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Technical Discussions
04:08 Jan-24-2012

Chieg

NDT Inspector, - ,
Mongolia,
Joined Dec 2010
11
3394 views
Help me (Thickness measurement)
Hello everybody

I tested pipe thickness of Ultrasonic. Pipe thickness is 10mm. So after tested some pipe thickness is 6 mm

I need acceptance criteria of thickness measurement.

Help me

Thanks
 
 
07:21 Jan-24-2012

Jon Wallis

NDT Inspector, - ,
Netherlands,
Joined Feb 2010
493
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

You observed loss of wall from 10mm to 6mm if I understand you correctly.
I'm sorry Chieg but it is impossible for anyone here to offer you advice of accept or reject based on the information you have provided.
Often with wall thickness examination the acceptance or otherwise is down to the client, unless they tell you what the minimum thickness is, you cannot make a judgement.

 
 
07:59 Jan-24-2012

Chieg

NDT Inspector, - ,
Mongolia,
Joined Dec 2010
11
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

Jon Wallis
You understood correctly.
We are using this pipe for 5 years. I tested 26points, 78 measure. So same point 6mm. I cant write report because i haven't acceptance criteria.

 
 
08:51 Jan-24-2012

Ovidiu

NDT Inspector, thermography,
ISCIR,
Romania,
Joined Dec 2005
16
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

Chieg,
Ussualy, from the point of view of operator there are no acceptance criteria for thickness measurements unless there is a written procedure that states minimum acceptance thickness. Otherwise,simply hand over the results to customer. The decision it up to him.
Regards,
Ovidiu

 
 
09:21 Jan-24-2012
Ed T.
Re: Help me (Thickness measurement)
In Reply to Ovidiu on 08:51 Jan-24-2012 .

If you're sure the measurements are correct, and the owner hasn't provided you with an Acceptance Criteria, you need to turn the results over to your Engineering Department for disposition.

 
 
14:37 Jan-24-2012

Andreas

NDT Inspector, Specially in the oilfield,
Tuboscope Vetco(Deutschland)Gmbh,
Germany,
Joined Oct 1999
81
Re: Help me (Thickness measurement)
In Reply to Ed T. on 09:21 Jan-24-2012 .

I agree that you represent your measurements only on the report.
I like to know what kind of pipe it is and if you taken the measurent only after 5 years of use , or you check the same point in intervalls.


Regards

Andreas

 
 
15:16 Jan-24-2012

I R Stephenson
NDT Inspector, Auditer / Cross Checker,
STS { Stork Technical Services } Australia,
Netherlands,
Joined Aug 2011
40
Re: Help me (Thickness measurement)
In Reply to Ovidiu on 08:51 Jan-24-2012 .

You can write a report, just report exactly what you found, no more no less, ~ don't get into a conversation or give an opinion, don't allow yourself to be drawn into the old " well with your quals and experience you can tell us/you must know " you will then have commited yourself to what could be a whole lot of pain later on ~ and leave it up to them.. If they haven't furnished you with an acceptance criteria then there's not much else you can do..

 
 
21:09 Jan-24-2012

Manuel Haces

Director, - Wire rope inspection,
Haces Inspección del Noreste,
Mexico,
Joined Jun 2002
87
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

It should be an informative report, describe correctly how you do the test. Criteria for rejection, should be made by Engineerign and calculation. This is what we do over here.

 
 
23:47 Jan-24-2012

Chieg

NDT Inspector, - ,
Mongolia,
Joined Dec 2010
11
Re: Help me (Thickness measurement)
In Reply to Manuel Haces on 21:09 Jan-24-2012 .

Everyone thanks very much for replying

We taken the measurement only after 5 years of use.

I R Stephenson

We haven't approved acceptance criteria So I must do it because I can't do it. How to do acceptance criteria and which use standard?

 
 
05:13 Jan-25-2012

collin maloney

NDT Inspector, - Plant Inspector ,
Bureau Veritas,
Australia,
Joined Nov 2000
103
Re: Help me (Thickness measurement)
In Reply to Chieg on 23:47 Jan-24-2012 .

there will be no minimum thickness, other than mill tollerance, since no code can account for all the variables with material type and pressure containment. This minimum thickness must be supplied by the owner on the basis of operating pressure, operating temperature, material type and pipe contents. As all have said, report the measured thickness and leave the decision to those qualified.

 
 
09:10 Jan-25-2012

S V Swamy
Engineering, - Material Testing Inspection & Quality Control,
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
656
Re: Help me (Thickness measurement)
You may take a look at the original specification for the pipe if available. For example, ASTM A 312 is one specification for piping and provides the specification for wall thickness variation acceptable in a freshly produced pipe.

In any case, a 40% loss of wall thickness is a serious matter and it needs investigation. If the spot is amenable for a visual inspection of the OD and ID, it would be fairly easy to confirm the loss of wall thickness due to corrosion, erosion or a depression.

Some pipes have internal planar inclusions and you may get less thickness readings at local spots without any external evidence. We came across this particular interesting situation when we took up wall thickness gaging of hydraulic piping of an extrusion press in our organization. We had nothing except the drawings and the nominal wall thickness to go by. After thorough and repeated checks and a few other tests, we could convince all involved that the peculiar low thickness readings at some locations were due to inclusions. Since there was no external damage to the pipe we could clear its continued use.

I hope you will find a suitable solution soon. Feel free to discuss more if needed.

Swamy
Quality and NDT Expert
Hyderabad
 
 
12:44 Jan-25-2012

Mark Nel
, Applications Advisor,
Technology Design Ltd.,
United Kingdom,
Joined Jul 2005
43 Stand of Technology Design Ltd
Re: Help me (Thickness measurement)
In Reply to S V Swamy on 09:10 Jan-25-2012 .

This thread has touched on a lesson that all technicians/inspectors should learn and understand early in their careers or, as Mr. Stephenson mentioned "...there could be a whole lot of pain later...".
Performing an inspection will produce a set of results either way but it is not always possible to offer a reasonable opinion on the results and certainly folly in the absence of specific procedural guidance. The technicians primary function is to perform the inspection according to a procedure or technique based on the relevant facts regarding the material, process, customer requirement etc. then to make judgments on the results but in the absence of acceptance criteria must not give in to his/her ego and commit himself (and by extension his employers) to opinions on acceptability. As all have said before - in this case only report the result, not it's relevance because there is no basis for comparative assessment. Do not start that conversation because it will draw you into a place that you don't want to be for longer than you want to stay.

 
 
14:34 Jan-25-2012
eko
Re: Help me (Thickness measurement)
In Reply to Chieg on 07:59 Jan-24-2012 .

hello Chieng

just for your information, base on API 5CT this is for seamless pipe, as i know, commonly we using 87.5% from nominal Wall Thickness for the acceptance.

eko
Heat Treatment Dept
Seamless Pipe Processing Plant

 
 
19:50 Jan-25-2012

Andrey Bazulin
R & D, -,
Scientific Center ECHO+,
Russia,
Joined Sep 2006
54
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

Chieg

Was this the bended pipe? Maybe the metall loss is due to errosion in a bend?

And of course the decision is one the owner of equipment.

I think that as minimum you should analyse code for pipe fabrication.

What kind of object did you inspected?

 
 
19:58 Jan-25-2012

I R Stephenson
NDT Inspector, Auditer / Cross Checker,
STS { Stork Technical Services } Australia,
Netherlands,
Joined Aug 2011
40
Re: Help me (Thickness measurement)
In Reply to S V Swamy on 09:10 Jan-25-2012 .

Who owns this pipe ?, who asked for the survey ? who is the customer ?
Find out who wants your results and hand them over, end of story, you are in the
" taking a ut survey business " with this NOT " I'm in the decision of what to do with it " business.. Complete it and let it go..

 
 
15:13 Jan-27-2012

S V Swamy
Engineering, - Material Testing Inspection & Quality Control,
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
656
Re: Help me (Thickness measurement)
In Reply to I R Stephenson on 19:58 Jan-25-2012 .

Dear Stephenson,

Yes, for the NDT technician, it may be the end of the story but for the QA / QC manager, it is not, when the management depends on him / her for certification of the pipe for further service. My role in my previous organization was managerial and not limited to the measurement aspect. In fact, I did not measure the thickness myself (my staff did it).

My earlier post / observations were more from that angle and also as a metallurgist.

Best regards

Swamy

 
 
08:39 Jan-30-2012

Lalit Mohan Kothari
Consultant, -,
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc,
India,
Joined Jan 2003
128
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

Chieg,
As most of the designing is done on 1.5 safety factors and if loss is such a high (40%) then it must be investigated. So just check with initials parameter of pipe during the time of design this will help you to find the life of pipes .causes of corrosion Â…., fluid inside of pipe etc ..then you can calculate the acceptance criteria of thickness from the design. It can be from 12.5 % to 20% or more range.
Please also check with UTFD also
Thanks & Regards,

Lalit Mohan Kothari

“Dreams and dedication makes powerful combination”

 
 
15:46 Jan-30-2012

I R STEPHENSON
NDT Inspector, Auditer / Cross Checker,
STS { Stork Technical Services } Australia,
Netherlands,
Joined Aug 2011
40
Re: Help me (Thickness measurement)
In Reply to Lalit Mohan Kothari on 08:39 Jan-30-2012 .

I am quite aware that when the UT tech hands his report in that it is then in the hands of QA/QC but if the UT tech does not have anything to work to then for him I'm afraid it is finished , how can he/she possibly accept or reject something, pipe, weld etc,etc if there is no acceptance/rejection criteria ? he/she would be foolish indeed to start giving opinions etc..

 
 
20:37 Jan-30-2012

Csaba Hollo

RSO, QA Rep,
Acuren Group Inc.,
Canada,
Joined Feb 2010
262
Re: Help me (Thickness measurement)
In Reply to Lalit Mohan Kothari on 08:39 Jan-30-2012 .

Lalit...too many assumptions.

This is simple. If there is an acceptance/rejection criteria, then a call can be made based on the data found as it applies to the criteria.

If there is no acceptance or rejection criteria supplied, then only results can be reported, with no further comments.

As an NDT technician, our job is to use the correct method, procedure/technique to get accurate results, and report them accordingly.

The original poster is looking for an acceptance criteria. That cannot be determined by anyone in this forum without more information regarding materials and use as outlined by Jon Wallis.

Often, many different tolerances are quoted for acceptance based on the application, damage mechanism, time and severity. These tolerances are based on years of experience with certain materials and applications, with known variables. There is no universal criteria that applies to piping in general.

Bottom line is, Chieg, if you need the acceptance criteria in order to complete your report, then you will need help from the owner's engineering group to come up with what they are able to tolerate for a minimum thickness of this pipe (or pipe system) so you can determine if it meets the criteria or not.

 
 
17:21 Feb-09-2012

Phil

NDT Inspector, Radiation Safety ,
BINDT, MIAQP,
United Kingdom,
Joined Mar 2009
151
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

Hi Chieg

Sounds to me as if you are doing a corrosion control survey, with these you usually do not have an acceptance criteria you just report your findings and the Engineers make the decisions, so just report your findings

. As sometimes you will be told if the thickness is below let us say 5mm you reject it, then fine if not just report what your readings are it is up to the engineers to decide what to do not you.

Regards

 
 
19:54 Feb-09-2012
John
Re: Help me (Thickness measurement)
In Reply to Phil on 17:21 Feb-09-2012 .

Chieg

The last time I work realizaeu thickness measurement, found lower values ​​as you. As he had no criteria to assess the situation, gave it to an engineer to calculate the thickness that I measured with respect to working pressure that the pipe work. Then, from calculations of the engineer can approve the pipe together.

 
 
13:29 Feb-10-2012

massimo carminati
Consultant, AUT specialist,
IMG Ultrasuoni Srl,
Italy,
Joined Apr 2007
502 Stand of IMG ULTRASUONI SRL
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

I agree with the previous post, but you should add other valuable informations other then "should be 10 and I measure 6". First thing you should strongly suggest an extention of examination around the damaged area in order to determine the type of damage (type of corrosion, erosion etc.) and to confirm this is really wall thickness loss or internal defects like laminations, inclusions or blistering.
Structural assessment calculation needs this type of information.

 
 
12:57 Feb-13-2012
John
Re: Help me (Thickness measurement)
In Reply to massimo carminati on 13:29 Feb-10-2012 .

In my case, I inspected an area and did not detect any defects. spent only for an engineer to calculate the thickness found could work in conditions that were working.

 
 
09:47 Feb-15-2012

Lalit Mohan Kothari
Consultant, -,
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc,
India,
Joined Jan 2003
128
Re: Help me (Thickness measurement)
In Reply to I R STEPHENSON on 15:46 Jan-30-2012 .

There are periodic safety audit/& regulation/RP in every country for inspection of pressure related objects and its reduced as per aging effects of objects(METAL) and accordingly the thickness is one of the testing in this practice .
pressure Can be increase after any R&M
Thanks & Regards,
Lalit Mohan Kothari
“Dreams and dedication makes powerful combination”

 
 
09:52 Feb-15-2012

Lalit Mohan Kothari
Consultant, -,
On ..IOCL and BARC(Bhabha Atomic Research Centre).etc,
India,
Joined Jan 2003
128
Re: Help me (Thickness measurement)
In Reply to Chieg on 04:08 Jan-24-2012 (Opening).

Final acceptance depends on owner of object either they are running their plant on full or partial loads
Thanks & Regards,
Lalit Mohan Kothari
“Dreams and dedication makes powerful combination”

 
 
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