The compact design of Heat Recovery Steam Generators (HRSGs) gives us a unique opportunity to innovate new tools for non-destructive testing. TesTex, Inc. in conjunction with Electric Power Research Institute (EPRI), has designed new testing devices utilizing proven innovative electromagnetic techniques.

• Low Frequency Electromagnetic Technique (LFET) is used to test the leading edge and trailing edge HRSG tubes.

• For the inspection of tube to header welds, we utilize a specially designed “claw” system outfittedwithourBalancedFieldElectromagneticTechnique(BFET)probes.

• Finally for internal tube inspection we have an advanced Remote Field Electromagnetic Technique (RFET) probe that works with the internal tube inspection tool.

TesTex Inc.535 Old Frankstown Rd.

Pittsburgh, PA 15239T. 412.798.8990F. 412.798.8995

www.TesTex-NDT.com

HRSG Inspection Tools

HRSG Inspection Tools

The Low Frequency Electromagnetic

Technique (LFET) can detect and quantify

wallthinningonHRSGfinnedtubesfromtheoutsidesurfacethroughthefins.TheLFETscanner moves along the tube as it measures

the strength of the return signal that is

emitted into the tube by the scanner’s exciter

coil. This technology is able to detect both

localized wall losses and general wall losses

suchaspittingandflowacceleratedcorrosionrespectively. The LFET scanners can examine

thefinnedtubesataspeedof3”persecond.

Scanning is performed from the outside of the tubes ontopofthefins.

ThepictureaboveshowstheLFETscanneronafinnedHRSGtube.

HRSG Inspection Tools

The side view phase plot shows the responses from 1/2” ID pits in the HRSG calibrationtubestandard.Thefirstrisein the signal is the 60% deep pit and the second rise is the 30% deep pit.

The Top View shows a simulated color B-scan.The60%deeppitisshownwiththe yellow to red shades and the 30% deep pit is shown in the green center yellow shades

The 3-D Window displays the pit responses from a side view perspective. Thefirstriseisthe60%deeppitandthesecond rise is the 30% deep pit.

The drawing above shows the pits that were machined on the inside surface of the carbon steel finnedHRSGtubecalibrationstandard.Thetubeisa2”ODwitha0.150”wallthicknessand0.75”longfins.

The LFET waveform from this calibration tube is shown below.

½” Diameter Pit 60% Deep on Inside

Surface

½” Diameter Pit 30% Deep on Inside

Surface

HRSG Inspection Tools

TesTexadaptedtheBFETtoinspectthe tube to header welds of HRSG units.TheBFETprobesandcamerasare placed on the welds using a C-clamp housing called “The Claw” that attaches to the tube. Once attached to the tube, the assembly moves circumferentially around the weld to detect cracking, lack of fusion, porosity, and other defects. Claws are customized as necessary for various tube sizes.

Picture above shows a failed tube to header weld in a HRSG

Two different views of the Claws attached to mockups of the tube to header welds. Each claw is outfittedwithtwoBFETprobesandtwocameras.

HRSG Inspection Tools

Claw picture testing a tube to header weld.

TheBFETwaveformaboveshowstheresponsefromasimulatedmachinedcrackthatis.050”deepin a header weld.

TheBFETwaveformaboveshowstheresponsewhengoingoveracleanweldwithnodefects.

HRSG Inspection Tools

The TesTex developed RFET system is used for the inspection of HRSG tubes from the inside surface when utilizing access holes cut into the header as shown in the picture.Theflexibleprobeheadattachedto a poly wand can test through a modest scale buildup inside the tube enabling the inspection of select tubes. There is also a camera on the probe end to capture video of the tube’s inside surface.

The RFET waveform shows 20-25% localized wall loss foundinaHRSGfinnedtube

1 2 3

1. Camera for visual inspection2.Drivercoilsaturatesthematerialwithanelectromagneticfield3. Individual channel coils sense changes to the electromagnetic field,whichindicatespitting,and/orgradualwallloss

Testex Flexible RFET Multichannel Probe Head

HRSG Inspection Tools

TesTex has developed an “Internal Inspection Tool” that can be inserted inside a header to allow a RFET probe to be pushed up the length of HRSG tubes to record thickness readings. Access is provided by removing the endplate from the header

The end of the header needs to be removed to provide access for the internal access tool to be inserted. The probe has a video camera on the tip as well as RFET coils to measure tube wall thickness.

The illustration above shows the Internal Access Tool inside a header pushing a probe up a HRSG tube for wall thickness measurements.

Four headers, one end cap removed for tool access

HRSG Inspection Tools

As TesTex is developing inspection tools for the HRSG industry, we are looking for mockups to help in the design and trial testing of equipment. Please contact us if you are willing to donate any HRSG headers for this purpose.

TesTexalsohasseveralNDTtoolstoexaminetheBalanceofPlant equipment. This includes the inspection of condensers, heat exchangers, pressure vessels, piping, and welds. Please contact us at 412-798-8990 for your Non-Destructive Testing needs.