Awesome pump or crappy false bottom?

[Seabee John]

I just finished a brew today and when I went to clean the hops out of my boil kettle I was surprised to find that my "Northern Brewer" domed stainless false bottom had been "sucked" into a concave form on either side of the dip tube. I was able to pop it back into place but wow.... either my march pump really sucks or the false bottoms from NB do.

 

[GilaMinumBeer]

I had one from MoreBeer work great for me for nearly 2 year and then POW collapsed. From that point on it would collapse under even the lightest of grain bills.

If figure that it was too weak to mess with anymore and bought a Sabco FB.

Life is too short to have to deal with a collapsed FB under 28# of grain.

 

[FireBrewer]

Heard some horror stories regarding those types of FBs. Indeed, dealing with a collapsed FB is one of the less glamorous points of brewing.

The March pump is only 1/25HP and has max flow of 8gpm...doesn't create that much suction.

 

[BrewBeemer]

The March pump can pump up to what 8-12 feet of head pressure or close to 2.5 pounds suction on the low end. A 12" false bottom has 113 sq/in of area if it's fully plugged with 2.5 pounds of suction your looking at 282.7 pounds of vacuum force not accounting for the wet grain weight pushing down.
No little 1/8" legs welded around the bottom for support preventing this problem or stainless 10-32 screws with nuts for support legs?
I have seen a 6,500 gallon stainless food grade tank collapsed from being pumped off with a broken vacuum brake stuck closed.
It looked like a hand crushed bier can a $94,000 316 ss tank wasted.
It doesn't take much pressure or vacuum to create a large force over a large surface area.

 

[MoRoToRiUm]

Why not add support feet/bars? Of you weld, would be easy as pie.

 

[happymonk]

Hmm original poster, are you using whole hops in your kettle? The rest, add a grant to run off from your mash tun, pump out of that, suction in the bottom of the mash tun is not good...

 

[FireBrewer]

The March pump can pump up to what 8-12 feet of head pressure or close to 2.5 pounds suction on the low end. A 12" false bottom has 113 sq/in of area if it's fully plugged with 2.5 pounds of suction your looking at 282.7 pounds of vacuum force not accounting for the wet grain weight pushing down.

I'll trust your math, but is that going to happen with a pump with a magnetically-coupled impeller that slips when it can't pump?

 

[runhard]

I've got a SABCO false bottom with the SS bolts as supports and that puppy has worked well with a lot of #s of grain on it so I would bet that it'd work well in a boil kettle with hops.

 

[Bobby_M]

You can make legs out of some stainless machine screws and a couple nuts.

 

[Dr_Deathweed]

mine from NB started collapsing as well, so I put a hose clamp and washer over my dip tube on either side of my false bottom. Have not had a problem since.

 

[BrewBeemer]

I'll trust your math, but is that going to happen with a pump with a magnetically-coupled impeller that slips when it can't pump?

If the pump has output it has input or vacuum if the FB is plugged up to a point of being sealed. Lets say the March pump can only go to 9' of head vs 12'. Take 9' x .432 psi (weight per / ft of water vertical),this 9' x .432psi = 3.888 psi pressure.
A 12" FB, 12 x 12 = 144 x .7854 = sq / in surface area of 113.09 sq / in.
Take 113.09 sq /in x 3.888 your at 439.7 pounds pulling dowward. Say add 30 pounds of wet grain to the 439.7 pounds then your at 469.7 pounds force on the FB. Wonder why it collasped without any leg supports? Nuff said.