Please confirm to me that PV Elite does not calculate the MAEWP of the nozzle flanges and the MAEWP from PV Elite is the MAEWP for the shell and head only.

If yes, can i put the value from "Vessel Design Summary" on the nameplate?

Hi Miera81

I assume the term MAEWP means the maximum allowable external working pressure. It is always better to be clear about the terms you use, as not everyone on the forum understands what you mean. I say this, because there are many foreign users of the forum that whose first language is not English.

Nozzle flanges are not analysed by PV Elite. It is assumed that nozzle flanges are standard B16.5 or B16.47 flanges, which do not need to be analysed (calculated). The maximum working pressure at the design temperature is stated in the flange specification in tabular form.

However, if you wish to compute the flange for external pressure, there is a check on the Configuration screen called 'Print Flange Calcs for External Pressure'. This will not give you the maximum allowable pressure, but will give you the calculation for the stresses and the flange thickness.

The U1 form as I understand it, only requires the MAWP, not the maximum external working pressure. Normally, if the vessel is to be 'U' stamped, and it is subjected to external pressure, that external pressure must be set to a minimum of 15 psig (101,3 kPa).

Hi Ray Delaforce

Sorry,
MAEWP means the Maximum Allowable External Working Pressure.

Thank you very much for your explaination regarding to Flange Calcc for External Pressure, I never used before. So its really helping me in future.

Refering to UG-119 (NAMEPLATES), we need to add Max. allowable ext. working pressure. Since my vessel is full vacuum condition, so the information need to add. Before this, i just used calculated value from PVElite and no question from our Autorised Inspector. But now, their querry is :-

"Usually a Design Engineer (DE) will use the MAEWP given by the software. The DE need to be aware that if the MAEWP stated on the Name Plate is 45.7 barg, it means all the re-inforcement calculations and the thickness of all pressure retaining parts must be able to withstand this Design Condition. Please make sure the software is considering everything for MAEWP 45.7 barg if you still want the MAEWP on the NamePlate to be 45.7 Bar."

Hi Miera81

The Authorise Inspector is asking (in my opinion) for something that is outside the requirements of the code. If you have an un-jacketed vessel comprising essentially a couple of shells and two heads, the maximum atmospheric pressure (according to the code) is 15 psi (103.42 kPa). You cannot get a higher external pressure - unless you intend installing the vessel under water! I can see no point is assessing a vessel for an external pressure that can never be reached. The code simply says: If you want the vessel to be code stamped, you must consider the vessel for 15 psi vacuum.

You can simply set the Maximum Allowable External Working Pressure to 15 psi and state is as the MAEWP. That is a clear statement in the code.

I was a vessel inspector in South Africa, and I never asked anyone for a MAEWP. As I was also the reviewing engineer, provided the vessel could take a full vacuum, that was all I was interested in.

Hi Ray Delaforce

Ok, noted. I will implement MAEWP is 15 psi.

Hi Miera81

If you do, you are following the rules of the code. The Authorised Inspector, I am sure, will not object.