Electric Resistance Welded vs. Seamless for Commercial HVAC Applications

[RobsVette]

I may have this in the wrong forum, so moderators, please feel free to move this if you see fit to do so.

Recently, a question came up where I work, on the reasons for specifying seamless pipe or electric resistance welded (ERW) pipe for condenser water systems.

My personnel feeling was that ERW piping was fine for most applications. The weld used to create a piece of ERW pipe, is comparable (if not better quality) than the welds used to join sections of pipe together. The only reason we tend to specify seamless piping on building services piping is if a welded joint is going to be X rayed, the seam is visible in the X ray and can possbily create an issue with the interpretation of the X ray in the area of the seam. Other than that, there is no tendancy of the seam weld to fatigue, rust of otherwise wear pre-maturely to the rest of the pipe.

Can you guys and gals please explain why you specify a pipe to be seamless as opposed to ERW? My personnel feeling is that for most applications that are not involving high amount of thermal stresses, where radiographic NDE will be used, ERW would be just as good as seamless.

Thanks for any help.
Rob

 

[BigInch]

It really just breaks down to cost issues by way of the mfg process. Seamless is easier (cheaper) to make when the diameter is 12" or under and ERW, UOE formed, or Helical, is easier when over 12". We stager the positioning of longitudinal seams at the 10, 12 and 2 O'Clock positions in order to avoid excessive contact of the seams with entrained water and condensates that tend to run along the bottom half of the cross-sectional flow area. There is no issue with radiographing of any of them.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[bimr]

Building services piping is typically specified as ASTM A53/A53M, Schedule 40, Type E or S, Grades A or B. Type E or S means that the piping contractor can use either Electric-Resistance-Welded or Seamless.

When piping is properly manufactured by a reputable supplier, seamless does not have any advantage over welded.

From a manufacturing standpoint, typically welded is more cost-effective as a result of the minimised labor input and reduced manufacturing scrap.

From a fabrication standpoint, welded is more cost effective because of the reduced number of field orbital welds needed to join individual lengths of tube together.

The decision whether to use a seamless or welded pipe depends principally on the wall thickness / diameter ratio and the specified pipe tolerances. Normally the cost advantages of the welded pipe outweigh the alternative,and mainly welded pipes are used

 

[moltenmetal]

Some here have concerns about small pipe (1/2"-2") which is seam welded due to difficulty in inspecting the quality of the seam weld.

We accept welded seam in both carbon and common stainless steel grades for most services, at all sizes of pipe and tubing. We mostly use pipe in the 1/2"-3" range, and tubing in the 1/4-3/4" OD range. We buy seamless when clients hard spec it. We do not accept A53 welded seam from China due to concerns over fraudulent millcerts, but otherwise we source world-wide. In over 15 years, buying many miles of pipe, we have found only one single through-wall defect in the seam weld.

We do not experience problems with interpreting RT results of butt welds on welded seam pipe.

We have however had MANY defects in seamless pipe and tube. Excessive ID roughness, ovality/non-concentricity, and also metallurgical damage near the mid-point of lengths (probably due to poor cleaning and/or improper annealing) has been a fairly frequent issue particularly with seamless product from China.