One of the tasks of the Working Party on the Mechanics of Particulate Solids (WPMPS) of the European Federation of Chemical Engineering has been to assess the reliability and reproducibility of measurements of the flow properties of particulate solids.
In 1979, J. Schwedes presented a survey of the various types of equipment used for measuring the flow properties of particulate solids and pointed out that the most widely used and versatile instrument for this purpose was the Jenike Shear Cell . The WPMPS therefore decided to investigate this measuring technique in more detail.
As a first step samples of a fine calcite powder were distributed to over 20 laboratories all over the world and in each laboratory the flow properties were measured using the Jenike Shear Cell available using the technique customary in that laboratory. A comparison of the measurements showed that there was some scatter in the results obtained.
After detailed analysis of all the experimental results it was concluded that for reliable measurements of the flow properties of particulate solids using the Jenike Shear Cell a standardised testing technique should be specified in sufficient detail to eliminate operator and equipment variation.
The only detailed description of the Jenike Shear Cell and its use is the manual prepared by Jenike & Johanson Inc., 'Flow Factor Tester and Consolidating Bench Operating Instructions (1979 version) . These operating instructions are only available on the purchase of a shear tester.
The WPMPS therefore set up a task group to draw up a Standard Shear Testing Technique (SSTT). Dr. A. W. Jenike provided further detailed instructions for operating the Jenike Shear Cell to aid the task group in its work. From these detailed instructions and the experience of members of WPMPS a new Standard Testing Procedure has been drawn up which in some details differs from that described in the Jenike and Johanson manual cited above.
Since a basic understanding of the principles of shear testing is needed for the reliable measurement of particulate solids flow, an introductory chapter 'Principles of Shear Testing' has been included as Chapter 2.
The present technique is based on the current state of the art but it is expected that the SSTT may need to be revised after further research. The SSTT is intended to help all those engaged in shear testing or who need to be acquainted with the technique. It is recommended that those who do not have practical experience should first attend a course on shear testing. Such courses are presented by several institutions and consulting companies.
Since the terminology used in discussing the mechanics of particulate solids is not completely standardised, the WPMPS drew up a Glossary of Terms on Storage and Flow of Particulate Solids which is included as an Appendix.