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What is the internal pressure of a still?


jlevac

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Hey Southernhighlander, it was me PeteB (Peter Bignell) that mentioned puke

Of all the discussions over the years on this forum, I think you have shown your understanding of this pressure issue better than anyone.

I am sure there are other still builders who understand as well as you but they have not posted.

If you look back to page 1 on this topic to post #12 you will see a photo of a fairly typical and simple pressure relief device that is commonly used in Tasmania.

If you decide to use this type then keep the diameter as large as practical to allow for a fast rate of puke,

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I'm trying to find out how to show an inspector that the pot still is an open system and has minimal pressure.

The compressor idea is an interesting one from a practical perspective. However, most inspectors understand pressure relief valves, especially when bearing the certification marks required in specific jurisdictions. Those are devices they see every single day.

You can find PRVs bearing the approval marks as low as, or in some cases lower than, 5psi. I'm talking about for the still boiler proper, not the jacket, which will likely be 15psi.

You can make the case that the system can't hold pressure, and it could be a logical argument, but realize that inspectors aren't engineers, and it isn't up to them to determine the merits of your argument. But a low pressure relief valve bearing a mark (ASME, etc) - That is a language that these guys speak. If you want to look like you have your stuff together, plumb the relief line to a safe outdoor location (so you aren't trading a dangerous pressure situation for a dangerous vapor situation).

These guys are busy, it's not their job to know how distillation equipment works, or to spend the time to figure it out.

By the way, the fact that a system is "open" by our definition, doesn't mean it can't build pressure if the equipment fails. Imagine a condenser bracket weld breaks, the weight of the condenser pulls the vapor piping and kinks it shut. Now you don't have an open system. Recent events should be clear in all our minds.

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Jeff Goens,

The first thing that you need to do before you do anything else is install an ASME rated pressure relief valve with a 5 to 15 psi rating and with the capacity to match your still boiler. If you need a valve of the proper capacity and section rating call me at 417-778-6100 and I will sell you one. You should also have a Vacuum Relief Valve of the proper capacity and I have those as well. The next thing that you should do is have the manufacturer supply you with a spec sheet. If you built the still yourself then you are the manufacturer and you can create your own spec sheet.

Laws differ from state to state but most fallow the international boiler code. I have sold equipment to over 80 distilleries with some systems as large as 800 gallons with 18.5' tall vodka columns. I supply spec. sheets/cut sheets upon request. I have helped many of my customers pass their inspections and all of them passed in the end. I think that there are at least 2 approaches to dealing with the inspector concerning this. Typically the inspector looks at the spec sheet and see's that the inner still boiler is open to atmosphere and that is that. So you could push that case and if your inspector asks you again about pressure tell him ( if the still is a simple pot still) that there is 0 to .25lbs of pressure, which is really no pressure at all but just in case the system gets closed somehow, tell him that you have a safety relief valve of the correct capacity to deal with that and show him the valve. The 2nd approach is to state that the vessel's inner boiler operates at less than 15PSI and that the inner boiler has an ASME pressure realief valve rated at the correct capacity for a boiler of that size. Out of the more than 80 distilleries that I have supplied equipment to I don't know of anyone that used the 2nd approach for the inner boiler.

Here is the basic code concerning the 2nd approach or if you have a steam jacket that operates at less than 15psi this applies to you as well. A pressure vessel operated at less than 15 psi and equipped with a safety valve (pressure relief device) that does not exceed 15 psi is exempt from periodic inspection requirements ( except as to all provisions relating to construction, installation, alteration or repair) Please see the below for OR. Most states are similer, but some states like AZ don't even have state boiler codes..

“Pressure vessels being operated at gauge pressures of less than 15 pounds per square inch and equipped with a pressure relief device set to open at a pressure that does not exceed the lesser of the pressure vessel’s maximum allowed working pressure or 15 pounds per square inch gauge pressure……….are exempt for ORS 480.510 to 480.670, except as to all provisions relating to construction, installation, alteration or repair…” In other words, a pressure vessel operated at less than 15 psi and equipped with a safety valve (pressure relief device) that does not exceed 15 psi is exempt from periodic inspection requirements.

Question: Does the operating pressure of the vessel, the safety valve, or the vessel’s maximum allowable pressure determine whether a pressure vessel is exempt from periodic inspections under ORS 480.525(3)(d)?

Answer: The safety valve determines the vessel’s exemption status because the valve establishes the highest possible operating pressure of the vessel. For example, if a vessel is being operated a 5 psi, but has a safety valve set at 50 psi and a maximum allowable operating pressure of 100 psi it is not exempt. It is not exempt because it has the potential to be operated at 50 psi with the existing safety valve. Since the vessel can be operated at higher than 15 psi it must receive an operating permit and a periodic inspection. To exempt this pressure vessel, the owner could relace the 50 psi safety valve with a 15 psi safety valve.

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there will be zero pressure inside the pot.So, you dont need worry about it. During the normal working,the vapor will generally go through the alembic which is wide enough designed.

Penny

DYE team

pennyjiang@zjdayu.com

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Always install a pressure relief valve. Your relief valve should never be higher than 10 PSI .. If you get 10 psi in a still you have a real problem and need to shut it down... Safety First.. Always use a pressure relief.

We don't build anything without Pressure Relief.. We have stills all over the USA and other countries. We have never had any problems with inspectors when installing our equipmen, partly because of the safety pressure vacuum relief.

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Hi Rob,

You should never have a relief valve on your boilers over 10 psi because your boilers will probably bust at 15 to 25 psi if you are only using 1/16" to 1/8" copper. My inner boilers are tested at 46 PSI and they are probably good for over 100psi. However I would never put anything over 15 psi on my inner boilers and I usually always go with a 5 psi. Rob do you put the same valve on all of your boilers? Are your pressure relief valves ASME section viii? Do you have ASME section viii safety valves on your steam jackets or are you building steam jackets yet?

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  • 1 year later...

Following up on this thread, I am looking for a source for a low pressure (0-10 PSI) pressure gauge to install in the steam jacket of my mash tun.  I would like a center back mounted gauge with NPT connection (I can work with any size up to 3/4").

I have found one at http://www.supplyhouse.com/Burnham-100325-01-Steam-Pressure-Gauge-for-IN-INPV-Boilers that goes up to 30 PSI which would work, but was hoping for a 0-10 or 0-15 PSI gauge since I won't get near 30.  There are also plenty of gauges online from McMaster-Carr and Grainger, but what I'm finding is that most are limited to 140 deg F, which I don't think will work with steam.

The jacket does have a pre-set relief so it's not necessarily a safety issue, but I would also like to monitor the steam pressure inside the jacket with a gauge.  Thought I would check with the forum to find out if any of you have purchased anything similar and where from.

Thank you! 

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In case it's not obvious, the siphon needs to be installed vertically pointing upwards.  The tubing is primed with water before you mount the gauge.  The water acts as a buffer between the steam and the gauge, preventing hot steam from hitting the gauge.  Instead, the steam pushes on the water, and the water pushes on the air pocket above the water.

If you want to maintain your back mount gauge and come straight out, you need a coil siphon like this.  This one is installed horizontally.

 

59af001765d67_ScreenShot2017-09-05at3_50_33PM.png.7864d98d1346e92f9ea0d323fade5280.png

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