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Technical Discussions
Kaushal
Engineering,
BHEL, India, Joined Feb 2014, 18

Kaushal

Engineering,
BHEL,
India,
Joined Feb 2014
18
18:50 Sep-29-2014
LPI Indication

Dear all,
IS there any relation between LPI indication Vs Depth of defect.

 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 181

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
181
22:06 Sep-29-2014
Re: LPI Indication
In Reply to Kaushal at 18:50 Sep-29-2014 (Opening).

No.

Gerald R. Reams
ASNT Level III

1
 
 Reply 
 
GOWRISANTHOSH PALIKA
NDT Inspector,
Royscan engineering pte ltd, Singapore, Joined May 2008, 52

GOWRISANTHOSH PALIKA

NDT Inspector,
Royscan engineering pte ltd,
Singapore,
Joined May 2008
52
05:55 Sep-30-2014
Re: LPI Indication
In Reply to Kaushal at 18:50 Sep-29-2014 (Opening).

We all know that LPI can only detect surface opening defects.
For now if we speak about surface opening defects, YES there is a relation between LPI indication vs Depth of defect.
The relation is "Probability of Detection (PoD) increases as the depth of defect increases".

Regards
Gowrisanthosh Palika

 
 Reply 
 
RENGARAJU. B. N.
NDT Inspector, NDT Level-III/Radiation Safety Officer(RSO)
Marine and Heavy Engineering Company, MALAYSIA., India, Joined Sep 2014, 106

RENGARAJU. B. N.

NDT Inspector, NDT Level-III/Radiation Safety Officer(RSO)
Marine and Heavy Engineering Company, MALAYSIA.,
India,
Joined Sep 2014
106
06:16 Sep-30-2014
Re: LPI Indication
In Reply to Kaushal at 18:50 Sep-29-2014 (Opening).

The relation between Flaw depth and PT indication can be described briefly as under:

1. A Rounded PT indication growing fast in diameter shall indicate a flaw which is deep. The flaw is acting like a reservoir and is continuously feeding penetrant which shall be cause for rapid expansion of diameter.

2. For further establishing a relation, what we need first is to assess the rate of penetrant bleed out from the moment developing dwell time is over. Note, the rate is going to decrease with passage of time. So, fix the total time that you are going to observe, and also the intervals with in this period when the rate of bleed out shall be measured. Take the average of the bleed out rates at the end of the observation time. From this you can have the volume of penetrant coming out from flaw over a period and as the initial diameter of indication would have been noted in the start, one can estimate the depth of the flaw.

3. Practically its a cumbersome method, but yes, it is possible.

 
 Reply 
 
Kaushal
Engineering,
BHEL, India, Joined Feb 2014, 18

Kaushal

Engineering,
BHEL,
India,
Joined Feb 2014
18
06:17 Sep-30-2014
Re: LPI Indication
In Reply to GOWRISANTHOSH PALIKA at 05:55 Sep-30-2014 .

Sir,
You mean to say that rounded indication of 5mm having less depth as compared to 10mm rounded LPI indication.

 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 181

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
181
16:26 Sep-30-2014
Re: LPI Indication
In Reply to Gerald R. Reams at 22:06 Sep-29-2014 .

To clarify my answer of NO:

The size and "seeability" of an FPI indication can vary widely from many causes.

For the indication:
Quality of the procedure
Cleaning Process
Cleaning quality
Surface preparation
Thickness and density of developer
Viewing conditions
Lighting conditions
Inspector physiology
etc., etc., etc.

For the discontinuity:
Depth
Width
Length
Shape
Contents
Contaminants
Surface roughness
etc., etc., etc.

Other than a very loose approximation; size of indication and size of defect are not directly related.

Gerald R. Reams
ASNT Level III

 
 Reply 
 

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