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CasselBrewery
03-16-2015, 04:56 AM
Hi,

We've recently switched from PBW to Caustic in hope of better results and more accurate cleaning. At the end of the PBW wash cycle on an FV the tank came out spotless but it's what we don't see that was worrying us so we switched to caustic.

Concentration is between a PH of 13-14 at 160F (we've let a sample cool before taking PH reading.)

After a few wash we realized that the krausen line was still in the tank and needed a light brush to take it off, this was after an hour recirc. So next wash we decided to monitor the PH at every 10 minutes. Well within the first 10 mins the PH dropped to 6. I'm sure this affects the effectiveness of the caustic to do its job properly.

Why is that? We made sure there wasn't any C02 remaining by flushing the FV with compressed air, we also let it open for at least 30 minutes in case of any remaining C02, then we proceeded to the wash cycle.

Could it be because there was "some" C02 left in the FV? Could a very small amount cause such PH swing?

Maybe it's our water?

Any suggestions?

Thanks!

dick murton
03-16-2015, 03:19 PM
It really doesn't take much CO2 to destroy the effectiveness of caustic. 22.4 litres of pure CO2 will change 40 grams of caustic to carbonate, and if there is more than this pro-rate, then it will start to convert to bicarbonate - which is what I believe is happening. Not having given any figures of the size of your tanks, how much caustic solution you are using or how strong the caustic solution is makes any other form of comment really difficult, but you should be able to work out how surprisingly little CO2 needs to be left to wreck the volume & strength of caustic you are using. If it was the water, then it would not give you the pH you have got at the start of the clean.

CasselBrewery
03-16-2015, 03:51 PM
It really doesn't take much CO2 to destroy the effectiveness of caustic. 22.4 litres of pure CO2 will change 40 grams of caustic to carbonate, and if there is more than this pro-rate, then it will start to convert to bicarbonate - which is what I believe is happening. Not having given any figures of the size of your tanks, how much caustic solution you are using or how strong the caustic solution is makes any other form of comment really difficult, but you should be able to work out how surprisingly little CO2 needs to be left to wreck the volume & strength of caustic you are using. If it was the water, then it would not give you the pH you have got at the start of the clean.

Ah! then that explains it perfectly! Since we do have a white powder coating in the cone so carbonate (our tanks are 15bbl). Damn! It's a strong chemical but also a flimsy one in front of little C02.

Thanks for chiming in!

Cheers

liammckenna
03-17-2015, 04:31 AM
Ah! then that explains it perfectly! Since we do have a white powder coating in the cone so carbonate (our tanks are 15bbl). Damn! It's a strong chemical but also a flimsy one in front of little C02.

Thanks for chiming in!

Cheers

We do a few things to help mitigate CO2 in the caustic cycle.

For fermentors, we cold rinse the tank when it is emptied, removing much of the gross soiling. We generally leave that tank venting for 12 hours before proceeding to a wash cycle.

For fermentors, we acid wash first with a weak concentration, drain, rinse and immediately progress to caustic circulation. Spotless every tie.

This rinsing and washing helps remove most of the resident CO2 before caustic circ.

Good luck.

Pax.

Liam

CasselBrewery
03-17-2015, 05:44 AM
We do a few things to help mitigate CO2 in the caustic cycle.

For fermentors, we cold rinse the tank when it is emptied, removing much of the gross soiling. We generally leave that tank venting for 12 hours before proceeding to a wash cycle.

For fermentors, we acid wash first with a weak concentration, drain, rinse and immediately progress to caustic circulation. Spotless every tie.

This rinsing and washing helps remove most of the resident CO2 before caustic circ.

Good luck.

Pax.

Liam

Thanks for your reply Liam! That is greta info and we will try that next wash cycle

What acid are you using prior to caustic cycle? Phosphoric/Nitric?

dick murton
03-17-2015, 06:03 AM
Regarding use of acid and caustic - I have been involved in a couple of major brewery CIP projects implementing the system widely used in continental Europe, which is to give a wash with recirculated caustic first (some people don't even do a pre-rinse), to remove the proteinaceous and oily residues, dump the caustic, rinse and then give an acid wash.

This way, the caustic is rendered useless by the soiling and also the CO2 pickup - so is not fit for re-use on two counts. If you use just enough to create a consistent recirc for 5 to 10 minutes, that is normally enough - certainly for 2000 hl vessels!!

liammckenna
03-17-2015, 06:15 AM
Thanks for your reply Liam! That is greta info and we will try that next wash cycle

What acid are you using prior to caustic cycle? Phosphoric/Nitric?

It is a phosphoric/nitric blend (diluted to only about .5% for this acid prewash)


Pax.

Liam

CedarCreek
03-17-2015, 06:33 AM
We noticed a similar problem. We fixed it by draining the tank of any beer/yeast left and then before we rinse we close all ports but the co2 arm and the bottom valve. We hook up a shop vac to the co2 arm and let it rip for 5 min. Has worked great for us.

TGTimm
03-17-2015, 09:01 AM
You should also be aware that, with enough CO2 to neutralize a pH 13 solution, you have enough CO2 in your tanks to pose a serious health risk when you enter the tank to do some manual scrubbing.

Be sure those tanks are completely flushed--open the manway, remove the bottom fitting, open the top fitting(s), let sit for a goodly period of time. You might consider buying a gas tester and implementing a confined space permitted entry procedure--before OSHA fines the heck out of you ($2,000+ per violation) and makes you do it (or worse yet, you lose an employee)!

aaron inkrott
03-18-2015, 03:16 AM
Like CedarCreek, we use a modified shopvac to lower CO2 w/in our FVs. Would love to use compressed air, but don't have that ability yet. We have a CO2 meter that we use to gauge total ppm inside the tank. Once it reaches <3000ppm, we run caustic. Ideally you want to run caustic near atmosphere, ~400ppm, but we don't have a CO2 capture in our tank farm to get it that low. If you recapture your caustic to clean other tanks throughout the week, be sure to continually check pH, like dick mutton said, it's likely turning into carbonate and is no longer effective.

-Aaron

Inthelab
03-18-2015, 09:37 AM
http://www.grainger.com/product/ALLEGRO-Conf-Sp-Fan-1UFG6

This guy will clear the CO2 from a 200bbl tank in 15 minutes. Just drape the hose in the manway and let it rip.

Matt Falco
08-27-2015, 01:26 PM
Caustic strength is negatively affected by water hardness, soil levels, acids, and carbon dioxide. If your water is hard, either soften it or use extra caustic. Always do a hot rinse before caustic to remove excess soil. Your caustic should be clean when cycle is complete. Always start with caustic, then rinse, then acid wash. If you use caustic, you must follow with acid.

45 minutes @ 160 deg F for caustic, 35 minutes @ 120 deg F for acid. Acid cleans the beer stone you make during caustic cleaning. Acid also passivates the steel in your tanks after the caustic corrodes it. Never run acid before caustic. Makes no sense...

Purge tanks of CO2 with a blower fan connected to a tri-clamp fitting, 45 minutes of purging should be enough.

CasselBrewery
08-27-2015, 01:39 PM
Caustic strength is negatively affected by water hardness, soil levels, acids, and carbon dioxide. If your water is hard, either soften it or use extra caustic. Always do a hot rinse before caustic to remove excess soil. Your caustic should be clean when cycle is complete. Always start with caustic, then rinse, then acid wash. If you use caustic, you must follow with acid.

45 minutes @ 160 deg F for caustic, 35 minutes @ 120 deg F for acid. Acid cleans the beer stone you make during caustic cleaning. Acid also passivates the steel in your tanks after the caustic corrodes it. Never run acid before caustic. Makes no sense...

Purge tanks of CO2 with a blower fan connected to a tri-clamp fitting, 45 minutes of purging should be enough.

Thanks for your reply Matt!

Ah this is something we don't do, run acid after caustic wash. Although we do keep an eye on the beer stones. What acid do you use?

Great idea on the blower! Will rig something up!

Thanks!