B31.8 pipe wall thickness calculation 1

[canecutter]

After arriving at the "nominal wall thickness" using B31.8, is the mill tolerance for a given material considered before selecting the appropriate commercially available pipe.

 

[BigInch]

Mill tolerance need not be considered for wall thickness calculations according to B31.4 or B31.8. Any wall thickness within mill tolerance is assumed to be exactly as the standard pipe tables dictate. The pipe is produced with an average yield stress somewhat higher than specified and any wt produced within the allowed mill tolerance is within an acceptable range of accuracy of Barlow's formula, t = P*D/2/F/SMYS After calculating your wall thickness, you may then select the next largest wall thickness from the standard wall thicknesses in stock, or if your guantity of pipe is significant, you could ask a mill to produce your pipe to any wall thickness you chose.

Example: If your calculation indicates that you should use 0.369" wall thickness, you could select the next commercially stocked standard (probably 0.375" wt), or ask a mill to produce a 0.369" wt for you. It could yield significant savings in material and transportation costs if the pipeline was several hundred miles long.

BigInch-born in the trenches.

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