advanced technologies for heat exchanger tubing karl marx

7/29/2019 Advanced Technologies for Heat Exchanger Tubing Karl Marx

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DISCUSSION OF ADVANCED

TECHNOLOGIES FORHEAT EXCHANGER TUBING

ADVANCED SERVICES / TUBING

GROUP

ACUREN INSPECTIONpresented by

Karl Marks


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Introduction: Inspection Techniques

NDE techniques which are most common and currently being used in theindustry include; (IRIS) Internal Rotating Inspection System, (ET) EddyCurrent, (RFT) Remote Field Testing and External Reference Remote Field

Testing, (X-RFT).

The discussion today will focus on the four applications mentioned above,along with the advantages and disadvantages associated with each test.


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IRIS(INTERNAL ROTATING INSPECTION SYSTEM)

I.D. O.D.

This technique uses unique waterdriven rotating mirror to direct an

ultrasonic beam, which is reflected

90 degrees to the internal tube wall.

The water acts as a water couplant

and transmit sound waves from the

ultrasonic transducer to the tube

wall.

The IRIS presentation can be

displayed in a B-scan (Cross-

sectional view) or C-scan showing

the tube wall thickness and isolated

corrosion areas along the tubelength.


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IRIS INSPECTION PRINCIPLE:

This technique used to inspect all tube material types, (ferromagnetic andnonferromagnetic) in diameters ranging from 5/8 up to 3 inches indiameter (Large tubes or pipes have been inspected with special probedesigns).

IRIS accuracy is operator dependant, measurements can be within + or -0.005 if tube conditions are good.


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IRIS SCAN OF RFT MULTI-PURPOSE STANDARD


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IRIS COMPUTERIZE COLOR B-SCAN & C-SCAN DISPLAY

BOILER TUBE O.D. EROSION CORROSION

(APPROX. 270 Deg.)


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IRIS SCAN OF O.D. BAFFLE FRETTING


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INTERMITTING AREAS OF DATA


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I.D. SCALE AND DEPOSITS -

DIFFICULTIES OF IRIS TESTING


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ADVANTAGES OF IRIS INSPECTION

Used to inspect any tube material type ferrous or nonferrous.

Provides accurate remaining wall thickness, (empirical data +/- .005).

Can detect gradual wall loss, pitting, baffle fretting, steam erosion, andimpingement erosion at tube sheet area.

Can distinguish between I.D. and O.D. defect orientation.

Can be used as prove up to other test methods.


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DISADVANTAGES OF IRIS INSPECTION

Cleanliness of the tubes is a major factor and requires thorough tube cleaning(removal of all scale, deposits, chemical residue and/or oil residue prior toinspection.

Slow inspection speeds of 20 to 40 tubes per/hr.

Requires flooding the tube with water for sound coupling.

Cannot detect cracks (Special probe design is needed).

Limited to isolated pit detection and pit size (diameter).

Adequate water pressure, quality of water, maintaining adequate flood in tubes,

regulating consistent turbine speed, pull speed, probe centering, and tubecleanliness are all variables that must be in sync in order to achieve data andthat will affect the quality of data.


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EDDY CURRENT TESTING


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EDDY CURRENT TESTING PRINCIPLE (ET)

The eddy current technique is based on the induction of an electromagnetic fieldin the component being examined and can detect various forms of internal and

external damage. It employs an internal probe specifically designed for the tube

I.D. If the probe should encounter indications as it is pulled through the tube, the

eddy currents are interrupted, causing a impedance change in the coils, which are

measured on the eddy current instrument. (Below is a bobbin coil display)


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EDDY CURRENT TECHNIQUES

ITS CRITICAL TO USE THE PROPER EDDY CURRENT TECHNIQUES AND

PROCEDURES. THERE ARE THREE PRIMARY TECHNIQUES USED:

DIFFERENTIAL TEST (LOOKING FOR SHARP DEFECTS: PITTING,

CRACKING, & ETC.)

ABSOLUTE TEST (LOOKING FOR GRADUAL WALL LOSS AND

THINNING)

ARRAY COIL TECHNOLGY (LOOKING FOR CRACKING, PITTING,

AND/OR CORROSION NEAR OR UNDER STRUCTURES)


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EDDY CURRENT INSPECTION

Eddy Current is a electromagnetic application used in the industry for theinspection of non-ferrous material, which has a high sensitivity for detection,sizing, and characterization small volumetric defects.

In such alloys as:

Stainless Steel

Titanium

Brass

90/10 Copper Nickel

Inconnels

Hast. C-276, B2. Monel-400

etc.


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DATA INTERPRETATION Example:

Typical ASME Calibration Standard Run


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DATA INTERPRETATION CAN BE VERY COMPLEX

(IGSCC)


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O.D. CORROSION / MIC

(Microbiological Influenced Corrosion)


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O.D. CORROSION / CREVICE CORROSION


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LACK OF FUSION OR UNDERCUT


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MIXING OUT SUPPORT STRUCTURE /

DETECTS FRETTING, PITTING, AND CRACKING


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RELEVANT OR NON-RELEVANT?


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RELEVANT OR NON-RELEVANT?


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ADVANTAGES OF EDDY CURRENT TESTING

High Examination Rate (80 100 or more an hour).

Applies to any non-ferrous material (Non-magnetic & slightly

magnetic alloys).

Repeatability - compare historical and subsequent test results to

establish corrosion rates and remaining life.

Discriminates between I.D and O.D. defect orientation.

Sensitive to gradual wall loss, cracking, very small pitting,

vibration, and etc.


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DISADVANTAGES OF EDDY CURRENT TESTING

Not used on materials that are magnetic (ferrous).

Permeability changes caused by magnetic deposits can causeunwanted signals.

Accuracy of interpretation is highly dependant upon operatorsexperience.

Equipment is both sophisticated and expensive.

Standard bobbin coil application cannot inspect tube sheet rollarea looking for circumferential cracking (Special probesdesigns are available).


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REMOTE FIELD TESTING (RFT)

Exciter Receivers

Direct field


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REMOTE FIELD TESTING (RFT) PRINCIPLE:

REMOTE FILED TESTING IS AN ELECTROMAGNETIC TECHNIQUE THATUITILIZES AC EXCITATION TO GENERATE AC MAGNETIC LINES OF FLUX.

A THROUGH WALL TRANSMISSION WHICH IS DETECTED 2-3 TUBEDIAMETERS AWAY BY INDUCING A VOLTAGE INTO PASSIVE SENSORS.

WITHOUT ANY MAGNETIZATION OR SATURATION.

RFT PROBES CONTAIN TWO TYPES OF COILS USED COMMONLY IN ASINGLE ORDUAL ARRANGMENT.

ONE COIL IS THE EXCITER COIL, WHICH TRANSMITS ANELECTROMAGNETIC FIELD THROUGH THE TUBE WALL AND THE

RECIEVER COIL WHICH SENSES THE FIELD AS IT COMES BACK INTHROUGH THE TUBE WALL.


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PROBE TYPES: SINGLE EXCITER / SINGLE PICKUP


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COMMONLY USED PROBE: DUAL EXCITER /

SINGLE PICKUP


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TYPICAL REMOTE FIELD CALIBRATION

(MULTI-PURPOSE STANDARD)


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RFT GRAPHICS OF WASTAGE & SMALL PITTING


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RFT & IRIS comparison of 50% degradation

(SA-214 .750 x .083)


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DETECTION OF MIC IN 2205 DUPLEX / USING RFT


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ADVANTAGES OF REMOTE FIELD TESTING

Applies to any Ferrous material (Carbon Steel).

Tubes require little cleaning prior to inspection.

Inspect tubes with low fill-factor and still maintain good sensitivity.

Data acquisition rate of 50 up to 70 tubes per/hr (Depends on wall thickness andsample rate).

Good sensitivity to gradual wall loss, pitting, vibration, and steam erosion andcracking

Capable of testing heavy wall tubes (Up to .180)

Capable of inspecting up to 3 inch diameter tubes (Larger diameters w/specialprobe designs).

RepeatabilityCompare historical test results to establish corrosion rates andremaining life calculations.


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DISADVANTAGES OF REMOTE FIELD TESTING

Limited detection and sizing of small defects (


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MAGNETIC FLUX LEAKAGE (MFL)

STEELTEST


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X-RFT (EXTERNAL REFERENCE

REMOTE FIELD TESTING)

Similar to standard RFT probe except the coils and sensors are much

closer together to only pick up the near-field portion of the induced field.


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X-RFT TECHNOLOGY DESIGN FOR AIR COOLERS

External Reference Remote Field Testing (X-RFT) is an electromagnetictechnique using the Remote Field Technology connected with an externalreference to elimate extraneous noise by having a balanced system.

The X-RFT is used primarily for the inspection of air cooler tube inspection.

This method utilizes a 2nd probe placed in a reference standard or tube ofsimilar material and dimensions of that to be inspected. This enables thesystem to mix out any unwanted noise to determine the defects depth.

The data is digitally collected and stored for analysis.

The purpose of this application is to detect I.D. inlet erosion/corrosion as wellas isolated pitting, channeling, etc.

Note: Recent advances in technology has allowed for the use of the internalelectronic reference mode within the instrumentation eliminating the need fora 2nd reference probe. These probes are known as NFT or Near Field Testingprobes and are used in the same manner as X-RFT and achieve the sameresults.


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X-RFT ILLUSTRATION


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INLET EROSION/CORROSION


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X-RFT (DISCOVERY OF TEST RESULTS)


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X-RFT (Example of 50% degradation from ferrule end)


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X-RFT (Example of general wall loss from ferrule end)


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ADVANTAGES OF X-RFT

Good sizing capabilities for Inlet Erosion & Corrosion.

Detects small diameter pitting.

High data acquisition rate, (5060 tubes/hr)

Detects gradual wall thinning (I.D.)

Capable of inspecting 3 diameter tubes, (larger w/special probe designs)


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DISADVANTAGES OF X-RFT

Limited O.D. sensitivity; defect must be 60% through-wallbefore detection

Volumetrically dependant; less sensitive to pits under 1/8

diameter.

Permeability and geometry will affect sensitivity to small

defects and sizing.

Probe must maintain good fill-factor (Centered) for sensitivityfor detection of small defects.

Accuracy of interpretation is highly dependant upon operator

experience.


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CONCLUSION:

Some of these methods provide qualitative data and somequantitative results

Each of these different methods have distinctive advantages and

disadvantages

It is imperative to choose the correct tube inspection technique for

the job at hand

Also, it has been proven that a combination of methods can

provide the best inspection results

Like most advanced inspection techniques, the techniques are

operator dependent, and it is important to evaluate your inspectionprovider to assure they are qualified and experienced personnel

advanced technologies for heat exchanger tubing karl marx

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