Measuring corrosion levels of ductile iron pipes using scanned images

(1)

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC :

https://nrc-publications.canada.ca/eng/view/object/?id=8737c603-844e-4585-938f-a0169888cbbd https://publications-cnrc.canada.ca/fra/voir/objet/?id=8737c603-844e-4585-938f-a0169888cbbd

NRC Publications Archive

Archives des publications du CNRC

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Measuring corrosion levels of ductile iron pipes using scanned images

(2)

http://irc.nrc-cnrc.gc.ca

M e a suring c orrosion leve ls of duc t ile iron pipe s using sc a nne d im a ge s

O R A L - 9 2 4

M a k , H . ; W o n g , B .

J a n u a r y 2 0 0 9

The material in this document is covered by the provisions of the Copyright Act, by Canadian laws, policies, regulations and international agreements. Such provisions serve to identify the information source and, in specific instances, to prohibit reproduction of materials without written permission. For more information visit http://laws.justice.gc.ca/en/showtdm/cs/C-42

Les renseignements dans ce document sont protégés par la Loi sur le droit d'auteur, par les lois, les politiques et les règlements du Canada et des accords internationaux. Ces dispositions permettent d'identifier la source de l'information et, dans certains cas, d'interdire la copie de documents sans permission écrite. Pour obtenir de plus amples renseignements : http://lois.justice.gc.ca/fr/showtdm/cs/C-42

(3)

Measuring Corrosion Levels of

Ductile Iron Pipes Using Scanned

Images

Helium Mak, Brian Wong & Steven Kruithof (London) Dennis Krys & Zheng Liu (Ottawa)

January 21, 2009

(4)

Overview

• Introduction

- Project Information, Objective

- Preparing Sample, Processing Scanned Images

• Challenges • The Process • Test Results • Conclusion

• Questions & Discussions

(5)

Introduction

24 JUN 2008 Project Started

09 JUL 2008 Received Two Samples

13 AUG 2008 Returned Sample A to Ottawa

16 OCT 2008 Returned Sample B to Ottawa

16 DEC 2008 Submission for Construction

Innovation March 2009 Issue

09 JAN 2009 Research Report Published

(6)

Objective

To develop a corrosion volume measurement method using laser scanning:

• Use existing equipment

• Use Matlab

• Accuracy (?)

(7)

Image

(8)

Image

200901191519 Rough Draft for Surface Measurement - Sample B.jpg

(9)

Image

(10)

Image

200901191931 EST 0.08 Step 1 - Start Pos.bmp

(11)

Challenges

• We want to develop a method requiring a single scan only.

• Each scanned image is in its own space.

• Even two images are aligned, their points and scanned lines are not.

(12)

The Process

(13)

Image Alignment

original corroded Align corroded to original

Calc xform Matrix: P_ha=P_hbxT T=P_hb-1_xP ha Apply xfm to corroded P_a=P_bxT

×

P_hb _P_ha P_b P_b P_b,P_a

(14)

Image

200901191936 EST 0.08 Step 1 - Combi T.bmp

(15)

Image

(16)

Image

200901191947 EST 0.08 Step 3 - After.bmp

(17)

Image

(18)

Image

200901191953 EST 0.08 Step 5a - After.bmp

(19)

Corrosion Depth Calculation

original z

- ₌

corroded z corrosion depth ∆z

z

x

original image

image after corrosion

surface grid sample points

(20)

Complications

Surface normal not align with z-axis

• Rotate images before CD calculation

– Plane fitting

– Plane normal angle calculation – 3D images rotation

Edge effect of surface fitting

• Calculate CD in reduced zone (10%)

– Boundary detection & line fitting (quadrilateral)

– Image cropping

44-LON0000-L IRC LONDON GENERAL

(21)

Mathematical Operations

original image

aligned corroded

exposed surface original

oriented exposed surface

(22)

Tests & Test Results

(23)

Corrosion Simulation

• Manually isolate the exposed surface from the probe image and move it deeper by:

• 0.08 mm

• 4 mm

• 4 mm +/- 5% noise

• Perform on two samples given

(24)

Results

4.00mm

4.00mm with

(25)

Some Less Favourable Results

(26)

Overall

Sample A Sample B

Tilt angle with z-axis 2.43o _{/ 0.002}o _6.64o _{/ 0.004}o

Corrosion depth (mm) 0.08 4.00 4.00 ± 0.08 4.00 4.00 ± CD Medium 0.083 4.032 4.050 0.083 3.997 4.094 CD Std σ 0.088 0.052 0.105 0.032 0.074 0.263 Corr. Vol. (mm3₎ _37.06 ₁₈₁₂ ₁₈₂₄ _41.83 ₂₀₀₀ ₂₀₃₄ Corr. Area (mm2₎ _449.3 _449.3 _450.4 _500.3 _500.3 _500.3 Mean CD (mm) = d 0.082 4.03 4.05 0.084 3.998 4.065 Accuracy (%)* 97.5 99.3 98.8 95.0 99.95 98.38 % 100 1 0 0 × ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ₋ − = d d d Accuracy

(27)

(28)

Lessons Learned

• Method feasibility depends on proper surface treatment (dirt, rust, etc.)

• Small surface features (e.g. pits) may be a challenge

• Corrosion volume is not good for comparison because corrosion area varies between

measurements. Use mean corrosion depth instead:

area corrosion volume corrosion depth corrosion mean =

(29)

Future Improvements

• Use multiple scanned image technique. • Corrosion feature detection and analysis.

• Auto-determination of the corrosion surface. • Incorporate the image alignment algorithm in

(30)

Questions & Discussions

(31)

Enquiry and/or Feedback

Please contact Authors in London as follows:

Address: National Research Council of Canada

800 Collip Circle

London, Ontario N6G 4X8

Phone: (519) 430-7000

(32)