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From Powder and Bulk.com

Ask Joe! ColumnFlow Properties Testing - Jenike Shear Testerby Joseph Marinelli, Solids Handling Technology

The picture that you see of me as Ask Joe on Powder and Bulk Dot Coms home page and above, shows

me holding something. Some people have told me it is a coffee cup, dish, etc. In fact, it is the bottom half of aJenike shear cell lled with corn grits. The Jenike Shear Tester is the device that is recognized as one of the

standards for testing bulk solids by ASTM (D-6128-97) in the US and in Europe.

Although there are additional means to characterize solids ow properties, the Jenike method has been scruti-

nized and perfected over the years and remains the preferred approach. It is classied as a direct shear tester

that is capable of providing information on a solids cohesive strength as well as its wall friction properties.

These are the two main considerations when designing a bin or hopper to ensure reliable material ow.

Our rst photograph (above) shows a Jenike Shear Tester, which is composed of a strip chart recorder that re -

cords a signal from a load cell located in the blue rectangular box (shear unit), mounted on the front. This unit

also contains a small motor that drives the load cell horizontally into a sample located on the stainless steel

circular base (shear cell not shown).

The second photograph shows a shear cell in place. Notice the protrusion

from the box that is the load cell stem. The shear cell is in two parts that al-

low the top to be sheared across the bottom, while a normal load is applied

by the weight hanger. A shear cover comes in contact with the load cell stemto provide the linear motion.

This test allows us to measure the strength of a bulk solid as a function of

pressure applied to it. This information is then used to determine the opening

size required to prevent arching and ratholing in a bin or hopper. In subse-

quent articles we will describe this evaluation in more detail. This test can

be run to simulate the affect of several environmental conditions on material

owability, namely, the affect of moisture, particle size reduction, tempera-

ture, and time of storage at rest. All these factors come into play when

evaluating a materials owability.

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The Jenike Shear Tester is also used to measure wall friction properties. From previous articles, you will

remember that friction is developed between a solid and the walls of a bin or hopper. This friction determines

whether the solid will slide on the wall (mass ow) or adhere to the wall and preferentially slide on itself

(funnel ow).

Our nal photograph shows that the bottom cell of the shear cell arrange-

ment has been replaced with a sample of wall material. The weight hanger

applies the load simulating pressures acting in a bin and shear force is

recorded as a function of this pressure. The information gathered duringthis test, results in a wall friction angle that is subsequently converted to a

hopper slope for mass ow.

The test procedure should not be considered simple, because it requires

constant practice to maintain skills. As well, the testing process can be time

consuming and as such, you should evaluate your testing requirements

before adding this type equipment to your laboratory.

Contact our author:

Joe MarinelliSolids Handling Technologies, Inc.

1631 Caille Ct.

Fort Mill, SC 29708

Phone: 803-802-5527

Fax: 803-802-0193

Email: joe@solidshandlingtech.com

Web site: http://www.solidshandlingtech.com

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Welcome to Ask Joe!, a monthly column by our resident materials handling guru, Joe Marinelli of Solids Handling

Technologies. Joe addresses the issues that bug you the most. And Joe knows!! Formerly with Jenike & Johanson,

Solids Flow and Peabody TecTank, Joe is an expert on materials handling.

For past articles, Ask Joe! Archived Articles.

Guest articles for the Ask Joe! Column are always welcome, for more information please contact Joe Marinelli directly at

his email address: joe@solidshandlingtech.com.

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