Sanitizing Kegs with Boiler Steam

[ScottV]

I just recently put online a nice new Lang Minimat 3000, which is a semi autimated keg cleaner. I choose the model which sanitizes the kegs with steam prior to a CO2 flush and pressurization step. All the piping in the steam system is black iron, up to a steam filter which is rated to produce culinary quality steam by 3A standards. It is supposed to take out 95% of the solids 2 microns or larger. I then piped copper from the filter to the cleaner which is only a about another foot of pipe.

I have noticed that some of the kegs will retain some condensate from the steam cleaning step, and the condensate tastes and smells awful. Like an ashtray, or worse. I am hoping that by increasing the timing of the CO2 purge i should be able to evacuate all of the condensate.

My question is this...is it possible to get steam from a cast iron boiler that doesn't taste like it is dirty. I thought the filter would do the job but it really hasn't. The boiler is still pretty new, only a month of use.

Does anyone else out there use steam directly off the boiler to sanitize kegs or equipment?

I have seen a brazed plate heat exchanger set up inline for producing steam with the boiler steam and filtered water, does anyone know of a good suppplier of this type of setup?

Any help or suggestions would be appreciated as always

Scott

[Diamond Knot]

Scott,

We had this same issue with our steam/water mix valve.....which is why we had to bail on using it. The open demand for steam.....meaning.....the boiler was allowed to flow through the water wide open, created a "venturi" effect that draws the boiler condensate through the pipe and into our mix valve. We were getting the same water look and smell as you.

What you'll probably have to do is this:
1.) Ensure the steam supply line coming off the steam main form the boiler is coming from the TOP of the steam main. Make sure it goes vertical for a foot or so at least. Many condensate cary-ove rissues are due to this alone.

2.) Make sure the pipe diameter is large enough that water isn't completely filling the pipe, and allows gas to pass an doesn't create the venturi.

3.) Barring the above, you may have to put a steam trap in the system just ahead of or at the point where the steam supply breaks off the main to go out to the keg washer. The closer to the keg washer the better. Condensate going through the pipe will fall through the trap, and should return to the boiler.

4.) REALLY throttle down the steam pressure going into the keg if there's a steam regulator somewhere on the washer or you may have to install one. If it is releasing the steam to the keg at a full 15 psi, it is dumping the entire line pressure all at once.

I think your problem is compounded by the fact that your boiler is probably like ours..............it heats really quickly but has no reservoir....no buffer, as it were.....and the steam line pressure drops considerably (almost to zero?) when the washer calls for steam. It drops very, very fast.

Anywho, bounce these things around and hit me back on my home E-mail for more discussion.........

[dick murton]

One of the problems with using steam direct from a boiler is just what you have come across. This can be attributed to iron pickup from the boiler and pipework, the raw water quality, any recovered condensate and water treatment. Not being familiar with the standards you say you are sticking to, make sure the steam is hot enough - about 135 deg C (whatever pressure that takes) and goes through a steam trap and filter (sounds like it does already).

As a most definitely non micro brewery we use water direct from the boilers for one of the rackers, this being softened feed water, and get away with it. Our new racker has a plate heate exchanger generating pure steam from filtered, RO treated water, to ensure no taints.

I think if the steam temperature is high enough, (but saturated), and the purge effective, then you should get so little condensate that this does not become a problem. Recommended steam time is 135 C for one minute.

Hope the attached file helps re steam temperatures

[Diamond Knot]

Dick, Thanks for the chart........easy to read and use!

Scott,
Just a few additional observations after I got home from work.......

The 135C temp equates to a 275F which would require a 30 psi delivery pressure, which, if I recall, is well outside the parameters of your 15 psi boiler. The best you could possibley get is about 250F under good circumstances. Also, that would almost have to be a "steam in the keg" pressure at the time of cleaning in order to hold those temps throughout the cycle.

I had this same debate with the contracter who installed our steam lines and fired up the boiler for us (I'm a lot of things, but no pipefitter). I was seeing so much condensate in the somewhat hot water we were making it was severely unusable. I thought it was residual oil in the pipe, and you can try to blow out the line to clear it, but it wasn't. Also, barring corrosion inhibitors, most boiler chemicals do not go with the steam.

I believe it is clearly boiler condensate for the reasons above. Regrettably, I don't think your unit can achieve the recommended 135C provided by Dick, so you'll either have to run longer or take a different tac.

[cpelz]

Hi Scott, Brian-

You guys always seem to have the same problems as us.

We've been running a Bulldog washer/racker for the last two years and I've been generally happy with it.

I think I made a mistake buying their steam (super hot water actually) generator for sanitization though. It's an Alfa Laval brazed heat exchanger with gauges, a PRV and flow regulator hung off it. It's meant to heat tap water under a bit of back pressure and deliver super heated water which flashes to saturated steam in the keg. We're running it off our low pressure boiler and are lucky if the H/E sees 13 psi steam and delivers 225 deg steam. This would require an 11 hr sanitization hold time according to Dick's chart. It gets 38 secs. Half the keg cleaning time is steaming up to temperature, sani hold and purging. The manufacturer claims a throughput of 17.5 bbl. per hour (with chemical sanitization) but we're looking at an 8 hr day to empty a 30 bbl. tank (this includes a lot of non-machine related inefficiencies I'm sure.)

What's my point? I guess commiseration, fishing for fixes and maybe warding someone with a low pressure boiler off steam sanitization. At some point down the road we may have to retrofit with a chemical system.

[Larry Horwitz]

you never, never, never want to sanitize kegs with the steam straight off of you cast iron boiler. Ever. Not unless you want your beer to taste like pipe dope, iron, and oil. Also if you have any kind of water treatment in your boiler (i.e. caustic to regulate pH) your putting that into your keg...without rinsing it out! You need a clean steam generator. several have been discussed here so get yourself one. The softened water idea is very good esp if your water is at all hard.

[ScottV]

can you point me in the right direction of any threads dealing with manufacturers of clean steam generators.

thanks,

scott

[cpelz]

Your keg washer/filler manufacturer might be the best place to start.

www.sussmanelectricboilers.com seems to have some interesting units. They list applications including distillation, sanitization and autoclave use. The Sussman representative at Cole Industrial I just got off the phone with wasn't familliar with the smaller units. Since I'm superheating water with a heat exchanger on our low pressure system, their in-line steam superheaters caught my eye.

I saw Sound Brewing had an IDD kegging unit for sale that used a Sussman boiler for steam generation, though I'm not sure whether it was a closed or open loop system.

-Clarke.

[gitchegumee]

Back to this discussion again; I'm installing a brewery with a keg cleaner that uses direct steam from the boiler to sterilize. BESIDES the issues with steam purity, I'm wondering what happens when this steam condenses inside the keg.

If there is NOT a CO2 pressurization cycle, then the condensing steam will generate a vacuum which certainly will suck up whatever nasty bacteria are on, or near the spear valve. This will leave an environment of air, bacteria, and a handful of condensate below atmospheric pressure in the keg.

If there IS a CO2 pressurization cycle to 15 psig, then the condensing steam will render the 1 bar CO2 to nearly zero psig when the keg reaches ambient temperatures. This will leave an environment of nearly no CO2 pressure and a handful of condensate inside the keg.

Is my analysis sound? There's got to be a better way. Is there? I'm about to recommend a chemical solution to the brewer if I can't find one!

[NinkasiSwain]

Back to this discussion again; I'm installing a brewery with a keg cleaner that uses direct steam from the boiler to sterilize. BESIDES the issues with steam purity, I'm wondering what happens when this steam condenses inside the keg.

If there is NOT a CO2 pressurization cycle, then the condensing steam will generate a vacuum which certainly will suck up whatever nasty bacteria are on, or near the spear valve. This will leave an environment of air, bacteria, and a handful of condensate below atmospheric pressure in the keg.

If there IS a CO2 pressurization cycle to 15 psig, then the condensing steam will render the 1 bar CO2 to nearly zero psig when the keg reaches ambient temperatures. This will leave an environment of nearly no CO2 pressure and a handful of condensate inside the keg.

Is my analysis sound? There's got to be a better way. Is there? I'm about to recommend a chemical solution to the brewer if I can't find one!

Hey Phil -

What was the answer to this question? Kinda going through something similar at the moment. Hadn't thought through the steam being its own compromise of the beer, but now just intrigued at how you resolved this question. Clean steam source? More CO2 pressure at pressurization? Thanks!

[dick murton]

In large breweries, the pressurisation is sufficient to cool the keg slightly, and more to the point, cool the steam so the steam condenses, blow the condensate out, and then pressurise to the target pressure. However, since this step is immediately followed by the fill cycle, and normally remains sealed on the filling head, there is no risk of the CO2 being drawn in. If you are going to steam sterilise and fill the kegs somewhat later, then you will simply have to take a bit of time playing with the pressurisation cycle so you get a feel for how long you need to apply the CO2. I suppose you could always spray a little water on the outside of the keg whilst the CO2 is applied, but I have never heard of this happening anywhere - but then my experience is based on immediate filling into a hot keg following the CO2 purge / pressurise.

Although you are steaming the keg, the keg will not be filled with pure steam, to the exclusion of air / CO2 / nitrogen, so I have a feeling you will simply have to counter pressure the keg. The pressure will drop a bit of course.

If we assume 135C and 30 psi pressure, then according to my calcs, at 25 C, there should still be 1.5 bar (circa 22 psi) pressure. Now this applies to a non condensing gas such as CO2, but it suggests to me there shouldn't be a problem, as the incoiming CO2 will be heated a fair bit.

As another thought, when kegs are rejected from a fully automated cleaning filling racking machine at the point just prior to filling (e.g. for lab micro checks), they always appeared to have residual gas pressure which had to allow the spear to be safely removed.

[NYSBrewer]

Hey Scott.

We met with prospero last week to discuss bottle/canning options and he recommended a seperate small clean steam boiler for the sanitation of the bottling line and kegs. I dont have my notes with me, so I cant remember the supplier he had, but give them a call and they can put you in the right direction.