Vessel Design vs. Ambient Temperature

You should refer to ASME Section II - Part D

It shows that the allowable stress for 516-70 is the same (138 MPa) from -30 to 250 deg C.

Hence, the thickness would not change from 26 to 43 deg. C.

Dear Jibril,

Change in ambient temperature will widely affect many aspects of engineering. It will hit the change in specially gas handling rotating machinery, air compressor, air fan, furnace & heater design and air coolers.

But I've never heard that ambient temperature may affect the shell and head thickness.

One exception. If the ambient temperature is low temperature like a vessels in polar area, then they may affect the mean metal temperature although process service is ambient.

In conclusion to your specific question, change in ambient temperature ( e.g. 26 deg. C to 43 deg. C) will not affect vessel head/shell thickness in design.

Changing the ambient temp. from 26 ^oC to 43 ^oC will not have any effect on the mechanical properties of the material ASME SA516 Grade 70.

Where from Table 1A of ASME II Part D for Max. Allowable Stress Values S for Ferrous Materials, the 1^st column indicates that S = 138 MPa within a range of temp. from -30 ^oC to 40 ^oC.

The attached link is an actual case for a pressure vessel as a reactor to plot the relation of the MAWP versus Temperature, from which you can find that the allowable tensile strength S of material SA 515 Grade 60 shall not affected by the small changes in ambient temperatures. The significant changes in S can be noticed nearly at 250 ^oC and above.

Link: MAWP_versus_Temp_of_a_Pressure_Vessel.

Within that temperature range, the changes are negligible. For extended temperatures, for design purposes, one would need to account for the CLTE, Young's modulus and Poisson's ratio changes; then, would need to find the maximum stress (von-Mises for a malleable material) under maximum thermal and mechanical load and compare it to the yield strenght of the material. Cyclic load must also be considered in determining the life. For all these I would suggest using a FEA package.

Dear all,

Thanks for all the responses I received. It really is rewarding being around you guys.

The issue is now cleared.

Regards,

Jibril