Boiler tube welds require a rapid volumetric inspection method. Traditionally, radiography (RT) is used, but this technology has several drawbacks. RT is insensitive to mis-oriented planar defects, it does not provide immediate feedback to the welders, and is disruptive to other activities. Mostly, safety regulations are getting more and more severe worldwide drastically restricting the use of radiography.

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Phased Array and TOFD
Boiler Tube Weld Inspection
Application Solution

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Overview
• Inspection Challenge
• Recommended PA UT Solution
• Results – Comparison with RT
• Benefits of Zetec Solution
• Suggested Kit

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• The industry requires a rapid volumetric NDE
technique for boiler tube welds, to minimize outage
time and budget
• Traditionally, radiography (RT) is used, but has several
drawbacks:
Inspection Challenge
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- RT is insensitive to planar defects,
if angle between planar flaw and
beam is > 8°
- No immediate feedback for welder
- RT is disruptive to other activities
- Safety regulations are getting
more severe worldwide
Lack of fusion defect missed by radiography

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• Encoded Phased Array UT paired with TOFD offers a
reliable and efficient alternative volumetric inspection
solution “in Lieu of RT”
• Solution to deal with low clearance, variety of
diameters, and the presence of weld caps :
• Circ-it Scanner
• Low Profile PA UT Probes & Wedges
• LIMBOTOFD™ Integrated Probes (*)
• Flexible Inspection Technique
(*) Trademark of GB Inspection Systems Ltd.
Recommended Solution
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• Circ-it scanner (from Jireh Industries) :
one-axis manually encoded scanner
• Variety of diameters:
from 21.4 mm to 114.3 mm (0.5” to 4.0” NPS)
• Low-profile design: radial clearance 11 mm
• Modular and flexible design:
• Quick change links for infinite adjustment
• Single or dual PA probe scanning configuration
• With or without TOFD
• Cable management system for irrigation lines and
probe cables
Scanner
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Scanner
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• Extra thin 1D linear array probe: 11 mm (0.433’’)
• Curved array for optimized focusing in thin tubes: r = 35 mm
• Designed for sectorial scanning
• Multiple probe frequencies available
• 5 MHz for rough inspection surfaces (with OD pitting)
• 7.5 MHz for standard inspections
• 10 MHz for optimized detection and characterization of small
volumetric indications (porosities, slag...)
• Choice of 16 or 32 elements to optimize steering capability
Low Profile Phased Array Probes
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Low Profile PA Probes
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All probes with ZPAC connector, dual connector optional,
recommended generic probe highlighted
Probe Type
Frequency
(MHz)
Number of
Elements
Pitch
(mm)
Active
Aperture
(mm x mm)
ZPA-PB1D-AT-5MHZ-16-REX-2.5M-ZPAC
ZPA-PB1D-AT-7.5MHZ-16-REX-2.5M-ZPAC
ZPA-PB1D-AT-7.5MHZ-32-REX-2.5M-ZPAC 7.5 32
5 16
8 x 10
0.5 8 x 10
7.5 16 0.5 8 x 10
0.25 8 x 10
10 16 0.5 8 x 10ZPA-PB1D-AT-10MHZ-16-REX-2.5M-ZPAC
ZPA-PB1D-AT-10MHZ-32-REX-2.5M-ZPAC 10 32 0.25

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• Extra thin assembly: 11 mm (0.433’’)
• Wedge kit to cover 0.5” to 4” NPS, and flat
• Interchangeable rexolite wedges
• Wedges optimized to minimize the distance between
probe and weld center line
• Irrigation and easy scanner interfacing
Low Profile Wedges
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• Extra low profile (10 mm) TOFD probes
• Curved wedges shaped to pipe diameter
• Integrated wedge for easy deployment
• 10 and 15 MHz frequencies available
• Multiple beam angles available, 60°LW or
70°LW recommended for boiler tube welds
• Active element diameter 3 mm, for complete
coverage of examination volume
LIMBOTOFD™ Probes
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• High-speed inspection : acquisition
from 2 sides, in less than 1 minute
• One-line circular movement, with
sectorial scan for weld coverage
• Full skip inspection: capability to use
from 40° to 80°SW
• Accurate imaging using on-line
S-Scan and Dynamic Merge on TOPAZ
• 2 Side PA and TOFD dedicated layout
• Examination methodology adaptable to
applicable codes and requirements
Inspection Technique
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Sample datafile for 2” NPS pipe
Results
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Alignment
makes flaws
easy to track
between all
channels
Dedicated
layout for
optimal data
review
Weld overlay
for easier flaw
characterization

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Results – PA Comparison with RT
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Courtesy of RWE Power Intl.Ltd
Wormhole piping Group porosity Wormhole piping

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Results – PA Comparison with RT
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Courtesy of RWE Power Intl.Ltd
Root crack Isolated pore Lack of side wall fusion
(not visible on radiograph)

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• Coal Generators GENSIP Programme (UK) organized Round-
Robin NDT exercise (2013 – 2014) to assess performance and
reliability of PA UT
• 50 tubes with various diameters, and containing various flaw
types were inspected by 10 NDT service companies
Results – PA Comparison with RT
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Two-dimensional scoring system : detection on X-axis,
sizing and characterization on Y-axis
Results – PA Comparison with RT
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QualityofSizingandCharacterization(%)
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
Detection (%)
0 10 20 30 40 50 60 70 80 90 100
Detection of Rejectable Flaws (%)
0 10 20 30 40 50 60 70 80 90 100
QualityofSizingandCharacterization
OfDetectedFlaws(%)

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• PA UT & TOFD detects all weld defect types, but better suited
for planar defects : lack of root fusion, lack of root penetration,
weld toe crack, weld root crack
• RT is better suited for volumetric defect types: porosity,
inclusion
• Education on expected flaw types is important : well-trained PA
UT operators will have success for defect characterization on
all defect types, for wall thickness > 7 mm
• PA UT can have some difficulty to characterize volumetric
defect for small thickness (< 7 mm)
• Weld overlay is important to help position and diagnose flaws
• PA UT & TOFD offers through-wall sizing capability, length
sizing is less accurate than for RT (over sizing)
Technical Benefits of PA UT & TOFD
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• PA UT combined with TOFD can detect all defect
types, and offer through-wall sizing capability
• Non-disruptive to other activities
• scanner, industrially proven design,
adapts to a wide variety of boiler tube diameters
• and integrated units,
compact and easy to setup
• UltraVision Touch™ on-board software, guarantees
an efficient inspection workflow, from set up to
analysis and reporting
Benefits of Zetec Solution
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