thumper runs dry every time!

[partonken]

ive just started using a stainless steel thumper and every time it runs down to a half cup of liquid even when i fill it 3/4 full. Any ideas. thanks ken from ontario

[LWTCS]

Running too hard.
How far away is it from the heat source?

[partonken]

i usually run it at 7 to 8 out of ten on my 1800 watt stove top. I was under the impression that you run thumpers fast and hot. the stainless thumper is about 3 feet away.

[rgreen2002]

How big is the thumper...particularly in comparison to the size of your boiler?

[partonken]

My thumper is from brewhaus at 3 litres. And my still is a PS II , 30 litres.

[GrassHopper]

Bingo. Thumper is too small. Should be 1/3 to 1/2 the size of your boiler.

[jedneck]

Are you breaking the seal at the end of the run? If not it is prolly sucking back as the boiler cools down.

[BoomTown]

Are you breaking the seal at the end of the run? If not it is prolly sucking back as the boiler cools down.

I agree with Jed, I've had this happen....if it isn't about a 'suck back' I think it may be about what the output from the thumper is...if it's too small and the thumper gets too hot, it's possible that it's simply shuntting off the fluids instead of stabilizing the vapor temperature to keep the water and expel the alcohol. Larger thumpers do a better job of setting up that temperature 'shelf' that keeps the vapor separation point instead of pushing the hot water out too. This is easily detected by monitoring the ABV of the output, and the temperature of what's coming out of the chiller.

[LWTCS]

Bingo. Thumper is too small. Should be 1/3 to 1/2 the size of your boiler.

That is a rule of thumb/generalization usually intended to prevent over filling .

Either way the goal is to find a gradient/rhythm that will allow for phase change without flooding or running dry.

The OP hasn't learned to drive his rig yet.

[LWTCS]

Yes could also be the vacuum at cool down

[GrassHopper]

Bingo. Thumper is too small. Should be 1/3 to 1/2 the size of your boiler.

That is a rule of thumb/generalization usually intended to prevent over filling .

Either way the goal is to find a gradient/rhythm that will allow for phase change without flooding or running dry.

The OP hasn't learned to drive his rig yet.

Yeah, I see what you're sayin'. Even with a 30 ltr pot if the still is ran correctly, you shouldn't have flooding problems once dialed in.
Thanks!

[rgreen2002]

Wouldn't a thumper 1/10 the size of the boiler be the issue for both? Can't fill enough to get a real phase shift and with that small a volume the suction gradient could possibly suck up almost all of the volume.

I don't run a thumper, but I still would like to understand the thumper. The boiler to thumper arm is somewhat "closed" in the sense that it runs right into the thumper underwater (or underwash/undermash, underwhatever)? This is how the suction gradient would arise and pull volume back into the boiler?

Sorry to hijack the thread but it could be useful info...

[skow69]

I don't run a thumper, but I still would like to understand the thumper. The boiler to thumper arm is somewhat "closed" in the sense that it runs right into the thumper underwater (or underwash/undermash, underwhatever)? This is how the suction gradient would arise and pull volume back into the boiler?

Right. When the boiler heats up the contents expand (among other things). When it cools down they return to standard size. And there is some vapor in the headspace that condenses. The vapor occupies something like 1600 times the volume of liquid. So there can be a lot of volume reduction, which results in lower pressure. The higher (atmospheric) pressure in the headspace of the thumper then pushes the contents up the pipe until the pressure is equalized between the two vessels.

I can hear mine gurgle when it sucks the last of the liquid into the boiler, just like the straw when your milkshake is gone.