Diagram of vacuum steam with failed-open trap

ariccio

I'm making slow progress convincing the people in my building that the thermostatic traps on our two pipe steam system can fail in a way that lets steam through! Slow progress on sharing the basic knowledge. Dan Holohan was right when he said there's a lot of good stuff out there if you just read a little bit.

There is one more thing that would help - a diagram of a two pipe vacuum return steam heat system with at least one failed-open steam trap.

There are many many many diagrams and illustrations on the web that show what happens to a two pipe steam heat system that lacks a vacuum pump when a steam trap fails, but I struggle to find one *with* a vacuum pump.

Do any good ones exist or should I just draw it up myself?

neilc

@EdTheHeaterMan

EdTheHeaterMan

I could draw it, if I understood it... I need to do some research. I think a power point would be better because it will show how the system is supposed to work, then illustrates what happens when it does not work.

EdTheHeaterMan

I thought I saw this somewhere before.
Look at You can look at this video and possibly find your answer starting at hour 2 minute 15 where Dan talks about large buildings with vacuum pumps on steam systems. https://www.youtube.com/watch?v=U07Mp5DeFX4 (it actually starts at 2 hour 13 seconds if you want a little history).

EBEBRATT-Ed

@arrccio
When you say a "vacuum steam system" are you referring to a system with a mechanical vacuum pump?

If so in most cases this system is largely the same as a two-pipe steam system. The main difference being smaller piping because the vacuum pump helps move the condensate and steam through the system.

If the traps ar blowing through it will quickly damage the vacuum pump.

Message @Pumpguy . He probably has a drawing. I have an old Nash steam book somewhere that would explain it.

Pumpguy

Sorry, I don't have a drawing showing what happens when a failed trap lets steam into the return lines.

The symptoms would be the same as a non-vacuum gravity return 2 pipe system. These would be no temperature difference between the steam side and return side piping, clouds of steam and vapor discharging from the condensate pump's tank air vent, and with no system pressure differential, poor heating from the radiators with non-failed steam traps. Might even damage the previously operating traps too.

The real problem with a vacuum return system that has failed open steam trap(s) is how the temperature affects the return line vacuum. The laws of physics just don't allow vacuum to be produced in a closed system that has high temperature water or steam present.

If you can control the flow of steam into the radiation using an orifice or other valve so the amount of steam is around 80% of the condensing rate of the radiation, there will be no steam at the radiator outlet to leak into the return line.

As far as the vacuum pump itself is concerned, it wants condensate temperature as low as possible. Many vacuum condensate return pump sets are fitted with a high temperature limit switch that turns off the vacuum pumps when, for example, 160*F. temperature is reached.

All too often, as we see discussed in other steam posts here, the supply steam pressure is much too high, and with a 2 pipe vacuum system with a failed open trap, this kills the return line vacuum, and damages the vacuum pump too.

My recommendation is to cut back on the steam pressure to less than 1 PSI. This will allow cooler condensate in the return lines, and the cooler condensate will allow the vacuum pumps to operate more efficiently, creating a more favorable pressure differential through the system.

The attached file has more to say on how condensate temperature affects return line vacuum.

Probably the best argument to resolve the problem of steam in the return lines is fuel costs. Steam that isn't in, or going to, the radiation is steam that is just being waisted, and it takes fuel to make that waisted steam. The less steam used to heat the building is less fuel being burned to make that steam.

ariccio

@EdTheHeaterMan the link is broken, but I'm almost certain that I know which video you're referring to.

That video and this video are really fantastic:
https://youtu.be/YADkNK0O1UA?si=z9IPlkmoyVRd8Zh5

I may end up doing a PowerPoint.

@Pumpguy you're right about the fuel costs! But the problem I am dealing with here is at least partly a sociological problem not unlike the mind-numbing problems I see in my pandemic response day job (did you know that most of the decisionmaking MDs literally do not understand how air works, and also fill with misogynistic fury when aerosol scientists try to tell them so?)


They have the heat cranked up so high to heat the cold apartments in this wildly unbalanced system that my apartment is now into the mid 80s with the windows closed, and low 70s on a thirty degree day with the windows wide open. That's not free of course.

But they're starting from a position of believing that they know how it all works already, and that "knowledge" includes a very strong belief that thermostatic steam traps never ever fail open silently. Dogma and denial are mean mistresses, and it takes a lot of effort to push by them. The fact that some kid with a penchant for (gasp) reading is telling them that they're wrong is enough to make them dig it in a bit further. And it's not a matter of being diplomatic  - been doing that, even taking some out to lunch, for two years! - it's just entrenched dogma.

With enough time, Planck's principle ensures that things will change, eventually. I don't want to wait decades though.

Yes, it's slow and miserable, but also, it's where I live, so....

ChicagoCooperator

I know and feel your pain dealing with failing traps in a multi-family situation. Our board decided to not pursue trap replacement despite hefty rebates and I think it's caused other problems in the system...

Pumpguy

@EdTheHeaterMan, I know exactly what you're saying.

I one time had a very knowledgable sales engineer of pumping equipment for steam heating applications tell me about a conversation he once had about with a consulting engineer regarding the piping arrangement for the job they working on.

After pointing out certain changes that needed to be made, the consulting engineer replied to the sales engineer "I DON'T CARE ABOUT YOUR EXPERTISE, THIS IS THE WAY I WANT IT".

EdTheHeaterMan

fixed the link. https://www.youtube.com/watch?v=U07Mp5DeFX4

ariccio

@ChicagoCooperator yup, incentives available here too.

Boston has the right idea, just mandating they all be changed every six years. Not perfect, but is absolutely the kind of "**** it! We'll take the choice away from you" energy that I'd expect after decades of this.

Mad Dog_2

You can draw it.  Do you have Patrick Linhardts book on Steam? That will good you great examples that a monkey 🐒 could understand.   Mad Dog 🐕 

ariccio

@Mad Dog_2 can you share a link?

In other news, I think we might have graduated from "it doesn't need to be done" to "well, yeah, it probably should be done but it's so expensive and also would not save any money so why bother?"

EdTheHeaterMan

Mad Dog_2 said:

You can draw it.  Do you have Patrick Linhardts book on Steam? That will good you great examples that a monkey 🐒 could understand.   Mad Dog 🐕 

And who would know better! Matt?

ariccio

(btw, I meant a link for the book!)

reggi

ariccio said:

(btw, I meant a link for the book!)

2nd Google search result for "Patrick Linhardt " or 😔  https://steamupairoutwaterback.com/