... for computer-controlled measurement of flow properties of powders and bulk solids (e.g. flowability, internal friction, time consolidation and caking, bulk density, attrition).
Suitable for measurements for product characterization and quality control, comparative tests, silo design.
The Ring Shear Tester RST Mk II is supplied with the renewed RST-CONTROL v3 measurement and evaluation software. The software is to be installed on a PC (Microsoft Windows® 7/8/10/11* operating system) that is connected to the ring shear tester via USB or RS-232. RST-CONTROL controls the ring shear tester and, if required, automatically measures flow properties (yield loci), wall friction, compressibility, time consolidation, and more. RST-CONTROL supports the preparation of the measurement with the help of step-by-step instructions, and it automatically evaluates the test results.
*) Microsoft Windows® 7, Windows® 8, Windows® 10, and Windows® 11 are registered trademarks of Microsoft Corp., USA
Generally, our Ring Shear Testers are delivered with a shear cell and a software package, so that different types of tests can be performed with this equipment, e.g. flowability tests (yield locus tests), time consolidation tests (caking tests), compressibility tests and attrition tests. For special applications, e.g. for time consolidation tests conducted on several samples simultaneously, for wall friction tests, and for tests with small powder specimens, we offer accessories as listed below.
The Ring
Shear Tester RST Mk II is generally delivered with one shear
cell type M. This shear cell is the "standard shear cell"
for this tester with a specimen volume of 900 ml. Thus, this
shear cell offers a wide range of application, especially if
not only fine materials, but also bulk solids with larger
particles (e.g. granulates) have to be tested. Since 2022, a
new design (shear cell M v2, picture below) has been
available that offers advantages in terms of cleaning and
weight.
Shear
cell type S (200 ml sample volume) corresponds in principle
to the shear cell type M, but its main dimensions
(diameter, height) are only 60 % of the main dimensions of
type M . Shear cell type S is advantageous if a lot of time
consolidation tests have to be run, because compared to
shear cell type M less sample material is required, and less
weights to adjust the consolidation stress are needed.
For applications where only limited amounts of powder are
available, the shear cells type MV10 and SV10 have been
developed. These shear cells correspond to shear cells type
M and type S, but with a reduced specimen height of 10 mm.
The XS shear cell has an even smaller volume. With its small cross-sectional area, it is intended primarily for achieving high stresses (see table). It is connected to the ring shear tester with an adapter (see picture below).
The
table below gives an overview.
| Name | Description |
|---|---|
| M | "Standard shear cell" with about 900 ml specimen
volume, cross-section about 220 cm² Maximum particle size depends on the type of powder and is about 10 mm for broad particle size distributions and 5 mm for narrow particle size distributions. |
| S | "Smaller volume": About 200 ml specimen
volume, cross-section about 85 cm² Maximum particle size depends on the type of powder and is about 5 mm for broad particle size distributions and 2.5 mm for narrow particle size distributions. |
| MV10 | "Small volume": About 220 ml specimen volume at
large cross-section of 220 cm² Maximum particle size depends on the type of powder and is about 2 mm for broad particle size distributions and 1 mm for narrow particle size distributions. |
| SV10 | "Small volume": About 85 ml specimen volume,
cross-section about 85 cm² Maximum particle size depends on the type of powder and is about 1.5 mm for broad particle size distributions and 0.75 mm for narrow particle size distributions. |
| XS | "Very small volume / large stresses": About 48 ml
specimen volume, cross-section about 32 cm².
This shear cell is intended to apply large stresses
on the specimen (maximum about 165 kPa). Maximum particle size depends on the type of powder and is about 1 mm for broad particle size distributions and 0.5 mm for narrow particle size distributions. |
For time consolidation tests in combination with the time consolidation bench (see above) weights are required for the adjustment of the consolidation load.
Available sizes:
2 kg, 1 kg, 0.5 kg, 0.2 kg, 0.1 kg, 0.05 kg.
Accuracy: min. +/- 1%
Dimensions: thickness 10 mm to 14 mm, other dimensions
depend on weight.
Weights are available as set or separately.
A time consolidation test examines how a bulk solid consolidates when it is stored at rest (e.g. in a silo or IBC). To measure this, the bulk solid specimen is first consolidated with the ring shear tester, then stored under constant load, and finally sheared to failure. All of this can be done automatically with the ring shear tester, without having to remove the shear cell with the bulk solid specimen from the tester. The disadvantage, however, is that the tester is blocked by this specimen. Therefore, the use of a time-consolidation bench for external storage is recommended.
When using a time consolidation bench, the specimen is consolidated with the ring shear tester, then removed from the tester and placed on a time consolidation bench. The consolidation stress is exerted on the specimen through weights. After the consolidation period is over (e.g., after some hours, a day or a week), the specimen is returned to the ring shear tester and sheared again to measure the strength of the consolidated powder. Thus, one obtains a quantitative result on the increase of strength during the consolidation time, which is known as "caking".
The
time consolidation bench without cover (type 1SM-O) serves
for the storage of one shear cell (type M, S or XS, maximum
load 15 kg). The consolidation load is transferred to the
powder specimen through a vertical loading system provided
with a plate on top on which an appropriate amount of
weights is placed.
The
time consolidation bench type 1S-O serves for the storage of
one shear cell type S ore XS (volume ca. 200 ml, maximum
load 15 kg). The consolidation load is transferred to the
powder specimen through a vertical loading system provided
with a plate on top on which an appropriate amount of
weights is placed. The design without cover allows a more
intensive contact between the powder specimen and the
ambient atmosphere. This is preferable if the behavior of
the powder in dependence on the ambient conditions has to be
studied, e.g. by storing the time consolidation bench with
shear cell and powder specimen in a climate cabinet or an
oven.
The
picture on the right shows the closed time consolidation
stand 1S-C. The shear cell, which is not visible on the
image, is located in the cylindrical protective container,
which serves to shield the shear cell from the ambient
atmosphere. Conditioned air or gas can be blown into the
interior of the protective container via a hose connection.
The 1S-C time consolidation stand is based on the 1S-O open
time consolidation stand, which is fitted with a protective
cover. Existing time consolidation stands of type 1S-O can
be converted to type 1S-C by adding the protective cover.
Wall
friction cells are required for the measurement of the wall
friction angle or coefficient of wall friction (friction
between a bulk solid and a wall material).
For
the test, an annular wall material specimen ("coupon") is
placed in the shear cell with the bulk solid specimen on
top, i.e., the bulk solid is located above the wall material
like on a hopper wall or a chute, which is absolutely
necessary in order to avoid underestimating the wall
friction angle in the case of segregating bulk solids. Wall
material coupons can be made by the customer according to
dimensions given in the tester's manual.
The picture above shows the current version of the wall friction cell (shear cell type WM v2), which offers advantages in terms of cleaning and weight. For fine-grained bulk solids (powders), there is an optional rough lid (picture below, principle as for the RST-XS.s ring shear tester) instead of the normally used lid with vanes/pockets which is preferable for coarse-grained bulk solids.
| Name | Description |
|---|---|
| WM | "Standard" wall friction cell, specimen volume
about 240 ml, outer diameter of the wall material
coupon about 215 mm. Optionally with rough lid for optimization for fine bulk solids |
| WS | Wall friction cell with specimen volume of about 95 ml, outer diameter of the wall material coupon about ca. 134 mm |