19th World Conference on Non-Destructive Testing 2016
Application of ultrasonic methods for manufacture of
pipelines and maintenance
Mitko MIHOVSKI 1, Pavel CHUKACHEV 1, Yordan MIRCHEV 2,
Vladimir SERGIENKO 3
1
Institute of Mechanics, Sofia, Bulgaria
2
BGSNDT and Institute of Mechanics - Bulgarian Academy of Sciences, Sofia, Bulgaria
3
V. A. Belyi, Metal Polymer Research Institute of National Academy of Sciences of
Belarus, Gomel, Belarus
Contact e-mail: nntdd@imbm.bas.bg
Abstract. Ultrasonic method is universal for inspection of manufacture and
maintenance pipelines. In this paper the features of application and possibilities to
obtain correct information about state of pipeline are presented. The following
application fields of ultrasonic method are reviewed in work:
• QualТtв Мontrol oП manuПaМturОН pТpОs (Обport Мontrol);
• InspОМtТon oП аОlНs in pipeline fitting;
• AssОssmОnt oП tСО pТpОlТnО statО Тn aНvanМО prОparОН МrТtТМal arОas (usТnР also
metallographic analysis, hardness test);
• CorrosТon ТnspОМtТon Тn maТntОnanМО usТnР
Pipeline internal gauge (PIG) for inspection;
Guided wave technique;
Convention ultrasonic thickness testing to assessment of corrosion
damage in advanced prepared critical areas on pipeline.
• AssОssmОnt oП mОМСanТМal strОss statО Тn surПaМО oП pТpОlТnО;
• AssОssmОnt oП aНСОsТon between reinforced (repair) material and pipe
surface;
• InspОМtТon oП qualТtв, mОМСanТМal propОrtТОs anН tСТМknОss oП rОТnПorМОН
material for pipelines repair.
The information in this work are presented used developed written practice
procedures for laboratory testing and for maintenance of pipelines.
Introduction
In data presented in [1] and in accordance with the strategy for the development of Russia
until 2030 the unified system of gas supply, which is the largest in the world, includes 160
000km pipeline and 300 compressor stations.
In pipeline material has a significant amount of discontinuities that occurred during
the manufacturing of pipes and welds as well as during maintenance.
To discontinuities in the manufacturing of pipeline are included: change of integrity,
discontinuities in welds and change in physical and mechanical properties.
Discontinuities in manufacturing of gas pipelines are associated with problems in
pipe laying, break protective coating, mechanical wear and increased mechanical stresses in
the material.
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In maintenance primarily discontinuities are associated with corrosion and erosion
damage, changes in mechanical stress state at environmental influences, fatigue cracks,
changes in the material structure in emergency situations and others.
Presented data in [2] show that the percentage defects of external corrosion in
maintenance are 29%, of internal - 2.5%, wrong manufacturing of pipeline- 23%, of fault in
maintenance- 16% and production of pipes in factories- 14%.
In defects break integrity of the pipeline has gas leakage, often leads to significant
material damage (loss of gas, fires, pollution of the atmosphere) and in many cases, human
sacrifices.
Based on years of experience in manufacture and maintenance of pipelines has a
constructed system for managing the technical condition and defects, which includes:
assessing influence of many factors on maintenance of the pipeline, monitoring testing,
system for risk assessment and the effective work of transit systems. This system is
constructed with consideration of:
- Significant date from non-destructive testing and diagnostics;
- Development of general and specific standards and regulations.
The systems included internal and external pipeline inspection included remote
control and diagnostics (for pipeline underground).
As most perspective method for non-destructive testing and diagnostics of defects
state, mechanical state and the physically-mechanical properties in recent years have
ultrasound method with its various applications for internal and external pipeline
inspection.
The purpose of this work is to present the possibilities of using ultrasound methods
at different stages of manufacturing pipelines for transportation, for installation and there
maintenance. Conditional in the work are refered the following stages:
- Manufacturing of gas pipelines;
- Welding of basic pipelines elements;
- Assessment state after placing pipes (over- and underground);
- Maintenance inspection;
- Rapier.
All activities of control and diagnostics used ultrasonic methods is regulated by
legislation. These documents are shown into reference in work. Special attention is paid to
industry standards STO Gazprom, GOST and EN.
In table 1 are written name of this standards and procedures in which they are
specificities
Table 1 Methods and regulations.
Methods
Traditional
and
modern 2-2.4-083
methods
for
ultrasonic 2-2.3-292
testing:
- Guided Wave
- TOFD
- Phased array
- Tandem
Assessment of mechanical 2-2.3-220
stress state
2-2.3-238
12503
14782
28702
52330-2005
52890-2007
52731-2007
2
EN
EN ISO 16810
EN ISO 17640
EN ISO 11666
EN ISO 10963
EN ISO 16828
EN ISO 17635
1. Manufacturing of pipes
1.1. Automated ultrasonic testing of seamless and welded (except submerged arc-welded)
steel tubes for the detection of longitudinal and/or transverse imperfections
The tubes shall be tested by using an ultrasonic shear wave technique for the detection of
longitudinal and transverse imperfections. Lamb wave technique may be applied for the
detection of longitudinal imperfections. The requirements for testing are in accordance with
standard EN ISO 10893-9:2011 [16].
1.2.Ultrasonic testing on plate edges
The longitudinal strip/plate edges shall be 100 % ultrasonically tested for the detection of
laminar imperfections over a width of at least 15 mm, plus, if appropriate, the total width of
edge material which shall be removed from each original strip/plate prior to seam welding,
in order to detect the relevant minimum imperfection length, Lmin, as given in Table 2 in
standard EN ISO 10893-9:2011 [17].
1.3. Mechanical stress testing in predefined critical areas in pipe during maintenance
In the system of Russian legislation are presented two standards [7], [8], which regulate the
application of ultrasonic methods, for evaluation of the mechanical stress.
52890-2007 [7] regulates the basic requirements for determining the
mechanical stress. Use volume ultrasonic waves that propagate in radius direction on
controlled pipes. The standard is applicable to pipes of steel (seam and seamless) with ratio
the wall thickness to the outer diameter 20 times and to pipes with a diameter greater than
325mm.
In the process of measurement is recorded the initial velocities (time of propagation)
in the material in the absence of mechanical stresses, taking into account the acoustic
anisotropy of the material, microstructure etc. factors. Depending on the measurement
conditions, the current primary acoustic state of the material is carried on specially prepared
samples or on the test pipes.
1.4.Measurements of velocities and attenuation for spreading ultrasonic waves in medium
Measurements are realized with specialized equipment with high accuracy when measuring
the velocity and times of volumetric ultrasonic waves. Emitted and received of the waves is
realized with special transducers for transverses polarized waves and normal transducers
for longitudinal waves. Increasing accuracy of measurement can be achieved using method
of multiple echoes. The attenuation measurement is written in EN ISO 16823.
1.5. Assessment of mechanical characteristics- elastically modulus
The determination of longitudinal and transverse velocity of sound in a material makes it
possible to approximately calculate tСО PoТsson’s ratio-  , ВonР’s moНulus oП ОlastТМТtв- E
and shear modulus- G. The formulas for calculating these factors are as follows
3

C
1  2 t

 Cl

 C
2 1   t
  C l



Ct2 (3Cl2  4Ct2 )
,
, G  Ct 2 ,
E

2
2
2
C
C

l
t
 
 
 



2
(1.5.1)
where  is density, Cl , Ct are ultrasonic longitudinal and transverse velocity.
The elastically modulus is used for assessment of allow pressure in transits
petroleum pipelines.
1.6. Ultrasonic thickness measurement in point on critical areas, where is conducted
monitoring during the maintenance of pipe
Ultrasonic thickness measurement is done by pulse-echo method, according to standard EN
14127 [15]. This standard specified procedures for determining the thickness including and
thinning and detection and characterization of discontinuity encountered in general and
pitting corrosion. In these procedures, information characteristics of the echo in
determining the thickness are: time distribution of information received ultrasonic signal
and the location of the probe on the contact surface. The measurements are done on points
in area, where is most possibility thinning of pipe wall from different factors during work
conditions. The good accuracy for measured thickness is achieved used ultrasonic
electromagnetic acoustical probes and equipment with A-scan presentation of signals.
Automated ultrasonic thickness testing is done according requirements of standard EN ISO
10893-12 [20].
2. Welding of pipe in main pipelines
2.1.Automated ultrasonic testing used normal and angular beam probes for welds and head
affected base material
This technique is mainly used for the pre service inspection of pipelines. The ultrasonic
techniques and settings will be selected according diameter, weld thickness and preparation
(chamfer) to be inspected. The scan movement consists of a single line scan along the weld.
In accordance with EN ISO 10893-11 weld seam of the tube shall be tested using an
ultrasonic shear wave technique for the detection of longitudinal and/or transverse
imperfections. Unless otherwise agreed on by the purchaser and manufacturer, testing shall
be carried out in two opposite directions of sound propagation for the requested type of
inspection, clockwise and anticlockwise for the detection of longitudinal imperfections and
forward and backward for the detection of transverse imperfections. The application,
restriction and acceptance level are written in EN ISO 10893-11 [19].
2.2.Automatic ultrasonic testing of welding with TOFD and Phased array methods
TOFD is considered a non-amplitude technique but some minimum and maximum
sensitivity must be established and a method of duplicating scan level from system to
system should be incorporated into the procedures. TOFD sensitivity may be configured by
setting the amplitude of the lateral wave or by setting the response off a calibration target
such as a tip diffractor or a side-drilled hole.
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Application of both TOFD and phased array techniques together for zone
discrimination of welds, decrease time testing and increase probability of detection for
various type and location discontinues in welds. Engineering Critical Assessment (ECA also called Fracture Mechanics, Fitness-For-Service or Structural Integrity) is used to
evaluate discontinues on scan image from phased array technique. TOFD technique is used
for crack detection in welds and is well written in standard EN ISO 16828 [21].
2.3. Assessment of mechanical stress state in area around welding used normal beam probe
for longitudinal ant transverse waves spread to radial direction
Measurements shall be done with certified equipment. Normal probe for emitted of
longitudinal and transverse ultrasonic waves is used. The measurements are usually in the
echo-pulsed mode. Surface in the measuring zone mast be a roughness Ra2.5m. As
contact medium is used an epoxy resin. Mandatory is monitoring the temperature of the test
material. In order to increase the accuracy of the method is used multiple echoes signals
received in an area of a plane opposing walls in the pipe and in the absence of signals from
a discontinuity in the volume of the material.
2.4. Assessment of mechanical stress state in surface and subsurface of welds and head
affected base material by Rayleigh and creeping waves
Assessment is done used calibration dependences for material between ultrasonic velocities
of spread surface waves CR and mechanical stress- . The dependence between them is
give with next relationship
C R   . ,
(2.1.4.1)
where CR=CR-CR0 (CR0 velocity in material without mechanical),  is acousticallymechanical coefficient specific for investigated material and head treatment.
2.5. Assessment of adhesion of insulating protection coating of pipe used longitudinal,
transverse and Stonely’s waves
Echo-pulse method is used with normal duel and angular probes. Adhesion contact state is
assessment with information characteristics amplitude and phase of echo signal.
When echo signal in material is reflected from air layer (delimitation between
protection coating and basic pipe material) with thickness more than 2-3µm at frequency
around 4MHz, amplitude is decrees and phase is shifted at 180 compare to reflected signal
from acoustical denser medium(good adhesion contact between protection coating and
basic pipe material).
3. Ultrasonic testing during maintenance (monitoring)
3.1. Ultrasonic testing for volumetric and surface discontinuities and corrosion damaged
used internal pipeline non-destructive evaluation systems
Usually internal pipeline inspection are used three different tools: one gauge tool, one
cleaning tool and the in-line inspection tool, which maps potential corrosion and metal loss
as well as the exact curvature of the lines via an inertial navigation system.
The gauge tool is used to detect substantial anomalies of the internal diameter along
the pipeline which may potentially obstruct the inline inspection tool during its run. The
cleaning tool is sent through the pipe to remove small particles of dust that may have
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accumulated in the pipeline during the operating time and tiny particles of coating material
from the pipelines inside that may have become loose. The main inspection tasks are
performed by what is commonly referred to as an intelligent combo tool since it combines
arrays of sensors to perform different integrity inspection tasks. The tool constantly
measures its distance travelled via wheels rolling along the inner pipe walls – which helps
map measurement along the length of the pipeline.
3.2. Ultrasonic thickness measurement in predefined critical areas (monitoring)
Monitoring of thickness in critical areas is important information about assessment of
corrosion process in pipe wall during services of pipelines.
3.3. Guided wave ultrasonic testing for wall thinning
Guided wave offers an alternative application for ultrasound wall thickness of pipes. At this
stage there is no European standard for its application. Individual companies have
developed documented procedures for control with guided wave technique. This technique
The application of this technique is performed by an ultrasonic system, consisting
of: array circular ring with a number of transducers, equipment for controlling the circular
array (multiplexer) and notebook with program product for displaying the signal in the scan
image and control the multiplexer. Four most produced guided wave systems are developed
and presented to the market until now from Plant Integrity Ltd (www.plantintegity.com),
TWI, Guided Ultrasonic Ltd (www.guided-ultrasonics.com), MKC Korea
(www.mkckorea.com/english.html) and the new systems from company OLYMPUS.
Restrictions for guided wave are related to the following characteristics of the
manufacture, installation and operation of controlled pipeline: geometry and components,
insulation, content of fluid in the pipeline, the pipeline status, noise around the pipeline and
others.
3.4. Assessment of mechanical stress state in assumed area with discontinuity for
prediction of method and materials for pipeline fiber-reinforced composite repairs.
Assessment of mechanical characteristic of used composite material
Assessment of mechanical stress state in area with discontinues in services of pipeline give
initial characteristic used for numerical calculation of necessary pressure applied from
outside to inside of pipe for safety work with working pressure. When value of pressure,
mechanical and geometrical characteristic of pipeline and working pressure is known is
define elastically and mechanically characteristics and dimensions of material used for
reinforced (repair) of pipeline.
3.5. Acoustic emission testing for monitoring and localization of discontinues
Acoustic emission (AE) is an excellent tool for detecting and locating leaks in buried
pipelines. Access to the pipeline is required only locally for mounting AE sensors. Pipeline
is pressurized and AE tested in 600m-1000m long sections at a time. The AE sensors detect
the turbulent flow at the leak orifice, and with the use of digital AE systems and specialized
software, the position of the leak is provided. The technical description and the physics of
the AE leak detection technique, presents the application, limitations and requirements of
the method is describes in
52727 [3].
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Conclusion
In this work are presented the possibility of different techniques for application of
ultrasonic testing of manufacturing pipelines for petroleum industry and assessment of
pipeline state during maintenance.
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