Then I suggest you to use, instead of rod bars (or bridge tacks), what in the States are called "strongbacks" and in your country (Argentina) "perros". Any piping foreman will know what I'm talking about. If not, let me know your fax number and I'll fax you a drawing.
I've used them extensively back in my days of erector engineer with no problem at all. Also, their use is allowed by the Codes (B.31 etc.), provided you apply the tacks with the same eletrode (rod or wire) type with which the weld will be done, and grind thoroughly the rest of the tack after the strongback (perro) has been removed.
Giovanni S. Crisi
Sao Paulo - Brazil
P.S. Did you like the "4 a 1"?
I think it depends on your application. On inside process or power piping I think you'll see quite a few things welded on the pipe for fitup purposes. But in cross country pipeline work, where the pipe is and always has been considered sacred, even an arc burn on the pipe/fitting means a cutout. In that world you wouldn't want to suggest tacking bars across the joint.
I'd look closely into what is considered acceptable practice in your specific field, and go from there.
JTMcC.
Thank a lot Giovanni for your suggestion and I agree with you about "perro" being the more extendended fitup system in Argentina,except for pipelines, but my question is more related metallurgic considerations.
For example if you intend to use construction rod bars (very high carbon content), etc.
P.S. "3 a 1" game before like me much more.