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 Home Brew Forums > Damaged False Bottom
04-30-2013, 04:29 PM   #11
Bobby_M
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Quote:
 Originally Posted by mpcluever For me, I use the braided silicone hose, but my roommates all use the plain flimsy silicone hose that you can crush with your fingers. The way I've seen it explained is that the PSI in the hose is much less than the force being exerted on the false bottom.
Well, I did the math in a previous post. The PSI in the hose is based on the cross sectional area so it's around -3psi max. You multiply the pump pressure that by whatever area the false bottom is.

Here's a quick calculator for those who don't like math: http://www.areaofacircle.info/

An 18" diameter FB has an area of 254 square inches so even 7psi (max of the chugger or march) x 254 is 1778 pounds of force.

While seeing your inlet hose crush under the vacuum of the pump is a pain, it's much more preferable to collapsing your false bottom. Even with legs, and stands, 1700 pounds is enough to form a false bottom around any supports.
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04-30-2013, 07:35 PM   #12
Poobah58
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Quote:
 Originally Posted by Jaybird DAMN Poobah drive a truck on that thing or what? You have no idea how many times I have seen that happen to those fasle bottoms. Its really the reason I came up with my stands the way I did. B3 false bottoms kept failing on people. Its amazing how much vacuum is created under a false bottom when using a pump and how much pressure really is pushing/pulling down on it. Sure makes for a hard brewday man sorry to hear it. I think I would get a hold of the company you got it from and see if they will warranty it for you man, its worth a shot. Dude I love your tagline! Makes me chuckle every time I see it... Cheers Jay
Thanks Jay... I just bought one or your stands yesterday. I'm going to cut of the legs off the damaged unit and try to bang it straight. If it doesn't work I'll be buying a FB also!
Kind of hard to blame the manufacturer. This is probably the 9th or 10th time I used this and the other times have been trouble free. My mash got stuck and created almost a ton of force. Learned my lesson on what to use beneath these things.
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04-30-2013, 07:43 PM   #13
Poobah58
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Here's my rig. It's an old pic. The kettles have changed but the manifold and hoses are still used. That thermoplastic hose on the left wasn't fazed! I'm going to add a vacuum gauge and keep an eye on things from now on.

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04-30-2013, 09:27 PM   #14
Jaybird
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Quote:
 Originally Posted by Poobah58 Thanks Jay... I just bought one or your stands yesterday. I'm going to cut of the legs off the damaged unit and try to bang it straight. If it doesn't work I'll be buying a FB also! Kind of hard to blame the manufacturer. This is probably the 9th or 10th time I used this and the other times have been trouble free. My mash got stuck and created almost a ton of force. Learned my lesson on what to use beneath these things.
Yeah I saw that order come in the other day. Ill get the out to you soon. I am backed up a bit in the shop but I am working night and day to catch up. I don't see any reason you cant bang it straight enough to work. I will build your stand so you will have plenty of support around the edges for that false bottom. I think those from B3 are 18 ga if I am not mistaken.
Thanks for the order! Damn nice looking set up man!
Cheers
Jay
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05-01-2013, 03:14 AM   #15
Poobah58
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Thank Jay!!!

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05-02-2013, 04:16 AM   #16
WPStrassburg
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The pressure under the fb and within the suction hose is constant and independent of the area of the false bottom or hose diameter (unless you have significant friction losses in the hose). The force (the real factor that is going to bust your equipment) depends on the area of the fb and hose. If the fb areas is large enough you could crush a 1/4" (or 1/2" or 1" thick!!!) thick piece of metal and not cause the hose attached it to flinch.
March and LG don't have a curve for their pumps that shows the NPSH (net positive suction head) that the pumps need before they break suction, but if we assume they suck as hard as they can push (which they cannot) the force on the suction side can add up pretty quick if you have a stuck mash and the pump is able to put full suction force on the fb.

Also grist weight has very little bearing on the force that can be put on the fb as the grain is usually pretty neutral in buoyancy and puts very little weight on the fb due to gravity since it is more or less floating in the water. You can stick a 5# mash and do as much damage with the pump suction as you can do with a 50# mash grist bill.

Quote:
 Originally Posted by Bobby_M Well, I did the math in a previous post. The PSI in the hose is based on the cross sectional area so it's around -3psi max. You multiply the pump pressure that by whatever area the false bottom is. Here's a quick calculator for those who don't like math: http://www.areaofacircle.info/ An 18" diameter FB has an area of 254 square inches so even 7psi (max of the chugger or march) x 254 is 1778 pounds of force. While seeing your inlet hose crush under the vacuum of the pump is a pain, it's much more preferable to collapsing your false bottom. Even with legs, and stands, 1700 pounds is enough to form a false bottom around any supports.
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05-03-2013, 12:11 AM   #17
Poobah58
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Big shoutout to Homebrew Stuff! They're sending me a new FB. We talked about pressures generated when a pump is attached. I think even they found it hard to believe. They are coming out with a beefier FB soon. May even suggest to their customers to beef it up further when using a pump. Thanked them for being a class act! Think I'll cut the legs off and use Jaybird's base and I'll be good to go...

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05-03-2013, 12:37 AM   #18
Yooper
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Quote:
 Originally Posted by Bobby_M It is possible... like this.. the march can pump 17 ft of head so 7psi. If your pot is say 16" diameter the FB would have 200 square inches. 200 x 7 is 1400 pounds of down force.
Quote:
 Originally Posted by Poobah58 Big shoutout to Homebrew Stuff! They're sending me a new FB. We talked about pressures generated when a pump is attached. I think even they found it hard to believe. They are coming out with a beefier FB soon. May even suggest to their customers to beef it up further when using a pump. Thanked them for being a class act! Think I'll cut the legs off and use Jaybird's base and I'll be good to go...
That's good news!

I ruined my 12" false bottom by using my pump to recirculate. It turned totally inside out, even with the ball valve on the output side slowed. I didn't run it wide open, not at all. But it was convex when I finally got done on that horrible brewday.

I ended up buying a new FB from Jaybird.
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05-03-2013, 02:19 AM   #19
SavoryChef
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I have the same false bottom and it looked just like mine. Lol. I bought a jay bird false bottom stand.. problem solved

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05-03-2013, 02:30 AM   #20
Jaybird
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Yeah Marcus at HBS is a great guy for sure. Thats killer that he is going to send you another false bottom. Good to hear!
I will get your custom stand out of the shop in a couple of days.

Cheers
Jay

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Need a False Bottom for your Keg, Kettle or Cooler?

I have been making custom False Bottoms for just about everything since 2008

Nor Cal Brewing Solutions, Reddings local homebrew store
(530)243-BEER and (530)221-WINE

Still have questions PM me here or hit the website.

http://www.norcalbrewingsolutions.com and like us on Facebook https://www.facebook.com/NorCalBrewingSolutionsfor Facebook only promos too
Smoke Cigars? www.stogietoys.com

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