pressure/vacuum issues with pot still and thumper

[Sorghumrunner]

We've begun production with our self build 100 gallon steam heated potstill with thumper. I'm having some issues of pulling a vacuum which opens the vacuum check valve, which is causing surges. I was hoping someone may be able to offer some ideas of what the source of this problem is. Improper sizing of condensers, venting, too much steam to the pot? Contact me off-list if you are so inclined...

chris@devilsdistillery.com

[Panoscape]

We run a 100 gallon main on electric elements and a 55 gallon thumper. We get a pretty good vacuum in the main due to the transfer of liquid from the main to the thumper, but it's never popped the check valve. The main is charged with 75 gallons and the thumper has about 20 to 25 gallons. We have about 19 feet of surface area for our condenser.

You might try using a manifold, where you can attach a pressure gauge, relief/ball valve and your check valve all on one pipe. This way you can monitor the vacuum and use the relief valve well before the check valve's setting. It might help to mellow out the surges. But, that's just a guess.

http://www.gwkent.com/manifold-1.html

[Sorghumrunner]

We run a 100 gallon main on electric elements and a 55 gallon thumper. We get a pretty good vacuum in the main due to the transfer of liquid from the main to the thumper, but it's never popped the check valve. The main is charged with 75 gallons and the thumper has about 20 to 25 gallons. We have about 19 feet of surface area for our condenser.

You might try using a manifold, where you can attach a pressure gauge, relief/ball valve and your check valve all on one pipe. This way you can monitor the vacuum and use the relief valve well before the check valve's setting. It might help to mellow out the surges. But, that's just a guess.

http://www.gwkent.com/manifold-1.htm

Thanks Panoscape. The check valve is a ball type, and is set for about .5psi, which may just be too sensitive for this setup. We load about 100 gallons in our still, and 15 gallons in the thumper. Works out to 5-8" of water column in the thumper. .5 psi should be about 13.8" WC.

I think adding a pressure vacuum gauge would be helpful, just need one that is sensitive enough.

[Panoscape]

Just checked our vacuum break pressure, it's .09 psi, so it's very low. I bet it pops a lot to help equalize the pressure. But, I've never heard it break. This might be doing the trick to help even out our run, small vacuum breaks that don't build up into one large one.

[fldme]

Do you have a vent on your condenser. If not this will stop it.

[Sorghumrunner]

Do you have a vent on your condenser. If not this will stop it.

We do not, and were trying to decide on the best place for one. Would this be just after the condenser before the parrot? is a vertical open pipe sufficient?

[fldme]

Just after the condensor. Tee off and run a pipe ip high enough to carry any vapors away. This should stop it. That liquid coming through will make it pull a vacuum.

[Natrat]

Yup...good placement, and good notion. I might also point out that any air the still sucks IN....has to come OUT...which can be frustrating at best and dangerous at worst. I had a still that did this, and I put a cup extension on the parrot to keep the splashing to a minimum.

If your parrot is on a triclamp, then a tee with an extension upwards works just fine.