API 5L X60 pipe versus X65Q

[Angoil]

High everybody,
I am currently working on the detailed engineering phase of an offshore project. In one of our client piping classes it is specified to use PIPE API 5L X60. All the offers we received from approved supplier are for grade X65Q, quench and tempered heat treated pipe. As per suppliers, it is not possible to find X60N in stock. As per our client piping specialist it is not recommanded to use X65Q intead of X60. For him the problem come from the fact that X65 is quench and tempered and not normalized as the X60 can be. Moreover, in the code asme B31.3 in the TABLE A1 giving the allowable stress values, for X60 and X65 there is a note (55) saying that "the stress values apply to either nonexpanded or cold expanded material in the as-rolled, normalized, or normalized and tempered condition". Meaning that we don't know the values for a pipe in X65 that has been quench and tempered, so that we don't know the stress value to use to recalculate the pipe wall thickness.
Does anybody understand this note 55 of table A1 of ASME B31.3 ? What to do in case of pipe that is quench and tempered ?
Thanks to all for your advice

 

[metengr]

Normalized versus quenched are two different heat treatment operations related to cooling rates to achieve a desired microstructure or strength level in a steel. The resulting microstructures from cooling by either normalizing or quenching may not necessarily be the same depending on microalloy content and net section thickness. The bottom line is X65Q is not acceptable for use per ASME B31.3 based on note (55). I don't have the API 5L specification handy but it would be worthwhile to check if quenching is permitted as an alternative to normalizing by the Supplier, based on thickness of the steel.