Is a Spunding Valve a "diode"?

[Zippy123]

While researching my impending keezer project, I have fallen into another rabbit hole: CO2 exclusion. That research led me to the use of the Spunding Valve. That research left me with a basic question that I cannot answer even with the power of Google and Duck Duck Go:

• Is a Spunding Valve a "diode"? (Remedial lesson on electricity: A diode allows current to flow through wire in one direction but not the other.)

It seems the spunding valve must be one-way, allowing regulated pressure out of a vessel but preventing backflow into it. Since I cannot find a definitive answer in the wild, I have turned to the community. Thanks in advance.

 

[day_trippr]

It wouldn't work if it wasn't one-way only

Cheers!

 

[MaxStout]

Sort of like check valves in oxyacetylene torch lines. Gas goes out, nothing comes back in.

 

[Broken Crow]

Owing to brain-damage, I've lost most of this stuff, but if you're looking for a simple electronic analogy it would probably be more specifically a capacitor-diode as the amount of passage is adjustable....maybe more a type of transistor?

 

[passedpawn]

While researching my impending keezer project, I have fallen into another rabbit hole: CO2 exclusion. That research led me to the use of the Spunding Valve. That research left me with a basic question that I cannot answer even with the power of Google and Duck Duck Go:

• Is a Spunding Valve a "diode"? (Remedial lesson on electricity: A diode allows current to flow through wire in one direction but not the other.)

It seems the spunding valve must be one-way, allowing regulated pressure out of a vessel but preventing backflow into it. Since I cannot find a definitive answer in the wild, I have turned to the community. Thanks in advance.

Short answer is yes. You're suggesting that the pressure setting of a spunding valve is analogous to the forward voltage (Vf) of a diode, and that's true. Diodes don't really have adjustable Vf (though diodes of different chemistries have different Vf, and Vf increases with current).

A better analogy would be a pressure relief valve, with adjustable cracking pressure. In fact, that's not an analogy, it's what a spunding valve is!

 

[mac_1103]

A better analogy would be a pressure relief valve, with adjustable cracking pressure. In fact, that's not an analogy, it's what a spunding valve is!

 

[Zippy123]

Sometimes I should just trust my instincts. Thanks everyone.

 

[Broken Crow]

Sometimes I should just trust my instincts. Thanks everyone.

Don't be content already! I'm hoping @doug293cz will notice this thread and help educate us all.

 

[doug293cz]

It wouldn't work if it wasn't one-way only

Cheers!

How so?

Sort of like check valves in oxyacetylene torch lines. Gas goes out, nothing comes back in.

A check valve is pretty analogous to a diode, as long as it has a low "cracking" pressure.

A spunding valve would be analogous to a diode in series with a variable zener diode. A zener diode conducts in the "reverse" direction when a specific voltage threshold is reached, which is significantly higher than the forward conducting voltage drop (Vf.) The regular diode and zener diode would be in reverse polarity from each other.

Brew on

 

[passedpawn]

A spunding valve would be analogous to a diode in series with a variable zener diode. A zener diode conducts in the "reverse" direction when a specific voltage threshold is reached, which is significantly higher than the forward conducting voltage drop (Vf.) The regular diode and zener diode would be in reverse polarity from each other.

I literally typed the same thing and decided not to post it. Except I have not ever seen a variable zener diode. And, unlike the spunding valve, you'd need to current-limit diodes or the avalanch current would kill them dead quickly. Hey this is fun. Let's find electrical analogs for everything in the brewery haha

 

[MaxStout]

If your kettle or fermenter has a leak, it's a ground fault.

 

[passedpawn]

If your kettle or fermenter has a leak, it's a ground fault.

... and a boilover is an overvoltage event.

 

[MaxStout]

I'm a former EE, so having fun with this one.

Having 3 kegs filled on a staggered, rotating basis: 3 phase power.

 

[MaxStout]

Pressure drop in a CO2 line: voltage drop from I^2R losses.

 

[sibelman]

The question is reasonable because some PRVs have been known to fail to re-seal after an over-pressure event (or, at least, when manually opened).

Restating the original question: is there any substantial risk of air ingress via a spunding valve? If so, which types are most/least likely to experience that failure mode?

IIRC, in a video about SPUNDit (and others?) the presenter said there's more than one style of construction in spunding valves (diaphragm vs.?)

 

[mac_1103]

diaphragm vs.?

spring loaded prv

 

[doug293cz]

I literally typed the same thing and decided not to post it. Except I have not ever seen a variable zener diode. And, unlike the spunding valve, you'd need to current-limit diodes or the avalanch current would kill them dead quickly. Hey this is fun. Let's find electrical analogs for everything in the brewery haha

I have not ever seen a variable zener diode either, although Wikipedia mentions them. It is possible to build a circuit that functions as a variable zener out of a transistor, a regular zener diode, a comparator, two fixed resistors, a variable resistor, and a voltage source. And if the voltage source is stable, you don't even need a zener for the circuit, and only one fixed resistor.

Brew on

 

[doug293cz]

Restating the original question: is there any substantial risk of air ingress via a spunding valve? If so, which types are most/least likely to experience that failure mode?

There shouldn't be any backflow unless the spunding valve malfunctions. The valve has to shut at the set pressure for it to work. If it didn't shut, then the chamber pressure would just equalize with atmospheric pressure.

Brew on

 

[passedpawn]

I have not ever seen a variable zener diode either, although Wikipedia mentions them. It is possible to build a circuit that functions as a variable zener out of a transistor, a regular zener diode, a comparator, two fixed resistors, a variable resistor, and a voltage source. And if the voltage source is stable, you don't even need a zener for the circuit, and only one fixed resistor.

Brew on

Well yes, that is a voltage regulator. Most linear voltage regulators are designed that way. When you look at the spec for an adjustable voltage regulator, the feedback voltage (Vref) is the internal zener voltage.

 

[DuncB]

How so?



A check valve is pretty analogous to a diode, as long as it has a low "cracking" pressure.

A spunding valve would be analogous to a diode in series with a variable zener diode. A zener diode conducts in the "reverse" direction when a specific voltage threshold is reached, which is significantly higher than the forward conducting voltage drop (Vf.) The regular diode and zener diode would be in reverse polarity from each other.

Brew on

You took the words out of my mouth, but I was speechless.

 

[Lalo_uy]

An image is allway better, no pressure back flow will open the ball.

 

[doug293cz]

Well yes, that is a voltage regulator. Most linear voltage regulators are designed that way. When you look at the spec for an adjustable voltage regulator, the feedback voltage (Vref) is the internal zener voltage.

And a spunding valve is a pressure regulator, and a zener diode is a fixed voltage regulator.

Brew on