ASME Section VIII and re-rating a vessel's MAWP
ASME Section VIII and re-rating a vessel's MAWP
(OP)
I was looking through Section VIII on how to re-rate a vessel's MAWP. At first crack, it seems all I can do is use the design calculations and hope the manufacturer underrated the vessel. Does anyone have any experience with this?





RE: ASME Section VIII and re-rating a vessel's MAWP
It will be unusual to gain more than a few PSI as there is normally just not that much fat in it.
Re-rates are normally done under the NBIC, rather than ASME I believe.
Regards,
Mike
RE: ASME Section VIII and re-rating a vessel's MAWP
Re-rates of pressure retaining items are not covered in ASME B&PV Code because this is a construction code not an in-service repair or alteration code. One could also look at API. However, these are not ANSI standards, like ASME B&PV Code or the NBIC.
RE: ASME Section VIII and re-rating a vessel's MAWP
Thanks,
AIUS
Oregon
RE: ASME Section VIII and re-rating a vessel's MAWP
As pointed out by SnTMan rerating involves all pressure containing and pressure/temperature impacted components of the vessel, as well as all applicable loadings. The analysis may also need to consider piping loads, wind, seismic conditions, liquid level, skirts, saddles, internals, external attachments, vacuum, steamout, etc.--the list can be very extensive. Original calculations are not needed but a knowledge of the materials of manufacture, and such parameters as joint efficiency, original hydrotest pressure, fillet weld sizes, impact testing temperature, and component thicknesses, are required. For vessels built to API-ASME, it is also desirable to know whether or not the vessel received PWHT.
Having personally been involved with literally hundreds of rerates, I would recommend that only those who are very experienced in pressure vessel analysis should tackle such a project. Ideally, these tasks should be left to those who also have prior experience performing rerates.
RE: ASME Section VIII and re-rating a vessel's MAWP