It looks like a fun question is a brewing about pump options and
requirements. I received a great lesson from Dave Berg and it is worth
repeating and expanding. "A pump has one working end." The other end
just sucks.
A centrifugal pump is an interesting device especially if you are
planning on pumping hot liquids. The closer the liquid temperature gets
to boiling, the more inlet head pressure is required. Trying to lift
boiling or near boiling liquids above the vessel reduces the atmospheric
pressure on the liquid and also lowers the boiling point. The result is
cavitation due to steam.
About the only style (other than positive displacement) of pump used
with hot liquids would be a centrifugal pump with an impeller. Most
folks use the magnetic drive version because the pump is completely
sealed. The internal magnet is cast onto a impeller and the external
magnet is connected to the motor shaft. The other option is a wet seal
but the cost explodes at this point.
If you look at a pump book, it typically gives GPM ratings at various
head pressures and also list the maximum head available. What you
typically want to do is to determine how much flow you require, ensure
the pump is close to the appropriate temperature range, and then
calculate the drag of the circuit to ensure you have adequate pressure
to perform the required task.
Bottom line is simple. If you are making a rims system, choose a pump
with low hp, flow, and head pressure. If you are planning on a
counterflow cooling system and speed is important, move toward the
higher pressure or larger HP version.
One last note: If you are planning on moving sparge water from a
holding location to a mashtun or lautertun and if your water contains
temporary hardness, the pump will cavitate as it disassociates the
carbon dioxide and calcium from the warm water. Before you move the
water, recirculate and watch the CO2 bubble. When the bubbles are done,
the water works fine!
OK, I needed a break from work and now need to get back.
Next last note: Design plumbing and hoses for easy disassembly after
each usage. A hose clamp connection is not a sanitary fitting and needs
to be disassembled to ensure sanitation.
Rick O
>> englandkris(a)hotmail.com 02/05/03 11:10AM
>>>
What do I want in a pump? More specifically does it matter if the
pump is Impeller driven vs Magnetic driven?
Kris
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