This weeks case, The Case of The Missing Swing Joint

RayWohlfarth

This weeks class is about why a swing joint is needed on a cast iron sectional steam boiler and what can happen if it's not there. If you have a weird problem you found on a boiler project, I would like to hear about it
Thanks

https://www.youtube.com/watch?v=4XIyKLWGgh0

EBEBRATT-Ed

Many swear you can't use welded pipe on a boiler. I disagree. It is the distance of the horizontal runout connected to the boiler riser that matters. Make that 2-3 ' and you have no issue. Obviously, no swing is bad, but you see it all the time, for some reason some boilers seem ok with this, and some do not but I think it will always shorten the life of the boiler.

RayWohlfarth

@EBEBRATT-Ed I have seen boilers with welded piping last for decades Some manufacturers require threaded joints tho.

Mad Dog_2

I've seen welded headers WITH screw pipe swing joints...as long as you have some compensation for expansion and contraction.  It awe-inspiring the damage that can be done by Steam and hot water 
Heating systems with no wiggle room. Mad 🐕 Dog

RayWohlfarth

@Mad Dog_2 it is awe inspiring and we think we can control it

Mad Dog_2

Like a Tidal wave or blizzard...ya gotta absorb it and let it do its thing. Mad Dog

Steamhead

What model Smith was that? What do the instructions for that model say about piping?

RayWohlfarth

@Mad Dog_2 I hear that
@Steamhead Its been a while since I was there but I knew they required a swing joint

WaHeat

ok, I'll ask it. What is a swing joint?
I have an idea, but this video isn't clear

Lance

A swing joint is a dance hall playing big band music to swing your hips to.

ScottSecor

@Steamhead it looks likes a Smith 28 series to me.

I am not suggesting swing joints are not helpful with hear boiler piping on steam boilers. However, I have seen many cast iron steam boilers without swing joints, or flanges that lasted a long time (over twenty years). I have seen screwed risers and headers, welded risers and headers were trouble free.

For reference, we installed two Weil McLain 1288 steam boilers in 2004 at a local school. We used all welded pipe except the three 5" x12" nipples (per unit) where they thread into the boilers on one end and threaded into the flanges at the other end. Above the flanges we used 5" welded nipples and elbows that faced left that connected to an 8" welded header. About a year after the installation I happened to be on site when the insurance/state inspector came for the annual inspection. He commented on the installation, but mentioned he just went to a seminar and his company now recommends all threaded fitting near the boiler, and the header if possible! Not sure if it was Hartford Steam, FM, or maybe Travelers insurance companies. By the way both of these boilers are still functioning quite well, there have been no issues with the boilers of the piping as of last week.

In my experience the 28 series was without a doubt the most popular model (of this size boiler) in my area. The 28 series (steam and hot water) was also the most problematic, specifically the ones installed in the 1980's and 1990's. We found many had bad sections that had to be replaced, sometimes only a few years old. The newer ones we serviced and installed were much more reliable.

ChrisJ

EBEBRATT-Ed said:

Many swear you can't use welded pipe on a boiler. I disagree. It is the distance of the horizontal runout connected to the boiler riser that matters. Make that 2-3 ' and you have no issue. Obviously, no swing is bad, but you see it all the time, for some reason some boilers seem ok with this, and some do not but I think it will always shorten the life of the boiler.

Perhaps we should rename swing joint "Spring joint" since that really seems to be what it does.
The extra horizontal piping allows for the piping to flex.

I still find it impossible for the 100 year old threaded joints I cut apart to have been "moving" back and forth for a century and yet not leak and not have any wear and were impossible to turn apart using 48" long wrenches...

ScottSecor

@ChrisJ good point on those threaded joints not leaking and being pretty much impossible to "unthread" after fifty or a hundred years. To add to your point, almost every steam boiler I've seen that was installed in the 1970's or earlier that had threaded nipples had cast iron fittings. Cast iron fittings are not known for flexing.

ChrisJ

ScottSecor said:

@ChrisJ good point on those threaded joints not leaking and being pretty much impossible to "unthread" after fifty or a hundred years. To add to your point, almost every steam boiler I've seen that was installed in the 1970's or earlier that had threaded nipples had cast iron fittings. Cast iron fittings are not known for flexing.

No, cast iron in ways doesn't flex much, but the steel piping does. Luckily.

Actually I don't know if cast iron can give at all, I think it's a fairly weak material.

RayWohlfarth

@WaHeat Here is a picture of one. It absorbs the expansion and contraction of the pipes. Hope this helps

Adk1guy

I understood swing joints from the time they were explained but my trainer wanted extra elbows so the joints could literally swing. It seemed to me that steam kind of welds joints together and the threads no longer could move but if the various legs are long enough they will bend much like you see a horseshoe build into pipelines every so often.

EBEBRATT-Ed

I agree with @Adk1guy

EdTheHeaterMan

Lance said:

A swing joint is a dance hall playing big band music to swing your hips to.

I have to say that I wish I thought of that! I am going to nominate you for a First Place LOL of the Month Award.

EdTheHeaterMan

@WaHeat
Here is the reason for the expansion joint.
When the boiler makes steam the boiler gets hot first and the pipes are still cold. The boiler expands as in the center illustration, the pipes will not give way as shown. So the boiler gets additional tension compressing the sections together as the 2 risers and the header act as a clamp trying to hold the boiler from expanding. Those cast iron connectors may be push nipples for neoprene gaskets. Whatever the connections are made of, they will eventually fail or a section will crack under the extreme stress of the heat expansion over and over again from each steaming cycle.

By adding the swing joints, as in the illustration on the left, the boiler can expand while the rotation of the risers compensate for the expansion. Shortly after the boiler expands the pipes will get hot and will also expand and the risers will rotate back. Think of it like taking a tin can lid and bending it on a crease. If you continue to ben that crease over and over again, the lid will eventually break in to two pieces. But Boilers cost more that tin can lids so you don't want that stress to happen on a regular basis

EdTheHeaterMan

Adk1guy said:

I understood swing joints from the time they were explained but my trainer wanted extra elbows so the joints could literally swing. It seemed to me that steam kind of welds joints together and the threads no longer could move but if the various legs are long enough they will bend much like you see a horseshoe build into pipelines every so often.

If that swing joint is exercised every steaming cycle, that joint will not "weld joints together". The joints that do not get exercised on every steaming cycle will rust together and be almost impossible to unthread 20 or 50 years from now. But if you take a big enough wrench to a swing joint fitting , It will come apart more easily than the ones you are talking about. Ask me how I know.

ChrisJ

EdTheHeaterMan said:

Adk1guy said:

I understood swing joints from the time they were explained but my trainer wanted extra elbows so the joints could literally swing. It seemed to me that steam kind of welds joints together and the threads no longer could move but if the various legs are long enough they will bend much like you see a horseshoe build into pipelines every so often.

If that swing joint is exercised every steaming cycle, that joint will not "weld joints together". The joints that do not get exercised on every steaming cycle will rust together and be almost impossible to unthread 20 or 50 years from now. But if you take a big enough wrench to a swing joint fitting , It will come apart more easily than the ones you are talking about. Ask me how I know.

And how exactly does a binding style joint, such as NPT not loosen and start to leak from moving constantly? Even small amounts?

That's the part I'm having trouble buying.

RayWohlfarth

@EdTheHeaterMan I used to be able to take apart this boilers

EdTheHeaterMan

ChrisJ said:

...And how exactly does a binding style joint, such as NPT not loosen and start to leak from moving constantly? Even small amounts?

That's the part I'm having trouble buying.

Because it is not loosening. It is staying at the same tightness. The amount of rotation on that pipe thread connection is measured in less that .01 degrees of rotation.

Think of it like this. If you turn the threads 6 times and the threads seal and there is no leak you are done. But if you turn it 1/6th of a turn more... Did you stop any more leaks? No that thread connection was already leak free. Now turn it back 1/32nd of a turn. Do you get a leak? NO. You need to turn it back at least quarter of a turn or more before that joint leaks.

But you could continue to overthink the whole process. OR Just do it because I said So!
(That is how my mother got me to stop asking WHY?)

EdTheHeaterMan

RayWohlfarth said:

@EdTheHeaterMan I used to be able to take apart this boilers

You could still do that... all you need is people. I got people.. I just point and it gets done. See... I just got that boiler put together. Point again and the tools are loaded on the truck.
...all you need is people Ray!

ChrisJ

EdTheHeaterMan said:

...And how exactly does a binding style joint, such as NPT not loosen and start to leak from moving constantly? Even small amounts? That's the part I'm having trouble buying.

Because it is not loosening. It is staying at the same tightness. The amount of rotation on that pipe thread connection is measured in less that .01 degrees of rotation. Think of it like this. If you turn the threads 6 times and the threads seal and there is no leak you are done. But if you turn it 1/6th of a turn more... Did you stop any more leaks? No that thread connection was already leak free. Now turn it back 1/32nd of a turn. Do you get a leak? NO. You need to turn it back at least quarter of a turn or more before that joint leaks. But you could continue to overthink the whole process. OR Just do it because I said So! (That is how my mother got me to stop asking WHY?)

Ok and now do that thousands of times.

EdTheHeaterMan

@ChrisJ

.... thousands of times

...a year for 50 years and look at the results. Just find a 50 year old boiler with swing joints, there are thousands of those out there. When you find one let me know if it is leaking. I have found many in my career that were perfectly dry, under all that insulation. And have moved those 2-1/2" and 3" pipes with a 48" pipe wrench. The non swing joints not so much. They get the sledge hammer treatment.

Keep overthinking it. When it is time to move on, you can just install swing joints "because I said so."

Mad Dog_2

I'm with you Fast Eddie.   Your detailed explanation makes the most sense from my 40 years working on old pipe. Mad 🐕 Dog

RayWohlfarth

@EdTheHeaterMan you're right and it made me smile thanks