Let me try this again, this time with a 1" supply pipe. Surely that will cause trouble!

ethicalpaul

You may find this video to have a clearer message it's communicating than my last one, thank you for the feedback on that one.

In this one I run all my steam through a 1" pipe to feed my system. We'd be concerned if a homeowner came here looking for help and they had a single 1" supply pipe going to their header, right?

https://youtu.be/Uz-8TWtbpiM

Big Ed_4

Thanks for the video .. Thinking the increase of system pressure caused by the smaller supply condensed the steam .

jesmed1

Nice experiment Paul. I'm just a lowly homeowner/engineer who doesn't have any experience with steam heat, but I have read LAOSH. As I understand it, the whole question of near-boiler piping size is an attempt to regulate the exit velocity of the steam as it leaves the boiler.

Dan talks about this question on pp 42-43 of LAOSH, and he quotes early steam guru Ara Marcus Daniels from 1928 saying "Steam boilers are not provided with means for assuring dry steam…hence velocity of flow through outlets of such boilers should be relatively low—not over 15 feet per second—if the carrying over of water with steam is to be avoided." Dan then looks at specs of some older boilers and lists the exit velocities for them. All but one are below 15 fps.

Then Dan notes that a book from 1936 says excessive steam velocity will interfere with the backward flow of condensate. And you showed that in your video with the condensate film on the walls of the sight glass being blown upward by the steam velocity. Dan follows that book quote with a table showing the maximum recommended velocity for different size riser pipes on a 1-pipe system, based on condensate flow. The max recommended velocity for a 3" riser is 29 fps, and Dan observes that Ara Marcus Daniel's 15 fps max is only half that, which is very conservative.

Dan then looks at the specs of some modern boilers. The 7 modern boilers he choose have exit velocities ranging from 25 to 37 fps, in some cases more than double Daniel's 15 fps max. Dan then observes that this means most modern boilers have exit velocities that exceed the max velocity against which condensate can drain, meaning that the headers and equalizers must separate out the condensate before it gets out into the system.

But it seems what your video showed is that, if no water droplets are being generated inside the boiler by surging, the exit velocity doesn't really matter. As Dan showed, modern boilers already have exit velocities above the condensate backflow limit, so they're already pushing the condensate up the walls even with correctly-sized near boiler piping. And as you showed, even higher velocities don't matter if there are no water droplets leaving the boiler in the first place.

It sounds like this is another instance of a very conservative "rule of thumb" (don't exceed 15 fps) having been established back in the day when boilers may have been more likely to generate water droplets due to poor water quality, maybe different boiler geometry, maybe less control over water lines levels, etc. Apprently modern boiler mfrs have learned that they can safely exceed 15 fps but are still trying to keep velocities reasonable enough so that if there is surge, keeping the velocity down minimizes the effects.

It reminds me of the Mythbusters episodes about dropping a penny off the Empire State Building. They built a small vertical wind tunnel to find the terminal velocity of a penny, which turned out to be around 65 mph. or about 95 fps. The Ara Marcus Daniels' 15 fps limit is presumably the terminal velocity of a water droplet, so if the surrounding steam is traveling slower than 15 fps, the droplet will fall, and if higher than 15 fps, the droplet will rise. But as with many old heating "rules of thumb," this may be conservative.

What I take away from your video is that, if the boiler isn't surging or producing water droplets some other way, excessive steam velocity isn't a problem. So the important factor is having water clean enough, and the water line low enough, that water doesn't get carried out of the boiler exit in the first place.

Dan mentions seeing many steam guys using anti-surge tanks. I assume like this:

https://www.tfi-everhot.com/anti-surge-steam-separator.html

Does anyone ever recommend those to homeowners with surging problems? That might be less costly than replacing all the undersized/badly installed near-boiler piping. Because as you showed, if you have clean dry steam, pipe size doesn't matter much.

ethicalpaul

Nice summary! I have a feeling it won't necessarily stop folks from telling homeowners they have to repipe their boilers but I hold out some hope 🙂

PhilKulkarni

I would appreciate if someone clarified what good water quality means. If it means no oil on the water surface and a PH above 7 then I have it in my 63-03 boiler. The next term I seek clarity on is surging. If it means the water line fluctuates more than +/- 0.25” when the boiler is operating then I have no surging, but my water line is approx 2.5” from the bottom of the sight glass. Does this mean I have significant carryover? I do get a fair amount of rust despite using 8-way. I am using distilled water to refill after draining the rust once a month. Could the carryover be caused by suspended rust particles?

It is important to note that none of these conditions are causing any heating issues.

Lastly, if undersized takeoffs cause carryover due to a high steam velocity, then Bernoulli tells us that oversized pipes should lead to a lower carryover at the same pressure. In my case I have a 3” single takeoff to a 2” header. The spec is 2” takeoff and 2” header. The 3” takeoff gives me a 44.4% greater cross sectional area, consequently this should result in a velocity that is 44.4% of the velocity with a 2” takeoff. Yet, despite a 55.6% reduction in exit steam velocity, I get wet steam- steam that is not 100% vapor.

But wait, that is not all. My 3” takeoff is 25” tall from the boiler cover to the header, which is at least 10” higher than the min (24” from the boiler water line). I point out this because I thought that a lower exit steam velocity and a taller takeoff would result in negligible carryover, all else being equal. Alas, that is not the case. I know this might come across as a contrarian viewpoint but it is what it is- a healthy mix of empiricism and stoicism.

I had an oversized Burnham that died after 34 years. It had a drop header and it too operated with the water level nearly at the bottom of the sight glass. It needed to be blown down every other week but no heating problems whatsoever. I am beginning to believe there are elves in every boiler.

EBEBRATT-Ed

The Thermoflow thing is just a "slow place in the road" to let the steam rise and the water to drop out. Same thing a header does.

I have always felt that riser size may be more important than the header. Why use the header to separate the water and steam/? Keep the water in the boiler where it belongs.

The funny thing about steam is there are probably more boilers piped wrong than right that still work fine.

But we know big risers and big headers work "all the time"….almost.

So, when to cut corners and when not to?

I say pipe to the mfg. minimum and skim it good.

ChrisJ

My opinion is the header is there for a similar reason as the equalizer and Hartford loop.

The Hartford loop is to keep the wet return from siphoning out of the boiler. In order for this to work you need to break the siphon with a vent, the equalizer. Since we have that there anyway, we might as well pipe a header into it that will drain any water that blows out right back into the boiler rather than it having to make the long journey down the main(s) and back. Water leaving the boiler rapidly via the mains is also bad, so if we can slow it or prevent it…..

None of it is needed if everything is correct, but it all helps when things aren't correct.

I've personally watched an improperly piped boiler (no header at all) blow a ton of water up into the main and shutdown on low water. Would this happen if it had a proper header and equalizer, or would it all return quick enough to prevent the LWCO from tripping? @ethicalpaul Have you tested that yet? I can't remember.

jesmed1

@EBEBRATT-Ed

If headers are successful at removing water, why did Dan say in LAOSH that many of the steam guys he met were using anti-surge tanks? Maybe in theory headers were supposed to be removing all the water, but in practice apparently they weren't. Maybe the surging was so bad due to poor water quality that it would overwhelm even properly sized/designed risers and headers, and the anti-surge tank was just a band-aid for dirty water?

A 12-inch diameter anti-surge tank has 4x the diameter of a 3-inch riser or header, which means the steam velocity will be reduced by a factor of 16. That's a huge drop that should be highly effective in allowing the water to drop out, and apparently it works well, and better than whatever header arrangement was being used by the steam guys Dan referred to.

You said "keep the water in the boiler where it belongs," but @PhilKulkarni posted above that even with an oversized riser (3-inch vs. recommended 2-inch) he gets wet steam. So evidently there are some cases where even oversized risers can't keep the water in the boiler. That's also a case where an anti-surge tank that reduces steam velocity by a factor of 16 right at the exit should be effective.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1878941#Comment_1878941

I didn't see where @PhilKulkarnihad any problems at all?

Can you point out where because I keep missing it. The amount his water moves in the gauge glass seems perfectly normal, I think he was asking for confirmation more than anything.

The only question I have is where his water level is. Does it start out normal and drop to that, or is it always low?

jesmed1

@ChrisJ I was commenting on @PhilKulkarni 's third paragraph where he was commenting on the effect of using a 3-inch riser vs. the 2-inch spec, and he said "Yet, despite a 55.6% reduction in exit steam velocity, I get wet steam- steam that is not 100% vapor."

Phil did also say that none of the things he mentioned in his post were causing problems. He was just observing that even a larger riser that significantly reduced steam velocity didn't give him dry steam.

So there are two different points being made, one by Paul and one by Phil, that:

1. Higher steam velocity doesn't necessarily cause carryover (Paul)
2. Lower steam velocity doesn't necessarily eliminate carryover (Phil)

Eastman

Great video. What's next?

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1878879#Comment_1878879

You know, I thought this too at first but I changed my mind. I'll tell you my reasoning, see what you think.

I think the only place where the pressure increases is below the constriction (in the steam chest). I believe inside the 1" pipes the pressure is actually less due to the increased flow through there. So that would tend to increase vaporization instead of condensation. So I think it's just condensation from the pipe surfaces.

EBEBRATT-Ed

I just remember the Weil McLain video with the glass piped boiler that is still (probably) circulating on you tube it's probably 15-20 years old. That thing was throwing a lot of water.

It is a mystery I have seen horribly piped boilers with no kind of water treatment or blow down work absolutely fine. You stare at them and say it can't work but it does.

The ones that are piped right usually have no issues that can't be tweaked out.

But when they are bad you don't know where to start.

According to @ethicalpaul video we should try fixing the water quality first and if that doesn't work attack the piping.

I have seen boilers piped right that you couldn't keep the water in them until they were skimmed so maybe its true.

STEAM DOCTOR

Need to be totally honest. I didn't watch the video (yet). I have long wondered about the 15 ft per second rule. That rule was "established" in a previous generation, when steam boilers had humongous steam chests. If those boilers needed piping that would sustain 15 ft per second, then what would our boilers, with their relatively tiny steam chest, need. 10 ft per second, 5 ft per second..... We all know that's not the case. I think a lot of the old rules of thumb, were instituted to cover all types of situations. The idea is basically give blanket rules for everything, and then you will always be safe. Will cover for bad water quality, overfired boilers, under piped or poorly boilers, undervented systems, tiny residential and humongous commercial and everything in between. Sort of like the speed limits. They don't always make sense. We all know that when it's 2:00 in the morning and the roads are totally empty and clear and straight, the rush hour speed limit doesn't make much sense. But it's one blanket rule to cover all scenarios.

jesmed1

https://forum.heatinghelp.com/discussion/comment/1879006#Comment_1879006

OK, so let's take @PhilKulkarni 's case. He says he has a 63-03 boiler, and with a 3-inch riser he's still getting wet steam. According to the following table, worst case velocity for a 63-03 is 14 fps for a single 3-inch riser. That's even below the probably-conservative 15 fps target, and yet he still says he gets wet steam. So there has to be some other factor like chamber geometry, water line height, etc, and/or a combination of the above, that makes some boilers more likely to generate wet steam than others, even at low exit velocities. For whatever reason, Paul's boiler doesn't seem to have that problem even with a high water line and high exit velocity.

https://heatinghelp.com/assets/documents/Steam-Velocity-Table-Peerless-Boilers.pdf

EBEBRATT-Ed

It does make you wonder when we see all the horribly piped boilers that run with no issues. Opposing supply risers, undersized headers, undersized risers.

All the old Weil McLain glass piped boiler videos are still on u tube.

Amazing what steam does. In one video he closes the steam supply valve and lets the boiler build some pressure when he opens the valve the water flashes and sucks water out of the boiler because of the velocity increase.

jesmed1

It looks like this is one of the videos you mentioned, Ed. He lets the pressure build to 5 psi, and even with the burner off, when he opens the valve, the superheated boiler water flashes to steam and throws massive amounts of water up into the clear pipes.

https://www.youtube.com/watch?v=L1Bc55LXDX0

That is a dramatic demo, but it doesn't really represent normal operating conditions which are more or less steady-state. During the steady-state portion of the video around 5:30, you can see the boiler water frothing through the glass window, and with the water line about halfway up the sight glass, the steam in the clear pipes appears dry. You can even hear someone say "that's dry steam." So again the question is, why do some boilers produce nice dry steam like that, and some boilers like Phil's produce wet steam even with oversized risers? Is it just water quality, and some people cannot or do not get enough oil out?