where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

Iris Inspection Services, Inc.
We are the world's largest supplier of air cooler, boiler and exchanger tubing inspection services.
768 views
Technical Discussions
Michael Trinidad
Consultant,
LMATS Pty Ltd , Australia, Joined Jan 2003, 138

Michael Trinidad

Consultant,
LMATS Pty Ltd ,
Australia,
Joined Jan 2003
138
04:11 Mar-02-2001
MFL (Magnetic Flux Leakage) is it an ET, MT or a method alone?

I see this topic is being revisited, so I have re-posted in the 2001 fourm so we don't have to go searching.

A question was asked by Jasmine in NZ regarding Hall effect sensors and the effect of speed. I have worked with a few different types of MFL equipment, steel wire rope testers, tank floor testers and pipe scanners. Some equipment show variations with speed, some have speed compensation software etc.

If the instrument only uses coils with no speed compensation the output signal will vary with speed which is Faraday's law.

If the instrument only uses hall effect sensors what would cause the same effect, this was a dilemma I had with a particular machine. I have been told fom the manufacturers of hall effect sensors that because they are solid state semiconductors and the measure of the deflection of electron flow in a magnetic field is instantaneous. The cause in my particular case was a fixed sampling rate on the equipment being used not any measurable effect from the hall effect sensors.

To find out more about hall effect sensors it is better to ask the actual sensor manufaturer's.

I hope this helps and as there is such small literature on MFL that the disscussion continues.


Kindest Regards


Michael Trinidad



 
 Reply 
 
Andre van Vuuren
Andre van Vuuren
03:08 Mar-02-2001
Re: MFL (Magnetic Flux Leakage) is it an ET, MT or a method alone?
As a tube inspection man I feel very strongly that MFL should become a "stand alone technique" instead of been lumped with ECT as RFT was in the not so distance past.
After all how long did it take for "the power that be" to remove the words "eddy Current" from "REMOTE FIELD EDDY CURRENT TESTING", to read "Remote Feild Testing" which is now a "stand alone technique".

MFL is mainly a volumemetric inspection technique used on carbon steel tubing. There is no changes in the phase or signal shape as there is for RFT and ECT.

For wall thickness measurements you have a good responce from the hall element and the probe has to be pulled at a steady & constant speed. I would only use the MFL technique where internal pitting was evident and due to customer or other restraints the use of other techniques was NOT an option.

The uses and aplications of MFL have also greatly increased along with the use of computerised software. After all why does anybody who specialises in tank floor inspections wants to sit through a 40hour ECT course when maybe 2hrs (if he's lucky)are spent on MFL?

I have also noted that European market has placed a greater emphasis on "saturated eddy current" instead of MFL for the inspection of carbon steel tubes. Does anybody know the reason for this?




 
 Reply 
 
Michael Trinidad
Consultant,
LMATS Pty Ltd , Australia, Joined Jan 2003, 138

Michael Trinidad

Consultant,
LMATS Pty Ltd ,
Australia,
Joined Jan 2003
138
05:27 Mar-03-2001
Re: MFL (Magnetic Flux Leakage) is it an ET, MT or a method alone?
MFL is used in the NDT of steel wire ropes, tank floor scanning, plate scanning, pipe scanning (internal/external) and tube scanning as you mentioned. I too have used some MFL on the inspection of tubing and concur with your limitations however I consider them to be a equipment limitation not a fault of the method. MFL used on other products such as tank floor scanners and rope testing can show a high degree of accuracy given good software and operator training.

MFL and RFT have a few things in common and that is:

1. There is a very limited amount of reference material on both methods.
2. There are many known and unknown variables that affect the signal
3. The operator must know what he is doing

My reason behind posting this topic was the above two points. I am very interested in all questions and comments on both MFL and RFT as with these comments may come a better understanding for everybody concerned.


Kindest Regards


Michael Trinidad



 
 Reply 
 

Product Spotlight

FAAST-PA! OEM Patented phased Array for high speed UT inspection

Multiangle, Multifocus, Multifrequency, Multibeam. Instead of stacking UT electronics and having m
...
any PA probes, FAAST-PA is able to transmit all delay laws within ONE single shot in Real time.
>

EKOSCAN Phased Array

In order to always fit your needs, EKOSCAN can manufacture any type of UT transducer, either convent
...
ional or Phased Array. As an ISO 9001: 2015 certified company, EKOSCAN is extremely careful as far a material selection and manufacturing processes are concerned. Our probes guarantee our customers the benefits of latest innovations regarding piezo-composite, backing, impedance adaptation layer, etc. Specific probes for hostile environment: high temperature, high pressure, corrosive environment,etc. Specific probes designed to fit your specific application: optimization of every parameter to guarantee you the best detection.
>

Immersion systems

ScanMaster ultrasonic immersion systems are designed for high throughput, multi shift operation in a
...
n industrial or lab environment. These fully integrated systems provide various scanning configurations and incorporate conventional and phased arrays technologies to support diverse applications, such as inspection of disks, bars, shafts, billets and plates. All of ScanMaster immersion systems are built from high accuracy scanning frames allowing for scanning of complex parts and include a multi-channel ultrasonic instrument with exceptional performance. The systems are approved by all major manufacturers for C-scan inspection of jet engine forged discs. Together with a comprehensive set of software modules these flexible series of systems provide the customer with the best price performance solutions.
>

AMIGO2

TSC Amigo2 - ACFM technology has developed a solid reputation for accurately detecting and sizing
...
surface-breaking cracks through paint and coatings. As the industry demands increased performance in speed, signal quality, and portability, it’s time for an evolution. It’s time for Amigo2.
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window