Sharpe Mixers Meets with U.S. Secretary Gary Locke

In 2004, Sharpe Mixers participated in then Governor Gary Locke's "Governor's Mission to China". The trip was a success and paid immediate dividends as Sharpe quickly became a leading provider of fluid-gas desulferization absorber mixers in China.

Now holding the title of U.S. Commerce Secretary, Locke recently returned to Washington state to discuss the progress of the president's National Export Initiative. A select handful of small and medium-sized business owners from the Seattle area were invited to his keynote address and a roundtable discussion. Amongst the attendees was our CEO/President, Jay Dinnison.

Dinnison said, "I was honored to have been included in this small roundtable discussion with Secretary of Commerce Gary Locke. Sharpe Mixers received help on several occasions in years past when he was Governor Locke of Washington State, and he remembered us as one of the success stories from his Trade Mission to China in 2004. He also met with one of our customers in 2005 to help seal a pending order that was key in our success in China. Sharpe Mixers has since sold around a thousand mixers into China and continues to do business in the region."

He further explained, "Secretary Locke was visiting Seattle to discuss President Obama’s National Export Initiative and get input from businesses on how to better serve this purpose. He explained that US manufacturing exports have increased 22% in the past year; showing that President Obama’s goal of doubling US exports over the next five years is currently on track. I made a number of contacts at the meeting and received information on how to further promote Sharpe Mixers in other countries as well. While I can’t say our exports have increased recently as a direct result of this initiative, there is no disputing that Gary Locke’s assistance in the past has resulted in many millions in business for us overseas. Sharpe has also seen an increase in business in 2010 as a result of Obama’s American Recovery and Reinvestment Act; a welcome boost to our business which had seen a drop after the financial meltdown in 2008. I am very excited for the future of Sharpe Mixers under the current administration."

Shear vs. Viscosity

What is shear vs. viscosity?

A Pascal second is 1,000 cp (most viscosity is reported as mPs; milli Pascal seconds these days) So 0.5 Pascal seconds is 500 cp

Inverse second is the shear rate. So this result would imply that the viscosity is shear dependent (non Newtonian)

By taking a minimum of three readings of viscosity at different shear rates we calculate the shear rate dependence using the least squares method of curve fitting. As the relationship is exponential it can be plotted on log/log and calculated for any shear rate. Note that we use different spindle speeds for this method, we know (or can calculate) the so called shear rate constant for the known geometry of the specific spindle. Also note that only cylindrical spindles can be used for this method because the geometry is well defined. Disc spindles are not appropriate.

For mixer design the “apparent” viscosity is dependent on the impeller speed and the impeller’s own shear rate constant. Although Sharpe has not determined the shear rate constant for our impellers we do use published values, which are fine as the margin of error is no big deal when working with power law fluids.

For the HF218 the constant is 10

For Axial it is 11

For anchors and double helix it is 20

So the “apparent” viscosity of a HF218 at 350 rpm would be determined from the viscosity vs. shear rate at a shear rate of 350rpm/60 X 10 = 58/sec

Baffle recommendations need to be determined at low shear rates (as at the tank wall the viscosity is by definition infinite; the shear rate would be zero and dividing the shear stress by zero is infinite)

Typically a shear rate of 2/sec is used for baffle design. In most cases baffles need to be small or not used. For example a lime slurry may have a viscosity close to the tank wall of over 10,000 cp. Standard baffles for this would simply create dead zones and effectively reduce the tank diameter for mixing by the baffle width x 2. So for stuff like fruit slurries (ketchup, pop tart fillings, etc.) with very high “shear thinning index” on center, no baffles, slow speed to minimize cavity formation is the correct design.

By Jeremy Higginson, P.E.
Direct of Engineering

RD Dry-Running Mechanical Seal Update

In our original post about our dry-running RD seal we mentioned that the next generation would be fully ASME BPE compliant as a standard, unlike seals from other manufacturers: http://sharpemixers.blogspot.com/2009/07/next-generation-dry-running-mechanical.html. We introduced new grades of elastomers for specific use in high end biopharm applications. These elastomers meet or exceed the requirements of USP grade materials. The seal elastomers have the following properties:

• Available in EPDM (standard), FPM (Viton®^a equivalent⁾, Silicone, & FFPM (Kalrez®^a equivalent⁾.



• Full traceability



• Properly postcured



• Contain no ingredients derived from animals



• Free from melamine and mercury



• Complies with the FDA Code of Federal Regulations for rubber and rubber-like materials under Title 21, Paragraph 177.2600.



• Complies with the 3-A Sanitary Standards for rubber and rubber-like materials used as product contact surfaces in dairy equipment, number 18-03, Class II.



• Compound has passed testing in accordance with the current USP section <87> and <88> Class VI – 121°C or ISO/AAMI/ANSI 10993-5, 6, 10 and 11.

The seal has gone through some design changes as well to better meet the requirements of BPE:

· The ID of the debris well is tapered for drainability.

· The debris well flush ports are angled for drainability.

· Debris well gasket has been replaced by an o-ring which mounts close to the flange hole.

· Heat number for wetted metal parts are etched on the parts.

· Silicone Carbide (standard) and Tungsten Carbide static faces are available, as well as Hastelloy® ^b C-276 & AL-6XN®^c metal parts.

· Various finishes, including electropolish & passivation are available.

a - Viton® & Kalrez® are the registered trademarks of DuPont Performance Elastomers.

b - Hastelloy® is a registered trademark of Haynes International, Inc.

c - AL-6XN® is a registered trademark of Allegheny Ludlum Corp.