Relief Valves for Still in Spirit Industry 1

[Ally0138]

Hi all,

A client in the spirits industry has asked me to review the sizing basis for their pressure relief valves on their stills.

I've done some quick rough checks and I am concerned that their existing relief valves may be undersized.

Some specfic questions I have, before I get into a more thorough review:

1. Are there any other specific codes / standards I should be aware of relating to pressure relief of stills for spirit production? In addition to the usual standards pertaining to overpressure protection (e.g. BS EN ISO 4126 / 23251 / etc.)
2. Are there any other good engineering practices / conventions I should be aware of relating to pressure relief of stills for spirit production?

Thanks in advance for any help or advice anyone is able to provide.


Additional Background Info:

The client doesn't have a huge amount of information on their existing relief valves. They have some basic datasheets / inspection / test certificates which give orifice sizes, set pressures, and max. relieving pressures, but they don't give any details of the sizing cases used or the rated flows of the relief valves. The supplier is notoriously difficult to get any additional information out of - I'm not holding my breath for them to be able to answer any questions that we may try to put to them.

I'm an experienced process engineer, however I'm relatively new to the spirits industry (my background is mostly oil & gas), so I'm looking for some general advice on over/underpressure protection of stills, as there may be relevant codes/standards, or typical practices I'm unfamiliar with, etc.

I'm based in the UK - specifically Scotland, as is my client. So we are bound by Scottish / UK legislation and generally work to BS EN ISO standards.

Another thing to note in this case is the design pressure of the stills and the set and relieving pressures of the relief valves all are below 0.5 barg, therefore it is my understanding that the Pressure Equipment Directive (PED) and Pressure Equipment Regulations (PER) do not apply.

 

[LittleInch]

At <0.5 barg, you tend to fall out of Pressure vessel codes and standards and more into low pressure tanks so codes like API 2000 and similar apply.

You might find under-pressure / vacuum conditions from sudden lowering of what I assume is basically very low pressure steam or vapour might be more crucial than high pressure as the ability of a still to withstand any negative pressure is probably very low.

Avoidance of fugitive emmissions is also more of an issue at low pressure than higher as sealing forces are so much lower.

I don't know a huge amount about still but my understanding is that they basically operate at close to atmospheric conditions at temps between 90 and 110? C vapour or maybe less.

So what are your credible over / under pressure scenarios?

A drawing or some pictures might help.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Latexman]

In my experience, most regulations in the spirits industry are to make it easier for the taxman to collect his dues.

Good Luck,
Latexman

 

[The Obturator]

There are specific designs of Pressure-relief Valves made for the brewing industry that may be similar for spirit production. These can also be dual pressure/vacuum relief types. Some are made as higher pressure designs (ie., 1 bar +) but modified for low pressure settings - these may even be required to be set and mounted upside down and/or have lightweight internals used. From experience, different connections are used also. It might be an idea to post a sample data sheet. But to answer your question, the relief case needs to be known and understood.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[MortenA]

@Ally0138, as Littleinch said, since its not a pressure vessel you should consider ISO28300 (API2000 outside US). Although its for oil storage its mostly generic for any low pressure vessel.

Beware of vacuum/under pressure. A low pressure column will have low tolerance for under pressure. E.g. if they plan to CIP/clean the column. If you introduce water into the column while its full of steam you can draw a high vacuum. But its a little strange that tehy make a pressurized column with a design pressure less than 0.5 barg (as opposed to an open column)?

--- Best regards, Morten Andersen