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Still classification as "pressure vessel", "boiler" or?

Beach Time

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I have been surfing the forum about the issue of local (city/county/state) jurisdictions (many who may have never seen or approved a still previously) and how they approach the classification of a distillation vessel. I have found some limited discusion and was hoping we could get some more people to share their experiences. Sorry if this has been covered somewhere else, if so I just failed to find it. So here is my limited experience so far, I call the state boiler officer and ask what a still would be classified as (pressure vessel, etc) the response was he was unfamiliar with still specifically but thought that it would fall under the definition of a boiler which is...

("Boiler" shall mean a closed vessel in which water is heated, steam is generated, steam is superheated, or any combination thereof, under pressure or vacuum for use externally to itself by the direct application of heat from the combustion of fuels, or from electricity or nuclear energy. The term "boiler" shall include fired units for heating or vaporizing liquids other than water, where these units are separate from processing systems, and are complete within themselves).

It goes on to state that all boilers must be ASME approved and stamped, except for a State special which requires a full set of plans approved and signed-off by a licesnsed PE.

Obviously all the stills operating out there, especially those self-made and hand hammered copper stills are probably not ASME stamped or have had their design blue-printed and analyzed and approved by a PE.

What are your experiences regarding how to manage this issue? Did your inspector treat it like a water heater? I realize there is a wide range of local regulations and probably even wider range of interpretation and enforcement of them. In the end all state and local pressure vessel & boiler regs in the US are a derevation of ASME standards so there is a lot of similarity from state to state. I have always thought the under 15 psi rule excluded a still, but the text above does state pressure or vacuum for a heated vessel.

Any comments appriciated!

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I am in South Africa, so our regulations are a bit different from yours. But because we are hardly world leaders when it comes to technology, our regulations tend to be a mix of the American and Europeans rules - so hopefully it will give you some relevant guidance.

In SA a boiler is defined as any apparatus which converts a liquid into vapor, using a heat source other than steam or the ambient atmosphere. A pressure vessel is any vessel holding gas or vapor, or a liquid above its normal boiling point - subject to a long list of exclusions. Two of these exclusions are that the pressure must be above 40 kPag (5.8 psig) and the diameter must be above 150 mm (6 inches).

This means that any steam heated reboiler is a pressure vessel and not a boiler. The boiler regulations are a lot more stringent than the PV regs. And a steam coil is usually exempt on the 150 mm rule.

Years ago I project managed a plant where we converted ethanol into acetaldehyde by passing it in a mixture of air over a silver gauze catalyst and removed the heat of reaction by using the reactor to reboil one of the distillation columns. I tried to get the reactor registered as a reboiler (pressure vessel) but because it generated vapors (in the column) from a source other than steam I got stuck with having to treat it as a boiler.

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Thank you for the input, looks like the best argument is that a still is an open system and not a pressure vessel or boiler.

I did find this link to the National Board or Pressure Vessel Inspectors in Columbus, OH which deciphers each State regulation in less legal wording... http://www.nationalboard.org/SiteDocuments/NB-370.pdf

Those in the US this might be useful, especially in selecting steam boiler capacities in those States like Ohio that have stationary operator requirements.

By the way meerkat, I saw a real sexy looking copper alambic brandy pot still made in South Africa, Leo Investments Trust... Have you seen their equipment?


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