Why no vacuum on single-pipe?

ethicalpaul

dabrakeman said:

@ethicalpaul Thanks. What level of vacuum were you able to hold with your test?

Not enough to be useful yet. Even with an epdm o-ring and a brass ball. Unless I “helped” with too much closing force, it didn’t hold more that a few seconds.

And I found one of those 1/4” Apollo 6100 series check valves on Amazon for $20. It has a plastic ball cone seated against a nice bronze machined fitted...seat. It doesn’t hold either. I could defeat it with my lungs.

the combination of very light cracking pressure and very strong vacuum hold is difficult to achieve.

dabrakeman

How much vacuum do you need? Seems steam would travel with very little vacuum just like it does with very little positive pressure. Maybe 2 or 3 inhg might suffice? You guys would know better and probably have some case studies of what works and doesn't.

ethicalpaul

I don’t actually need any. But for this to have an effect at all I have to hold just about all I can get—that is, intrusion of air at the end of the cycle must be stopped as much as reasonably possible.

PMJ

The main thing is just to maintain the radiators as the lowest pressure point in the system AFTER the burner goes off to deliver what is in the mains and the residual heat in the boiler that will produce some more steam - mostly to the coldest places. The more vacuum the better but some is a lot better than nothing. 

SteamingatMohawk

Some wild ideas.


1. How about using soft tubing (not the clear stuff, something more like yellow fuel line), a ping pong ball and some kind of homemade guide, like a cutoff funnel or wire cage. The obvious challenge would be to get it to seal when it seats.

Ping pong ball specs:
The international rules specify that the game is played with a sphere having a mass of 2.7 grams (0.095 oz) and a diameter of 40 millimetres (1.57 in).

You can't get much lighter than that.

2. Another thought is, what pressure does it take to bleed air backwards into a MoM by blowing on an upside down rad vent? Having never taken one apart, I don't know enough about the internals of a MoM to know if air could be blown in.

Food for thought. Enjoy.

Dan_NJ

If someone came up with a workable solution, one that could be threaded on there in place of whatever orifice is there already, that would be the perfect solution. You could sell ... hundreds of them? Dozens at least

AMservices

Can anyone dig up a patent from an original vacuum vent?
If we see how they worked back then, maybe someone could recreate it with materials of today. 
But I think I read somewhere (probably the LAOSH) that the original single pipe vacuum vents weren't that reliable. Probably always experienced imbalance on start up and only worked because the coal fired boilers ran all day and filled the system every cycle.  

When 2 pipe vapor vacuum systems were invented is when steam heat became more elegant in its operation and far more easier to seal the system. Only having 1vent (not 1 on every radiator) made things much more manageable. 
If you think about it, ask yourself everything you need a single pipe vacuum vent to do. 

1st. It needs to vent the air

2nd. It needs to close at steam temperatures 

3rd. It has to stay closed with a vacuum trying to pull it open

4th. It needs to be able to open so more air can vent out mid cycle.  

2 pipe systems can be balanced and steam traps, trap steam so the main vent only needs to let air out and keep it out. 

Running air lines to a single vent is a lot simpler of a concept then reinventing something that only worked (at all) with a coal fired boiler. 
Air lines make Balancing easy. You don't have to worry about rusty water breaking the vents. You don't have hissing vents blowing boiler air in the living space. You make your single pipe system into a elegant vapor vacuum systems that's self balancing and pulls heat out of the boiler for long after the burner is off. 

Nobody wants steam systems back on the shelf more then I do. 
I've retrofitted 4 systems with vacuum pumps in the effort to make steam the most efficient it can be. All of them worked very well. 
But single pipe vacuum vents working with digital thermostats and automatic fuel systems... is a pipe dream.

kenlmad

@AMservices

Some patents for a vacuum air vent.

https://patentimages.storage.googleapis.com/87/03/a8/dde560129fac0c/US2147984.pdf

https://patentimages.storage.googleapis.com/ac/0a/b9/bffbb99a1f4f87/US2163909.pdf

https://patentimages.storage.googleapis.com/88/44/b4/9404df45cb2ccf/US2300962.pdf

https://patentimages.storage.googleapis.com/f7/04/cb/d8d202c1d664bb/US2338495.pdf

ethicalpaul

Dan_NJ said:

If someone came up with a workable solution, one that could be threaded on there in place of whatever orifice is there already, that would be the perfect solution. You could sell ... hundreds of them? Dozens at least

Like this? 

Dan_NJ

That could be the one, looking forward to your next round of tests!

Gsmith

Generant in Butler NJ offers a disc check valve that claims cracking pressure as low as 1" water column, about 5 ounce/in^2 and a ball check advertised at 0.15 psi (about 2.4 ounces/in^2) see their products here: https://www.generant.com/ ( I have not ever used them so don't know if the advertised properties are correct). Also, some years ago someone on this forum was posting about radiator check valves he was experimenting with made from rifle cartridges, but I can no longer locate the post.

kenlmad

Here are pics of my Hoffman No 16A Vacuum Vent. It's for a main, not a radiator. It uses a "floating" disc to seal the vent opening. The concept is essentially the same as @ethicalpaul 's design.

kenlmad

The patent below shows Hoffman Specialty Co.'s design for both the "ball" check valve and the "disk" check valve.

https://patentimages.storage.googleapis.com/19/69/1f/d439fa43973609/US1708622.pdf

Is it just me, or do others find these old steam heating apparatus patents interesting? Yes - I've become a steam geek.

PMJ

I find what folks did 100 years ago with a small fraction of the design and manufacturing tools that are available today astounding, and enormously inspiring. Apparently much less energy spent on complaining about things back then, much more time spent working on something.

Somehow we have managed to dumb down the home steam system, abandoning things like vacuum on the claim that it was no longer useful without a coal fire. I think George Hoffman would be very disappointed.

Great to see this kind of interest.

dabrakeman

@kenlmad Have you tried to see what kind of vacuum level that Hoffman 16A would hold?

ethicalpaul

PMJ said:

I find what folks did 100 years ago with a small fraction of the design and manufacturing tools that are available today astounding, and enormously inspiring. Apparently much less energy spent on complaining about things back then, much more time spent working on something. Somehow we have managed to dumb down the home steam system, abandoning things like vacuum on the claim that it was no longer useful without a coal fire. I think George Hoffman would be very disappointed. Great to see this kind of interest.

I’m disappointed in George Hoffman’s company which stopped selling their vacuum radiator vent, but maybe they discovered it didn’t actually provide any benefit, 🤷🏻‍♂️

DanHolohan

ITT owed the company when they stopped making the vacuum radiator vents. The vents weren’t selling well enough. I was around for that. No one was talking then about what we’re talking about now. Steam knowledge was basically lost by the ‘70s. 

I found that inspirational. 

ethicalpaul

Absolutely understandable, but I'm still disappointed

Does anyone know why they still sell the #76 main vacuum vent?? I know it's because people are buying it, but why are people buying it? Is it people who still have 1 pipe vacuum systems? Or is there a two pipe system that uses it?

Thanks @kenlmad for posting that pic of your Hoffman, and thanks @Gary Smith for posting about Generant. I remember you or someone else posted about them before and they are literally down the road from my house so I definitely have to check them out, and I think I have to look at disc-type check valves to absolutely minimize the cracking pressure.

kenlmad

dabrakeman said:

@kenlmad Have you tried to see what kind of vacuum level that Hoffman 16A would hold?

I have not, but now I will. I'll have to go get adaptors from HD. My MityVac brake bleeder pump seems at best to be able to hold a vac at 15 inches Hg. Is that sufficient?

ethicalpaul

It will give you a good idea. That’s what I’m using in my tests. I think you’ll find it will hold whatever vacuum you can manage to show it (as in it won’t fail) but the interesting thing will be how long it holds it.

PMJ

ethicalpaul said:

PMJ said:

I find what folks did 100 years ago with a small fraction of the design and manufacturing tools that are available today astounding, and enormously inspiring. Apparently much less energy spent on complaining about things back then, much more time spent working on something.

Somehow we have managed to dumb down the home steam system, abandoning things like vacuum on the claim that it was no longer useful without a coal fire. I think George Hoffman would be very disappointed.

Great to see this kind of interest.

I’m disappointed in George Hoffman’s company which stopped selling their vacuum radiator vent, but maybe they discovered it didn’t actually provide any benefit, 🤷🏻‍♂️

If it never worked old George went to a lot of trouble to get a patent on it and then published a whole bunch of whoppers in his literature. I guess we will never know for sure - but I bet some are out there somewhere still working.

ethicalpaul

We might find out yet

SteamingatMohawk

I did some calculations to see what pressure would be needed to lift a ping pong ball off one of the MoM vent orifices. The fact I used the weight of a ping pong ball is not as important as the pressure that is needed to lift that weight. As the orifice diameter increases, the required pressure decreases.

If anyone wants to know for a different weight, just give me the weight and I'll redo the chart.

In the pic above that shows a collar on a MoM, perhaps a plastic bead without a hole would work, if a metal one is too heavy.

jumper

DanHolohan said:

ITT owed the company when they stopped making the vacuum radiator vents. The vents weren’t selling well enough. I was around for that. No one was talking then about what we’re talking about now. Steam knowledge was basically lost by the ‘70s. 

I found that inspirational. 

Perhaps even earlier? Contractors installed what manufacturers like ITT & DunhamBush sold. When was latest that one pipe steam was installed?

ethicalpaul

dennis53 said:

There is an Apollo check valve that claims 0 psi cracking pressure: Apollo 61-100-A1(fxf) or 61-200-A1(mxf). Smallest size listed is 1/4" npt.

I got ahold of one. It has very low cracking pressure if you get the springless one (or remove the spring) but it doesn’t hold a vacuum very well, it’s a hard plastic ball cone seated against metal. I’m sure it hold liquids and probably higher pressure gas pretty well

AMservices

@ethicalpaul have you tried 2 checks in sires?
That's the only way I've had luck with check valves holding vacuum.  
The difference between us is I was less worried about cracking pressure using a vacuum pump. 

I believe it's easier for a 2 pipe with 1 vent to make a vacuum because the volume of steam collapsing is far greater then the volume of air that is able to leak by the steal ball on the old air eliminators .

mattmia2

kenlmad said:

dabrakeman said:

@kenlmad Have you tried to see what kind of vacuum level that Hoffman 16A would hold?

I have not, but now I will. I'll have to go get adaptors from HD. My MityVac brake bleeder pump seems at best to be able to hold a vac at 15 inches Hg. Is that sufficient?

You could probably make a preliminary test that will tell if it is worth trying to invest in something more permanent with the rubber adapters that come in the kit with the vacuum pump.