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What is the internal pressure of a still?


jlevac

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Depends if it's clogged or not... if you've got a clog then you've got a potential bomb on your hands.

Best bet is to install a pressure relief / vacuum safety valve on any vessel. I'm putting one on my 100 gal main and the 55 gal thumper. $100 for a valve is real cheap insurance that it won't go boom.

http://www.gwkent.com/vacuum-pressure-relief-valve-1-1-2in-tc-15-psi-1.html

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You don't even have to get a "clog" to build up pressure.

If there is no cooling water in the condenser for whatever reason (eg. forgot to turn on) then the vapour won't be able to escape fast enough through a 1/2 inch outlet and pressure will build.

Under normal running an alembicn pot still (no plates) and without a parrot, will have an internal pressure of zero psi. It is open to atmosphere via the condenser. Recently I taped a sheet of plastic loosley over my hatch and the plastic acted like a very sensitive pressure gauge. It occasionally bulged out gently, then inwards but often it was just loose, is same pressure inside and out.

With a parrot attached there could be a couple of inches of water pressure build up if the condenser is not cool enough. 2 inches of water is 0.07 psi.

With a plated column with bubble caps there will be a slight increase in pressure at each plate as the vapour pushes down under the caps.

If the liquid on each tray was 1/8 inch deep at the caps, then an 8 tray column would produce roughly 0.036 psi. The velocity of the vapour and the turbulence would increase this pressure slightly, but the pressure is still miniscule. UNDER NORMAL CONDITIONS

As a friend of mine says "1/10 th of a flufteenth of a psi"

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I've seen a lot of those standard PVRVs installed on stills, but it seems to me that a better way to go would be to vent any ethanol vapor to the exterior of the building with a valve like you see on top of a boiler than to vent it indoors. Anyone seen stills configured that way?

Also, Panoscape, the PVRV that you linked to doesn't crack until 15psi. Perhaps the one on this page would be more suitable: http://www.tcwequipment.com/Products/Valves/Valves.htm. It cracks on both the pressure and vacuum relief with hardly any pressure or vacuum at all. I've used them in the past and they work great.

Nick

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Thanks Nick, much appreciated. The 15 psi where the lowest I could find at the time, but I like your selection better. Will be returning the 15 psi breakers for the lower ones. Thanks!

FYI - the manufacturer is discontinuing these 3.5 w.c. valves due to low sales. TCW only has two 1.5" left after I purchased two. So if you need these in the future, best get them now.

3.5 w.c. = .13 psi

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i've seen many stills run just a simple tube out to a 5 gallon bucket of water for their over pressure relief. under normal use this will never bubble through, and of course under vacuum it will just suck the water up. pretty foolproof.

I agree vent to outside is a good idea, but be sure you're not venting near a potential ignition source.

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  • 2 weeks later...

Anyone have a recommendation for a low pressure steam gauge? Maybe 0-3 psi? I've been meaning to install one on my still to answer this same question, but can't find anything lower than 15 psi that's rated for steam use.

A while back while experimenting with my still running hotter than normal and 100% reflux, my bottom plate stopped draining and condensate started to fill up the column. I assume it was the pressure differential between the pot and plate. It's a side mounted column with drain that returns to the pot, and it was about 24" in height from the water level in the still and the level in the plate. 24" of water column is almost 1 psi.

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Is this a Holstein Still? Just wondering as I had the same problem with mine. Simple fix. Although Holstein said they never heard of this before several other Holstein owners contacted me. All that was necessary was to affix a no hub rubber connector to one end of the drain back from the column and add a piece of copper pipe to the other end, long enough to always be submersed in the liquid that is in the pot. Been running this now for 5 years with no problems at all. Coop

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Thanks for the tip Coop, but I'm having trouble visualizing your solution. So did your drain normally enter the pot above the liquid level, and you just added and extension to submerge it? Mine isn't a Holstein, and my reflux drain returns near the bottom of the pot where it's always submerged.

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i've seen many stills run just a simple tube out to a 5 gallon bucket of water for their over pressure relief. under normal use this will never bubble through, and of course under vacuum it will just suck the water up. pretty foolproof.

I agree vent to outside is a good idea, but be sure you're not venting near a potential ignition source.

The attached image is typical of the pressure relief system used in most of the distilleries in Tasmania. Same principal mentioned in the above quote but it looks a little more professional

post-962-0-04327200-1369266701_thumb.jpg

It is just a longer version of the "U" trap under a wash basin. At least one side of the "U" is clear to see that it contains enough water

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  • 6 months later...

So, with this setup, or a hose to a bucket, do you just refill the water after draining the still? I assume it would get sucked into the still whenever you empty the still.

Is it still common to have an actual prv on the still for safety redundancy?

The attached image is typical of the pressure relief system used in most of the distilleries in Tasmania. Same principal mentioned in the above quote but it looks a little more professional

attachicon.gifphoto.JPG

It is just a longer version of the "U" trap under a wash basin. At least one side of the "U" is clear to see that it contains enough water

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  • 5 weeks later...

15 pound pressure relief valves ($25) from most beer supply stores should be good enough to provide a safe environment. We couldn't find anything less than that without spending a lot more money. If you are watching your still like you should be you really don't need anything. We put ours in to make the city fire department happy.

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  • 1 year later...

This is an old thread, but I'm having this same issue with my state building inspector. The inspectors words are stated below, but I need to show what the internal psi is for a pot still. Are there any documented studies showing this that I can use as a reference? Thank you.

Occupancies

H-2- distilling if still runs at a pressure greater than 15 lbs., if less than 15 lbs. the distilling will be classified as a H-3, need manufacturer’s specifications to determine the still’s operating pressures

H-3- for the barrel storage

M- retail area for tasting

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This is the best a can help you with, becouse a live inside EU.

Here can you go in and control what the safety valve can handle in saturned steam.... and with a safety valve that have a set pressure as low/5psi as this below a think and hope that yours discussion is over with the goverment.... don’t forget to lead the safety valve outlet to outside of the building....

http://www.apollovalves.com/_literature ... safety.pdf


5psi= 0,35kg/cm2

http://www.amazon.com/Apollo-Valve-13-211-Bronze-Pressure/dp/B008837YUK/ref=sr_1_3?ie=UTF8&qid=1436550337&sr=8-3&keywords=Safety+valve++5+psi


Apollo Valve 13-211 Series Bronze Safety Relief Valve, ASME Steam, 5 psi Set Pressure, 3/4" NPT Male x Female


Brand Name

Apollo Valve



Part Number

13211B05


Cheers from a Legally manufacure inside EU

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Is there a calculator to check this? We have off readings on the probes on one of our stills and I'm trying to figure out if its a pressure issue. Is there a way to plug in the temperature reading? We get a really high boiler temperature reading (220F) and I'm trying to figure out if its a pressure issue or faulty probes.

Thanks!

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With a parrot attached there could be a couple of inches of water pressure build up if the condenser is not cool enough. 2 inches of water is 0.07 psi.

Hey guys, I just built my parrot the other day, and if it is an attached one I do recommend a pressure relief system for both pressure and vacuum reasons. It can be as simple as a hole drilled in the precharge tube.

post-11612-0-45269100-1441304894_thumb.j

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Hi Everyone.

I put 15 psi ASME rated Apollo safety valves on my steam jackets and I put 5psi Conbraco pressure relief valves on my inner boilers. We also put Vacuum relief valves on the jackets and inner boilers. The pressure relief valve on the inner boiler should be plumbed so that the ethanol vapor will escape outside the building away from any ignition source.

Something that everyone should keep in mind is that your pressure relief valve must be sized for lbs per hr of steam going to your steam jacket and the same goes for your inner boiler (I usually put the same capacity valve on my inner boiler as I do my jackets). The valves that I use are marked with the lbs of steam they can handle. If you have a 1/2" diameter safety valve on the steam jacket of your 500 gallon still that runs on 500lbs of steam per hr then the valve will not release enough pressure and you will end up with a runaway boiler situation if pressure starts building. The same is true for the inner boiler of the still. You must have safety relief valves of sufficient capacity. A pressure relief valve that you buy from your hardware store for $30.00 may have enough capacity for a 50 gallon water heater but not for your 100 gallon still. Also the valve must be the right valve for the job. If it is going on a steam jacket then it must be a an ASME section viii but the ones for your low pressure steam boiler must ASME section iv. If anyone needs safety, pressure relief or vacuum valves I have them at some great prices. The 5 psi pressure valves for your inner boiler start at $39.00 We will have them on our web site http://distillery-equipment.com very soon. If you would like to order by phone just call 417-778-6100 and ask for Paul. Jlevic, as for the pressure of your inner boiler, just tell them that it is an open system that is open to atmosphere.

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............................ You must have safety relief valves of sufficient capacity. A pressure relief valve that you buy from your hardware store for $30.00 may have enough capacity for a 50 gallon water heater but not for your 100 gallon still. ......................

I totally agree with Southernhighlander, it is not just pressure but also how quickly the valve can release the surplus pressure.

I have mentioned this before, you should also consider what is being released through that valve. If it is just steam, that can release quickly through a correctly sized valve.

but what if it is "PUKE" That stuff will not travel very fast through a simple spring loaded relief valve.

You need what is sometimes referred to as a "pop top" , as soon as the critical pressure is reached the valve completely opens, and it needs to be a large diameter.

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I give complete spec sheets to my customers who need them. If your still manufacturer cannot do that for you then there may be a problem.

One of my customers had this problem once. The customer called and told me that the Boiler inspector needed proof that his still's inner boiler was an open system, so I was thinking about this for a minute when I heard an air compressor kick on. I asked the customer if he had a compressor there and he said yes, that there were some finish carpenters there. I had the customer close up the still and open the drain valve, then he put the air hose into the drain valve with some rags around it. When he thought that he had a good seal I had him tell the inspector to go feel the compressed air come out of the parrot. Once the inspector felt the air blowing out of the parrot he passed the still.

If you have a still with 21 plates you will only have 2 to 4 PSI if you are running it right. If it is a simple pot still around .25psi is probably about right. I don't usually list internal still boiler pressures on my spec. sheets. I just state that it is an open to atmosphere system. Of course I list jacket specs. etc as well as all of the other pertinate specifications. As far as the jacket goes, if you are running at low pressure less than 15psi, all that you are required to have is an ASME section viii pressure relief valve on the jacket of the still. Also, we test all of our low pressure steam jackets to 60 PSI air pressure here at the shop.

I agree with PeteB about the mash puking out of the pressure relief valve. In an over pressure situation the mash will usually start blowing out before the vapor. Our pressure relief valves that are on top of our inner boilers have large enough bores to handle that and they are pop top valves. Pressure relief valves can also be mounted on our columns but they should be vented to a safe place.

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