Greetings. I suggest leaving the diameter range blank. It does not need to be mentioned on a WPS per ASME IX. Reason being, if you happen to suggest, Let’s just say, a diameter range of “UNLIMITED” on your WPS, and during production there is material in the form of pipe that meets the diameter range specified, but at the same time is less than or greater in thickness than what is allotted. The weldor could assume that he or she is in the right, due to staying within the diameter range specified, but failed to stay within the specified thickness range. The thickness range qualified takes precedents. The weldor, in most cases, will not know this and in doing so will fail to meet critical aspects of the WPS, unwittingly.
Example: WPS per ASME IX specified thickness range is 1/16” to 1/2”. The specified diameter range is “UNLIMITED.” During production, weldor, welds on 24” NPS x (SCH80) 1.219” Wall. The weldor will feel that he or she is in the right because of the fact that the diameter range is specified as “UNLIMITED.” Can you see how this might be confusing and unknowingly cause an issue that results in the WPS not being followed correctly? You might say to yourself, the persons following the qualified WPS should conform to the thickness range specified, but in my experience I’ve seen this scenario play out on more than one occasion. I personally leave this subject matter blank for any qualifying ASME IX WPS, and I always suggest this because of the very scenario that is mentioned above. I hope this makes sense to you, I don’t know if I conveyed it correctly or not so that you may understand the point that I’m trying to make. Cheers.....
--
Regards,Jamie Reyes
J.R. Machine Company, Inc.