High Viscosity
High Viscosity
(OP)
Is there a viscosity value (or range) that differentiates low viscosity fluids from high viscosity fluids? Or is it all more complicated than that?
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RE: High Viscosity
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: High Viscosity
Good luck,
Latexman
RE: High Viscosity
Fluid mechanics considers a viscous fluid as that whose viscosity is sufficiently large to make the viscous forces a significant part of the total force field in the fluid.
RE: High Viscosity
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: High Viscosity
RE: High Viscosity
RE: High Viscosity
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: High Viscosity
BigInch and Latexman (vide supra) rightly underscored the relativity of viscosity values. Even water, with 0.89 cP at 25 Celsius, is considered a high-viscosity fluid when referred to its molecular weight. Compare with pentane having 0.23 cP at the same temperature. The comparative anomalous high cohesivity of water is attributed to hydrogen bonding.
RE: High Viscosity
See,
Sixty-three Anomalies of Water
http://www.lsbu.ac.uk/water/anmlies.html
Actually surpirzing we can drink the stuff.
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: High Viscosity
I currently have a problem with a customer that told me their product was about 8000 CPs, and I sized the pump and suction line accordingly. The engineer that I worked with has moved on, and the new engineer was researching his flow meter selection. I talked him into letting me test the product, and....it's actually closer to 30,000 Cps! It's a short discharge line so I'm very close to acceptable on that end, but the suction conditions and inlet side of the pump are never going to work. The good thing is that nothing is installed yet so they can take the one black eye and modify it before they installed everything and have it not function correctly.... then they would really take a beating.
Bottom line is ALWAYS pay attention to the viscosity. I hate surprises...and they can be VERY expensive.
RE: High Viscosity
I hope the shear rate was varied, and then the shear rate profile reversed, during the test to determine if the product is Newtonian, non-Newtonian, and/or time dependant.
Good luck,
Latexman
RE: High Viscosity
Low Viscosity = 0 - 500 SSU (~100 cps)
Most Centrifugal pumps start to have serious degredation of Flow, Head, and efficiency over 500 SSU. The rule of thumb is over 500 SSU = don't use a centrifugal pump. Now before I get people started, I know that you can use a centrifugal pup at higher viscosities it is just not typically practical.
Medium Viscosity = 500 - 20000 SSU (~100 - 4300 cps)
This viscosity range is outside of typical centrifugal applications but can be moved by most all positive displacement pumps. ie. Gear, Piston, Diaphragm, Screw, etc.
High Viscosity = >20,000 SSU (>4300 cps)
At these thicknesses if you have a glass full of the liquid and you turn the glass sideways you have to wait for the liquid to start pouring out. ;)
Here special consideration must be taken with the pump. Make sure the pump is large enough and running slow enough that it takes a bite of the fluid. For example, a gear pump may appear appropriate but when running the gear teeth just push the fluid back instead of taking a bite out of the liquid. Valves in piston & diaphragm pumps need additional time to seat before pump reverses it's stroke. Pumps will need to be oversized, slowed down and/or specialty pumps such as Progressing cavity or peristaltic pumps may be required.
2,000,000 cps is the highest pumpable viscosity that I have ever seen a pump rated for. That's about the viscosity of chunky peanut butter. Anything thicker than that.... get a shovel.
Hope this helps.
ThePumpGuru
RE: High Viscosity
I did an application about 3 years ago pumping some recycled gum...customer claimed it was 4,000,000 Cps....and it was the most nasty thick stuff I have worked with. The pump was turning about 8 rpm, and taking .75 gallon per rev.
RE: High Viscosity
BigInch
http://virtualpipeline.spaces.msn.com