5/22/2008

CUSTOMER CHALLENGE: How Do I Mix Different Viscosities?

BROOKFIELD ANSWERS: We know from experience that mixing fluids, even viscosity standard fluids which are 'Newtonian', does not have a convenient formula for combining specific volumes to come up with a known viscosity. It's a matter of trial and error to experimentally determine what works and then using that recipe going forward.

Submitted by: Russ

5/13/2009

CUSTOMER CHALLENGE: I would like to know if there is a way to give one single viscosity measurement for a non-Newtonian solution (ie. this solution has a viscosity of this) without constraining it a specific shear rate. I was thinking of using the coefficient of thixotrophy (slope of the viscosity-1 verse rate of shear graph) but don't know if there is a better or easier way.

BROOKFIELD ANSWERS: There isn't one "universal" measurement that can be used to describe a particular non-Newtonian material's rheology, to the best of my knowledge. However, as long as you clearly identify your experimental procedure, including the Brookfield viscometer's/rheometer's Spring Torque Range, Spindle and Speed, temperature, time before reading, etc., then others may be able to reproduce your results.

Submitted by: anonymous

3/2/2008 1

CUSTOMER CHALLENGE: "How can I evaluate storage stability?"

BROOKFIELD ANSWERS: Storage stability can be evaluated by testing retained samples periodically using an up-down speed or shear rate ramp. The test data provides a "flow curve" showing viscosity vs. shear rate. This signature curve will shift downward over time if the sample becomes"thinner", which implies that suspensions are settling out. If the curve shifts upward, the sample is "thickening", which implies that fluid is possibily escaping or evaporating. In either case, performing the same test each time is important to observe whether the viscosity data is changing.

Submitted by: Robert from New Jersey

2/26/2008

CUSTOMER CHALLENGE: "How Can I Understand the Rheology of a Fluid?"

BROOKFIELD ANSWERS:

The preferred method used by Brookfield to understand the rheology of a fluid is to perform an up-down speed or shear rate ramp with the viscometer. The data from the test provides a "flow curve" which characterizes how "shear thinning" the material is. For most materials,viscosity decreases as shear rate increases; this type of behavior is called "pseudo plastic".

Customers can do this test themselves or send a sample to us for evaluation. Please call or email if we can be of further assistance with the materials that you are evaluating.

Submitted by: Sook from New Jersey

4/25/2008

CUSTOMER CHALLENGE: "How do I get consistent readings from Batch to Batch - cooking soups, sauces, beans, gumbo, etc?"

BROOKFIELD ANSWERS: The key is to measure viscosity using a spindle and rotational speed that can provide meaningful data. Formulations like gumbos have lots of food chunks; the vane spindle or T-bar spindle should be used running at low rotational speed (usually less than 10rpm). Soups which are homogenous can easily be measured with standard disc spindles between 10 and 100rpm; if there are other ingredients like pieces of vegetables, you may want to consider the vane spindle again. Sauces require the same scrutiny, although the traditional method has more often been the T-bar spindle for thicker formulations like mayonaisse. The method for consistency is to measure each batch and record viscosity readings that must fall within a predetermined range for acceptability.

Submitted by: Gardere from New Jersey

5/22/2008

CUSTOMER CHALLENGE: How can I better understand the Viscosity of Material Being Pumped?

BROOKFIELD ANSWERS: ANSWER: Understanding the viscosity of the material being pumped can help you to properly specify a pump for a given situation. Engineering firms use standard calculations to evaluate pressure head across the pump, volume flow rate, viscosity considerations, etc. If the material is unusual inany respect, it may be beneficial to run a viscosity flow curve on the material to get a precise picture of how it behaves. If we can be of assistance, we have an office in Harlow, Essex in the UK that I can put you in touch with.

Submitted by: Roger from the UK