Annular plate thickness

[oldisgold981]

hello guys,
i was going through TANK software report and found that it calculated annular plate thickness = 12.7mm
i have calculated the annular thickness myself stresses product and hydrostatic stresses comes out to be 191 and 192.7 MPa respectively . As per table 5.1a i think the required thickness shall be 11mm as the bottom shell course thickness is 39.
can someone guide how the tank software got this value ?

tank is 80m diameter and 20m height , there is no corrosion allowance. design pressure is ATM.

 

[HTURKAK]

Apparently Annular Bottom-Plate Thicknesses acc. to Table 5.1a should be 11.0 mm .The excerpt that you have attached shows some CA is added and moreover 13.0 mm is user specified .

 

[oldisgold981]

Thank you Hturkak for your reply. There is no corrosion allowance considered in this case. i specified 13 mm just to clear the model.
i just don't understand how tank calculated this value of 12.7mm.

 

[HTURKAK]

What is the selected width of annular ring? What about seismic loading? Apparently ( if there is no corrosion allowance considered, no seismic loading which may thickness ), Minimum thickness acc. to Table 5.1a will be 11.0 mm.

 

[Geoff13]

It's almost like the software is following the USC code rules, but then reporting in SI units.

For instance 12.7 mm does not exist in Table 5.1a. It only exits in Table 5.1b as 1/2" (exactly 12.7 mm). This was the clue that got me thinking about this idea.

The 39 mm is 1.535", which would put you in the last row of Table 5.1b where 1/2" is the required thickness at the stress you calculated for ring 1.

I have never used TANK software so I don't know if you can select whether the USC or SI rules should be used. Hopefully you can specify SI and then get the results you expect.

 

[oldisgold981]

Thank you Geoff13 for your reply. It seems what you have mentioned makes sense . As i changed the bottom shell course material to high strength and used 36 mm thickness then tank software selected 11mm thickness. Before software was interpreting 39mm more than 1.5 inch so it was going to the last row of the table.

Thank you so much Geoff13 and HTURKAK for helping.