Welded 6 inch header

Steve_210

Because we don’t have an in-house welder, we would always used threaded headers in the past the biggest was 4 inch.
here my plan is to weld the 6 inch and tread everything else. Don’t see an issue if I allow for expansion. Just want to get some opinions I have seen discussions here in the past.

gerry gill

well, just think about where the expansion is going. If you do a threaded drop header giving you 4 screw joints to absorb expansion, i don't see an issue with the header being welded. I have welded 4'' headers but have always used drop header risers which were screwed on them.

ScottSecor

I'm going to assume we are talking about steam here. We use welded headers regularly on larger jobs. Not sure you can buy 8" or 10" threaded fittings locally any more. 6" threaded fittings and nipples are hard to come by these days as well.

I know most, if not all manufacturers want at least a few of the fittings and nips threaded near the boiler. Oddly, we rarely see sectional failures due to welded steel pipe. Most common around here (NJ) is threaded nipple into the boiler, threaded flange on top of that and all welded after that. Of course on most commercial cast iron boilers there are multiple risers. so multiply this by two, three or sometimes four.

One of my favorite welded headers (that we use on commercial hot water boiler installs often) is a large diameter header (often 6") with multiple three inch or four inch threadolets and welded caps on both ends. This allows us to have threaded risers and a welded header, kind of the best of both worlds. This type of header is not really practical on bigger jobs with five and six inch risers.

EBEBRATT-Ed

When you come up with the risers and go horizontal make the horizontal a good distance. Even a welded header can flex if you don't close couple things and make it too tight.

Steve_210

Thanks guys yes, using a drop header with swing Joints

Steve_210

Yes, Steam I have 2 4 inch risers thanks for all your help.
A Welder friend said he would weld pretty much all of it. I just wanted to see if anybody had issues with that.
if I have a drop header with treaded flanged unions, seems to me like I’m good for expansion. Thanks.

WMno57

Detroit Nipple Works will make threaded nipples up to 12". They also have large fittings.
https://www.detroitnippleworks.com/faqs/

The Steam Whisperer

The pattern I have seen with the Weil Mclain LGB steamers, which seem very sensitive to welded headers, is that boilers with welded offset 2 riser headers last about 14 years. Failure mode is almost always leaks between the sections at the seals. Boilers installed with 2 threaded risers and headers or smaller single risers sizes last about 24 years. I consider a 14 year life unacceptable and only the rich can afford the cheaper welded installations. On large boilers we use a welded header but with threaded drop risers, which allows all sorts of expansion and contraction. Also, the header drain and return going back into the boiler needs to be threaded in order to make this corrosion prone piping easier to replace in the future without the huge set up fee for a certified welder. Many installation diagrams also show required threaded joints here also so expansion and contraction of the piping doesn't stress the castings.

Steve_210