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Big mouths and breaking vacuum

Lard
Lard Member Posts: 115
edited October 2019 in Strictly Steam
I have three big mouth vents on a 1” manifold at the end of a 4” main that make a heck of a racket when they open on vacuum. It sounds like a very long and deliberate bout of flatulence. The mounting location is in a stairwell of a church that is open to the sanctuary. Short of scheduling a shutdown during the sermon, I believe I either need more vents or some vacuum breakers.

Backpressure is almost nonexistent at startup, so the venting seems adequate—it just struggles with the shutdown vacuum. What flavor of vacuum breaker is the best for this situation? I am having trouble finding something that cracks at the right pressure.

Thanks for all of the help here. This old beast is otherwise running the best it has in at least 30 years

Comments

  • mikeg2015
    mikeg2015 Member Posts: 1,180
    I’m using one of these. https://www.supplyhouse.com/Watts-0556031-3-4-LFN36M1-Lead-Free-Water-Service-Vacuum-Relief-Valve

    All of my whistling under vacuum at shutdown stopped. It’s on the very end of my antler.
  • mikeg2015
    mikeg2015 Member Posts: 1,180
    edited October 2019
    I can’t seem to find detailed specs with cracking pressure. I think it’s <1psi. So the positive is it will pull just a little extra heat out of the boiler after shutdown with a slight vacuum.

    1 psi vacuum is about 209F instead of 212F. Which isn’t really a whole lot. Like equal to 10 seconds of burner run time.
  • Lard
    Lard Member Posts: 115
    Unfortunate that those are imported. Has it been reliable? Aside from that, it looks like it is specifically rated for low pressure steam.

    What size of system are you using yours on? This system is 2140 EDR with a mixed bag of 6”, 4”, and 3” mains totaling 250’ so there is a lot of volume collapsing. I imagine I need a manifold of a few to actually do anything significant. There are some easily accessed abandoned takeoffs in the basement at the beginning of the 6” main that would be a good candidates for the manifold(s).

    Vacuum (and to a point, main venting) were not an issue until this year— the wet returns were nearly completely severed so it was very, very well-vented!
  • Steamhead
    Steamhead Member Posts: 14,574
    You could also use a check valve opening inward.
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  • Lard
    Lard Member Posts: 115
    Swing check I assume. I have not had the best of luck with swing checks totally sealing with such low pressure against the flap (even “good” ones...). I do have a brand new 1” swing check that I can try for the fun of it.
  • mikeg2015
    mikeg2015 Member Posts: 1,180
    Steamhead said:

    You could also use a check valve opening inward.

    I tried those and cracking pressure was too high when i tried them. Still whistled a lot. Even tried cutting down the spring, but then it won’t seal.

    Not sure swing check would consistently seal. You’ll almost need a upturned copper pipe after it to allow condensate to collect if it does leak to create a slight water seal. I’m thunking of doing the same with big mouths for when they vent a little. A short section of copper could collect it.

  • Shalom
    Shalom Member Posts: 164
    edited October 2019
    The Big Mouths have threaded outlets. Maybe you could attach a piece of pipe at the outlet and put the other end where it won't be heard? (edit: or rig up some kind of muffler, like for a yard tractor.)
  • Lard
    Lard Member Posts: 115
    I added a few of those vacuum reliefs (with shortened springs) and it seems to help quite a bit. Thanks for the suggestion!
    I am going to add some short stacks to the big mouths to catch/condense the steam and condensate that puffs out for a few seconds. After losing 70,000 gallons of water last year, I may be a bit obsessed...

    When testing, I found that one of the big mouths already failed. It does not even partially close (and barely moves in boiling water)—it appears that the disc has no fluid in it anymore. The weld around the disc perimeter looks somewhat iffy. Pretty disappointing considering it has only seen 20 cycles.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,357
    What are these big mouths of which you speak? (I've been away for a while.)
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Fred
    Fred Member Posts: 8,518

    What are these big mouths of which you speak? (I've been away for a while.)

    They are Barnes and Jones Traps that they converted to make vents. They have the venting capacity of about 2.5 Gorton #2's. Available at Supplyhouse.:
    https://www.supplyhouse.com/sh/control/search/~SEARCH_STRING=Big Mouth vent?searchText=Big+Mouth+vent
    Hap_Hazzard
  • Pumpguy
    Pumpguy Member Posts: 456
    You might try a Hoffman #62, 3/4" vacuum relief valve. I believe Xylem is the current manufacturer, formerly ITT Domestic.

    Typically they come set to break at around 2" Hg. vacuum. Being an adjustable spring loaded valve, you can adjust them to break at just about any vacuum you choose.

    These are commonly used on vacuum condensate return pumps.
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  • mikeg2015
    mikeg2015 Member Posts: 1,180
    Pumpguy said:

    You might try a Hoffman #62, 3/4" vacuum relief valve. I believe Xylem is the current manufacturer, formerly ITT Domestic.

    Typically they come set to break at around 2" Hg. vacuum. Being an adjustable spring loaded valve, you can adjust them to break at just about any vacuum you choose.

    These are commonly used on vacuum condensate return pumps.

    Those are kinda expensive and 2” of vacuum is enough to make some vents whistle. But they are good quality and will vent quickly.

    I think those are more commonly used on commercial LWCO’s and larger hydronic systems.
  • Lard
    Lard Member Posts: 115
    > @Pumpguy said:
    > You might try a Hoffman #62, 3/4" vacuum relief valve. I believe Xylem is the current manufacturer, formerly ITT Domestic.
    >
    > Typically they come set to break at around 2" Hg. vacuum. Being an adjustable spring loaded valve, you can adjust them to break at just about any vacuum you choose.
    >
    > These are commonly used on vacuum condensate return pumps.

    I have the vacuum issue resolved now. No more flatus sound! The Watts vacuum relief valves did the trick.

    I did look into those Hoffman valves (and a similar unit from Barnes & Jones) while I was checking around before— the adjustability is nice, but nothing I couldn’t do by tweaking springs in the less-expensive valves.
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