Dear all

To be honest,my question has little to do with caesar ii.
i am rather confused why the caculated wall thickness by b31.3 is so thicker than B16.39.
Take an example,in LNG industry,the caculated TP304 thickness under 1.86MpaG is about 2.1mm,with manufacure factor considered and errosion factor ignored, but the selected sch10s is 3.76mm.
Can anyone give light on this difference ,best regard and many thanks.

Hi,

Do you have Piping Catalog near to you? Can you give us the nearest upper schedule for this pipe?

My assumption is; Your pipe thickness must fall in the standard or practice. You may have calculated thickness with very economical selection but in the field, you need thicken it more so as to avoid failure with incidental loads. This issue is much concerned on small bore piping. But if you have 3” or more, then it’s another issue. These are just my opinion (My practices).

Regards,

xiaxiuqing,

The stainless pipe standard that you refer to is probably ASME B 36.19 and it is a dimensional standard - not a design standard. The dimensional standards enable a group of compatible pipe, fittings, and valves to be assembled together using off-the-shelf components. A custom thickness of pipe might be economical for long transmission pipeline of miles - Km. The pipe fittings in custom wall thickness would be 2X the cost of custom pipe.

The CaesarII calculations are implemented from the ASME B31 pping codes, as pointed in other queries of the forum. It is good to try to understand the design code more, so that the CaesarII results are understood and can be appreciated to then make design changes or adjustments.

The 1.86 MpaG converts to a litle less than 270 psig, and in the smaller diameters the wall thickness could be very thin. From your 2.1 mm wall thickness your pipe diameter could be Nps-12 (nominal 300 mm) and it is a moderate diameter. The 2.1 mm wall thickness is nearly thin enough to be difficult to weld without blowing through weld puddle, or handling the thin 2.1 mm wall pipe without denting or deforming it out of round.