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
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.
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.
15:16 Jan-24-2012 I R Stephenson NDT Inspector, , NDT Services, Netherlands, Joined Aug 2011 33
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 InspecciÃ³n del Noreste, Mexico, Joined Jun 2002 80
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 650
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.
Quality and NDT Expert
12:44 Jan-25-2012 Mark Nel , Applications Advisor, Technology Design Ltd., United Kingdom, Joined Jul 2005 41
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.
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 650
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.
08:39 Jan-30-2012 Lalit Mohan Kothari Consultant, -, On ..IOCL and BARC(Bhabha Atomic Research Centre).etc, India, Joined Jan 2003 128
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
Â“Dreams and dedication makes powerful combinationÂ”
15:46 Jan-30-2012 I R STEPHENSON NDT Inspector, , NDT Services, Netherlands, Joined Aug 2011 33
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 261
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
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.
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 485
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.
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
Â“Dreams and dedication makes powerful combinationÂ”
09:52 Feb-15-2012 Lalit Mohan Kothari Consultant, -, On ..IOCL and BARC(Bhabha Atomic Research Centre).etc, India, Joined Jan 2003 128