Header Connection Sizing

elfie

if you have a 15 section boiler with three 5 inch risers extending from top of boiler that connect to an 8 inch header.  this all seems fine and consistent with installation instructions.



and then the 8 inch connection transitions to a 5 inch connection that then routes thru the building to smaller 1 1/2 inch pipes that have a series of risers to feed radiators   - does this type of connection present any problems?



an 8 inch header carries 3 times more steam than a 5 inch pipe



as noted in a previous post there is excess capacity. 





at least it may make installing a new boiler easier since the main lines of steam beyond the steam boiler related connections are 5 inch.

Steamhead

The 8-inch header

by virtue of its larger size, slows the steam's velocity down to the point where any water that makes it that far will drop out of the steam flow and go down the equalizer back to the boiler. This helps produce dry steam.

elfie

header sizing

does the existence of the 5 inch piping network that extends further into the facility present a problem if a smaller steam boiler is installed?

Steamhead

Nope

as long as the header is right. And if it conformed to the specified piping configuration, keeping the 8-inch header would work well.

elfie

header size and main connection

in this situation there is a 3 million btuh boiler with three 5 inch risers going into an 8 inch header, which is then connected to a 5 inch main steam pipe



in this situation, the 5 inch main is supporting about 800 thousand btuh of radiator capacity (yes, oversized)



if there was more radiation in the facility, can the 8 inch main be connected to possibly three 5 inch mains?  given that large pipes can handle more steam, the sizing of pipes connecting to a header is important.



i have viewed a steam pipe table (really good table linked below) that shows the steam capacity of an 8 inch pipe handles about 3 times as much steam vs a 5 inch pipe.



 if you have an 8 inch header supporting a 5 inch main, does it mean velocity of steam going thru the 5 inch main might be on the high side.



http://www.engineeringtoolbox.com/sizing-steam-pipes-d_266.html





 

The Steam Whisperer (Formerly Boilerpro)

Velocity...

depends on teh boiler firing rate, the amount of radiation connected, and the air venting of the main/radiators.   An 8 inch header feeding a 5 inch supply is great, especially if the boiler is firing at the level matching the radiation!

Paul48

Transitions?

"and then the 8 inch connection transitions to a 5 inch connection"

The main transitions to 5" out of the top of the header, or at least 45* out of the header?

elfie

header connection

in this case the 8 inch header (for a 3 million btuh boiler) is connecting to a 5 inch main that is supporting about 750 btu's of radiation capacity.





when you have an 8 inch header, how do you divy up the connections to support 3 zones each having 1 million btu's of radiator capacity (ie. what would pipe sizes and # of connections to the header).



here is a header on top of a 500 btuh boiler that has a connection to two mains (riser pipe size is 4 inches (not sure why boiler needs two risers).

Paul48

Not

Did you get that picture from a site that shows "what not to do with near-boiler piping"?

elfie

near boiler piping

no, its from a facility that i am familar with



what are the piping issues of concern?  i know the welding is a problem.   thanks very much.

Paul48

Issues

It's welded pipe, which means no swing joints. Properly, the risers feed the header, the header feeds the mains. The mains should drop down into the header between the last riser and the equalizer.

Paul48

deleted

The Steam Whisperer (Formerly Boilerpro)

I believe Weil Permits this type of installation..

as does smith (IIRC).  This is probably why I see Weils failing after only about 15 years at the gasketed connections. I don't think any other Cast Iron Manufacturer permits welded connections like this, though, and I certainly wouldn't do it.

Hap_Hazzard

Image

Apparently that site doesn't allow the images to be linked to.



I think this image shows what you are describing. (Feel free to use it if you like it. I drew it myself.)



[aside]

Now that I'm actually building this header, I'm wondering how much the swing joints can really swing since the equalizer is straight. I'm not that worried about it since there's plenty of room for the pipes to flex, but in theory, shouldn't swing arms allow for the independent expansion and contraction of the boiler and header without the pipes pipes needing to flex? Is this typical, or have I screwed it up by not keeping the swing arms parallel?



Yeah, I know. I'm over-thinking this. :-/

Paul48

Thanks Hap

I didn't reallize there was an issue, because the image shows on my computer. Your graphics are great! It's an accurate representation of his situation.I only know that the swing joints provide a way for the near-boiler piping to expand and contract without transferring that force to the sections of the boiler.

elfie

swing joints help preserve sections

its more clear,



the vast benefit of swing joints is to protect the connections to the sections.



it the connections around the sections cracks it means you need a new section



so is this the basic risk if swing joints are not used?



is it worth redoing the work (ie. change from welding to swing joints?



a 15 yr live on a steam boiler is pretty bad.

Paul48

elfie

I would say that the current configuration gives you very wet steam. Whether it would be worthwhile at this point to re-pipe it probably depends on the age of the boiler. Hopefully, some of the experienced steam guys will weigh in with their thoughts. If it should be re-piped, they can show you exactly how to properly do it.

elfie

repipe?

the boiler age is 5 yrs -  why does header look like it creates wet steam?

 is it due to the welding job?



the system is a low pressure system and burner is cycling on and off frequently, like watching a yo-yo



would re-piping make sense since it may prematurely damage connections to the boiler



thanks

Paul48

Manifold

That "manifold" that your mains come off shouldn't be there, and is probably filling with condensate. The mains should come off the header like hap's picture. Does the boiler surge?

Steamhead

The "manifold" is probably the original header

which can be re-used as long as the piping to it is done properly.



Check which way it is pitched. If it pitches from front to back, bring the steam into where the plug is and drip the other end. If it pitches back to front, drip the end where the plug is.  Here are a couple pics where we did this, on smaller jobs.



Oh, and welded headers often make boilers leak prematurely, as described above, so it's well to change them to threaded drop headers. Replacing the header is much less expensive than replacing the boiler.

Paul48

Thanks Steamhead

I knew it wasn't proper, and I knew you would know how to properly configure it. I used the term "manifold", hoping he would see it as a non-functioning part of the system. What do you think about the boiler cycling on and off as he describes? Do you think it is related to the old header being full of condensate?

elfie

how serious a problem is header welding?

how serious of an issue is it to have welded header pipes vs swing joints??



does it matter that boiler is a low pressure boiler?



is it common to redo header piping from weld to swing?





thanks

Steamhead

Might be

but it's more likely that the boiler is oversized.



Another thing I like about using the old header this way is you don't have to demo it. Big time-saver! ;-)



Elfie, the use of a proper header is one key to good system performance and boiler longevity. It doesn't make sense NOT to upgrade this one.

elfie

oversize impact strain on welds

does the oversizing and frequent burner on/off cycles over a short period of time put strain on welded jouints vs swing joints?



i am hoping burn rate can be reduce with hopes it may lengthen burner cycle which may make boiler more efficienct (and improve on excess capacity)



thanks

The Steam Whisperer (Formerly Boilerpro)

I think it does...

The constant heating and cooling of the cast iron from short burner cycles must impact the stress caused by the welded header.  Even worse is the stress caused many more complete cool down and heat up cycles because the system fills so quickly with steam and then shuts off...if you are not maintaining constant steam pressure.  I've seen oversized gasketed section boilers start leaking in two or three years at the gaskets when combined with other causes of short cycling (improper thermostat settings and undersized transformers).

elfie

headers swing

i am in agreement that the welded headers should be replaced



and i called Weil Mclain and they were quite clear in saying that the welded job should be redone with swing joints (i had previously heard that Weil Mclain was ok with welding on this boiler which seemed odd)



i also had a question about adjusting the burner rate (due to oversizing) and they said that burner rate can be reduced by 20% from the gph spec rate per manual.



thanks for all the comments

The Steam Whisperer (Formerly Boilerpro)

You had heard correctly...

Welded swing joints are allowed on thier boilers, according to the manuals They are actually welded arms.  When in doubt, consult the manual.

The Steam Whisperer (Formerly Boilerpro)

You had heard correctly...

Welded swing joints are allowed on thier boilers, according to the manuals They are actually welded arms.  When in doubt, consult the manual.

elfie

info on welding header pipes

hi,



i couldnt find any comments in the weil mclain series 80 boiler manual about proper way to do header connections



per above comment, welded joints are allowed, and it also refers to welded arms



this seems contradictory to what tech support says over the phone



I understand why welded headers are a bad thing but then reading above adds confusion to issue.

The Steam Whisperer (Formerly Boilerpro)

Therein lies the problem...

if it is not speced, it will be welded on bigger boilers because it is cheaper and faster to weld.  If you look at the Peerless install manuals for a 210A boiler, it is in bold large print with a circle around saying threaded connections must be used.  Around here, all the big CI boilers are welded. That, along with lack of maintenance, oversizing and incorrect control settings are probably the chief reasons why the average life of steam boilers is now at 14.7 years for a piece of equipment with a design life of 30 to 40 years.



Weil has some good techs that know better, so you probably got a good one whcn you called.