Maximum Wall Thickness for Seamles Pipe

Hi,

You are referring to the 6" NB sch.40 pipe standard table. If i am buying a pipe, i used to request the mill certificate to check the specs of the pipe and materials properties for standards cross reference. However, there might be a time on the manufacturers side that the wall thickness comes out form the mill has been over on that specified tolerance. and that was neglected to returned back to the process. I should suspect as this what happen. and it was release for sales disposal.

Sch. 80 pipe will go to further thicker wall thickness which will be applied according to the requirements of the applications.

Bottom line, the user are in safe side when talking for maximum tolerance, provision for corrosion allowance as expected has been extended. Manufacturers side, it will not be good as certain losses will be considered.

regards

Common thickness testing requires that all corrosion and paint be removed at the point were the thickness sensor touches the pipe wall otherwise a false measurement can be given.

The pipe was taken back to bare metal by the UT equipment operator prior to the readings being taken.

New dual multi mode units and transducers can be used for thru paint readings.

Internal alignment of pipe walls shall not exceed 1/16" or the larger wall shall be beveled 30 deg.

.31" looks like sch 80 wall or possibly 120 for original wall.

The figure ±12.5% is a mill thickness tolerance. It means that when you buy a new pipe, you have to take into consideration an increase or decrease in pipe wall thickness by 12.5%, it is a mill tolerance and considered an acceptance criteria.

But if you have an old and or corroded pipe, you can use that pipe with the available thickness for the service adapted with the design pressure and design temp. and allowable tensile strength of material.

The design equation of the pipe wall thickness in accordance with the related code and standard is the governing point. So, if you calculate the thickness and you found that it is sufficient (i.e. the calculated thickness is equal to or greater than the min. actual thickness), even the pipe wall thickness tolerance is more than 12.5%, for the applied pressure and temp., it is considered an accepted thickness for that case.

Note: Corrosion allowance, erosion, ... etc. must be added to calculated thickness and compared with the actual thickness of pipe.

Thanks for the help, but can I point out that ASTM Standard A106 does not draw reference to a +12.5% tolerance, it does however state a tolerance of nominal wall thickness -12.5%.

Yes you can, because the -12.5% is the worst case to be taken into consideration.

DERA SIR

I UNDERSTAND, YOU ARE A DESIGNER IN PIPING FIELD. SO I WOULD LIKE TO COMFIRM MY THOUGHTS ABOUT NOMINAL WALL THK. IN PIPE & PIPE FITTING IS DESIGNATED FOR ACCEPTANCE FOR END USER AND MANUFACTURERE.PETICULAR PIPE OR FITTING SUTABLE FOR DESIGNATED /DESGNED USE FOR PARTICULAR TEMP PRESSURE RATING WITH ITS SUITABLE DESIGNED CHEM. & PHY. PPROPERTIES.

IN THIS CASE 6" NOMINAL SIZE SCH 40 /STD/40S IS HAVING WALL THK. 0.280" . CONDITION IS GIVEN THAT WALL THK. SHOULD NOT BE LESS THAN 87 1/2% TO THE NOMINAL W.THK. SO I FEEL IT REQUIR FOR USER TO BE CAREFULL WHILE USEING ANY PIPE OR FITING SHOULD NOT BE LESS THAN GIVEN LIMIT .IN THIS CASE ONE SHUOLD NOT USE LOWEWST LIMIT IS 0.248" COSIDERING ALL DEFECTS SUCH AS CORRSIO, ERROSIN ETC.

BUT I FEEL ,ONE USES WALL THK. ANY AMOUT OF GRATER THAN SPESIFIED SHOULD NOT AFECT ON HIS END USE. OF COURS NO MFGER. WOULD LIKE TO GIVE MUCH HIGHER W.THK. THAN + 12 1/2 % OR MAY BE SLIGHTLY HIGHER IN SAME COST. AS NOW A DAYS EVERY MATL. QUIT EXPENSIVE.

I THINK ONE CAN SAY THE IN THIS REGARDS IS NOM. W.THK. +/-12 1/2 %. BY ENLARG.

THANK YOU

V.D.DEODHAR.

Dear Vidyadhar

If you have a pipe with 6" NPS, Sch. 40, according to ASME B36.10M its nominal pipe wall thickness shall be 0.28" (7.11 mm), and for a tolerance 12.5% , the min. nominal pipe wall thickness shall be not less than 0.245" (not 0.248") (6.233 mm).

This mean that if you received a new pipe 6" NPS, Sch. 40, you can find its nominal pipe wall thickness is 0.245" (6.233 mm), you have to accept that thickness without any claim to the supplier, because the reduction of thickness still within the code tolerance. At beginning of 1st step in design of that pipe, the designer must take that tolerance, in addition to any corrosion and/or erosion.

For manufacture is the governing code ASTM A106 or ASME B36.10M.?

The material requisition must include and specify the both, ASTM A106, and ASME B36.10M. These specifications are very important for the mill producing these pipes, manufacturer/fabricator and designer.

DEAR SIR

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Sir,

What is the acceptance percentage for the entire lot if the thickness found not acceptable on random basis / sample basis? If we refer ASME B16.9 for fittings it is very much silent about the same.