Vodka still heating issue help please, long post

[AK2]

Hello all, I am having an issue with our vodka still.  I will attempt to be brief yet detailed to what I am seeing.

Vendome Vodka/Gin still.  Steam heat, pot base, 20 plate column with a dephlegmator at the top.  I used to be able to complete a run 9 8 hrs (1 hour warm up, 8 hours to finish).  During the pandemic we ran the still 6 days a week.  Towards the end of sanitizer we were having problems achieving 190, what was already a trickle slowed down to 1/2 of a trickle (if that is even a measurement).  Run times went to 15 hours.  We stopped making sanitizer over two years ago, and I have not had the need to make vodka since. 

Recently I received the order to make vodka.  I have tried to do so twice.  Each time I stopped the run after 3 to 4 hours due to the fact that I can not achieve 190 proof.  I have changed out the steam trap, taken the steam lines off (found no obstruction), taken condensate lines off (no obstruction), made sure the check valves are free and can move, flushed the steam side of the pot out with water (found nothing in the flush water), and did not see any fouling on steam side of the pot (granted, I could only look through the 1" holes for the drain/pressure relief piping, but from that tiny bit I saw it looked clean).  

I am pulling my hair out thinking of other causes to this issue.  I believe it is a steam issue as the pot does not boil like it used to.  I used to get a nice rolling boil, now the only boiling action I see is around the outer edges, the middle of the pot does not boil at all.  I have the same steam pressure as always, the valve allowing steam in appears to be in working condition.  I also have to keep the deph valve closed further than I used to to get condensate coming out.  To me this means that either my cooling water temperature has gone down or I am not getting enough energy into the system, and I have not changed anything on the cooling system.  These observations point me in the direction of either not enough steam getting in OR not enough condensate getting out (i.e. which blocks the steam from coming in).  

Has anyone else out there had this issue?  Can anyone give me some advice as to what else I should be looking at?  Any chance some sort of fouling has occurred on the steam side of the pot?  

 

I apologize for the long post.  Thank you in advance for any responses.

 

Adam

[JustAndy]

Is it possible you have water/mineral scale that built up inside the steam jacket that is obstructing heat transfer? Scale inside the pot is possible too but that would be more obvious. 

 

[Silk City Distillers]

Assuming you've got no issues with your steam supply - all the other equipment is working properly?  No boiler issues, etc etc?

Also assume that your heat up time has increased dramatically (this would indicate a steam flow issue, not a distillation/condenser/reflux issue).

I'd take off the upstream steam valves and check for blockages/restrictions on the inputs to the valve.  There may be screens, globe valves are easily clogged, etc.

Are you running the steam valves open wider than you normally would have previously?  I've got to assume you were turning down the steam flow once you hit boil.

 

[AK2]

Thank you both for your suggestions.  Next chance I get I am going to try and get that valve apart and take a look.  Your assumption is correct, warm up times have increased, and valve opening needs to be at 100%.  In prior operation after boil valve would only need to be between 30% and 40%.  If nothing is found in the valve I am going to try an acid wash in the steam jacket.  As JustAndy stated the alcohol side easily inspected, the steam side I could only look through the 1" hole for the drain and pressure/vacuum relief ports.  From that TINY observation it looks clean, but that is not to say I can say it actually is clean.

Thank you both again, I was leaning this way, it helps to have conformation on the next steps.  Hopefully I have time this week to investigate further, I will post an update IF something works!

 

Adam

[Silk City Distillers]

It’s unlikely you have scale buildup in the jacket, steam is pure enough that you shouldn’t be seeing any kind of deposits. At least not before a decade of regular use.

Rent or buy a cheap borescope from Amazon before you spend the time and money.

If your steam lines are black pipe, I’ll put my money on clogged valves.

Historically, you would have seen a strainer on the input of every valve to prevent this.  You don’t see that as often these days.

Is your agitator working well?  I’ve seen systems really see efficiency fall off a cliff when their mixers weren’t working.

[Kindred Spirits]

I would also recommend looking at your condensate lines. 

If they are blocked up, they won't let the condensate out in the right amount, which will prevent fresh hot steam from entering the system.

[AK2]

Update:  Thank you to all who gave advice.  Here is where it stands:  In my haste taking every single pipe apart to inspect, and both steam traps to inspect, I failed to inspect the pipe from the the main steam header line's steam trap and condensate return tank.  I inspected everything else, did not find anything, and thought to myself "there is no way anything made it past the strainer and the steam trap to cause an issue downstream".  I am an idiot, found a major blockage between the steam trap and the condensate return tank.  REALLY wish I would have done this 5 minute break apart and inspect before I posted!  

I will not be able to try the still until Friday, will let you all know if it works, but this is the most likely culprit.  The condensate could not fully exit the main header, which would cause condensate, not steam to enter the steam jacket.  It is uncertain at this time how material got past a strainer and the steam trap port.  That is a mystery for another time.  

 

Again thank you all for your advice, you gave me the pep I needed to keep looking.  I will post results of Friday's run.

 

Adam

[Silk City Distillers]

Well done @Kindred Spirits on the condensate line recco.

[Kindred Spirits]

29 minutes ago, Silk City Distillers said:

Well done @Kindred Spirits on the condensate line recco.

I just helped a client out with their steam system, it was the exact same problem.  The boiler pipe installer put in a 4" main for steam, but only put in a 1/2" condensate return main.

They didn't install any strainers and didn't even put enough steam traps in the system so each piece of equipment would have one. The condensate main clogged immediately from construction slag and all of the equipment would stall when steam was put to them.

[AK2]

Update #2:  Even with the condensate line cleared the still would not produce 190 proof.  188 proof all day long, open the cooling valve a little, distillation stops.  Next step is to look at the inlet valve upstream.  If and when I figure something out I will post it.

 

Adam

[Silk City Distillers]

Still the long heat-up time?

[AK2]

Update:  Upon further review the air actuated valve that allows steam to the vodka still was not fully opening.  There was also a very small hole in the air line (it was lying on an uninsulated part of the piping, melted slightly).  I had thought the valve was opening 100%, but in reality it was 75% or so.  Adjusted the valve to allow it to fully open.  Repaired air line.  Warm up time decreased, and the boiling action in the pot was much more vigorous.  Achieved a proof of 191 at one point, first time I have been able to go above 188 in about 5 trials!  I did not complete the run, however, I am very hopeful that the next time I get a chance to make vodka I will have the ability to do so.

 

Thank you again to all that gave input.  I had at least two issues:  condensate line plugged post steam trap, inlet valve not fully actuating.  After fixing those items it appears I can make 190.  

 

Adam

[Kindred Spirits]

Glad to hear you are back in operation