Can u please tell me that the MDMT calculated in PV Elite software is related to which pressure is it related to design pressure or MAWP or MAP new and cold condition.

MDMT must be related with some pressure, I think only MDMT doesn't have any meaning. For considering the MDMT calculated in software for name plate of vessel the presure must be known.

Dear Vishal,

The pressure used to compute the MDMT of each element is the operating pressure at the bottom of the element. This pressure is used to compute the reduction in MDMT per UCS-66.1. The basic MDMT of each element is a function of the thickness and UCS-66 curve (A, B, C or D).

Please tell me that operating pressure means design pressure plus static head.?

Also i want to know waht is the perfect significance of writing the " MDMT @ MAWP" as per ASME UG20. Is there chances of failure of vessel while MDMT is not onsidered up to MAWP?

Is it mandatory for all projects following the ASME code or it must be added to each and every vessel name plate?

Vishal,

Yes, it is design pressure plus static head.

In determination of the MDMT there are 2 steps, first the basic MDMT is looked up from the UCS-66 chart using the thickness of the component and its external pressure chart (A,B,C,D).

Next, the ratio of required thickness to the actual thickness is used to reduce the basic MDMT computed above. Basically, here you are getting credit for any excess thickness that you have over the pressure reqd. thickness. This is per chart UCS-66.1.

So, the design pressure (+ static head) will determine the req. thickness and this will affect the MDMT reduction. So, if the design conditions change the reduction will also change.

Sometimes you can get the MDMT using the exemption of UG-20(f). But, you have to satisfy the conditions of that section.

When determining the MAWP of the vessel. It is best to use the MAWP computed by the program and set it back as the design pressure and run the analysis one more time and make sure all the items even the small ones are ok.

No I think you make mistake,its clear that the design P should be greater than ope. P.
according to MEGYSEY design P is the 110%*ope. P or ope. P+30psi whichever is greater (at corrosponding static head).dont confuse yourself with static head.