Low temperature water pumps

[wbedard]

Hi all,

I am a good ways into designing a fairly typical "compound" system (freon loop cooling a water loop) and have run into a problem identifying a suitable water pump. This may sound surprising as I am certainly aware of the fine pumps typically used by most WC'ers. However, as you get into pumping low temperature (-20 to -40 deg C) mixtures of water and alcohol, glycol, etc., it seems that most of these pumps are out of their element. When you can actually find a _minimum_ fluid temperature rating for a pump, most seem to bottom out around 0 deg C. Could anyone suggest some good starting points (sites, companies, etc) for sourcing some decent low temperature pumps. These pumps should be useful/appropriate to the small percentage of WC'ers operating this type of system (ie. centrifugal, 120V, smallish form factor, etc.). Thanks in advance for any and all suggestions!

[BillA]

going to be quite a task for a small centrifugal, and it will not be made of any 'common' plastic

I have a small ss centrifugal rated to -40°C, but its submerged and shaft driven by an external motor
(not available separately in any case)

there are many small Teflon gear pumps but for 1 to 1.5gpm the new cost is probably as much as your computer

another route is with a Procon carbonator pump good for 4gpm with a 1/4 hp motor, but perhaps 1/3 hp needed at -40°C
(I've seen them in chillers covered in insulating mastic)

[punish3r]

The only pumps that I know of that'll do -40 C without problems are R-134a vapor transfer pumps. And they're designed to go a bit colder than that. And usually start at $500 US. I'm sure that you could build a small, sealed chamber with a sealed thrust bearing and a small rotary vane impeller connected through the bearing to an external drive motor. But hey, that's only if you have access to the tools to build the neccessary parts.

[bigben2k]

Did you check the specs on the Little Giant and Iwaki pumps?

[wbedard]

Thanks for the reply BillA. While the selection is certainly limited, I am coming up with some reasonable candidates. I have not called Iwaki (bigben2k) but the word from a distributor is that Little Giant doesn't make anything good for -40 that will fit my space req's (under 12" length). I do have a candidate from March (www.marchpumps.com) with their 809HS in stainless steel as well as a possible from Finish Thompson (www.finishthompson.com) with their KC5 in PVDF. Interestingly enough, FT stated they had never rated their pumps at the low end of the temperature scale but they would cut me a significant deal on a pump if I would "test" it for them. While I would want some clarification on where that would leave me should their pump fail, I told them I would keep the offer in mind...:>) I have about 4 more companies to contact that I think might have a good candidiate and I will certainly post here if I get any winners. Also, while I know most are not willing/able to pay for the kind of pump I am looking for, I am fortunately able to be a bit more "generous" with this project. I will keep everyone posted on what I find.