Author Topic: Constant Low OG - Old dog needs help.  (Read 237 times)

Offline Bud Brewson

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Constant Low OG - Old dog needs help.
« on: November 07, 2017, 05:13:13 PM »
Hello peers,

I need some help BADLY. This is a pretty embarrassing question but its causing me issues and not an efficient way to operate a brewhouse.

I'm running a 10bbl system.
My 2 roller mill is set to 1.4mm gap.

I'm constantly missing my pre-boil OG. I always come in lower than what is expected.
The final runnings coming out of the mash tun are between 1020-1030 so I'm leaving a lot of sugar in the mash.
Preboil volumes are ok. OG ALWAYS low.

How do i get the last of the sugar out of my mash!?!?!

Am I running off to the kettle too fast?
How long should it take to run wort from 10bbl mash tun to Kettle?
Does my mill gap have to be finer?

Please help! Old dog needs new tricks. feel like  a fool! :-[

Offline Ck27

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Re: Constant Low OG - Old dog needs help.
« Reply #1 on: November 07, 2017, 05:45:39 PM »
Hello peers,

I need some help BADLY. This is a pretty embarrassing question but its causing me issues and not an efficient way to operate a brewhouse.

I'm running a 10bbl system.
My 2 roller mill is set to 1.4mm gap.

I'm constantly missing my pre-boil OG. I always come in lower than what is expected.
The final runnings coming out of the mash tun are between 1020-1030 so I'm leaving a lot of sugar in the mash.
Preboil volumes are ok. OG ALWAYS low.

How do i get the last of the sugar out of my mash!?!?!

Am I running off to the kettle too fast?
How long should it take to run wort from 10bbl mash tun to Kettle?
Does my mill gap have to be finer?

Please help! Old dog needs new tricks. feel like  a fool! :-[

Mash Temp??? How long are you letting it sit?? You should wait 1 hour for it. Then do your sparge. I've always gotten good OG waiting one hour and using 158F as my temp

Offline BOB357

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Re: Constant Low OG - Old dog needs help.
« Reply #2 on: November 08, 2017, 02:23:46 AM »
1.4 mm = .055".  Most 2 roller mills come preset around .035" to .040", or right at 1 mm. That would definitely cause poor extraction and be the first thing I'd adjust.
Bob

Offline KellerBrauer

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Re: Constant Low OG - Old dog needs help.
« Reply #3 on: November 08, 2017, 06:14:53 AM »
1.4 mm = .055".  Most 2 roller mills come preset around .035" to .040", or right at 1 mm. That would definitely cause poor extraction and be the first thing I'd adjust.

Greetings Buds - I'm onboard with Bob.  A gap of .055 is too large.  My mill is set at .039 and I think I'm going to close it a bit to .037.  That said, I don't believe the milling will result in leaving extract in the mash.  In fact, a finer milling will result in greater brewhouse efficiency and more sugar.  So if you're leaving sugar behind now, adjusting to a finer milling will produce even more sugar to leave behind.

So, is there a history of this happening?

Your end runnings should be around 1.010 - 1.015.  So, without an understanding of your equipment and process, my suggestion would be to carefully examine your calculations.  You may be using too much grain for the amount of beer you're brewing.  If you're using BeerSmith, go through the Equipment Profile and make adjustments as necessary.

Also, there may be "channeling" in the mash.  That's when the sparge water follows the same path(s) through the grain bed.  There are a number of reasons for this issue.

My gut feeling, however, is to examine your equipment profile.  If your pre-boil volumes are good, than your Brewhouse Efficiency setting may be set too low.
« Last Edit: November 08, 2017, 07:23:49 AM by KellerBrauer »
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Offline brewfun

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Re: Constant Low OG - Old dog needs help.
« Reply #4 on: November 09, 2017, 03:22:22 PM »
I'm constantly missing my pre-boil OG. I always come in lower than what is expected.
The final runnings coming out of the mash tun are between 1020-1030 so I'm leaving a lot of sugar in the mash.
Preboil volumes are ok. OG ALWAYS low.
Quote

Don't feel anything but curious. Brewery engineering is a complex subject, especially as you scale up.

As the others have suggested, your mill gap is a bit wide. If you can borrow an ASBC sieve set, you can dial your mill in perfectly for your grain. You weigh and mill an exact amount of grain, then weigh the amount that is held in each sieve.

IIRC, a #14 mesh will hold 50 to 60% of the crush weight, the #30 mesh will hold 25% and the #60 will hold 10%. Your fines should be between 2% and 5%. I think some mills produce up to 10%, but that's a bit much for my preferences.

I've found that mill gaps are a range, not an absolute. Be aware that different base malts have different kernal sizes. I'd calibrate your mill for your house standard. Look for uniformity of kernal size. One of the most widely available American base malts has up to 50% kernal size variation, so, I end up using a slightly more expensive, but uniform variety. It pays off in long term cost and consistency.

Quote
Am I running off to the kettle too fast?
How long should it take to run wort from 10bbl mash tun to Kettle?

How much do you want to fine tune?  ;) 

I run a 1.15:1 ratio and look for first runnings of 22 to 26 P (>1.095 would be ok). I measure during vourloff, so if it's low, I'll continue until it rises. This means the first third of my runnings have half my sugar. Somewhere around halfway, the gravity begins to decline rapidly. I look for about 1 Plato/bbl.

The next thing to watch (mechanically) is your water velocity (as column inches per minute) through the grain bed. If your grain load exceeds 55 lbs/sq.ft., then you really need to pay attention to the column of water above the false bottom. Keeping the sparge to no more than 1" above the grain bed is good technique. Too much column velocity (which is different than flow rate) will cause the grain bed to compact.

I'll spare you the calculations, but you find good wort velocity references online. Or consult articles by the MBAA on the same subject to see optimal lauter design theory. I highly recommend you join the MBAA if you're not already a member.

Nearly always, the bottom line is wort velocity will equal about 60 to 90 minutes to fill the kettle.


Beer Appreciation is the space between pints.

 

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