cob06331 design and development of automatic scanning ultrasonic inspection of pipelines

8/4/2019 Cob06331 Design and Development of Automatic Scanning Ultrasonic Inspection of Pipelines

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Proceedings of COBEM 2011 21st

Brazilian Congress of Mechanical EngineeringCopyright 2011 by ABCM October 24-28, 2011, Natal, RN, Brazil

DESIGN AND DEVELOPMENT OF AUTOMATIC SCANNINGULTRASONIC INSPECTION OF PIPELINES

Marcelo Cavalcanti Rodrigues, e-mail: [email protected], [email protected]

Jos Carlos de Lima Junior, e-mail: , [email protected] Daniel Vasconcelos Mishina, e-mail: [email protected] Bosco de Aquino Silva, e-mail:[email protected]

Fbio Barreto, e-mail:e-mail: [email protected] University of Paraiba, Technology Center, Mechanical Engineering Department, Integrity and Inspection Laboratory (LII).

Abstract. Nowadays there is a need to develop automatic inspection systems for access equipment in service. The

industry invests in own inspection service and inspection training for provide longer life to equipment. The loss metal

measure by ultrasonic technical should provide easier access to inspections by ultrasonic; reducing costs and

minimizing the maintenance and inspection. The duct network in Brazil is about 22.000 km where is expected to

increase in coming years. The European Union operates over 778.000 km. This work shows the design of ultrasonic

inspection automatic system for metal loss measure in duct with a interface for measure of wall thickness. The

automatic inspection system has easy assembly and manufacture, low cost, good precision to data collect and larger

scanning area. The prototype was developed from the external gears revolution motion driven by pinion gear, byelectric motor, which carries the circumferential motion clockwise or counterclockwise. After reading the

circumferential area carried out a longitudinal motion, by electric motor, to the next checkpoint, forming a scanning

area. At the top of the external gear, there are places coupling of ultrasonic transducers. To the operate the system

there are the computer acquisition with the interface software that manipulates the data collected by ultrasound and

calculates the loss metal, the Controller that performs the communication between the computer acquisition and

automatic inspection system. The development of automatic scanning ultrasonic inspection of pipelines has big

advantages in comparison with the manual process. There is better control in positioning and minor deviations in the

samples due to the change in motion. Also worth noting is the versatility in controlling system, using a joystick without

the need to monitor, reducing the chances of human error during inspection. Significant gains in productivity, quality

and low cost can be expected. A major advantage of this system is low cost, being much simpler to build and costs only

a fraction of international competitors.

Keywords: automatic scanning, duct, ultrasonic inspection, interface, metal loss.

1. INTRODUCTION

The damage mechanism for petrochemical and petroleum equipments presents diversified way, that depending on

own environmental and operational work conditions. For an efficient control is essential to have knowledge of the

principle, the spreading way and prevention methods of the damages. It is necessary in many cases, live, identify your

extension and follow the damage progression. There are no standards for repair, but there are criteria that allow

assessing the damage and influence on the risk of operating equipment. The activity of evaluating integrity requiresmore engineering versus less intervention (Rodrigues, 2007).

The motivation of this work is an answer to the need to implement techniques for nondestructive testing to monitor

the phenomena of corrosion in metallic duct in real-time service and allow the realization of a predictive maintenance,

reducing possible costs unnecessary operations. The goal is to allow easier access to inspection in equipments.

The circumferential and longitudinal movements performed by device allow the most flexibility for inspection toscan in any direction along the duct. The device involves the coupling of one or more ultrasonic transducers. The

signals obtained by transducers are sent to a program for detection of damage and duct wall thickness.

2. ULTRASONIC TESTING

2.1 Basics principles

Ultrasonic inspection is a nondestructive method in which beams of high-frequency sound waves are introduced in

materials for detection of flaws in surface and subsurface of the material. The sound waves travel through the material

with some loss of energy (attenuation) and are reflected at the interfaces. The reflected beam is displayed and then

analyzed to define the presence and location of flaws or discontinuities (Santin, 2003).Nondestructive tests can be defined as an indirect way to verify the integrity of equipments through the interaction

between materials and any energy way, without any damages. Among ways of energy, the acoustic energy highlightsbecause has low cost of generation and detection, hasnt radiation, can spread in many ways without attenuation and can

detect a good amount of damage and properties of the material.


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The ultrasound testing instruments operate in the frequency range between 20 and 500 kHz are referred to as sonic

instruments, while those that operate above 500 kHz are called ultrasonic. To generate and receive ultrasonic waves, apiezoelectric transducer is employed to convert electrical signals to sound waves and back again. The transducer is a

piezoelectric crystal mounted in a waterproof housing that is electrically connected to a pulser and a receiver. In the

transmit mode a high-voltage, short-duration electrical spike is applied to the crystal, causing to rapidly change shape

and emit an acoustic pulse. In the receive mode, the sound waves (returning echoes) compress the piezoelectric crystal,producing an electrical signal that is amplified and processed by the receiver (Mechanical Engineers Handbook, 2006).

The Figure 1 shows this process.

Figure 1. A schematic of ultrasonic data collection and display in the A-scan mode.

The ultrasonic principle is based on the concept of sound conductivity. Tests by ultrasound are the non-destructive

testing method in which a high frequency ultrasonic beam is introduced into the material to detect internal damages.

The beam travels through the material is reflected by internal damages and interfaces being detected to determine the

existence and location of damages.The ultrasonic waves reflected by interfaces depend on the physical properties of the materials and the environment.

The interaction effect of sound waves with material is greater when shorter the wavelength as shown in Equation (1).

vf = (1)

Where v is the speed of sound along of propagation [km/s], fis the frequency in [MHz] and is the wavelength in[mm]. For example, the wavelength of longitudinal ultrasonic has frequency of 2 MHz that propagating in steel is 3 mm

and the wavelength of shear waves is about half this value, 1.6 mm. The relation between the sound pressure and the

particle amplitude is

vafp 2= (2)

whereis density and a the amplitude.Ultrasonic waves are reflected from boundaries between different materials or environment. Each medium has

characteristic acoustic impedance and reflections that occur in a manner similar to those observed with electrical

signals. The acoustic impedanceZof any medium capable of supporting sound waves is defined by

vZ = (3)

Materials with high acoustic impedance are often referred to as sonically hard, in contrast to sonically soft materials

with low impedances. For example, steel (Z = 7.7 g/cm3 x 5.9 km/s = 45.4 x 106

kg/m2.s) is sonically harder than

aluminum (Z = 2.7 g/cm3 x 6.3 km/s = 17 x 106 kg/m2 s).

2.2 Thickness measurement

The thickness measurement is the most frequent ultrasound test. The importance of thickness measurement by

ultrasound is the fact that the first test does not need access to the opposite wall for execution, without interrupting their


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operation. The simplicity of implementation and speed of implementation and achievement of results, where the

inspector can determine within seconds the thickness of a stretch (Santin, 2003).The storage of the measurements represents an important gain for the reliability, avoiding the possible error in

transcription of these, and the possibility of transferring this data to a computer.

For measuring wall thickness, must know the travel time of sound in the material, and then use the following

equation.

tvs = (4)

Where s is the displacement of the sound wave, v is the sound speed in the environment, tis the travel time. The

wall thickness is the half of displacement of the sound wave. Figure 2 shows how detects wall thickness w_th.

damagedundamagedtvtvthw )(2/1)(2/1_ = (5)

Figure 2. Portable equipment for measurement thickness.

3. DESIGN AND DEVELOPMENT OF AUTOMATIC SCANNING ULTRASONIC INSPECTION

With the goal of develop an automatic system capable of performing inspection of pipelines using ultrasound with

easy to assemble, installation, manufacture and low cost, accuracy in data collection, larger scanning area, movement in

areas of difficult access, interface for easy interaction, higher productivity, develop skills of mechanical engineeringstudents and present the NDT techniques.

Figure 3. Initial design of automatic scanning ultrasonic inspection.

3.1 Construction of Prototype

The prototype was developed from the movement of external gears driven by a pinion which performs the

circumferential motion and moves in longitudinal movements generated by electric engine.

At the top of the external gear, there is a local (case) for coupling ultrasonic transducers, which can increase the

scanning area of pipe surface. At the bottom of the external gear, the holes were built to house the balls and springs,where the distance between the transducer and the surface of the duct is varied by a spindle. The Figure 4 shows the

platform and external gear.

PipelineAutomatic

scanning

Motion system


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(a) (b)

Figure 4. (a) Platform with the pinion and electric motor; (b) External Gear with ultrasonic transducers.

From the designs, the parts were constructed with nylon and for the mounting were made the first tests. The Figure 5

and Fig.6 show the side, frontal view for prototype.

(a) (b)

Figure 5. (a) Side view; (b) Frontal view.

(a) (b)

Figure 6. Prototype of automatic scanning ultrasonic testing.

3.2 Operation of the automatic scanning ultrasonic testing

The automatic scanning works with two electric motors, capable of performing the movements around and along the

duct. The acquisition computer manipulates the data obtained by ultrasound, and calculates the thickness loss from the

interface developed. Next, the controller realizes the communication between the motion computer and automaticscanning ultrasonic testing.


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Figure 7. Block diagram for how work automatic scanning.

3.3 Construction of interface for automatic scanning

From an area to be inspected, must obtain the thickness values of the pipeline from general corrosion. The algorithm

developed to calculate the thickness loss, which is used to detect the peaks of the ultrasound to measure the arrival time

of the ultrasonic signal. The Figure 8 shows the grid of inspection for pipeline with corrosion region. Figure 9 shows the

interface configuration and the results of amplitude versus time with the thickness of the material inspected.

Figure 8. Grid of inspection.

The interface is designed to provide an environment of easy access and versatility. The inspector selects the material

to be inspected in the list that the program offers, give input with the value of the frequency and makes the choice of the

number of division the signal to achieve the highest points. When the system moves the results of the ultrasound signals

collected are shown on screen and recorded. Figure 9 shows the initial screen interface with some results.

Figure 9. Interface and results in amplitude versus time.

Next, the Fig. 10 shows the interface provides graphs of amplitude versus time beyond the value of the thickness of

the material inspected (duct), where the user must enter the data of the material being inspected, as the speed of wavepropagation, the original thickness of the material, etc.

Automatic scanning Acquisition computer/Interface/wall thickness

Controller Motion computer


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(a) (b)

Figure 10. Interface with data input sound speed and nominal thickness.

The Figure 11 shows the color map of the profile wall thickness for the corrosion region of duct.

(a) (b)

Figure 11. Wall thickness and color map for the corrosion region profile.

4. CONCLUSIONS

Industrial robots have become increasingly attractive, increasing production efficiency. But for industrial

applications in areas such as duct inspection, conventional robots are unable to operate effectively enough to justify the

high cost of implementation. It is therefore necessary to create new systems that can fill the gap in conventional

applications, where robots are not effective.

The tests were done at the Integrity and Inspection Laboratory of (UFPB/CT/DEM/LII) using the first prototype of

the automatic inspection. Currently the system controller is in the testing phase, with the main objective of providingprecision movements in each direction you want. The graphical interface is being implemented for the Labview system,

which will provide an embedded technology in the future.The development of automatic scanning ultrasonic inspection of duct has big advantages in comparison with the

manual process. There is better control in positioning and minor deviations in the samples due to the change in motion.

Also worth noting is the versatility in controlling the system, using a joystick without the need to monitor, reducing thechances of human error during the inspection. Significant gains in productivity, quality and low cost can be expected. A

major advantage of this system is cost, being much simpler to build and costs only a fraction of its international

competitors.

A system able to move more independently is our objective in the medium and long term needs for this are

investments in materials, equipment, professionals, etc., to present a product of great quality and credibility.

5. REFERENCES

Abendi, 2005, Site da Associao Brasileira de Ensaios No-Destrutivos.

Andreucci, R., 2008, Ensaio por ultra-som Aplicao Industrial, Abende.

ASM, 1997, Nondestructive Evaluation and Quality Control, volume 17, fifth printing, ASM Handbook Committee.


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Mechanical Engineers Handbook, 2006, Materials and Mechanical Design chapter 36, Volume 1, Third Edition,

Edited by Myer Kutz, John Wiley & Sons, Inc., Hoboken, New Jersey.

Rodrigues, M. C., 2007, Anlise da Integridade Estrutural em Hastes de Bombeio Por Cavidades Progressivas. Tese de

Doutorado, UFPB/PPGEM.

Santin, J. L., 2003, Ultra-som Tcnica e Aplicao, 2 edio, Pr END Consultoria Ltda, Curitiba, Brasil.

Transpetro, Portal, 2010, .

6. RESPONSIBILITY NOTICE

The author(s) is (are) the only responsible for the printed material included in this paper.

cob06331 design and development of automatic scanning ultrasonic inspection of pipelines

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