Steam Vent Idea - comments please

[mongota]

The vent caps do work. I use a black iron pipe nipple. The last time I fired my oven up after several weeks of inactivity, a few hours in to the burn I uncapped it and the inside of the pipe was wet with condensation and the cap had a little puddle of condensate in it. I left the cap off for the remainder of the fire.

[CapePizza]

If you do a search for breather caps on the forum you'll find plenty of info. I'll share what I did. We live in a very moist environment so I felt a breather cap would make sense for my build. I bought a hydraulic breather cap at Napa. They are not expensive. Mine was $13. Another member suggested this mounting method, as shown in one of the attached photos. I mounted it on top of my oven, resting the PVC connecting pipe right on top of the insulation. The PVC connector is held to the wire mesh with electrical locking nuts. I had used metal lathe to hold the insulation in place which also provided a good surface to embed the perlcrete layer. See attached.

[Mark1986]

Hi, I read this thread and I want to add the a steam vent to my dome. I don't have any idea on how much pressure 1 bar is, but would a configurable vent cap with a rating between 1 and 4 bar, open when I use it to vent the insulation layer? Or is there no pressure build up like that? Thanks!

[david s]

Yes you could certainly allow it to vent into the base of the flue pipe. Just drill a few holes in the appropriate position below where the stucco will meet the pipe. My solution is a little different in that moisture escapes between two terra cotta collars that support and seal around the pipe.
Some holes through the supporting slab also provide an escape for moisture in the underfloor insulation and do a great job keeping it dry.

[skulessa]

Hi All,

The idea of a vent for steam makes a lot of sense to me. I don't think it matters where on the dome the vent is placed and I don't think it needs to be at the top. If the moisture has turned to steam it will be under pressure and will exit through the vent no matter where the vent is placed.

I was thinking of creating a hole that communicates from the insulation layer into the flue of the chimney. It would always be open. Is this a reasonable idea or a bad one? If this is an okay way to go I'd rather do this than embed a metal pipe through the render layer. I'm assuming the pipe heats up?

Thank you for the advice.

[fox]

You just have to be carful not to pile on to much cement in one go as this will squash down the insulation.
Best to apply several very thin coats of cement mix until you have a firm base to lay a decent coat, using a vermiculite coat is good option as it is much lighter but ... is not as quick or easy to apply.

[snipe97]

Thanks David S. Been doing a lot of reading and figuring out the best approach. Planning a stucco finish so was thinking insulation -> chicken wire -> stucco (i.e. no vermicrete). Just trying to figrue wgat's best if I go the stucco route.

[david s]

I don’t tie down the blanket with chicken wire because it’s too time consuming and the vermicrete layer applied over it holds it in place. Placing a conductive material in an insulation layer is also counterproductive.

[snipe97]

I guess one more while i am at it: anyone have a great approach to fastening down chicken wire over the insulation? I haven't really been able to find a great solution searching through the forums.

[snipe97]

Getting close for my stucco layer and reading up on the steam vents. As a newbie, wondering whether i could just use a small piece of 3/4" copper pipe that i have laying around, cap it, and then maybe cut/drill a few slits in the pipe to vent the steam? I don't know if I would remember to take off any cap when need be so trying to eliminate that forgetfulness...plus I might have some teens that could want to use the oven when I am not around. They certainly wouldn't follow every step to boot up an oven after some heavy rains, humidity, etc. .

[SableSprings]

Yes Zoolander, your summary of the breather cap install and purpose is correct. You are hoping that any outside render makes your dome waterproof...but that's just not realistic. Lots of great products for waterproofing out there, but inevitably Mother Nature will win and moisture/water will find a way into the dome if it's standing in the great outdoors. The vent is just providing that easy exit for any moisture that does find its way into your oven's "guts" (insulation batting and/or firebricks ).

[Man Food]

I use simple 15mm brass plumbing connector and screw cap which is cheap and effective, though if you can get a purpose built breather cap it will save you having to unscrew it like I do

[Gulf]

Also, when you find a source for the breather cap, go with the smallest they have. It will still do what you want, but be less conspicuous. The Donaldson TRAP site (as the one pictured above) has a Where to Buy tab at the top of the page. Just select "industrial hydraulics" and plug in your street address. It will list any local venders.

[UtahBeehiver]

Google "hydraulic breather cap", most auto stores will have them or Grainger, ebay, etc. can be less than $10.

[david s]

Where were the Breather Vent Caps sourced from? I'm having trouble finding these and thought this would be as good a place as any to post this info.
The other great idea on this is david s breathable flue design, but seems to require some custom work with pottery materials. I'm thinking of casting something like that with the castable refractory - if David has any comment on that. It looks like two pieces with the top being essentially a collar to divert rain and the bottom piece used to mate the chimney to the flue. There must be some venting between these to allow the steam to escape, which may just be a function of not having an airtight fit?

Yes that's correct. I have some skills with clay and a kiln to fire wares. When I fire them I don't fully vitrify them so they're still porous which is suitable for this application. The less than perfect fit leaves some space between the two like a saucepan with an ill fitting lid. You could fabricate something from another material, like cast concrete with plenty of random fibres or fabricate a conical form in stainless which is what I did for my mobile oven as it has a removable flue.