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Author: Subject: Is propylene glycol as a circulating coolant compatible with a wide range of plastics(pump material)?
FireLion3
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[*] posted on 4-2-2018 at 22:56
Is propylene glycol as a circulating coolant compatible with a wide range of plastics(pump material)?


So, my lab space isn't climate controlled. I wasn't thinking ahead and temperatures in my lab space dropped below freezing, causing my rotovap condenser coils to shatter because there was water inside of them... I've decided to make a change to a non-water based system, and instead use a fan, copper pipe, and ambient air to keep the coolant cooled to room temperature.

I don't know anything about the compatibility of anti-freeze / propylene glycol. I have a cheap shureflo diaphragm pump that I want to recirculate the fluid with, but in my research I can't figure out what the pumps diaphragm material is made of... so I suppose the simplest question is, is propylene glycol generally compatible with most plastics? Thank you guys


[Edited on 5-2-2018 by FireLion3]
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Fulmen
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[*] posted on 4-2-2018 at 23:26


For specific applications, especially at elevated temperatures you should do a web search. But generally speaking it's fairly safe to most materials.



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[*] posted on 4-2-2018 at 23:32


As a quick answer I would say no. With a pump of that type, which likely has several different types of plastic, and there are several plastics that I can think of which PG solvates quite well, albeit slowly... So no.
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[*] posted on 5-2-2018 at 01:22


The type of circulating pumps used for hydronic heating will generally be good. If the power fails, you do NOT want the heating lines cast into a foundation slab to break if the temperature falls below freezing, so sensible people use some antifreeze mixed in.

If you do this, remember: Water has much better heat transfer characteristics per volume than glycol. Use no more than required for your area's lowest temperature, even then, you may need to use larger equipment or increased flow.

I have a couple of these systems at our warehouse and shop- See here for equipment, fluids and tech.

http://www.radiantandmore.com/uncopper.html

https://www.radiantcompany.com/details/fill/

https://heatinghelp.com/systems-help-center/antifreeze-for-h...

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatloss.h...









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[*] posted on 5-2-2018 at 20:10


For now I think I will just saturate the water with salt and hopefully that should deal with the issue. I read that the freezing point of saturated salt water is -21c/-5.8f and at this point in the season the worst temperatures I'm dealing with are around 20-30f at night.

Do you think this would prevent my condenser coils from freezing over if all the liquid is salt saturated? Or is there something I'm overlooking? I wouldn't want to test it and have another $300 mistake.

[Edited on 6-2-2018 by FireLion3]
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[*] posted on 5-2-2018 at 21:41


Use windshield washer fluid. It's a mix of methanol and water. Very low freezing temperature. Usually has a blue color. Additionally, mold doesn't grow in methanol, whereas it will sometimes grow in other alcohols. Also, propylene glycol is sticky to clean up if you accidentally spill some. Windshield washer fluid evaporates with no residue, by design. As an added bonus, it's like $2/gallon and works great for cleaning glassware.

Salt water is often corrosive to metals, but some salts are worse than others.

[Edited on 2/6/18 by Melgar]




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[*] posted on 5-2-2018 at 22:43


I'll definitely check out wiper fluid like you mentioned, plus the blue color will be a neat addition I think.

This popped a thought into my head. I notice in many laboratory videos online, I see people with colored fluid circulating through their condensers. Is that what they are using, or is there another reason for the color? Practical reasons to be able to see the fluid flow?
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