Distortion limit for ASME Section 8 Vessels

[prabhakar s]

Hi,

 

 

We have procured a Stainless Steel tank from one of our sub contrators. The thickness of the plate is 6mm. They have done hydrotest also. The tank is shifted to our Project site from the Sub contractors yard. We observed a distortion of 3mm near a Longitudinal seam (Both side of the weld seam).

 

I would like to know the allowable tolerance limit for distortion. Is 3mm acceptable? If it is so please give me the code reference.

 

We observed  a Grinding mark of 0.5 mm depth on 6mm thick Shell. what is the allowable limit for this? Is there any code reference?

 

Your early response in this regard will be highly appreciated.

 

 

Regards

Prabhakar. S

 

[Arunachalam A]

Code ASME Section VIII Div 1 talks the following tolerances:

 

1. shell/head ovality. as per UG 80/81

2. Fit up tolerances as per UW33

3. Weld reinforcement tolerances as per UW 35.

 

You need to assess the acceptance of tank/vessel based on the above tolerances.

 

Please give the design parameters of the vessel ( shell dia/thick/internal pressure/external pressure  etc). in order to assess the vessel

 

arun

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[GOPU NAIR]

Dear Mr. Prabhakar   Since you have not mentioned any code of Design/construction, I assume that the tank is just a storage tank.  Distortion of about 3mm at the weld joint will not make any diffenrence functionally.  Extent of distortion depends upon the length and diameter of the shell and how it looks visually.  To ascertain whether 0.5 mm local ground spot is acceptable, please carry out the measurement of actual thickness using thickness meter (UT based) or calculate the theorical requirement.  If local dent looks too bad meerge the same in a larger area to look better.       Gopal    --- On Fri, 28/8/09, prabhakar s <prabha...@gmail.com> wrote:

Regards Prabhakar. S   Love Cricket? Check out live scores, photos, video highlights and more. Click here.

[prabhakar s]

Dia of the Vessel- 2m

Shell, Head thickness-6mm

Design Pressure-Atmospheric pressure.

 

Regards

Prabhakar. S

[vipin george]

Hi!Prabhakar,
Please refer ASME Sec Viii Div1 ,Edition 2007 Addenda 2008, uw-31 & uw-33 for tolerances.

Thanks& Regards,
Vipin

On Fri, Aug 28, 2009 at 11:12 AM, prabhakar s <prabha...@gmail.com> wrote:

[prabhakar s]

Hi,

 

Thanks for your valuable information. I have got the clause. It is UG-80 Out of Roundness Tolerance. As per the June 2008 interpretation this clause is applicable for Weld distortion (Vertical Peaking) also.

 

 

Regards

Prabhakar. S

[Arunachalam A]

You can go upto 20mm( 1%) for the difference between minimum dia and maximum dia you measure.

 

Regarding 0.5 mm localised metal loss, you can exercise engineering judgement. You can apply Uw 35 tolerance on undercut  ( 1mm )for this or  UG 16 plate undertolerance of 0.25 mm.

 

arun

 

On Sat, Aug 29, 2009 at 11:22 PM, prabhakar s <prabha...@gmail.com> wrote:

Hi,

 

Thanks for your valuable information. I have got the clause. It is UG-80 Out of Roundness Tolerance. As per the June 2008 interpretation this clause is applicable for Weld distortion (Vertical Peaking) also.

 

 

Regards

Prabhakar. S

On Sat, Aug 29, 2009 at 5:13 AM, vipin george <viping...@gmail.com> wrote:

Hi!Prabhakar,
Please refer ASME Sec Viii Div1 ,Edition 2007 Addenda 2008, uw-31 & uw-33 for tolerances.

Thanks& Regards,
Vipin

On Fri, Aug 28, 2009 at 11:12 AM, prabhakar s <prabha...@gmail.com> wrote:

Hi,

 

 

We have procured a Stainless Steel tank from one of our sub contrators. The thickness of the plate is 6mm. They have done hydrotest also. The tank is shifted to our Project site from the Sub contractors yard. We observed a distortion of 3mm near a Longitudinal seam (Both side of the weld seam).

 

I would like to know the allowable tolerance limit for distortion. Is 3mm acceptable? If it is so please give me the code reference.

 

We observed  a Grinding mark of 0.5 mm depth on 6mm thick Shell. what is the allowable limit for this? Is there any code reference?

 

Your early response in this regard will be highly appreciated.

 

 

Regards

Prabhakar. S