Procedure for derating ASME Coded Vessel.

[vrkleo]

Hi,

A heat exchanger manufactured in 2006, but still not taken in to service. Code of construction is ASME Sec VIII Div 1 and the heat exchnager is code stamped. The equipment is installed outside USA/Canada.

Now the heat exchanger need to be derated (Without any physical change to the vessel) for lesser MAWP on channel side. Since NBIC doesn't cover de-rating, what should be the code / procedure followed?

1. Can de-rating be done by the end user and a new name plate be provided by himself as per API 510?
2. Is the code stamp still valid after derating as per API 510? My understanding is "NO", but looking for an option to have the code stamp intact.
3. What options I have to do the de-rating, but still to have the code stamp intact?

Thanks you very much for the support.

 

[metengr]

The concept behind derating is to reduce pressure or increase MDMT. In either case there is no safety issue and this is why derating is not discussed in the NBIC. This is a matter to discuss with the local regulatory body where the object is installed. They may have specific requirements to address derating so that the vessel may never be re-rated in the future. This is more of an enforcement issue rather than a technical issue. The code stamp doesot change because the vessel was originally built to ASME code. The code stamp will not be affected by the derating, it is still an ASME built vessel, period.

 

[vrkleo]

metengr,

Thanks for the response.