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 Post subject: Thickness Survey
PostPosted: Thu Apr 08, 2010 9:48 am 
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If i want to carry out thickness measurement on piping system to ascertain the remaining wall thicknes, what code do i use and what is the minimum allowable dimmunition of thickness in percentage?.


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 Post subject: Re: Thickness Survey
PostPosted: Thu Apr 08, 2010 11:52 am 
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Joined: Sat Dec 01, 2001 1:00 am
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Location: Essen, Germany
I suggest to consult the Code of Construction that was used for the design of the piping.

When you know the nominal new thickness, establish the required thickness, and measure the actual thickness, you can determine the remaining lifetime-
Just calculate the corrosion rate (mm/yr) and determine the remaining life.
An inservice inspection after half of the remaining life is a good idea.

NBIC can help for inservice inspection questions.

DK


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 Post subject: Re: Thickness Survey
PostPosted: Thu Apr 08, 2010 6:29 pm 
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Location: Chicago, Illinois USA
If i want to carry out thickness measurement on piping system to ascertain the remaining wall thicknes, what code do i use and what is the minimum allowable dimmunition of thickness in percentage?.

betrandma,

Use the material spec. For example SA106-B pipe then go to Section II Part A and the Code minimum allowed is 87%.

leem


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 Post subject: Re: Thickness Survey
PostPosted: Thu Apr 08, 2010 9:07 pm 
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Location: Essen, Germany
Leem,

The material undertolerance has maybe not been considered in the design. Some piping Codes allow to calculate with the actual thickness, some even with the actual Yield strength. Therefore the 12.5% undertolerance is maybe not available.
Also we do not know if Betrandma knows the nominal thickness of the new pipe.

In some counties I have seen piping systems where nobody knew the material, schedule, design code or required thickness. The piping was just there, and the owner wanted to know how to repair it after an explosion.

For this reason, the question shall be more precisely.

DK


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 Post subject: Re: Thickness Survey
PostPosted: Sun Apr 11, 2010 8:54 pm 
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Location: India
Let us assume it as a process piping,

To ascertain the remaining life --

check API 570(2006 edition), section 7.

Minimum allowable dimension of thickness in percentage --

The required thickness of the pipes shall be the greater of the pipe design thickness (or) the structural minimum thickness. For service with high risk, the piping engineer should consider in increasing the required thickness to provide for unanticipated (or) unknown loadings (or) undiscovered metal loss.

As per B31.3, Required thickness of straight pipe T = t + C
Where t is the pressure design thickness as determined by means of Internal (or) External pressure calculations & C is the corrosion allowance.(Refer 304,ASME 31.3,2004 edition)

Hope this will help you.

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Kareem


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 Post subject: Re: Thickness Survey
PostPosted: Wed Aug 10, 2011 4:50 pm 
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Thanks for your guys, i have to say it is truly useful.

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David
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Email:david@lordsteel.com
Lord Steel Industry Company Limited
Many Solutions, One Decision Here...


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 Post subject: Re: Thickness Survey
PostPosted: Tue Nov 08, 2011 12:09 am 
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Location: Delhi,INDIA
In most of the country regulatory body is there and and it is mandatory to carry out (corrosion )safety test for their vessels under factory act/PESO/IBR/RP on regular interval .As old design having extra safety factor so the 12.5% limit can be exceed .
Plant load also be consider with the use of pressure systems reduced accordingly

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Lalit Mohan Kothari
TUV-NORD INDIA
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