[MW:21963] Re: Allowable Thinning as Per IBR in Bends of Superheater U-Bends(1D) of Alloysteel Tubes(SA335T11/T22) after Forming

In your case the same will be < 16.6%

(ii) Thinning on tube bends.  Thinning on tube bends shall comply with the following.

(a) At any location around the bend extrados, the reduction in thickness (in percent) below the calculated minimum permissible design thickness of the straight tube, except where permitted by (b), shall not exceed:

          __100___

             4R + 2                                    

              D

where

R is the mean radius of the bend to the centre line of the tube (in mm).

D is the ordered outside diameter of the tube (in mm).

               (b) Bend thickness below the minimum value required under (a) shall be permitted in cases where the manufacturer can demonstrate by bursting tests carried out on at least three bends that the strength of the bend is not less than that of the straight tube.

               (c) Where the amount of thinning at any location around the bend extrados on cold formed bends exceeds 25% of the actual thickness of the tube on the straight the bends shall be suitably heat treated.  The actual thickness of the same plans as the line of the extrados at each and of the bend.

On Wednesday, April 16, 2014 1:51:30 PM UTC+5:30, Amit Udavant wrote:

Dear all

Can anybody put some light on the Allowable thining in the Wall thickness of "U" Bend of  44.5 OD X 4.5 mm WT of SA335 T11 or T22 Alloy Super Heater Tubes after Cold Bending of Size 1.0 D. as per IBR (Indian Boiler Regulation)

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Warm Regards
amit

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