qualification of rcp flywheel keyway inspection according ... · inspection qualification iii...

Inspection Qualification III

Qualification of RCP Flywheel Keyway Inspection According to ENIQ F. Mohr, G. Guse, intelligeNDT System & Services, Germany

INTRODUCTION New reactor designs are being built using state-of-the-art material, fabrication, and design practice

On each new reactor a base line inspection has to be performed after completion of installation. Each component has to be inspected in defined intervals. But before the first inspection on-site starts, the technique has to be demonstrated and qualified. Due to the new design there are some components in the EPR which were never inspected before and there is also no experience from older plant designs. Therefore new inspection procedures have to be developed and in some cases the new techniques must be developed from the scratch.

Correspondingly, new inspection techniques must be qualified to fulfill country specific codes and qualification procedures. For EU plants, the ENIQ mythology is normally applied

An example for such a development including qualification according the ENIQ procedure from scratch, is the ultrasonic inspection technique for the keyway inspection at the flywheel of the reactor cooling pump for the EPR in Olkilouto / Finnland.

INSPECTION TARGET The flywheel of the RCP reactor cooling pump in AREVA reactor type EPR is position on top of the pump.

(Figure 1) The dimension of the flywheel is 1850mm diameter and 394mm in thickness. So we are talking about a large and heavy disc. The disc has a centre hole of ~290mm in diameter for the pump shaft. To ensure the connection shaft to flywheel 3 keyways are located in the inner diameter of the centre whole. Due to stress calculations this keyways have to be inspected during the base line inspection but also afterwards during the regular inspection outages.

Reactor Cooling Pump

Flywheelside view

Flywheeltop view

Ø i.D.~ 290mmØ i.D.

~ 90mmØ i.D.

~ 90mm

Ø i.D.~ 290mm

Inspection areas

keyways

Reactor Cooling Pump

Flywheelside view

Flywheeltop view

Flywheelside view

Flywheeltop view

Ø i.D.~ 290mmØ i.D.

~ 90mmØ i.D.

~ 90mm

Ø i.D.~ 290mm

Inspection areas

keyways

Figure 1 Flywheelof RCP in AREVA EPR

The ENIQ mythology requires a technical justification which includes the definition of the inspection target. The size of the minimal detectable defect is based by the design simulation of a critical defect. The values are listed in Figure 2

R8

4 mm

Tilt = 10°

9 mm

4 mm

MINIMUM VOLUME

VOLUME OF EXAMINATIONCircumferential reference positioning axis

10 mm

10 mm

21,2 mm

The inspection volume is fixed by the size of the inspection target in TWE (through wall extent) which is 4mm.

The access is limited by size and position of the inspection holes. ( 90mm diameter and ~390 mm length).

The geometry of the flywheel demands a variation of angle of incidence to cover all defect orientations.

R8

4 mm

Tilt = 10°

9 mm

4 mm

MINIMUM VOLUME

VOLUME OF EXAMINATIONCircumferential reference positioning axis

10 mm

10 mm

21,2 mm

The inspection volume is fixed by the size of the inspection target in TWE (through wall extent) which is 4mm.

The access is limited by size and position of the inspection holes. ( 90mm diameter and ~390 mm length).

The geometry of the flywheel demands a variation of angle of incidence to cover all defect orientations.

Figure 2 Keyway inspection target

TECHNIQUE DEVELOPMENT FOR DETECTION The flywheel has beside the centre hole several smaller holes the diameters are 90mm and 75mm and they are located in 2 rings round the centre hole. Due to these holes the access to the keyways with ultrasonic beams from the outside diameter is very limited. The best solution to cover the full inspection area is to use the smaller holes as inspection holes. (Figure 3)

short pathshort path

long path

The full inspection volume adjacent to each key-way can be interrogated by ultrasonic beams coming from 3 inspection holes


long path


long path

The full inspection volume adjacent to each key-way can be interrogated by ultrasonic beams coming from 3 inspection holes

Figure 3 Access to the inspection area

The goal was to develop an ultrasonic probe which fits in the 90mm hole. The simulation of the

sound beam showed also that for a full coverage of a single keyway, the inspection has to be done out of minimum 2 and in maximum out of 3 inspection holes. (Figure 4) Only by inspection from 2 holes all required orientations of expected defects can be detected.

U=0°U=90°U=0°

U=90°

+T

+H

Section A - A

A

+T

Groove

Probe coordinate system

+a

+b

Coverage and insonification of the inspection volume are achieved by rotating and translating the probe through the inspection hole in a meander pattern. Probe coordinates (in a-b space) are mapped onto the flywheel coordinates (in H-T space).

U=0°U=90°U=0°

U=90°

+T

+H

Section A - A

A

+T

Groove


+a

+b

U=0°U=90°U=0°

U=90°

+T

+H

Section A - A

A

+T

Groove


+a

+b

Coverage and insonification of the inspection volume are achieved by rotating and translating the probe through the inspection hole in a meander pattern. Probe coordinates (in a-b space) are mapped onto the flywheel coordinates (in H-T space).

Figure 4 Coverage of the defect orientations

The simulation of the coverage of the inspection area can not be achieved by only one single

shot out of the 2 inspection holes. The probes have to rotate via the inspection hole axes. (Figure 5),

18°probe rotation fully covers the inspection volum e

PA probe in inspection hole

Detection target is the keyway-bore

corner

The probe rotates 18° to cover the full inspection volume and focusing on key-way corners.

inspection volume

18°probe rotation fully covers the inspection volum e

PA probe in inspection hole

Detection target is the keyway-bore

corner

The probe rotates 18° to cover the full inspection volume and focusing on key-way corners.

inspection volume

Figure 5 Coverage of the inspection areas

By rotating the probe in the holes geometrical indications were also detected. To reduce the data set only to the relevant data, the geometrical indications have to be eliminated. This can be done via filter taking care about time of flight (Figure 6).

12

3

45

180°

0°90°

6

0°

90°

270°

Graphical presentation of the ultrasound signals

1. Back-wall echo206mm@ 30o

2. Bore i.D207mm@ 0o

3. Keyway corner 218mm@ 345 o.

4. Keyway corner 205mm @343 o.

6. Indication surface via ½ skip228mm @ 248o.

5.Crack indication244mm @336 o.

12

3

45

180°

0°90°

6

0°

90°

270°


12

3

45

180°

0°90°

6

0°

90°

270°


1. Back-wall echo206mm@ 30o

2. Bore i.D207mm@ 0o2. Bore i.D

207mm@ 0o

3. Keyway corner 218mm@ 345 o.3. Keyway corner 218mm@ 345 o.

4. Keyway corner 205mm @343 o.4. Keyway corner 205mm @343 o.

6. Indication surface via ½ skip228mm @ 248o.

5.Crack indication244mm @336 o.

Figure 6 expected ultrasonic signals

The result of such a filter is demonstrated in the next picture (Figur 7a & 7b)

Total overviewCovers the metal path up 200mm to 260mm.Horizontal skew means:Scanning by angle variation in the axis of the hole.

Total overviewCovers the metal path up 200mm to 260mm.Horizontal skew means:Scanning by angle variation in the axis of the hole.

Zoom of metal path from 230mm to 260mm.By this reduction of the metal path the geometrical indications are filtered. Only the defect related indications are shown.

Zoom of metal path from 230mm to 260mm.By this reduction of the metal path the geometrical indications are filtered. Only the defect related indications are shown.

Figure 7a without filter Figure 7b with time of flight filter

Due to a groove in the lower surface of the flywheel disc the access to the inspection is additional limited as log as we using only straight beam ultrasonic sound prolongation. By the use of a phased array transducer skewing the angle of incidence in the inspection hole axis, the keyway can be inspected in the full length of the wall thickness. (Figur 8)

Illustration of Beam Steering to Detect Defects Shadowed by the Groove(Horizontal Phased Array)

Groove

Covered inspection area by horizontal skew

Lack of inspection area by 0°angle of incident

Limitation for TWE-Sizing by TOFD Technique

The gap must be closed by sizing from inside of the axle

hole

Illustration of Beam Steering to Detect Defects Shadowed by the Groove(Horizontal Phased Array)

Groove







hole



hole Figure 8 additional coverage by phased array

TECHNIQUE DEVELOPMENT FOR SIZING The before descript technique detect all defects in the inspection area. For fulfilling the requested criteria for sizing additional information of the defects are needed. An adequate solution for the sizing is the use of TOFT technology. For this technology 2 probes are needed, because they are working in transmitter / receiver mode. (Figure 9) The probe must rotate via the inspection hole axes but they have to rotate simultaneously. Therefore a specific manipulator was developed to fulfill this requirement.

Geometric signals (LW & SW) and diffracted signal from defect tip facilitates height sizing

TOFD Height Sizing Technique

RxTxLW

DE

Inspection volume

Inspection volume

TOFD probes in 2 adjacent

inspection holes


inspection holes


diffracted signal from defect tip facilitates height sizing LW = long wave echo

BW = backwall echoDE = defect echo

BW


TOFD Height Sizing Technique

RxTxLW

DE

Inspection volume

Inspection volume


inspection holes


inspection holes


diffracted signal from defect tip facilitates height sizing LW = long wave echo

BW = backwall echoDE = defect echo

BW

Figure 9 TOFT technique for sizing

This technology shows also geometrical indications. These indications can be easily

discriminate from the real crack tip echo. (Figur 10)

Measurement of flawwith a depth actual = 5mm, measured = 3,4mm

(139,7-136.3)mm

Direct long wave echo

Flaw tip echo

Backwall echo

Measurement of flawwith a depth actual = 5mm, measured = 3,4mm

(139,7-136.3)mm

Direct long wave echo

Flaw tip echo

Backwall echo

Figure 10 TOFT results

The TOFT technology delivers good and satisfied results. But not all crack orientations can be

covered. The missing part is quiet small. The goal to do everything mechanized can not be fulfilled in this case. There is no adequate technology available within an economic frame. Therefore the decision was made, if a relevant defect is detected in the not sizable area, the flywheel has to me dismounted and the sizing has to be done manually (Figure 11). This procedure was finally agreed and qualified.

►50,8°

►Groovee

►BW

►45,9°

►54,9°

By turning probe A and B simultaneous the surface

of the Keyway can be covered

►50,8°

►Groovee

►BW

►45,9°

►54,9°

Boundary of dead zone. Below this line no sizing with TOFT is possible

►50,8°

►Groovee

►BW

►45,9°

►54,9°

►50,8°

►Groovee

►BW

►45,9°

►54,9°

By turning probe A and B simultaneous the surface

of the Keyway can be covered

►50,8°

►Groovee

►BW

►45,9°

►54,9°

►50,8°

►Groovee

►BW

►45,9°

►54,9°

Boundary of dead zone. Below this line no sizing with TOFT is possible

Figure 11a Limitations of TOFT sizing

UT beam from TOFT

10

45°14,1

Area where flaw detection and sizing by TOFD is not possible (dead zone)

Limitation related defect orientation:

Possibility to size defect from shaft side

(requires dismounting of Flywheel)

Boundary of dead zone

UT beam from TOFT

10

45°14,1


Limitation related defect orientation:

Possibility to size defect from shaft side



10

45°14,1

UT beam

Coverage for flaws which are not possible to size b y TOFD-Technique



UT beam from TOFTUT beam from TOFT

Possibility to size defect from keyway side


10

45°14,1

UT beam

Coverage for flaws which are not possible to size b y TOFD-Technique



UT beam from TOFTUT beam from TOFT

Possibility to size defect from keyway side

(requires dismounting of Flywheel) Figure 11b Sizing areas by manual inspection

The following pictures (Figure 12 & 13) show the test block during the optimization of the manual sizing method and the tests in our laboratory in Erlangen Germany.

Manual sizing of defect from

keyway/bore surface

Manual Height Sizing Technique


keyway/bore surface


keyway/bore surface

Manual Height Sizing Technique

Figure 12 Development of manual sizing

Figure 13 Manual sizing on open test block

CONCLUSION

Qualification of NDE inspection techniques on new components following the ENIQ principles or comparable code requirements need a well planned an organized project. New technologies are sometimes required. According the ENIQ mythology the chosen technology has to be descript in detail in the technical justification. Simulations were used to argue for the right choice.

To find the right technology or to be able to combine different technologies the skills and the experience must be available on the vendor side. An other major impact on a positive result is the full understanding of the complete inspection chain. Starting on the sensor, the cable, the UT equipment and the analyze software have to be in-line.

IntelligeNDT System & Services GmbH within AREVA has built up great experience in world wide qualifications since more then 20 years. We also can provide deep knowhow about each element of the inspection chain in house.

Therefore we believe IntelligeNDT System & Services GmbH is a most competent partner for qualifications and for solving new inspection tasks.

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