Impact Test Reduction

[loilfan]

We have a low temp vessel where the MDMT was determined by impact testing (i.e. was not exempted in Figure UCS-66) to -50F. If we want to reduce the MDMT to a lower temperature (say -60F), are we able to use the reduction from the stress ratio in Figure UCS-66.1 without doing any further impact tests?

My thought is that this would be acceptable since the -50F impact test assumed a fully loaded material.

 

[Jano6924]

Take a look into UCS-66(i), this may be of help for you. However I believe that by doing so that would be considered as an alteration on exisitng vessel.

Regards.

 

[loilfan]

Thanks Jano6924, that's the reference I needed. And you are correct that this would absolutely be an alteration, albeit a non-physical change.

 

[metengr]

Yes, this is an alteration as a re-rating and would be under either rules from the NBIC Part 3 or API 510.