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# MAP & MAWP4

## MAP & MAWP

(OP)
Hi code experts,

In design view, I would not see the necessity of giving two symbols/concepts for the maximum allowable/working pressure at the design temperatures. the highest allowable design pressure shall meet the design temperatures, whatever the highest one of design temperature or the lowest one of MDMT.
In fact, the value of MAWP and MAP are same because for the same component or vessel the maximum allowable stresses shall be same for both calculations of MAWP at design temperature at corroded condition and MAP at MDMT at corroded condition(same material, same thickness).

FYI,
The MAP defined in ASME VIII-1, note (8) in Figure UCS-66.2
"the maximum allowable pressure (MAP) at the MDMT shall be used. The MAP is defined as the highest permissible pressure as determined by the design equations for a component using the nominal thickness less corrosion allowance and the maximum allowable stress value from the Section II, Part D, Subpart 1, Table 1A at the MDMT.
"

The defination of MAWP in code,
"maximum allowable working pressure: the maximum gage pressure permissible at the top of a completed vessel in its normal operating position at the designated coincident temperature for that pressure."

May make the two above in one.
The maximum allowable working pressure: the maximum gage pressure permissible at the top of a completed vessel in its normal operating position at the designated coincident temperature, both the highest and lowest for that pressure.

Regards,
Replies continue below

### RE: MAP & MAWP

MAWP is a single value for the entire vessel, limited by the weakest component.

MAP is a value for a particular component, and will be larger than (MAWP + static head above the component) for all components except for the weakest one that limited MAWP. It is only useful for the UCS-66.2 calculation.

### RE: MAP & MAWP

NO, NO
They are both confused.
Read again. Try to understand when and why to use MAP and when to use MAWP.

Regards

### RE: MAP & MAWP

OP,
Not meaning to cause offense but if you are seeking "expert" advice, then why do you have your own "expert" opinion on how to read the code?

#### Quote:

In fact, the value of MAWP and MAP are same because for the same component or vessel the maximum allowable stresses shall be same for both calculations of MAWP at design temperature at corroded condition and MAP at MDMT at corroded condition(same material, same thickness).
You have provided excerpts of definitions to, I guess defend your position???? Nothing you think you have "discovered" is new or original. The code provides methods and definitions which are not open for interpretation for a reason. Are there sometimes discrepancies, yes, news methods and technology, yes, which is why the code is constantly evolving. If your question was what's the difference between MAP and MAWP, I think most posters here would be happy to walk you through things but the way you are approaching this, as something you found, an obvious code discrepancy! is not the way to go about this.
I will refer back to r6155, read the code and understand when, where and why to use what definition.
I may be misunderstanding your intentions, but they result from how your post was written.

### RE: MAP & MAWP

In common useage MAWP refers to the maximum allowable pressure in the hot and corroded condition.

MAP refers to the maximum allowable pressure in the new and cold condition.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

### RE: MAP & MAWP

2
(OP)
@r6155 and Heaviside1925, please share your idear on MAWP and MAP, just like SnTMAN and Geoff13, whatever your idear is correct or not. Here is open technical discussion palce, but please don't make the meaningless comments and off the topicel of technical discussion. That will help to make the discussions in my posts here simple and clear in technical for all readers. Your comments here are off the topic and not techincal/professional that may make others boring.

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