Performance Of Long Range Ultrasonic Inspection Using

Magnetostrictive Sensor Guided Wave On Piping

Prawin K Sharan 1a

, Sri Krishna Chaitanya

1b, Bramhasiddananda Reddy

1c, Hari Kishore Maddi

1d

1Sievert India Pvt. Ltd. (A Bureau Veritas Company), 16 & 17, Plot-2, Sec.-2, Phase-II, Nerul, Navi Mumbai,

Maharashtra, India

asharanprawin@sievert.in,

bchaithanyas@sievert.in,

cbysani@sievert.in,

d harikishore.maddi@in.bureauveritas.com

ABSTRACT

Long-Range ultrasonic Testing (LRUT) Technology was useful for detecting the corrosion and

metal loss in pipes. The aim of the LRUT inspection is to test long lengths of pipe rapidly from a

single test location with 100% coverage of the pipe wall and to identify areas of corrosion or erosion for further evaluation using other NDT techniques such as radiography or conventional

ultrasonic testing. This technique is equally sensitive to metal loss on both the outside and inside

surfaces of the pipe. A technique of using Magnetostrictive sensor (MsS) for generation and

detection of guided wave is in practical use already. The torsional guided waves generated in pipes

by using MsS have great potential to be used as one of the tool in the structural integrity assessment of piping. Varieties of pipe materials are coming in the industry with the advent of new engineering

materials with tailored properties. MsS with the low frequency range of ultrasonic guided waves

can be extended to be useful as a tool for screening the Inconel & Stainless steel materials.

The present paper portrays the adoptability and limitation of LRUT technique in stainless steel,

Inconel materials & higher diameter pipelines with spiral welded and concerns the presentation of the results of tested signal and examples of long range guided wave inspection of Stainless steel and

Inconel structures that can be accomplished using the MsS. We have made a Case Study between

SS and Inconel while defect sizing and could able to get the satisfactory results. Hence,

Magnetostrictive sensor could be used on long range piping/tubing in-service systems and also their

ability to monitor the long-term structural integrity assessment for any type of pipe materials.

Keywords: Guided waves, Magnetostrictive sensing strip, NDE, Long range pipeline / piping /

radiant heater coils inspection.

1. Introduction

Most of the piping & pipelines the industries like Oil and Gas, Fertilizers, Petro Chemicals needs

NDT inspection for the integrity assessment studies. Ultrasonic Guided waves propagates along the

length of the structure like plates, rods, tubes, Pipelines etc. confined by the boundaries of the

Pipeline.

Long-range guided wave inspection technique is an effective method for rapidly surveying a pipe

for any service induced defects [1]. Lamb waves are propagated in plates or pipes (made of

composites or metals) only a few wavelengths thick. A Lamb wave consists of a complex vibration

that occurs throughout the thickness of the material. The propagation characteristics of Lamb waves depend on the density, elastic properties, and structure of the material as well as the thickness of the

test piece and the frequency. The wave is guided by the geometric boundaries of the medium; the

geometry has a strong influence on the behavior of the wave [2-6].

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Magnetostriction Criteria:

Magnetostriction is the changing of a material's physical dimensions in response to changing its

magnetization. For a wave generation, it relies on the magnetostrictive (or Joule) effect: the

manifestation of a small change in the physical dimensions of the ferromagnetic materials, in the

order of several parts per million in carbon steel, caused by an externally applied magnetic field.

For receiving elastic waves, it relies on the inverse magnetostrictive (or Villari) effect: a change in the magnetic induction of a ferromagnetic material caused by a mechanical stress or strain [1].

1.1 Analysis using Different Applications:

Guided waves can propagate in pipelines structure with three types of wave modes; those are Longitudinal, Torsional, and Flexural modes.

Fig.1 Dispersion curve showing phase velocity verse frequency for the tube of OD 219.1mm and

wall thickness 8.18 mm of carbon steel material

The advantages includes long range inspection capability, inspection at high temperature, structural

health monitoring (SHM) of pipes (8).

We have made a Case Study between SS and Inconel while defect sizing and could able to get the

satisfactory results. Hence, Magnetostrictive sensor could be used on long range piping/tubing in-service systems and also their ability to monitor the long-term structural integrity assessment for

any type of pipe materials.

2. Experimental Setup

For making DAC and TCG, in this sort of system to analysis the percentage of metal loss, System

will consider Butt weld (percentage of reflection equivalent to the 15% to 20% in the pipeline based

on the bead (weld bead height and width) as a reference otherwise end of the pipe (percentage of reflection equivalent to >90% of metal loss in the pipeline). The greater the S/N ratio the easier it is

to identify and interpret signals from small change of cross- sectional area (CSA) of the pipe.

Inspection was carried out using MsS3030® diagnostic system developed by SWRI, San Antonio, TX, USA and based on magnetostrictive technology. Permanent installation of the sensor is

Possible for the monitoring. The features of the system are given in table 1. MSS transducer uses

the direct and inverse magnetostrictive effect that occurs in ferromagnetic materials [1]. The

magnetostrictive sensor is applied locally on the section of the inspected pipe and consists of strips

of magnetostrictive material such as iron cobalt (Fe-Co) that are bonded on the pipeline, and transduction coils wrapped around the magnetostrictive strips and connected to the signal generator.

The strips of magnetostrictive material are initially magnetized using a polarized static magnetic

field. The signal generator sends the excitation impulse to the transduction coil that in turn, induces

a correspondent vibration into the magnetostrictive strip that will propagate as a guided wave

guided by & along the pipeline. Thus, polarizing the magnetostrictive strips, it is possible to induce the propagation along the pipeline of the fundamental torsional modes T (0, 1) or longitudinal

modes L (0, 1). Moreover, appropriately exciting the two coils, one can obtain the wave

propagation along a direction making negligible the propagation in the opposite direction. The

presence of defects due to corrosion and/or imperfections along the pipeline generates a reflected

wave which will be detected by the same sensor that was used in the transmission using the inverse magnetostrictive effect. In this phase, the transduction system acquires the reflected signal that,

when sent to the processing system, allows to locate the flaw.

Table 1 – Main features of MsS3030® diagnostic system.

S. No. Parameters Description

1 Sensitivity 3 % of “cross-sectional area” change

2 Frequency 8 to 250 kHz

3 Wave – operating

mode Torsional - Pulse-echo/Pitch-catch

4 Pipe size Tested 2-inch to 60-inch diameter pipe

5 Inspection range

10 to 50 m for every direction; the effective range depend on

pipeline geometry (diameter, number of joints, elbows, branches) and pipeline state (pipeline above ground or buried, pipeline

coated or uncoated)

6 Time required for

inspection A few minutes once the magnetostrictive strips are bonded

3. Different Application Areas & Results :

3.1 Inspection of Stainless Steel material with artificial defects using MsS System:

The experimental arrangement of the Stainless steel Pipe is schematically shown in figure 2. The generation of the torsional wave mode T (0, 1) is possible with orientation of the DC biasing and

AC field and used Fe-Co ferromagnetic magnetostrictive material. The data acquisition and signal

generation part comprises MsS 30303R system. The output of the inspection will be in terms of

cross sectional area (CSA) % reflection and corresponding distance as represented in the A-scan in

figure 3 and corresponding result in table 2. Because, it is non ferromagnetic material pipe, its range will be less and background noise will be a little higher than carbon steel pipe. It is important to

underline that this monitoring is made possible by the sensor simplicity (the used magnetostrictive

strips are 0.004 inch thick and 2 inch wide).

Fig 2. A schematic diagram of Stainless steel material with artificial defects

MsS Strip

Detailed Inspection Image & Result:

Fig 3. The A-Scan plot both positive and negative side with respect to MsS Strip and their % CSA

Reflection amplitudes

EP- End of Pipe,

D1-surface wall loss,

D2-10% Grove,

D3-20% Grove, D4-Through Hole,

Q1- Strip attachment,

MsS1- MsS strip (initial Pulse).

CSA – Cross-sectional wall loss area

Report:

Table 2 Results in % CSA reflection and the respective distance from sensor location

Inconel (non-ferrous) material (Onsite Inspection)

LRUT inspection was conducted on Inconel 800H material with below sizes.

Job Details: Inconel 800H Furnace Coil 152.4 mm OD*9.53 mm thickness*16600 mm length

Fig 4. A-Scan plot both positive and negative side with respect to MsS Strip and their % CSA

Reflection amplitudes

Table 3 Results in % CSA reflection and the respective distance from sensor location

3.2 Inspection of spiral pipelines

The strength of MSS technology lies in the simplicity of the sensor in terms of installation and

adaptability to different types of pipes. Moreover, in the case of spiral pipes ones, the inspection

set-up can have a specific configuration positioned between the strip and the magnetostrictive coil

transducer. In this way it is possible to perform repeated acquisitions continuous monitoring of the pipeline. The inspection range will be less than 40 ft depending on the pipe condition. Because it is

spiral welded pipe, its range will be much less than Seamless pipe. The spiral weld will reflect

guided wave so that the background noise will be a little higher than seamless pipe.

By the test illustrated in Fig. 5 and fig. 6, related to a 42-inch pipe, 13.5 m long and PE coated & buried line, respectively. It has been shown in figure [5], [6] that the acquired signals shown

significantly in the following two cases:

1. Acquisition with the bare spiral welded pipe;

2. Acquisition with the PE coating & buried spiral welded pipe;

Fig 5. A-Scan plot both positive and negative side with respect to MsS Strip and their % of

Reflection amplitudes of 42” OD and 9 mm thickness (Bare condition)

Table 4 Results in % CSA reflection and the respective distance from sensor location

Fig 6. A-Scan plot both Positive and Negative side with respect to MsS Strip and their % of Reflection amplitudes of 42” OD and 9 mm thickness (PE coating & Buried condition).

Table 5 Results in % CSA reflection and the respective distance from sensor location

The system has a good sensitivity, a range of inspection comparable to those of other systems and

can easily be used on pipes of different diameters.

4. Conclusions

In this study, we investigated spiral welded pipes and non-ferrous material by using MsS guided

wave technique and analyzed signals acquired in each frequency (32 kHz, 64 kHz, 90 kHz, 128

kHz, and 256 kHz).

From the studies carried out in different conditions/applications, it is observed that LRUT using MsS Technology is flexible to use in different kind of applications & different conditions of the

inspection requirements. It offers wide inspection capabilities with minimum surface clearance

requirements. Hence MsS Sensor could be used on Ferrous / Non Ferrous pipe, Seamless pipe/

pipes with spiral for screening the long lengths of pipes.

5. Acknowledgement

The authors express their sincere gratitude to Sievert India Pvt. Ltd. (A Bureau Veritas Company)

for permitting to carry out the investigation and also permitting to publish the results.

References:

[1] Kwun, H. And Kim, S. Y., G. M. Kight, “The magnetostrictive sensor technology for long range

guided wave testing and monitoring of structure”, Mater. Eval. 61:80-84, 2003.

[2] M. Redwood, Mechanical Wave Guides, the Propagation of Acoustic and Ultrasonic Waves in

Fluids and Solids with Boundries, Pergamon, New York (1960).

[3] J.D.ACHENBACH, WAVE PROPAGATION IN Elastic Solids, Elsevier, New York (1975).

[4] H.Kwun, K.A.Bartels “Magnetostrictive Sensor Technology and it’s Applications” Ultrasonic

36 (1998) 171-178.

[5] Hegeon Kwun ,Sang –Young Kim ,and Glenn M.Light “Long Range Guided Wave Inspection

of Structures Using the Magnetostrictive Sensor” (2001).

[6] “REVIEW PAPER ON APPLICATION OF MAGNETOSTERCIVE SENSOR TECHOLOGY” Glenn M. Light, Ph.D., Hegeon Kwan, Ph.D., Sang Y. Kim, Ph.D., Albert Parvin, SWRI, USA.

[7] E. Kannan, B. W. Maxfield and Krishana Balasubramaniam, “ SHM of pipes using torsional

waves generated by in situ magnetostrictive tapes”.

[8]“Guided – wave structural heath monitoringing of piping in processing plants” H. Kwun, S. Y. Kim, M. S. Choi and G. M. Light Structural Health Monitoring 2003.