMO III 32/128
2 Focus 32/128
3 Focus 32/32
Tomoview 2.1 R7
Tomoview 1.4R9
2003 2 TOMO III (1 Focus 32/128)
1 FOCUS 32/128
3 OMNISCAN 16/16
Tomoview 2.2R9
Tomoview 1.4R9

IMS developed in-situ manual phased array procedures for L-0 steeple and L-0 blades of a smaller ABB/GEC Alstom turbine of 380 MW (2 LPs/unit), for OPG Thermal Branch at Thunder Bay TGS (see Figure 6). Validation of the PA set-ups was performed on small EDM notches 3 x 0.5 mm and 3 x 1 mm placed in ground-outs and machine marks. An analysis pattern was validated. PA inspection was confirmed by pulling out random blades and inspect (video probe and MP) the steeple surface. No false calls or missing cracks were found.

Fig. 6: Phased array inspection of ABB 190 MW low pressure turbine- L-0 steeple. a) ground outs and mechanical marks; b) encoded scanning - feasibility study ; c) reverse engineering of L-0 steeple; d) UT data

Phased Array Inspection on Disk Rim Attachments - GE Turbine

IMS validated the procedure on EPRI samples and mock-up, on blocks with EDM notches 10x 0.5 mm, 6 x 1.5 mm, 10 x 3 mm, "pits" of 0.5 mm and by analyzing field data during inspections on 7 rotors. The GE turbine of 850-MW was inspected since 1999. The main features of this inspection are presented in Table 3. The inspection principle is presented in Figure 7.

Table 3: Phased array inspection of disk rim attachments ; Main features
  • ISD procedure for 5 (five) disks1999; field 1999-2003 [8 rotors]
  • Validation on EPRI disk blocks #3 and #4
  • Improved on EPRI mock-up and ISD blocks- June 2000
  • In-house built manipulator - DOLLY
  • Double-probe, one disk / file - 6 hooks
  • 2 days inspection of 10 disks; 1 file/disk [360 Mbytes]
  • Advanced sizing, including ray tracing and CIVA

Detection and sizing of SCC with a skip was validated by ray tracing model Imagine 3D (see Figure 8). Field inspection for detection and sizing with DOLLY manipulator is illustrated in Figure 9. Examples of phased array data on linear defects are presented in Figure 10.

Fig. 7: Principle of phased array inspection of disk rim attachments with double-probe (a) and UT data( b)

Fig. 8: SCC detection and confirmation with a skip technique (a) and Ray tracing on disk #4 (b).

Fig. 9: Field inspection for detection on disk 4 (a) and sizing with a single arm and X-Y manipulator (b).

Fig. 10: SCC detection and sizing with advanced set-up and X-Y single-probe manipulator.

Phased Array Inspection on Parson/Siemens Turbine Components

Feasibility study of PA on L-1 blade - Parson turbine of 580 MW - Thermal was performed in May 1999. Field inspection was done in July 2001, for Pickering 580 MW turbine. A history of this project is presented in Table 4.

Table 4: Phased Array Inspection on Parson/Siemens Turbine Components
  • Feasibility study for L-1 blade roots - Nanticoke - May 1999
  • Capability demo for row 9 and row 10 blades and rotor steeple July 2001
  • In-situ inspection - 1 rotor: August 2001
  • In-situ inspection - 2 rotors : March 2002; disk bore + peg holes
  • In-situ inspection - 2 rotors (cracks) - May 2002
  • In-situ inspection - 1 rotor - July 2002
  • Forced-outage inspection (outlet row 10 blades): 6 rotors [Oct. 2002-Feb.2003]

Field inspection was developed, commissioned and applied for the following components (see Figure 11 and 12): L-0 steeple, L-1 steeple, L-0 blade, L-1 blade, disk bore and peg holes (anti-rotating). DOLLY Manipulator was used for a single probe option, in very narrow spaces between the disks. Probe #26,# 27, #30, #34, 35 and #37 were designed by IMS and manufactured by Imasonic. The are capable to accommodate curved surfaces and narrow space between blades and disks.

Fig. 11: Parson/Siemens Turbine components: top - row 10 and row 9 mock-up; bottom; DOLLY manipulator for disk bore/peg hole inspection.

Fig. 12: Phased array field inspection on Siemens/Parson low-pressure turbine components: left: manual PA on blade roots and steeples; right: automatic inspection on disk bore/peg holes with DOLLY.

Validation of PA techniques was performed on mock-ups and freestanding blades, disks, rotor steeple blocks. An example of complex mock-up, capable to replicate the disk geometry and clearance is presented in Figure 13.

Fig. 13: Reverse engineering of Parson/Siemens rotor disks (right) and multi-purpose mock-up (left).

Reverse engineering (8) was applied to machine crack-like EDM notches in retire-from-service blades (see Figure 14). The UT results on cracks and 3-D EDM notches are illustrated in Figure 15.

Fig. 14: Complex 3-D notches developed by reverse engineering the cracks in the blades (8).

Fig. 15: UT PA results on cracks - Row 10 Blades hook 1.

Phased Array Inspection on Westinghouse Turbine Blades

IMS was asked by South Texas Project to perform on short notice an in-situ inspection of L-0 blades - outlet face platform only, for Westinghouse turbine of 1,250 MW. Procedure validation was done on very small elliptical EDM notches of 3x0.5 and 3 x 1 mm. A blade with real crack of 4 mm length was used to confirm the detection and sizing capability. Ray tracing and reverse engineering were used to justify the set-up, to plot the UT data into the specimen and for analysis / simulation of inverse problem (see Figure 16). Three rotors were inspected 100% with 3 phased array probes within 5-day window. More blades with cracks starting 3-5 mm from outlet face were detected and pooled out from one rotor.

Fig. 16: Detection and simulation of 3 x 1 mm target on L-0 Blade - Westinghouse turbine.

Phased Array Inspection of Welds and Other Applications

Phased Array was applied to inspect the welded rotor at Darlington NGS (see Figure 17). The weld defect was an intermittent lack of fusion between the runs with a vertical extent of 1.5 mm and a ligament of 8 mm. ISD data were incorporated into ABB Baden report, and the rotor was returned back to service.

Fig. 17: Detection and sizing of LOF on narrow-gap welded rotor; Probe #5, UT path = 190 mm.

Another inspection was performed on manway boiler welds to evaluate the defect nature called by UT mono-crystal inspection. The defect was an intermittent lack of fusion and the weld was not repaired (see Figure 18).

Fig. 18: Defect confirmation with probe #9 -T-waves for manway welds .

Other activities related to phased array technology are listed in Table 5.

Table 5: Phased Array Activities within IMS
  • Reverse Engineering [paper (8)]
  • Probe Development / Performance Assessment [paper (9)]
  • Commissioning of portable OMNISCAN [paper (10)]
  • Expand PA technology to CANDU pressure boundary
  • Feasibility Studies [SG, feeders, PDI]
  • Validation of Simulation Packages [CIVA, Imagine 3D]
  • EPRI SRA (HIP, PDI, turbine, SG), international activities

Conclusions

The recent developments in phased array technology for turbine components and weld inspection concluded the following:
  • IMS has a field capability to inspect in-situ the ABB and Parson turbine for rotor grooves and blade roots cracking; GE disk rim attachments are also included in the inspection capability and fieldwork.
  • Validation of PA techniques was performed on very small elliptical EDM notches, on crack-like EDM notches and confirmed on service-induced cracks (fatigue and SCC).
  • The new portable OMNISCAN machines improved the productivity with no compromise on detection and sizing (see paper 10 for details)
  • Reverse engineering of new blades, such as Westinghouse, is performed within one week. The file is integrated into ray tracing simulation and Tomoview specimen (see more details in paper 8).
  • The largest field job performed at Darlington NGS proved the phased array in-situ inspection is a reliable tool, capable to handle data analysis remotely and in real-time.
  • Weld inspection program is at the beginning within IMS-OPG, but will be implemented in the coming future.
  • IMS experience in phased array technology for turbine components (almost 8 years) will be transferred to other domains, such primary circuits welds, feeder thinning and cracking, SG tubes - CANDU size, in-service inspection based on station request ( outlet feeder pipe welds, pressurizer , Al welds ).
  • IMS-OPG is pursuing the standardization of probes, machines and system performance checking;
  • IMS technicians and contractors exposed to phased array technology demonstrated the capability to handle complex set-ups, detect and size small defects, reliable analysis and a very good productivity.
  • Simulation packages must be updated to handle IMS-OPG inspection scenarios. Validation of these packages will be considered in the near future.

Acknowledgements

The authors wish to thank the following organizations and people:
  • OPG Darlington Nuclear
  • OPG Pickering Nuclear
  • OPG Bruce B Nuclear [1999-2000]
  • Bruce Power [2001-2003]
  • OPG Thermal Branch [Nanticoke NGS, Thunder Bay NGS]
  • South Texas Project - USA
  • OPG - ISD Management [Neil Allen and Tim Dobson]
for funding PA technology projects and granting the publication of this paper.

References:

    1. A. Lamarre, N. Dubé, P. Ciorau: " Feasibility study of ultrasonic inspection using phased array of ABB L-0 blade root" 5-th EPRI Workshop Steam Turbine and Generator-July 1997-Florida, USA [ Workshop ]
    2. P. Ciorau, et.al." Feasibility study of ultrasonic inspection using phased array of turbine root and rotor steeple grooves-part 2" 1-st EPRI Phased Array Seminar-Portland, USA, Sept. 1998 [ Workshop ].
    3. P. Ciorau, et.al. " In-situ examination of ABB L-0 blade roots and rotor steeple of low pressure steam turbine, using phased array technology" 6-th EPRI Workshop Steam Turbine and Generator-Aug. 1999, St.-Louis-USA [ Workshop ].
    4. P. Ciorau, D. Macgillivray " Phased array ultrasonic examination of GE disk rim-capability demonstration and field application" 2-nd EPRI Phased Array Seminar-Montreal-Canada, Aug. 2001[ Workshop ].
    5. D. Mair, et.al. "Ultrasonic simulation - Imagine3D and SimScan: tools to solve the inverse problem for complex turbine components" Proc. Conf. 26-th QENDE Annual Review of Progress- Montreal, Canada, July 1999[ Conference ]
    6. P. Ciorau, et.al. " In-situ examination of turbine components using phased array technology" -CANDU Maintenance Conf.-Toronto, Canada, Nov. 2000 [ Conference ]
    7. J. Poguet, P. Ciorau: "Special linear array probes used for ultrasonic examination of complex turbine components" 3-rd EPRI Int. Conference in Nuclear Ind., Seville, Spain Nov. 2001 [ Conference ].
    8. P. Ciorau, et. al: "Advanced 3D tools used in reverse engineering and ray tracing simulation of phased array inspection of turbine components with complex geometry" 3-rd EPRI PA Seminar, Seattle, USA, June 2003 [ Workshop ]
    9. J. Poguet, P. Ciorau:" Reproducibility and reliability of NDT phased array probes" 3-rd EPRI PA Seminar, Seattle, USA, June 2003 [ Workshop ]
    10. P. Langlois, P. Ciorau, D. Macgillivray: "Technical assessment and field application of portable 16-pulser phased array instrument", 3-rd EPRI PA Seminar, Seattle, USA, June 2003 [ Workshop ]

© NDT.net |Top|