Spunding valve - McMaster pressure relief help

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jcaudill

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Hello all,

I have a spunding valve on top of my fermenter using the adjustable pressure relief valve from McMaster.

Stupid question - even though I tested this I'm puzzled. The more you open it - the more it should vent off right? The only reason this is puzzling me is because right now my pressure guage is reading nil but if I open the pressure relief almost to the point it comes off I can hear co2 escaping. So there is pressure - I wonder if it's just not enough to register.

Thanks in advance,
JP
 
Your gauge needs to be very low pressure increments to read the pressure. The full scale reading should be less that 10 psi maybe even 3 psi. What is the minimum rating on the valve for cracking pressure?
 
It's the standard 0-20psi valve you see a lot of people here use. I have a 0-30psi gauge - in 1 psi increments. It's been capped only for about 8 hours though.
 
I mean - there isn't a whole lot you can screw up :) I know in general it works because I hooked up my air compressor to it yesterday. But I just wanted confirmation that the more you open the more it vents.
 
Which valve is it? The one I have has an arrow on the valve for flow direction, but the instructions say the opposite. A note came with it saying that the arrow on the valve is correct.
 
You're fine. I checked mine, clockwise increases pressure, ccw decreases pressure. When I set mine this last time, I gained 5psi every 8 hours.
 
Well - my fermentation didn't work out - first brew on new equipment so learning all the nuisances. I missed the window of opportunity and built 0 pressure.

But - I am still not convinced about these pressure relief valves from McMaster unless I'm missing something. As a test - I plumbed the spunding valve to my air compressor. I set the output of the compressor to 20 psi and I wanted to use the pressure relief valve to maintain 15 psi. So I kept loosening it but it wasn't until about the point the valve was going to come completely apart (and it did eventually) that it relieved any pressure whatsoever and that was not out the little hole - it was around the threads. Is there some reason this isn't a valid test that I'm missing?
 
Well - my fermentation didn't work out - first brew on new equipment so learning all the nuisances. I missed the window of opportunity and built 0 pressure.

But - I am still not convinced about these pressure relief valves from McMaster unless I'm missing something. As a test - I plumbed the spunding valve to my air compressor. I set the output of the compressor to 20 psi and I wanted to use the pressure relief valve to maintain 15 psi. So I kept loosening it but it wasn't until about the point the valve was going to come completely apart (and it did eventually) that it relieved any pressure whatsoever and that was not out the little hole - it was around the threads. Is there some reason this isn't a valid test that I'm missing?

I had a look at the valve you're using, it says pressure and vacuum. It's not the McMaster valve that I was thinking of. Have you taken it apart and looked at the parts?
 
Yep - honestly I don't even understand it. It's a spring and a ball bearing. But the way it comes assembled the ball bearing blocks the little hole that I assume is supposed to vent. I am beginning to wonder if you're supposed to reverse the spring and ball bearing depending on if you want vacuum or pressure operation?
 
Yep - honestly I don't even understand it. It's a spring and a ball bearing. But the way it comes assembled the ball bearing blocks the little hole that I assume is supposed to vent. I am beginning to wonder if you're supposed to reverse the spring and ball bearing depending on if you want vacuum or pressure operation?

Probably. For pressure relief the ball should be on the side of the chamber closest to where it threads into your plumbing, and the spring should be on the end closest to the adjustment knob. The reverse for vacuum relief operation.
 
Ya ok - that is logical. Would be nice if they at least mentioned that when they ship them! I guess McMaster expects people to not be idiots haha.
 
Did you ever get this to work? I have a similar problem in that in either configuration I'm leaking CO2 out of the tip of the valve even when it's fully tightened down. I've got two valves with the same issue so I'm starting to think the issue is me.... :) Any suggestions?
 
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Well good to know. Thanks for the info. At least your bad experience (and mine) can hopefully divert others to a product that works. While it's twice the cost, I've already spent that much in a product that doesn't work (as I'm sure you can relate...). Thanks!
 
The other simple option is front the valve with a shutoff of some kind... simple 1/4" ball valve for example. You just need a way to keep it capped under it builds enough pressure.
 
I wouldn't rely on anything that forces you to manually shut off the vent. It's too dangerous. I bet with a little figuring and some prototype parts, one could construct a real DIY spunding. Assuming the machining is nice and clean, you can start with a reducing coupling:

4464K523L.GIF


Right where the reduction taper is, you'd put a 1/2" Viton rubber ball in.

Follow that with a compression spring, something like Mcmaster 1986K99.
9534kp2l.png


The easy finish is to just install a hollow pipe plug and adjust the coarse pressure with spring changes and fine adjustment by turning the plug in and out. For a more adjustable range, use a 1.5" long pipe nipple, then a pipe cap. Tap a 1/4" thread into the cap so you can put in a long bolt that would apply pressure to the top of the spring. A washer over the spring and then two jammed nuts would work.
 
Ya this is kind of how the big boy spunding valves are built. I'm not completely sure I follow your description above - having a hard time envisioning where the gas escapes. A lot of the spunding devices I've seen let gas escape into water - almost looks like the standard plastic fermentation air lock but has a spring running through the middle of it and an adjustment knob outside.
 
I know this is an older post, but I'm adding some info for future viewers.

I ordered 5 of the same valve from McMaster. They did come pre assembled for vacuum, so I did have to reverse the ball.

I tested the pressure and vacuum using my mouth (low pressure) and it leaked.

So what I did was put a small single layer of plumbers tape on the bottom. I then put the ball on top of that. Now it works fine.

Totally worth doing the fix since its less than half the cost of the graingers
 
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