Looking for help with pump for hot liquor recirculation

[ih8um]

We have a 40 bbl hot liquor tank that is powered by 3 tankless hot water heaters in a series. We have no issue filling the tank at 5-6 gpm at 185 degrees. When we recirculate with our 3/4 hp wash down pump, we are only getting 2 gpm. The line from the tank to the heater is 3/4". we have an 8' rise where it goes over a door, then back down to the input of the tankless heater, then it goes back up 8' on the way back to the tank. It goes into the tank midway through the height. We think the problem is the pump is undersized, however it is the pump that the previous owner had on the system at a different location. We also thought about making the lines 1" lines, but the heater is still 3/4" so this didn't make sense to me. The distance from the tank to the heaters is about 25'. Any advice on solving this problem would be appreciated. This keeps us from recovering our chill water. It all goes down the drain.

[gitchegumee]

40 bbl and you are not exchanging heat for your HLT from hot wort? If this is just for maintenance of HLT temperature, then a simple electric element in the tank will suffice. Cheaper and easier.

[dick murton]

True, but I much prefer to have a recirc loop from bottom to top to minimise layering, especially in something this size. Easier to get away without in say a 10 brl HLT. Assuming the question was what size pump, to some extent it depends on the shape of the tank but the pumps I have used typically have a flow rate of double the working tank volume, but then typically only need to run it for ten minutes or so to remove any layering.

[hydromike]

Going to the 1” lines is needed, but the pump you have will pump has the volume but not the pressure. I have just finished theexact same thing. If you have questions call me, 720-295-7663. I am also an engineer.

[gitchegumee]

An element in the bottom of a tank already provides convection currents that will ensure you are not "layered". It's done in hundreds of breweries around the world with no issues. If you must recirculate, then your HLP should be tied to the CIP arm, or a recirculation arm. You do not need a separate pump/loop/heaters/hoses. Cheaper and easier.

[ih8um]

Are you saying it is cheaper and easier to cut a hole in the double wall tank and weld a fitting for the element and then have an electrician wire it and buy a heating element, than it is to use an existing bottom port to run a pipe with a pump to an existing bank of hot water tanks and back to an existing top port? I am confused about that. I am interested in your solution.

[gitchegumee]

Yes. That is what I'm saying. I've done this several times. An element is about same cost the required pump. Electrical installation is easy for either pump or element-even for a novice. And an element is far less likely to fail than a pump + 3 hot water heaters. And cost less to operate. And take up less floor/wall space. So the capital required is comparable, maintenance is much less, operating costs also less. Installation cost may be more. Welding a 2" coupling into a tank isn't difficult. I'd have it done in a half day--mostly setup. So if you want a superior electrical long-term solution, this is it. If you're looking for a short-term solution, then perhaps hoses, pumps, and heaters are for you. If you choose that route, then the suction line to the pump should be larger than the discharge. And shorter. Never starve the suction of a pump-especially with hot water.

Be careful you know what type of insulation is under the cladding. I had a friend break his arm with a heavy drill & hole saw when he found "chicken wire" under the cladding which was used to hold the rockwool in place. That caught the teeth on a hole saw and sent the drill motor spinning. Also of concern is flush welding inside the tank--beware of confined spaces!