RECENT ULTRASONIC

TESTING TECHNOLOGY

DEVELOPMENTS IN

DOOSAN BABCOCK

Colin Bird – Consultant, NDT Department

Qualification of new techniques

Demonstrate how new inspection technologies can improve

plant efficiency by reducing down time.

Show that new technologies can be introduced where there

are no appropriate standards.

Demonstrate the challenge and some solutions to novel

technique qualification via two case studies.

Paper Objectives

Drivers for Change

– Cost Reduction

• Phased Array Technique 30 welds per shift per team

• Radiography 15 welds per shift per team.

• PA team 2 operators per team, Radiography 4 man team.

– Outage Time Reduction• No radiographic exclusion zones.

– Multiple phased array teams

– Work in parallel with welding teams

• Proven outage time compression of 10% to 30%.

– Safety Improvement

• No radiographic hazard.

Small Bore Pipe Inspection and Qualification

11 to 13mm gap

between tubes

Inspection Technique

– Pipe Diameters

• 25mm to 90mm diameter

– Wall Thickness

• 3mm to 12mm

– Material

• Currently ferritic tubing

• Developing austenitic capability

– Focused Phased Array Probes• 10MHz 32 element

– Scanner

• Bi direction bracelet scanner

Small Bore Pipe InspectionTechnique

1995 ASME Code case 2235

– Subject to proving trials

– Codes require detection of pores, worm holes, slag and planar flaws.

Why!

– UT is inherently less sensitive to pores than radiography

– Radiography is less sensitive to planar flaws.

• Planar flaws cause catastrophic failure pores may leak if the pipe becomes thin due to corrosion or erosion.

.

– Do we require manufacturing QA or Fitness for service.

Inspection Standards

14 September 2011 | 5

Small Bore Pipe Inspection Technique

3.1mm

6dB drop off sizing for smooth planar defects

Maximum amplitude sizing for echodynamicpattern 1 3 and 4 defect responses.

High inspection sensitivity to detect small pores requires a flaw

discrimination method.

3.9mm

2.8mm

14 September 2011 | 6

Inspection Development

Doosan commenced development in 2009 in collaboration with RWE.

Comprehensive practical trials

– Range of representative samples containing about 70 real defects*.

Tube butt welds 4-9mm thick.

Theoretical coverage modelling

Live qualification dossier.

GENSIP (2014)(Generator Safety Improvement Program)

Consortium of UK power generators plus China Light & Power.

EDF France (2014)

Qualification via ENIQ process. Technical Justification involving defect detection modelling and trials.

Inspection Qualification

Inspection Qualification - Modelling

Comparison of amplitude with small variations in target position

14 September 2011 | 9

GENSIP Qualification Trials

Collaborative Trial administered by E.ON.

10 companies performed blind trials using phased array UT techniques.

50 welds

10 flaw types

90 flaws

2 Days to complete trial including reporting

Radiography used as a control under open trial conditions.

14 September 2011 | 10

GENSIP Qualification Trial Results

Doosan Babcock

Radiography

14 September 2011 | 11

Conclusions from GENSIP Qualification Trials

Training of the inspection personnel with the procedure is necessary.

Reliability is not achieved by solely procuring the correct equipment.

There are weaknesses in radiography and phased array UT but the

weaknesses in phased array UT can be mitigated with training.

Drivers for HDPE Pipe Usage

and Inspection

– Corrosion resistance• Longer life

• Less time lost due to maintenance programmes

– Erosion resistance• Longer life

– Lower coefficient of friction• Smaller diameter for a given flow rate –

but usually lower operating pressures.

HDPE Pipe Inspection and Qualification

Location of defects.

Weld fusion line.

Weld flash.

HDPE Pipe Inspection and Qualification

Top and bottom arcs

from planar defect

Pipe bore weld flash

Inspection Technique

Drivers

– Corrosion resistance

• Longer life

• Less time lost due to maintenance

programmes

– Erosion resistance

– Longer life

– Lower coefficient of friction

• Smaller diameter for a given flow

rate –but usually lower operating

pressures.

Hurdles

– No defect acceptance standards

– No volumetric inspection

standards

HDPE Pipe Inspection Drivers and Hurdles for Usage

Location of defects.

Weld fusion line.

Weld flash.

No standards

– Zero tolerance agreed with EDF

Test Piece Manufacture

– Simulating LOF

– Implanting ultrasonic targets• Back fill ?

• Within welding process ?

– Target material• Stainless steel chosen

– Target location and accuracy• Location confirmation with x-ray

– Target Shape w.r.t. inspection method• Target shape, round, linear, oval

Undergoing Independent Qualification

HDPE Pipe Inspection Qualification

Experience

– Pipes from 350mm diameter to 1200mm diameter

– Pipe thickness from 35mm to 68mm

– Single sided inspection

– Temperature range 5° to 40 °C

Procedure

– Adapted to accommodate variable site temperature and conditions.

– Proven from many pipe system inspections.

HDPE Pipe Inspection Application

Robustly qualified, ultrasonic inspection techniques, applied in lieu of

radiography, can add value to utility power companies.

Small Bore pipe inspection and HDPE pipe inspections techniques have

been developed to a point where they can be applied to plant in highly

regulated environments.

To demonstrate that newly developed inspection techniques are reliable

extensive trials need to be performed under blind and semi-blind

conditions to the satisfaction of the utilities and their third party inspection

bodies.

Extreme care must be taken when designing technique trials for new

situations and materials to ensure that a meaningful result is achieved.

Conclusions

WCNDT 2012 18

Thin Wall Stainless Steel Pipe Inspection

Stainless Steel

Compressive stress

• Decrease ultrasonic reflection

• Variable ultrasonic reflection

– One sided access

Spigot

Tight defect tip

Customer Requirement

100% defect detection

Sizing accuracy ± 0.25mm

98% confidence

– Mean remaining ligament for

weld

WCNDT 2012 19

Thin Wall Stainless Steel – Defect Sizing

Accuracy of defect sizing

- Crack tip and root response positioning

- Not amplitude based - pattern analysis

-

WCNDT 2012 20

Stainless Steel Grain Structure

Assurance of defect detection

- Not amplitude based

- Detection of weld volume

- Very high inspection sensitivity

Weld root

Grain back scattered

energy