1. Technical background on guided wave testing (GWT)

2. Mss Equipment and software operation for GWT

3. T-wave pipe testing/inspection and calibration procedures

4. Data analysis and reporting software operation for level I

5. Other MsS Guided wave applications and pipeline monitoring

MsS Training Subject

Purpose

This procedure constitutes the written practice for the qualification and certification of nondestructive examination (NDE) personnal in accordance with the guidelines of SNT-TC-1A for use of magnetostrictively generated ultrasonic guided waves for inspection of pipe

This procedure applies to the following NDE methods

Method Abbrivation

Magnetostrictive sensor MsS

Definitions

Certification: Written and practical testimony of qualification

Experience: work activities accomplished in MsS under direction of qualified supervision including performing the MsS method and related activities

Qualification: demonstrated skill, training, knowledge, and experience required for personnel to properly perform the duties of a specific job.

Training: the program developed to impart the knowledge and skills necessary for qualification

APPLICABLE DOCUMENTS

Personnel qualification and certification in nondestructive Testing American society for Nondestructive Testing (ASNT)

Recommended practice No. SNT-TC-1A, 1975,1980, 1984, 1992 Editions.

These documents are used as a guide for the MsS certification to be through ASNT

RESPONSIBILITY

The director of the department of sensor systems and NDE Technology (NDE Department) in southwest research institute shell be responsible for the qualification and certification of NDE Personnel

A level III individual(s) designated by the director shall be responsible for the administration of the MsS training program and for the approval, administration, and grading of examination.

An MsS instructor shall be responsible

LEVELS OF MsS QUALIFICATION

MsS Level I Qualification:

A Level I Shall be qualified to perform specific equipment setups, calibrations and tests, and to record data according to specific written instructions. The Level I Operator may perform preliminary evaluation and interpretation of the data for the purpose of determining the acceptability and quality of data. The data Acquisition system (DAS) Operator shall be thoroughly familiar with the scope and limitations of the method and shall be responsible for on-the job training and guidance of trainees

LEVELS OF MsS QUALIFICATION MsS Level II Qualification:

A Level II Shall be qualified to setup and calibarate equipment and to interpret to evaluate the results, with respect to applicable codes, standards, and specifications. The Level II shall be thoroughly familiar with the scope and limitations of the method for which the individual is qualified and shall exercise assigned responsibility for on the job training of trainees and level I personnel. The Level II shall be able to prepare written procedures and to report the results of an examination. In addition to the duties and responsibilities of the level I operator, the level II shall be qualified and responsible for interpretation and evaluating results of MsS examinations and review data with respect to applicable codes, standards, procedures and specifications. The Level II shall be able to organize and report MsS Examination

LEVELS OF MsS QUALIFICATION

MsS Level III Qualification:

A Level III Shall be capable or and responsible for establishing techniques and procedures: interpretation codes, standards, specifications and procedures; and designating the particular examination method, technique and procedure to be used. An MsS Level III must have a level III MsS Certificate from SWRI. He shall be capable of interpretation and evaluating results in terms of existing codes, standards and specifications.

Physical background on Guided waves: What are guided waves? Comparision between convnesional UT and Long Range Guided

wave Inspecton. Guided waves in pipeline Dispersive characteristics of Guided wave Selection of Guided wave Modw for Long Range Wave

Inspection.

Guided wave Systems and probes: Commercial System Difference of continuous and discrete guidedwave testing

probes Near Field, Dead Zone, Operating Frequencies.

Contents:

Background on Long Range Guided wave Inspeciton.

Introduced for field use in late 1990.

Guided-wave Probe used.

Piezoelectric based- Teletest and Wavemaker

Electromagnetic based MsS System

Guided-wave used.

Mode Torsional and Longitudinal

Frequency Typically 10 to 250-kHz.

Comparisons

Conventional GWT (or LRUT)

Usage Local Spot inspection Rapid surveying of large areas

Waves Used Bulk Waves (compressional, shear)

Guided waves

Frequency Range 0.5 to 10MHz Under 250 kHz

Defect Detection Small defects Relatively Large defects

Inspection Range Inches On the order of 1 to 500 feet.

Nature of Guided waves

Guided waves exist in many different forms Longitudinal, torsional, flexural in pipe

Lamb wave, shear-horizontal wave in plate

Their properties (Velocity, displacement pattern) vary significantly with the geometric shape and size of the structure and wave velocity In contrast, bulk waves used in conventional UT depend only

on the structures material.

Comparison of Inspection Range

GWT is Volumetric Inspection

Prominent Features of Guided-Wave Technology

Rapidly provides comprehensive condition information on large areas of structure.

Requires minimal preparation Insulation removal, scaffolding, excavation, coating removal,

etc.

Inspection inaccessible areas remotely

Pinpoints where to use quantitative follow-Up Reduces inspection cost and enhances over all inspection efficiency

100% of Volume is inspected.

Particle Displacement in a Pipe

Guided Wace Modes in Pipeline

Wave Mode wave propagation direction Particle Displacement

Axial Symmetric Modes

Wave Mode wave propagation direction Cross-sectional View

Dispersion Curve of 4.5-inch-OD, 0.007 inch-wall Steel Pipe

Comparison of Two Modes in 4.5 OD, 0.337 wall steel pipe

Tone Burst Signal

Effect of Wave Dispersion

Dispersion wave mode- It is wave Packet broadens as the wave Propagate

Time

Am

plit

ud

e

Purpose of GWT

Finding defects in pipeline with high signal to Noise ratio (S/N) and with high spatial resolution (SR)

UT uses tone burst electronic pulse having low-number of cycles for high spatial resolution (SR)

Selected Wave Mode of GWT

T (0,1) Torsion Mode in Pipeline

SH0, Shear horizontal mode in plate.

Shear Wave mode in bulk material

These three wave modes are non-despersive and has the same velocity

Dispersion Curve of 4.5-inch-OD, 0.007 inch-wall Steel Pipe

Guided wave testing uses T(0,1) mode- Torsional mode or L(0,2) mode at non-dispersive frequency region.

Selected Wave Mode of GWT

T(0,1) mode is better than L(0,2) mode-

Not Effected By Liquid Contents in the Pipe

Shot Wavelength at the Same Frequency (i.e High Sensitivity)

No Dispersion at any frequency Range

Can find Axially Oriented Defects

Selection Criteria for Guided-Wave Mode and Frequency for Long-Range Inspection

Minimal wave Dispersion

Range of Inspection

Defect Size

Ease of mode control

Minimal complication from other wace modes

Best modes-T(0,1) in pipe

Commercial Guided Wave Systems

Magnetostructive Technology Is developed at South west Research institute

(www.swri.org)

Is trained and advertised by Guided Wave Analysis LLC (www.gwanalysis.com)

Piezoelectric Array Technology Is developed at imperial College

Is lincensed to 2 cmompanies Plant Integrity Ltd (www.plantinegrigy.co.uk) owned

subsidary of TWI

Guided Ultrasonic Ltd (www.guided-ultrasonics.com)

Same Characteristics of Guided wave Systems

The Same Characteristics 100 % of pipe is inspected

Battery operation of main system

Using torsional and longitudinal mode

Data analysis software

Wave propagation characteristics

Interaction with defects of guided wave

Attenuation at insulation, soil, and high viscous material

No inspection across flanges

Non detection of small, isolated defects (Pin-hole type) at long distances

Defect detection threshold increment after passing elbow.

Magnetostrictive sensor (MsS) System for Generating Guided wave

MsS probes

MsSR3030R

Magnetostrictive sensor (MsS) System for Generating Guided wave

MsS probes

2-inch-wide FeCo strip

FeCo Strip attached to the Pipe by using Shear Couplet

Ribbon Coils Placed over the strip

Comparison of Guided wave probes

Demerit of Using Discrete Probes (Non Axial Symmetric probes)

Generation of Flexural Modes

Existence of Near Field Zone (4 or 5ft)

Easy Flexural Mode generation due to sludge, internal corrosion, bad contact, tilt or unbalanced probe.

Poor direction control or bad cancellation

Only operating low frequency guided wave (usually less than 50kHz)

Torsional and Flexurial Mode Generation

Comparison between Continuous and discrete probes.

Flexural Mode Generation

Is due to non balance between probes caused by Probe itself

Localized corrrosion

Bad contact, tilt

Localized corrosion on surface or inside of pipe.

Probe insulation location needs to be located at no Sludge or internal Corrosion.

Poor Direction Control

No- Near Filed Length of MsSR 3030R System

Near field length

Is defined as the length from the probe to the position at which the axial symmetric guided wave covers the whole circumference of pipe with almost the same signal amplitude.

MsS System

Has no near filed length (0 ft) because the probe covers 360 degree of pipe circumference.

Short Dear Zone Length of MsS Sysem

Dead Zone Length

Is generated as a result of electric interference during the high-pulse electric signal transmission to the probe inside the equipment.

Dead Zone Length of MsS System

Is about 4inches at 128-kHz center frequency

Is 7 inches at 64-kHz center frequency

Is about 11 inches at 32-kHz center frequency.

Why the discrete probe can not operate at high frequency ?

MsS Probe

2-inch-wide FeCo strip

Operate at 16 kHz also.

Operate at 16-, 32-, 45-, 64-, 90-,

128-, 180-, 250-kHz center frequency

2-inch-wide Ribbon cable

32 kHz

2-inch-wide FeCo strip

128 kHz

64 kHz

Frequency Adapters

Interaction of Guided wave with defect

Guided Wave V= f

Where V- Velocity, f- Frequency and - Wave Length

Frequencies: 250kHz 128kHz 64kHz 32kHz 16kHz

Wavelength: 0.5inch 1inch 2inch 4inch 8inch

Defects in pipe Well

MsS Guided wave system

MsS Probe Is based on magnetostrictive effects Uses 2-inch-wide ferromagnetic strip (FeCo) and ribbon cable or

electric cables or electric wires Covers 360 degrees of pipe circumferece.

MsS System Has short dead zone length Has no near field zone length Has good direction control Generates less flexural modes (coherent noise) Operates at high frequency higher than 100kHz.

Operates at wide frequency range (16kHz to 250kHz)

Summary

The guided wave testing (GWT) Is a method using low-frequency ultrasonic wave for a long

distance Rapidly provides comprehensive condition information on large

areas of structure (Screening tool) Has three curve for checking wave modes form studying Uses torsional mode that is non-dispersive. Can generate using magnetostructive sensor (MsS) or a belt of

piezoelectric transducers Uses direction control fro inspection and monitoring. Needs to know dead zone length and near field length Operates at frequencies 16kHz to 250kHz Needs to operate wide frequency range for finding different

sizes of defect.

Why is Torsional Mode Used?

Free From dispersion-related problem-up to the cutoff frequency of T(0,2)

Wave Properties independent of Pipe size-up to Fc

Not Affected by Liquid in the pipe

Less prone to generate Flexural (extraneous) wave Modes

Easier and simpler to use than longitudinal mode operation

Economical for permanent installation for long term monitoring

Generation of T(0,2) Mode

Free from dispersion-related problem-up to the cutoff frequency of T(0,2)

If d=/2, the T(0,2) mode is firstly generated

Fc=V/ C= V/2d, where d is the wall thickness

For example, 1-inch-thick wall Fc=64kHz

Non-Dispersive up to Cut-Off Frequency

MsS Torsional Mode Generation and detection

Uses thin magnetostrictive strips placed around

pipe and MsS Coils placed over the strips

Strips are either shear-coupled, bonded, or mechanically coupled to the pipe

Residual magnetization is indiced in the strips (called Magnetic Conditioning)

T-Mode is generated/detected in the strips through Magnetostrictive effects (called Wiedmann effects)

MsS Probe For T-Mode piping Inspection

MsS probes

Magnetostrictive Strip Ribbon Coils Placed over the strip

MsS Principle

Generation- Based on the Magnetostrictive (or Joule, 1847) Effect.

Detection-Based on the Inverse Magnetostrictive (or Villari, 1865) effect and Magnetic Induction (Farady, 1831)

To Operate MsS, Both DC bias magnetic fields and AC Fields are needed

Relative orientation between the DC and AC fields determines the type of wave mode generated/detected.

MsS L-Mode Generation

HB DC Bias Magnetic Field

HAC AC Applied Magnetic field

HT= HB+HAC +Z L=Wave

HT=HB-HAC - Z

Total Field Strain

Torsional Mode Generation

Physical Properties of Strip Materials

FeCo (Heat Treated) Nickel (Annealed)

Saturation

Magnetostriction

60X10-6 35X 10-6

Curie Temparature 17200F, 9380C 6620F, 3500C

Yield Strength 73kSi 15kSi

Advantages of Iron-Cobalt Strips

Produce stronger signals- about 4 times larger than signals obtained with nickel

Can be uses for high-temperature applications

Mechanically stronger and, thus, can tolerate mechanical stresses

Disadvantages- more expansive; less available commercially

Properties of FeCo Strips and handling

Requires a sepecial Heat Treatment (HT)

May show discolored areas from HT

Discoloration does not degrade sensor performance

Mechanically strong, but some what brittle

To avoid the irregular cut

Use a good metal shearing tool

Gut in its natural curved shape

Do not put the strip in stressed state by straightening it for cutting.

Direction control of Guided wave

Achieved by employing two sensors and phased array principle

A -wavelength separation is used for both sensor placement and MsS transmitter / Receiver operation.

Nominal T-Mode Wavelength in steel pipe (V-3260 m/sec)

Frequency (kHz) Wavelength (inch) Quarter Wavelength

(inch)

250 0.51 0.13

128 1.00 0.25

64 2.00 0.50

40 3.20 0.51

32 4.00 1.00

20 6.40 1.60

16 8.00 2.00

10 12.80 3.20

8 16.00 4.00

Direction Control Simulation

Standard sizes of Ribbon Coil and Magnetostrictive Strip

Ribbon Coils Width-2inch

No. of Conductors-40

Magnetostrictive Strips Width-2inch

Thickness-0.004inch for Iron Cobalt

Coil Adapters

Designed to turn parallel conductors in ribbon into an encircling coil

Standard type

Dual Probe 32, 45, 64, 90, 128, 180, and 250 kHz operation

Standard MsS Probes

2-inch-wide Ribbon cable

32 kHz

2-inch-wide FeCo strip

128 kHz

64 kHz

Probe Installation methods

Mechanical Dry Coupling

Requires good pipe surface

High temperature application up to about 500 Celsius degree

Shear Couplant

Top of Paint without removing it

Relatively smooth surface

Many testing locations per day

Epoxy bonding

Rough Pipe surface or permanent monitoring

High Temparature (up to 200 0C)

Many Testing Locations per day

New Mechanical Coupling Tool

Mechanical coupling Ribbon Cable

Strip Preparations

For Pipe 16 inches in OD or smaller, cut the strips to a length that is slightly less (about 0.25 inch or so) than the pipe circumference.

For Pipes Larger than 16inches in OD, divide the total required strip length in to 2 ro segments

Segmented strips make handling and alignment easier during the bonding process.

Making Handles for Holding Strip During Epoxy Bonding

Cut 2-Wide making type of about 4 length

Fold the 2-wide masking tape at nearthe center and attach itself of 1 length

Attach the both ends of masking tape to the strip near the end

Repeat the above procedure to the other end.

Surface Preparation

Wipe any dirt or loose corrosion with paper towel

If the surface is rough, use a wire brush or sand paper

Paint is okay, if the panted surface is smooth

If the paint has blisters or is detached from the pipe surface, remove the paint and clean the area.

Reference Line Drawing

Place a Wrap-A-Round along the pipe circumference and align it properly

Draw a line along one edge of the Wrap-A-Round

Reference Line is necessary to align strips properly during the bonding process

Install Strip around pipe using shear couplent or Epoxy

Attach 2 wide masking tape on both sides of strip

Feco Strip

Masking Tape

Pipe

Epoxy Shear Couplant

Ms S Data Comparison (64 kHz Data from 16 OD Pipeline sample at ambient Temp)

MsS Test Procedures

Prepare Strips

Bond Strips around Pipe

Magnetize Strips for T-Mode Operation

Place MsS Coil over the strips

Connect MsS to instrument

Acquire Data

Strip Preparation and Bonding

Step 1: Cut the strips to right length

Step 2: Make Handles for holding strip during epoxy bonding

Step 3: Clean the pipe surface and draw reference line around the pipe

Step 4: Mix the epoxy and apply it to the strips

Step 5: Bond the strips around the pipe following the reference line and the keep them place by wrapping over the strips with a rubber band until epoxy cures

Preparing Epoxy Squeeze Tube

Install the epoxy in the epoxy squeezer and attach the nozzle in front of epoxy tube as shown below.

Mixing and Applying Epoxy Mix/Prepare the adhesive and apply to the contact side of

strips

5-Minite epoxy is only okay for bonding strip in a pipe of 8-inch or smaller OD

For 10 or larger pipe, use an epoxy having 20 or longer curing time

Bonding Procedures (for Pipes with 16 OD or less)

Place and bond the strips around the pipe and press them onto the pipe

While slightly wiggling and rotating the strips and squeezing out excess adhesive, adjust the alignment of strips.

Use masking Tape for Positioning attached strip

Attach 2 wide masking tape on both sides of strip

Feco Strip

Masking Tape

Pipe

Bond Procedures for Segmented strips (for Large Size pipes)

Mix/prepare the adhesive and apply to the contact side of the strips

Bond the Strip segment on the pipe and adjust its position so that one edge of the strips is aligned along the reference lines; when properly aligned, keep the segment in place by taping it down at both ends and a few other locations along its length

Repeat the process using the remaining strip segments

Use Adhesive whose working time is longer than the time needed to complete the bonding process of all strip segments around the pipe.

Bonding Procedure (Contd)

Wrap a rubber strap over the strips and keep strips pressed down during adhesive curing

After the adhesive is cured, remove the rubber strap.

Strip Conditioning procedures after bonding on pipe

Place conditioner over strips and move it around the pipe 2 or 3 times relatively constant speed abut 1-2 ft/sec); then remove is from pipe in a continuous motion

Any halt in motion may result in non uniform conditioning and degraded MsS Performance.

Ribbon Cable information

Place Ribbon calbe on top of attached FeCo Strip

This is one of most important procedure

Many inspectors fail

Reflection of Guided waves

Anomaly in pipelines includes corrosion, crack or weld etc..

When guided waves hits a change in cross-sectional area, they reflects back to word the MsS Probe.

Signal amplitude is proportional to Cross-sectional area of defect

What Determines GWT Signal?

Sr= rSi (ignoring attenuation) Sr-Detected signal amplitude r- Reflection coefficient of reflector Si- Transmitted signal amplitude

r-Reflection coefficient; dependant on wave frequency, reflector size (depth, circumferential extent and axial length) and shape

Phase-Dependent on reflector type (weld, defect)

To be meaningful, signal amplitude is converted from voltage to reflection (%)

Attenuation correction Calibration

Reflection Coefficient (r)

Impedance (Z) of Guided wave AV A-Cross Sectional Area

- Density

V Velocity

Reflection Coefficient (r) Calculation

r= Reflection Coefficient

Z1= Impedance of region 1

Z2= impedance of Region 2

Approximate Defect Sizing

Approximating Defect Sizing

Approximation of defect sizing

Defect size is proportional to reflected signal amplitude

r- Reflection Coefficient Ap Crossection area of the pipe

Ad Cross sectional area of pipe at defect location

Adefect Cross Sectional area of defect

Sr= rSi Y-Axis amplitude should be displayed with reflection coefficient (% reflection)

Y Axis plot of Guided wave data The inspection range and threshold sensitivity are set

by the signal-to-noise (S/N) ratio in guided wave testing. Signal to noise ratio (SNR) should be minimum 2 or 1 SNR

for detection The reflection coefficient or Percent reflection is

proportional to signal amplitude. The reflectivity or reflectance is proportional to the

power of energy.

If a signal has 3 SNR ratio (0.3 volt for signal, 0.1 volt for noise), its reflectance is 9.

If the data are plotted with signal amplitude or reflection coefficient, its amplitude is propotional to the defect cross-sectional area of pipe.

% Reflection and % CSA

r is the reflection coefficient

% Reflection and %CSA

Reflection of Guided wave in pipe

Acoustic impedance of Guided wave in pipe Z = V1A :Density of Pipe A- Cross sectional Area of pipe V1: Velocity of the guided wave Reflection of Guided wave

Zp : Acoustic Impedance at the pipe location with and without defects

Zdm : input impedance of the defect

Transmission line Model

Recursion relation for input impedance of two successive layers

K Wave Number Thickness of the layer

Defect Matching of a Notch Type defect for Defect Simulation

Pipe Sample Defect and Guided Wave

Pipe Sample: New Above Ground Pipeline 4.5 inch outer diameter 0.337- inch- thick wall

Defects: 2 Inch width 0.23- inch depth (deepest) 2-to 4- inch length with 0.25 inch step 7.17 percent maximum cross sectional area defect

Guided wave: 64 kHz, 2- Cycle L(0,2) mode wave Guided wave was directly generated in pipe without any

coupling medium.

Comparison of Experimental and simulated signals

Examples of Experimental and simulated signals

Calibration methods

Method 1 Indirect calibration based on geometric signals in the data (such as end or weld signals)

Typical R Value assigned 95 to 100% for pipe end and 10 to 25% for weld.

Calibration based on weld signal is subject to significant error

Method 2- Indirect calibration- based on the signals from a reference reflector (hose Clamp)

R is the reference reflector is determined separately

Fairly accurate on small size pipes

Method 3 Direct Calibration The transmitted signals is measured and used for calibration most

reliable.

Reflection coefficient of Hose Clamp Reference

Direct Calibration Procedures Attach a short (2) FeCo Strip

along circumference direction using double-sided tape

Magnetically Condition the strip

Place a short (1) MsS plate- probe on the strip.

Operating in the pitch-catch mode and using the plate-probe as the receiver with no direction control, detect the transmitted signal.

Calibrate using the transmitted signal amplitude as the reference

Wave Reflection from step-Wise wall thickness change in pipe

Phase-Checking for automatic identification of Reflector Type

Phase Relationship (to Incoming Wave) In phase when reflected from a weld

Out of phase when reflected from a defect

MsS data analysis and reporting software uses phase-checking for automatic reflector identification

Welds, attachments Positive (+) Phase

Defects, Pipe Ends Negative (-) phase

Patent Pending

Presentation Outline

Structure Program

Pipe Information

Data Acquisition

Different Data Display

Analysis & Report

Select Data

Select Frequency

Calibrate Distance

Calibrate Amplitude

Review & Correct findings

Finish Report

MsS Data Acquisition, Analysis and Reporting software for Pipeline Inspection

Inspection Report

Answering

Where is a defect?

Velocity and calibration

How Big is it

Y Axis scale of report

TCG and DAC plot

Threshold Level

MsS Data Acquisition and Reporting Software for pipeline inspection

Is a complete tool for acquiring data, analyzing data and generating inspection reports.

Is Composed of Three sections

Pipe information

Data Acquisition

Analysis and Report

Pipe Information

Cut- off frequency

Weld reflection

Inspection location information

Inspector information

Pipelines information

Pipeline note

=> Recording of Basic information.

Pipe Information in Report

Data Acquisition Cut-Off Frequency Operating Frequency

Directory and keyword of filename Data Reviewing

Data Display

Analysis and Report

1. Select Data

2. Select Frequency

3. Calibrate Distance

4. Calibrate Amplitude

5. Review and Correct Findings

6. Finish Report

1. Select Data

2. Select Frequency

3. Calibrate distance

Answering: where is the defect?

Look at X- axis Scale and signal width for spatial resolution

Velocity of Guided wave

Estimation with experience

Calculation with Dispersion curve Approximate Value

Dependence on elastic constants and density of material

Calculation using signal form known geometric Features (e.g. Weld)

Accurate

Calculation performed by system software

4. Calibrate Amplitude

Attenuation of Guided Wave

Attenuation Varies depending on Local Condition

Degree of Corrosion

Surrounding environment (buried, insulated, coated, etc.)

Average attenuation is used for Data Analysis

Signals from welds are used for this purpose

Attenuation Correction data

DAC Curve Plot TCG Data Plot

Y-Scale of Guided wave Data

The inspection range and threshold sensitivity are set by the signal to Noise (SNR) ratio in Guided Wave Testing

The Reflection coefficient or percent reflection is

proportional to detect cross-sectional area of pipe. The Reflectivity or Reflectance is proportional to the

power or energy

If a signal has 2 SNR Ratio (0.02 volt for signal, and 0.01 volts for noise)

SNR of reflection coefficient = 2 SNR of Reflectance = 4 Sr = r Si ==> Y-Axis is Amplitude should be displayed with

reflectance coefficient (% Reflection)

TCG Data Plot and DAC Curve

DAC TCG

Show what we found

Threshold level of GWT

Threshold Level is set to Minimum detectable defect

Signal-to-Noise(SNR) Should be the minimum 2 to 1 for Detection.

Threshold Level should be varied according to distance

Defect size with 5% Cross Sectional Area (CSA)

Conclusion on threshold Level

Look at Y-Scale of data plot

Lowe the threshold level (5% to 0.5 to 1%)

Know that 5% CSA is not the same as 5% wall loss

Set threshold level depending on the distance and pipe size

Check the threshold level depending on the pipe outer diameter

5. Review & Correct Findings

6. Finish Report

Contents of MsS Field test

Examples of pipeline, inspection, and monitoring

Inspection and monitoring procedure and cautions

Capabilities and limitations of the MsS Technology for

Long Range Piping Inspection and monitoring.

Effects of Geometric features in Guided wave

Effects of contents, coatings, and general corrosion

Inspection and monitoring range

Defect size of GWT

Examples of Pipe Inspection Applications

Piping Systems in oil, gas, and petrochemical facilities

Off shore piping system/ risers

Power generation piping systems

Pipelines at road crossings/leeve penetrations

Pipeline inspection Examples of Road Crossing

MsS Pipeline Inspection

Pipeline MsS Testing

Bridge Crossing Pipeline Inspection

Long-Term Monitoring using MsS Technology

Long-Term Monitoring of High temperature Pipeline

Monitoring of Buries Gas Transmission Lines

MsS Guided Wave Monitoring of Pipeline in a Tunnel

Poor Epoxy Bonding Epoxy is not completed hardened

=> Epoxy need to be mixed through

using too small epoxy to fill gaps between strip and pipe surface

=> Use enough Epoxy

Epoxy is hardened before finishing bonding

=> use epoxy having a longer setting time

Epoxy is not mixed at a cold Temperature

=> Find an epoxy that is not viscous at a cold temperature (about 0Celcius degree)

Strip is not attached against the pipe

=> Use Rubber band to hold the strip during epoxy curing

Poor Strip Conditioning

Too Fast or too slow movement of Magnets => Move Magnet with a speed of about 1-2 ft/sec

Go Stop Movement of Magnetic cart

Stop before removing magnet => Remove Magnet in a moving

Principle of Magnetic Motors

Moving magnet magnetizes the ferromagnetic strip behind it along the same direction. The highest density is behind the moving Magnet.

Moving with constant speed along the circumference of pipe makes magnetization be uniform

Example of Good and poor Condition data

Poor Amplitude level selection In order for the MsS to operate properly, the AC magnetic filed

(HAC) must be smaller than the bias field (HB) applied in the circumferential direction.

Demagnetization of circumferential magnetization

Signal-to-Noise ratio gets worse

Generate Extraneous mode signal

Transmitter Amplitude Level

For 8 or smaller pipe and low frequency operation (32-kHz or lower) ,set the transmitter amplitude to 25% level

For 8 to 16 pipe and low frequency operation (32-kHz or lower) ,set the transmitter amplitude to 50% level

For 16 and bigger diameter pipe and low frequency operation (32-kHz or lower) ,set the transmitter amplitude to 100% level

Suggestions of instrument settings in data acquisitions

Use TCG function for acquiring data, especially for long range

inspection

Dont cut data that have higher amplitude than the maximum or

minimum scale of Y-Axis

Reduce pulse reputation rate for short and low attenuation pipe

The sampling rage needs to be at least 10 times bigger than the

operating frequency

Suggestions of MsS Probe installation in pipeline

It is recommended to install the MsS Probe at least 3 ft apart from a big geometric features

Dont install MsS Probes in the middle of 2 geometric features

Dont install MsS Probe in the tapered section

Guided wave cannot inspect after passing two 90-degree elbows

Procedure for finding MsS probe installation Location in field

Find a big Geometric feature such as flange, valve, T-Joint, and elbow

Weld

Install MsS Probe at fare as possible from Flange or Valve because they

are completely block the wave Propagation

Install MsS probe at close as possible from the target inspection region

Install MsS Probe at good surface area along circumference of the pipe

If pipe has generalized corrosion with many dents, fill in the dent area

with epoxy before attaching ferromagnetic strip

Finding MsS Probe installation Location in Field

Capabilities and limitations of the present MsS Technology for Long Range Piping Inspection

Capabilities and limitations of the present MsS Technology for

Long Range Piping Inspection

Effects of Pipeline Geometric Features and other Conditions

on Inspection capabilities

General Capabilities Good for detecting and locating defects such as corrosion metal loss

areas, circumferential cracks, and deep (over 70% wall) axial cracks

Can inspect over 500 feet length of piping in one direction for detection

of 2% to 3% defects on straight bare or painted lines (here, % means

defects circumferential cross-sectional area relative to total pipe wall

cross section.

Can roughly estimate defect size; needs more R&D to achieve defect

characterization

Can distinguish between welds and defects

Effects of Pipeline geometric Features and on inspection capabilities

Features Effects

Flange/Valve Prevents wave propagation forms end point of the inspection range

Tee Causes large disruption, limits inspection range up to that point

Elbow Short radius 900 elbow, causes large disruption in wave propagation,

limits inspection range no farther than elbow region

Long Radius 900 elbow has negligible effect

Bend Has negligible effect if bend radius >3 times of OD

Other wise, bend behaves like elbow

Side Branch Cause a wave reflection and thus produces a signal, no significant

effects on inspection capabilities

Clamp Causes a wave reflection and thus produces a signal, no significant

effects on inspection capabilities with high frequency guided wave

Weld

Attachment

Causes a wave reflection and thus produces a signal if attachment is

large (such as pipe Shoes, can reduce inspection range.

Interaction of Guided wave with defect

Guided Wave V= f

Where V- Velocity, f- Frequency and - Wave Length

Frequencies: 250kHz 128kHz 64kHz 32kHz 16kHz

Wavelength: 0.5inch 1inch 2inch 4inch 8inch

Defects in pipe Well

Interaction of Guided wave with defect

Guided Wave V = f

250kHz 128 kHz 64 kHz 32 kHz 16 kHz

V

V

Pipe Wall

Defects

Frequencies

Guided wave inspection for finding generalized corrosion in an insulated pipeline

Finding Corrosion defects with high frequency guided wave

Finding external pits with GWT

Merits on High frequency GWT

High frequency guided wave

Is good for inspecting pipeline having pipe support, clamp, etc with high sensitivity

Has high sensitivity with short wave length for finding generalized pitting corrosion

GWT with multiple center frequencies (32, 64, 90, 128 kHz)

Allows finding different sizes of defect

Is good for corrosion under insulation (CUI) inspection

Effects of Geometric Features in GWT

Effects of Pipe Support Example: Pipe Support having a small pipe on concrete block

Effects of welded pipe support

Effects of Clamp on Pipe

Problem of longitudinal welded support on wave propagation

Solution of Longitudinal welded support on wave propagation

Effect of contents, coatings and general corrosion

Effect of Pipe Contents Gases No Effect Liquids and sludge have same effect

Viscosity (fluid Fraction) depends on different fluids and temperature

The viscosity of liquids decreases as the temperature increases

Liquids of Low Viscosity Almost no effect on the torsional mode Affects the longitudinal mode test

Liquids of high viscosity (Asphalt or wax) and sludge Heavy viscous liquid or sludge of heavy depends attenuate

the signal and reduce the test range.

Insulation, Coating and Wrappings

Mineral wool insulation- no effect Operates at 32, 64, 128, and 250kHz

Paint Improves the signal Operates at 32, 64, 128, and 250kHz

Epoxy Coating Small effect (~ 1dB/m) Operates at 32, 64 kHz