Rapid detection of sewer defects and blockages using ... Simon Tait.pdfSchool of Engineering, Design and Technology Rapid detection of sewer defects and blockages using acoustic instrumentation

School of Engineering, Design and Technology

Rapid detection of sewer defects and

blockages using acoustic instrumentation

Kirill V. Horoshenkov, Simon J. Tait, Tareq Bin Ali and Anna

Romanova

Pennine Water Group,

University of Bradford, UK


Outline

• Concept

• Instrumentation

• Laboratory facilities

• Acoustic data presentation

• Acoustic signatures of sewer pipes

• Field Testing and Prototypes

• Potential Uses

• Conclusions


Concept


Prototype


Laboratory facilities


Sensor in a 150mm laboratory pipe


Detection of local defects: Instrumentation

perforations/cracks

blockage

Chirp

Deconvolution

Impulse response


Effect of local defects: data for a 150mm pipe

400 – 1000 Hz

Sound propagation in pipes: Horoshenkov et al, Patent Application GB081519905, August 2008.


Reflection from pipe end


Reflection from lateral

connection


Reflection from porous

blockage


Reflection from rigid

blockage


Reflection from crack in

150mm pipe


Field Prototyping and Testing

• Defect identification using database of spectrograms

• Location of defects

• Measurement of pipe length and diameter


Comparison CCTV – Acoustic Identification

wall crackblockagejoint

ConditionDefects

byCCTV

Defects*by

Acoustic Method

Acousticvs. CCTV

(%)

Acousticdistance RMS

Difference(m)

Next manhole 24 20 83 0.21

Lateral connection 95 86 75 0.48

Crack (all types) 69 57 71 0.42

Joint - displaced 22 16 55 0.27

Total 210 179 71 0.35


Acoustic measurements of hydraulic energy

losses

• 150mm clay pipe blockage simulation by concrete models –

different sizes

• Simultaneous measurements from DS & US of pipe end

• From three discharges, experimentally obtained:

- Hydraulic energy head loss.


Theoretical background - Acoustics

0 2 4 6 8 10 12 14 16 18 20-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

Distance [m]

Inte

nsity [

V2/V

2]

blockage4 5 6 7 8 9 10 11 12 13 14

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

Distance [m]

Inte

nsity [

V2/V

2]

Reflected acoustic energy


Energy Loss due to Blockage

• Water levels – from manometers;

• System energy head loss (hf), and pipe roughness.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

To

tal en

erg

y h

ead

(Z

f, m

)

Distance from pipe inlet (m)

No mould

15 mm

30 mm

40 mm

55 mm

60 mm


Hydraulic – acoustic relationship

• Acoustic data can be used to identify the head loss in partly filled pipes

• Relationships are independent of water level in the pipe

• Results may be used to estimate hydraulic energy losses.

0.0

0.5

1.0

1.5

2.0

2.5

0.00 0.05 0.10 0.15

Aco

usti

c e

nerg

y,

DS

& U

S (

ET

)

Hydraulic energy head loss (hf, m)

0.42 l/s, DS

1 l/s, DS

1.8 l/s, DS

0.42 l/s, US

1 l/s, US

1.8 l/s, US


Potential Uses - Current

• Rapid defect location

• Rapid and objective identification

- without the need for operator analysis

• Rapid surveying tool

• Rapid inspection tool to optimise CCTV inspection

• Performance assessment - hydraulic losses

Potential Uses - Future


Conclusions

• An acoustic method of condition detection is an fast

alternative to CCTV.

• This method can detect standard conditions such as

lateral connections, blockages, cracks and their

combinations.

• Acoustic signatures can be recorded and stored in a

database for automatic condition detection and

recognition.

• Low power and data storage requirements

• Field prototype tested

• Future uses – performance assessment

Documents

Rapid detection of sewer defects and blockages using ... Simon Tait.pdfSchool of Engineering, Design and Technology Rapid detection of sewer defects and blockages using acoustic instrumentation