“Solutions for Sustainable Infrastructure”

Condition Assessmentof Large Diameter Mains

Bethany McDonald

Northern California Pipe Users GroupDecember 14, 2010

Outline

• Pipe materials– PCCP

– Metallic

• Leak detection in large mains

• PCCP assessment– Focus on PipeDiver

• Condition assessment of metallic mains

Prestressed Concrete Cylinder Pipe Cross Section

Steel CylinderSteel Cylinder

Concrete CoreConcrete Core

MortarMortar

Steel WiresSteel Wires

The Problem -Corrosion

AA

BB

DDCC

Split Bell

Leadite Joint Seal

Circumferential CrackBlow-out

Longitudinal Cracking

Wall Corrosion

Blow-out

Failure Modes of Metallic Mains

Multiple Cause Failure

Need a broad tool box to identify various warning signs

Longitudinal crack Wall Corrosion

Bell Splitting

Leak Detection in Large Mains

Leak Detection Credentials

• Over 12 years of experience including successful PPIC program

• ~2,900 leaks identified to date representing estimated 142 MGD in water saving

• Significant field experience with over 360 inspection projects completed

• In‐house decision support service capability

• Specialize in large diameter pipelines >12”

• Experience with multiple pipe materials

Why Look for Leaks?

• Knowledge about condition of pipeline– Minimize risk

– Optimize repair & replace programs

• Reduction of emergency response costs

• Water production cost savings – physical treatment and distribution

• Environmental sustainability – conservation of a natural resource

Summary of Inspection DataRegion Miles Inspected # Leaks Leaks/ mile

Worldwide 2,009 2,966 1.48

North America 442 496 1.12

Europe  991 2,023 2.04

Asia Pacific  185 150 0.81

Africa & Middle East 275 257 0.93

Material Miles Inspected # Leaks Leaks/ mile

Concrete  597 417 0.70

Cast Iron 708 1,871 2.64

Ductile Iron  124 142 1.15

Steel  184 87 0.47

Fiberglass 18 4 0.22

These are “High Value” Leaks• Typically have a volume loss 20 times greater than 

small diameter mains

• Estimated to leak for an average of 10 years prior to surfacing

• AWWARF concludes average cost of a distribution main break is $5,000 to $10,000. The typical cost of a large diameter main rupture is $500,000

• Large diameter main ruptures have significantly more impact on the community and environment

Leak DetectionMethods

Internal Leak Detection Options

SmartBall®• Long point-to-point

transmission pipelines• Minimal laterals

Sahara®

• Complex interconnecting networks

• Urban centers

The noise of flowing water in a large diameter pipe masks the sound of small/medium sized leaks making them harder to find with external tools

Internal tools pass right over the leak

SmartBall Description

Power Supply

On-Board Memory

Acoustic Sensor

Microprocessor

Temperature Sensor

Rotation Sensor

Pinger

•The protective foam ball cancels apparatus noises & provides a slightly negative floatability with direct water absorption

•Aluminum core contains data acquisition system

•Data is logged on a 4 GB, security digital card

Insertion

RetrievalAirdrie

approach and departure from MH#1

0

100

200

300

400

500

600

700

800

900

1000

230 240 250 260 270 280 290 300 310 320

Run time (min)

Dis

tanc

e (m

)

Vel = 0.33 m/s

Vel = 0.33 m/s

Tracking

SmartBall Inspection Process

SmartBall Inspection Process

Sahara Description

Surface

•Technology first introduced in 1995 by WRC in London. Significant experience gained in urban environments

•Tethered cable provides high degree of operator control

•Inspection results are provided in real time

•Platform technology offers leak & gas pocket detection, video inspection, wall thickness

Sahara Equipment Overview

Electronics Stack Cable Drum Insertion Tube

Cable Winch

Tracking DeviceSensor and Parachute

Project Deliverables

Surface locations during/post survey

Summary table in report

Survey map in report, and GIS file with GPS data

• Pilot project using tethered inline leak location started in 2007

• Included two leaks on 48” lines deep underground, crossing underneath a major highway.

– These leaks could not be located with traditional leak location equipment.

• One large leak turned into a break the day before it was scheduled for repair.

– Unfortunate, but confirms that leaks precede breaks

Philadelphia, PA

Distance Surveyed 19.5 milesLeaks Located 47 leaksAverage Size TBD gallons per dayLeak Frequency 2.4 leaks / mile

50,000

More ApplicationsIn‐line Video Inspection

Odessa, TX• Inspection of a 14” PCCP line

• Line remained in service

• Tuberculation build up discovered and joints inspected

Sewer Force Main Inspection

Grand Forks, ND• Inspection of 30” and 36” PCCP 

and PVC lines over 8 miles

• Two day inspection – 10.5 hrs

• Two leaks and six air pockets identified

PCCP Assessment

PCCP Assessment Methods

Visual & Sounding

Electromagnetics

Acoustic Fiber Optics

• P‐Wave and RFTC

• Detects and quantifies wire break damage

• Provides estimate of wire breaks in each pipe section

• Provides location of wire breaks

Electromagnetic Inspections

Typical Inspection Results

External Verification – Pipe 105

• Determine repair needs

• How many wire breaks is too many?

• Perform risk evaluation

• Rehabilitation

Engineering Evaluation

Validation: Pipe 32

Validation: Pipe 6

Large Diameter Long Distance Live Inspection

TANK TANK37 km

PipeDiver Launch

Retrieval

Condition Assessment of Metallic Mains

Condition Assessment of Metallic Mains

• Leak Detection– Sahara

– SmartBall

• Average Wall Thickness– Using Sahara and SmartBall Platforms

• Pipe Wall Defects and Anomalies– Using the PipeDiver Platform

• Relies on the measurement of acoustic pulses as they propagate along the pipe

• Propagation velocity of an acoustic pulse is directly proportional to the stiffness of the medium that it travels through

• Higher propagation velocity indicates higher wall stiffness

• Stiffness of the pipe wall reflects the condition of the pipe

PWA Average Wall Stiffness/Thickness

• Acoustic pulses are induced into the pipe

• A receiver records the acoustic pulses as they propagate along the pipeline

• 3‐inch interval (0.25s)

Acoustic Pulsers SmartBall™

SmartBall PWA

Relative Stiffness v.s. Distance From Insertion Location

0

1

2

0.0 3.7 7.3 11.0 14.6 18.3 22.0 25.6 29.3 32.9 36.6

Distance From Insertion Location [m]

Rel

ativ

e St

iffne

ss

Relative Stiffness vs. Distance from Insertion Location

Anomaly AnomalyJoints

Distance from Insertion Location [m]

Rel

ativ

e S

tiffn

ess

SmartBall PWA Results

Remote Field Eddy Current (RFEC)

• Emitter sends signal into pipe wall

• Signal travels through pipe wall

• Detector receives signals

• Defects appear twice: once as each of emitter and detector pass by

Identification of corrosion pits

Corrosion Pit

Dual detection as exciter & detector pass pit

Upstream direction, distance in meters

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Legend:Negligible Wall Thickness Loss

Light Wall Thickness Loss

Moderate Wall Thickness Loss

Heavy Wall Thickness Loss

Nominal pipe

Pipe data N/ASmall leak pinpointedLarge leak pinpointed

Results: Leak Detection & Acoustic Wall Thickness Testing

“Solutions for Sustainable Infrastructure”

Thank you

• Warning signs• Outer coating damaged or lost• External corrosion pitting• Pinhole leaks in barrel• Heavy corrosion throughout pipe wall• Bedding loss from long term leakage

Corrosion Blow-Out

• Warning signs• Use of Leadite joint sealer• Cracks at bell end• Leaking joints• Longitudinal cracks• Bedding loss from long term leakage

Joint Failure (Bell Splitting)

Cracking Failure• Warning signs

• Hairline cracks in pipe• Circumferential (mostly small diameter)• Longitudinal (mostly large diameter)• Spiral (mostly medium diameter)

• Pressure-dependent leaks• Severe, visible cracking• Bedding loss from long term leakage

SmartBall Performance• Leak location accuracy (within 3 feet)• Highly sensitive to leak noise (0.25 gpm)• Operates in all kinds of pressure pipes (DI, Steel, GRP,

PVC...)• Applicable to diameter 12” and above• Inspects up to 9 miles per day from a single deployment• Operates through 4” valve openings• Complies with usual water quality standards

Sahara Specifications

• Insertion:  2” tap (1 7/8” opening)• Diameters:  12” and up (4” to 10” in special cases)• Pressures:  5 to 200 psi• Flow Rates:  2 to 12 ft/s (1 ft/s for very short distances)• Distances:  ½ mile (6,000 ft in ideal conditions)• Bends:  135° total bends (270° for very short distances)• Line Valves:  Cannot survey past inline butterfly valves• Laterals:  Should be closed as sensor passes by, but sensor can 

generally be withdrawn if it goes down one

Information Obtained

Spectrogram

Power Cure

•Exact leak position•Approximate leak size•Direction of main•Depth of main (SmartBall)•Location of main

• 15,000‐ft 14” Cast Iron Pipe• High risk line• Two leaks were found, one small 

and one medium sized. The larger one had already eroded away a void 7’ x 5’ x 3’ deep under this pipe in a main thoroughfare that carries heavy traffic. 

• Bobby Walden ‐ Ops/Maint Mgr: “It was remarkably accurate, within inches”

• Rebecca West – Tech Srvcs Mgr –“savings of $2 to $4MM by not having to replace a critical line”

Spartanburg Water System, SC

GIS Pipe Mapping• Web based interface

• Visual consequence of failure and risk management

• Accurate asset monitoring for repair and replace programs

• Data inputs: manual inspections, electromagnetic inspections, leak identification, fiber optic monitoring

• Internal inspection 

• Distance measurements and pipeline features recorded 

• Immediate identification of pipes in a state of incipient failure

Visual & Sounding

RFTC DataRFTC Data

PHASE

AMPLITUDE

Data AnalysisData AnalysisDistress Man Hole

Fingerprint

DISTANCE NO DISTANCE

+ =

Interpreting the Signal

NO BREAKS

MIDDLE BREAKS

END BREAKSJOINT DISCONTINUITY

CYLINDER VARIATIONS

Quantification - Measurement

DISTRESS LOCATION

BASELINE

SIGNAL LENGTH

• Distressed pipe signal

• No breaks signal used to establish a baseline

• Superimpose the 2 signals when making the measurement

Factors Affecting RFEC/TC SignalFactors Affecting RFEC/TC Signal

Variation in Wire SpacingWire Anchoring

Thickness Variations Shorting Straps Installation

Diameter Variations Wire Splice

Material PropertiesJoint Configuration

Recorded Wire Break

Acoustic Monitoring

• Acquires acoustic data

• Filters noise

• Transmits wire break information

Unfiltered Filtered

Data Acquisition Unit

VALUE ADDED SERVICES

• Acoustic fiber optic (AFO) monitoring

– Wire break notifications

SAMPLE WIRE BREAK NOTIFICATION

Pipeline Selection: SmartBall

Longer pipeline length = increasing ease of use

More complex network

= increasing

 risk

SmartBallMaximum Value

• Most efficient for use on long mains• Frequent laterals with unknown locations bring some risk• Long cross‐country mains: SmartBall’s “Sweet Spot”

Pipeline Selection: Sahara • Long cross‐country mains may lack existing taps• Small diameter mains often have too many bends• Urban transmission mains: Sahara’s “Sweet Spot”

Sahara MaximumValue

Longer pipeline length = increasing ease of use

More complex network

= de

creasing

 ease of use

SmartBallMaximum Value

Sahara MaximumValue

Pipeline Selection: External Tools

Larger pipeline diameter= decreasing sensitivity

More complex network

= increasing

 sen

sitiv

ity

SmartBallMaximum Value

External ToolMaximumValue

• When more sensitive inline tools are not feasible• Hydrant access on small mains offers improved sensitivity• Can be used to “fill in gaps” between inline inspections