[6d bend]

….but I was just curious if a welder could get an electrode in there to make one good weld why couldn’t one ell simply be welded to another, with one weld and without any “pup” at all (in effect a minimum “pup” length of about nothing, and which scheme if possible would appear to minimize at least any issues of two close together welds on a very short “pup”)? …..

Fitting to fitting is perfectly acceptable, but not always possible, ie when coming off a rack to a defined height, may require the use of a pup.

Other reasons for “pup” pieces, would be to allow for field fit up, such that only a small section of the design would require modification should field conditions change, due to equipment being set at incorrect height.

The field fit up reason is very important to keep in mind, as many “fast track” jobs require that piping construction isometerics are issued prior to final certified drawings being issued.