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schnackshack

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Hey guys,

So I have a sight glass on my mash tun that no matter what seems to always empty when I’m mashing.

I use the HERMS coil method with a brew pump. I have a grain bag/false bottom combo that leaves about 3 inches of clearance for liquid to collect under the false bottom. This bottom 3inch pocket is where my sight glass bulkhead enters the kettle as well as my kettle drain bulkhead.

When I run the pump, the sight glass seems to always go dry, even though there’s plenty of liquid, saturated an inch or so above the grain. The recirculating line coming back into the mash tun is always flowing, so this leads me to believe that the pocket of liquid under the grain bed (below the false bottom) is always full.

Am I missing something? Could this be some type of Venturi effect? Any thoughts are welcome.
 

eric19312

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Your sight glass is tell you that you are running your pump too fast and compacting the grain bed. As the bed compacts your pump keeps pulling on the liquid below the false bottom creating a pressure difference...basically it is sucking the wort out of your sight glass. I understand what you are supposed to do is watch that level in the sight glass and adjust your pump speed so that you are getting a relatively small inflection. Next brew you might adjust your crush to a little coarser so that you can run your pump a little faster without compacting. Incrementally over time you will work out the ideal crush and pump speed for your system.


edited to add:
here is a great explanation if you want to get into the weeds (especially third paragraph under Controlling Bed Compression section)
http://brewlikeapro.net/lautering.html
 
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Jtvann

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Is your sight glass plumbed directly online with your pump?

Take a look at the Ssbrewtech 20g Infussion mash tun. Just as an example, it has 2 sight glasses. One is above the false bottom, one is below. Like mentioned above, as you recirculate, you'll the the one below drop some on relation to the overall liquid level.

If on the other hand you have your sight glass in line with your pump and not completely separated, the pump will suck it dry every time.
 

wilserbrewer

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Read the article....interesting.

There will always be a pressure differential above and below the FB while the pump is running.

The article mentions typical drawdowns in the sight glass up to 10” on a much larger commercial tun.

As you mention, your return line alway flows well, so apparently your not sticking the mash....

Try to slow the return and see if the drawdown in the sight tube is not so drastic.
 

day_trippr

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[...]
As you mention, your return line alway flows well, so apparently your not sticking the mash....[...]
But the mash might be compressed and channelled.
I would check the mash extract efficiency as it should provide insight as to what was going on...

Cheers!
 

kh54s10

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I question the need for a sight glass on a mash tun at all. You can get the amount of strike water before adding it to the tun. Same with the sparge water if batch sparging. I don't fly sparge so I don't know any need there. After strike, you don't really care what level is in the tun. When batch sparging I collect the amount of wort needed for boil off. That measurement is in the boil kettle.
 

eric19312

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I question the need for a sight glass on a mash tun at all. You can get the amount of strike water before adding it to the tun. Same with the sparge water if batch sparging. I don't fly sparge so I don't know any need there. After strike, you don't really care what level is in the tun. When batch sparging I collect the amount of wort needed for boil off. That measurement is in the boil kettle.
Check out the article I linked. The reason for having one has nothing to do with knowing the volume of your mash and everything to do with understanding if you are getting ready to stick your mash. I just watch my flow rate through a rotameter and if I see it starting to slow I back off flow and probably get in there and stir. But if buying a new mash tun and in market for some extra bling I'd consider the sight glass option.
 

day_trippr

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I totally rely on my mlt sight gauge for exactly ^those^ reasons. It has never let me down wrt warning of an impending stuck bed when setting my recirculating rate...

Cheers!
 
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schnackshack

schnackshack

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Thanks for all the suggestions! Can always depend on HBT for some good discussion.

I don’t think my mash has ever been stuck, at least not that I’ve ever noticed, and I’ve never really had drainage/flow problems so it must be the pump is simply drawing too fast; creating that pressure differential.

So far I’ve had my pump wide open. Any suggestions on how fast the mash flow should be with a HERMS setup?
 

Jtvann

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Well I just had my first experience with a stuck mash. Wasnt even really stuck. Flow didn't stop at all. All I really noticed was that my temp controller was a little spikey.

I decided to go stir it a little and noticed that my bag was getting pulled into the pot more. Tried to pull it back out and .... nope. That joker was sucked in hard. Killed the pump and pulled bag hard, then a bunch of air bubbles came up from the sides.

Stirred and reset things, slowed flow to a trickle. Mash went on just fine. This was my first time using a .025 grind. Even had 1lb rice hulls. Well I didnt see the true result until I was cleaning after the brew day. I had 5 nice little divot/dents in the bottom of my pot where the false bottom feet had set. False bottom was fine, not warped at all. Dents are cosmetic, but dang.

I used to do a lot of things wrong, and probably still do in brewing. I used to pressure ferment ales just because I could for example. Ask yourself, why are you recirculating fast? I get why to recirculate, I have a false bottom, I have to. But why fast. It causes problems, multiple problems. Theres zero benefit to recirculating fast vs very slow. As slow as you can go and still maintain your temp is the best.
 

augiedoggy

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Hey guys,

So I have a sight glass on my mash tun that no matter what seems to always empty when I’m mashing.

I use the HERMS coil method with a brew pump. I have a grain bag/false bottom combo that leaves about 3 inches of clearance for liquid to collect under the false bottom. This bottom 3inch pocket is where my sight glass bulkhead enters the kettle as well as my kettle drain bulkhead.

When I run the pump, the sight glass seems to always go dry, even though there’s plenty of liquid, saturated an inch or so above the grain. The recirculating line coming back into the mash tun is always flowing, so this leads me to believe that the pocket of liquid under the grain bed (below the false bottom) is always full.

Am I missing something? Could this be some type of Venturi effect? Any thoughts are welcome.
Mash tuns traditionally do not normally have sight glasses for the reasons you have discovered. I use a $30 inline flow meter to measure and adjust mash flow and address the issues above.
 

postalbunny

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Mash tuns traditionally do not normally have sight glasses for the reasons you have discovered. I use a $30 inline flow meter to measure and adjust mash flow and address the issues above.
What flow meter do you use? A Reliable $30 flow meter sounds exciting...
 
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schnackshack

schnackshack

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Mash tuns traditionally do not normally have sight glasses for the reasons you have discovered. I use a $30 inline flow meter to measure and adjust mash flow and address the issues above.
Sounds fun! Mind posting a photo of your setup with the flow meter?
 

Bobby_M

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Thanks for all the suggestions! Can always depend on HBT for some good discussion.

I don’t think my mash has ever been stuck, at least not that I’ve ever noticed, and I’ve never really had drainage/flow problems so it must be the pump is simply drawing too fast; creating that pressure differential.

So far I’ve had my pump wide open. Any suggestions on how fast the mash flow should be with a HERMS setup?
Something close to 1 quart per minute or a little faster. Running the pump wide open will compact the grainbed so bad that you wouldn't be able to stick a mash paddle into it.
 

augiedoggy

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Something close to 1 quart per minute or a little faster. Running the pump wide open will compact the grainbed so bad that you wouldn't be able to stick a mash paddle into it.
Flowrate depends on the amount of surface area your false bottom has though. As home I have a 15.5" false bottom and recirc is done at about 1.8gpm with 91% BH efficiency at the pub we use a roughtly 28" diameter false bottom and recirc at between 4-5gpm (86% efficiency) we use rice hulls at the brewpub but they are not needed on my home system where I crush with a credit card thickness gap.
 

postalbunny

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Digging that style flow meter... no electronics. Going to get one so I can start to get solid numbers on my recirc rate besides just eyeballing it. It would be good to know at what rate i'll stick my mash.

Not a fan of the manometer on the SS using two sight glasses because i imagine they'll get dirty eventually.
 

augiedoggy

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Digging that style flow meter... no electronics. Going to get one so I can start to get solid numbers on my recirc rate besides just eyeballing it. It would be good to know at what rate i'll stick my mash.

Not a fan of the manometer on the SS using two sight glasses because i imagine they'll get dirty eventually.
if your commenting on the sight glasses on our the kettles in my photos, they actually stay completely clean since theres only water in my HLT and the boil kettle sight glass comes completely clean during the high pressure CIP with the sprayball. The pbw and acid both recirculate thru the site glass during the whole cip process. Real CIP is completely different as far as its effectiveness than the type more commonly used on homebrewing setups with underpowered pumps.

The stainless flowswitch for the rims is probably the biggest PITA to clean out of everything. the flow meter I linked comes completely apart for cleaning pretty easily.
 
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