Static head and MAWP

[pianoman1]

I just read through a couple long and very interesting posts on the difference between pressure vessel Design Pressure (DP) and MAWP. They referenced that, for vessels with some height, DP applies to the top of the vessel and adjustments are made on the way down to account for static pressure. But, I'm still confused.

I have a 90 foot tall vessel with a nameplate on it that states the MAWP as 150 psig interior @ 220F. There's also additional design info provided on the fabricators drawings that identify the DP and MAP as 150 psig @ 220F and the hydrotest pressure as 226 psig @ 32F.

My question is this - can I operate the top of this vessel at 150 psig, which would be ~190 psig at the bottom? Or does the MAWP apply to any point in the vessel, which would limit the top to ~110 psig.

Thanks for any feedback.

 

[pianoman1]

I should add that the vessel is designed for liquid service, medium consistency pulp stock, SG~1.0. The capacity is given in gallons and the weight empty and full are noted on the design drawings.

 

[SnTMan]

pianoman1, the DP, MAP, MAWP, what have you should apply to the top of the vessel. The designer should have then added appropaite static head to design of vessel componenets. See, for example in Sec VIII Div 1, UG-21, UG-22(j) and UG-98.

Regards,

Mike

 

[pianoman1]

Thanks, Mike. I did dig out the code and it makes sense now.