case study bringing a solution to market inspection of ... · presented by bruce stetler ... ect...

Case Study

Bringing a solution to market

Inspection of Twisted tubes in

Heat Exchangers

Presented by Bruce Stetler

NDTMA February 12, 2014

Topics discussed

•  Background on Heat Exchangers, both Standard and Twisted tube design

•  Engineering and modeling a prototype •  Carrying out tests on the prototype •  Results on calibra?on standards •  Field trials •  Conclusions

Ø  However, there are limitations associated with these type of exchangers, which include inefficient usage of shell side pressure drop, dead or low flow zones around the baffles where fouling and corrosion can occur, and flow induced tube vibration, which can ultimately result in equipment failure.

STANDARD EXCHANGERS

Ø  Over 85% of all heat exchangers in oil and gas, chemical, petro-chemical, and power generation are accommodated through the use of conventional shell and tube type heat exchangers.

TWISTED TUBE HEAT EXCHANGER AVANTAGES TO THE INDUSTRY

•  Over the last 20 years, TWISTED TUBE heat exchangers have made their way into the Refinery and Chemical industries.

•  TWISTED TUBE tubes geometrical design creates a swirl-flow or forced fluid motion along the curvature of the tube by inducing greater heat transfer.

•  The tubes are interlocking and free of baffles or supports, which allow them to have a higher heat transfer coefficient than other tubular heat exchangers (up to 40% higher).

•  Tubes come in a variety of sizes from .625” up to 1” inch in diameter with material types such as stainless, titanium, brass, monel, carbon steel, duplex, and nickel (to name a few).

Ini?al assessment

As we know Eddy Current is a electromagnetic application used in the industry for the inspection of non-ferrous material in such alloys as: Stainless Steel, Titanium, Brass, Hastelloy, Monel…

EDDY CURRENT TESTING

Eddy currents have the sensitivity to detect a wide range of corrosion and erosion (process or mechanical) such as:

•  baffle fretting (vibration), impingement erosion, tool gouges, corrosion, pitting, stress corrosion cracking, MIC, etc.

EQUIPMENT USED FOR R&D

•  ECTANE – ERNMI •  MAGNIFI 3.2B2

www.eddyfi.com

Booth #24

Conventional ECT bobbin probe

For reference we used a standard bobbin probe 11mm (.433”) diameter (Eddyfi probe). Tube material was Titanium .750” x .049” nominal wall.

Bottom (Dip)

Top (Crest)

Tube Dimensions Tube OD Tube ID Tube WT Straight sec6on 19.05mm (.750") 16.28mm (.604") 1.38mm (.054")

Twisted Top (Crest) 22.23mm (.875") 19.46mm (.766") 1.38mm (.054") Twisted Bo>om (Dip) 15.43mm (.607") 12.66mm (.498") 1.38mm (.054")

Constant ID 12.71mm (0.500")

Bottom (Dip)

Top (Crest)

Two Titanium calibration standards

No.# 2 calibration standard / Top (crest) pit Standard and one thru-wall bottom (dip) and 2 in straight section.

No.# 1 calibration standard / bottom (dip) pit Standard, but also has several top (crest) defects.

# Machined defects Diameter Depth Loca6on 1 Thru wall .052" 100% Straight 2 OD Flat boYom hole .187" 40% Straight 3 Thru wall .052" 100% BoYom 4 2x Thru wall (at 180?) .052" 100% Top 5 OD Flat boYom hole .078" 80% Top 6 OD Flat boYom hole .109" 60% Top 7 OD Flat boYom hole .187" 40% Top 8 4x OD Flat boYom hole (at 90) .187" 20% Top 9 2x Thru wall (at 180) .078" 100% Top

# Machined defects Diameter Depth Loca6on 1 Axial EDM notch .40" 100% Top 2 Oblique EDM notch .40" 100% Top 3 Circ EDM notch .40" 100% Mid 4 Thru wall .052" 100% BoYom 5 OD Flat boYom hole .078" 80% BoYom 6 OD Flat boYom hole .109" 60% BoYom 7 OD Flat boYom hole .187" 40% BoYom 8 OD Flat boYom hole .187" 20% BoYom 9 4x OD Flat boYom hole (at 90?) .187" 20% Each 90 ? 10 Thru wall .078" 100% Top

Noise level

11mm (.433”) Standard ECT bobbin probe results bottom dip hole (on calibration standard #1)

Calibration done at 1V, 40˚


Noise / lift-off



No Cir. detection

20% absorb in noise

100% bottom thru-wall hole

Bottom

Top

11mm (.433”) ECT bobbin probe results top crest hole (on calibra+on standard #1)

Noise / lift-off

Top (crest) 100% hole @ 74 deg. (rotates clockwise approx. 52 deg.)


Bottom (dip) 1V, 22˚

Bottom

Top

Bottom (Dip)

Top (Crest)

Eddyfi ECT- twisted probe concept

Twisted bobbin coils (Diff. & Abs.): The differential signal on the twisted bobbin will be used to create sizing curves for analysis (Top/crest and bottom/dip defect responses).

2 absolute coils (180 deg. Apart): The absolute coils will be used to discriminate top (crest) defects from the bottom (dip) defects.

Slip ring assembly: Allows the probe tip to rotate through the twist.

Standard bobbin coils (Diff. & Abs.) To be added for inspection of straight sections

Diff. & Abs)

ABS -1

ABS-2

Eddyfi ECT-‐ twisted probe design movement

ECT Twisted bobbin bottom defects calibration #1

•  To reduce lift-off and noise on both twisted bobbin and top coils we rotated each signal to get the noise level horizontally.

•  #1 calibrate standard we used the bottom 100% thru-wall hole at 1volt, 19˚,

then we created sizing curves for bottom (dip) defects. •  Next two slides will also show the top coils detection, to confirm top defects

location (see blue circles) •  By using the <Slew> (aligning the strip chart data) process from Magnifi we

can now align the top coils signal with the twisted bobbin signal. This will allow us to distinguish between the location of the indication in the bottom (dip) or top (crest).

ECT Twisted results (on calibration standard #1 / bottom /dip)


TOP 1 Derivate signal TOP 2 Derivate signal TWISTED DIF HP

Filter signal

TWISTED DIF

TOP 1 ABS TOP 2 ABS


Filter signal

TWISTED DIF.

TOP 1 ABS TOP 2 ABS

ECT Twisted results (on calibration standard #1 / disguising top/crest defects)

100% TWH TOP/CREST @ 59 deg. 61%

ECT Twisted bobbin using top coils calibration standard #2

•  Again to reduce lift-off and noise signal on both twisted bobbin and top coils we rotated each signal to get the noise level horizontally (no calibration required).

•  Then for the top defects we will create new curve with calibration standard #2. •  By using the <Slew> (aligning the strip chart data) process from Magnifi we can

now align the top coils signal with the twisted bobbin signal. This will allow us to distinguish between the location of the indication in the bottom (dip) or top (crest).

ECT Twisted results (on calibration standard #2 Top/Crest defects)

TOP 1 Derivate signal TOP 2 Derivate signal TWISTED DIF HP Filter signal

Hole located on top crest

TOP 1 TOP 2

Bundle simulation

•  At this ?me only calibra?on tubes were scanned to determine the probe detec?on limita?on.

•  Both calibra?on tubes were surrounded by similar ?tanium twisted tube samples to simulate field condi?ons.

•  Top (crest) defects are s?ll highlighted by blue circle.

Bundle simulation on calibration standard #1 (bottom/dip), surrounded by similar twisted tube


Filter signal

Calibration hole located on bottom appears at 97%

TWISTED DIF

TOP 1 TOP 2

Bottom (dip) #1 calibration curve of approximately 104 degree separation.

BOTTOM CURVES for ECT

Size Measure

100o % 19 deg

90o % 25 deg

80o % 37 deg

70o % 50 deg

60o % 62 deg

50o % 74 deg

40o % 86 deg

30o % 98 deg

20o % 111 deg

10o % 123 deg

0o % 135 deg

Bundle simulation on calibration standard #2 (top/crest), surrounded by similar twisted tube


Filter signal

Hole located on top appears at 93%

TOP 1 TOP 2

Top (crest) #2 calibration curve of approximately 60 degree phase separation.

TOP CURVES -‐ Bundle for ECT

Size Measure

100o % 46 deg

90o % 52 deg

80o % 59 deg

70o % 66 deg

60o % 73 deg

50o % 79 deg

40o % 86 deg

30o % 93 deg

20o % 100 deg

10o % 106 deg

0o % 113 deg

ECT Titanium comparative results

•  By comparing the standard bobbin probe we found the Eddyfi ECT – twisted probe concept had very good detection for bottom (dip) defects and top (crest) defects, even if surrounded by other twisted tubes.

•  By using the twisted bobbin coils for analysis we can use the two top (crest)

coils to locate the defect position and then select the proper sizing curve for analysis.

•  Note: these results can be obtained only by using Magnifi software with its specific process such as median filter, slew, and automatic landmark recognition.

•  We expect data collection speeds to be at 12 inches per/sec.

CONFIDENTIAL

Probe head time life After used the twisted probe on site we were able to inspect between 1000 – 1500 tubes, originally we were expected to inspect at least 500. We pushed the probe in at 2ft/sec then with a pulling speed of 1ft/s (see picture below)

© 2010 Eddyfi. All rights reserved. 25

CONFIDENTIAL

Next probe design We believe that a closed design like below will be eventually better, as this design will push internal deposit outside of the tube where the first design cannot, moreover this design will be more robust and easier to assemble from a manufacturing perspective The first design has epoxy over the crest coils, and not by positioning both crest coils into both shoes, so instead of the epoxy in contact, it will be machined plastic shoes, we think that the improved design will increase longevity. (target 2000 tubes)

© 2010 Eddyfi. All rights reserved. 26

Engineering ?me

•  Ini?al Assessment 4 hours •  Applica?on Specialist & Modeling 20 hours •  Prototype development 40 Hours •  POD of Prototype 20 Hours •  Manufacturing 5 hours •  Tes?ng of finished product 30 hours •  Total 119 Hours

Eddyfi RFT twisted tube design

Single driver coil (exciter coil)

Twisted bobbin coils (receiver)

2 Top (receiver absolute coils)

Slip ring assembly

*Preliminary tests have been performed on a carbon steel twisted tube (1.0” OD / .109” WT) with a prototype probe. Results are pending…

Ques?ons?

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