SUMMARY-Design and Development of Automated CERCHAR Abrasivity Index Apparatus For Measurement of Rock Abrasivity
SUMMARY-Design and Development of Automated CERCHAR Abrasivity Index Apparatus For Measurement of Rock Abrasivity
SUMMARY-Design and Development of Automated CERCHAR Abrasivity Index Apparatus For Measurement of Rock Abrasivity
Numerous tests used in identifying the rock abrasiveness exist which can
help in estimating wear. One of the widely used rock abrasion test is the
CERCHAR Abrasivity Index (CAI). This test is used for estimation of bit life and
wear in various mining, tunneling and drilling applications. The test is simple and
can be considered for field application. This apparatus will help in predicting the
wear of the drilling bit. It will also permit the optimal selection of bit, replacement
rates and scheduling maintenance and the life expectancy for the drill bit.
testing principle is based on a steel pin with defined geometry and quality that is
wear produced on the tip of the pin. The use of this test in various research
institutes has led to CAI being a standard parameter for hard rock classification.
measured worn flat diameters on the testing needle with the following equation:
𝑑
𝐶𝐴𝐼 = 10 ∗
𝑐
table below:
The main objective of the study was to design and develop an automated
materials.
The materials used for stylus was the standard alloyed cold-work tool steel
with a Rockwell hardness of HRC 55 and a conical tip angle of 90°. It should have
The rock samples were cut in cubical shape in order to execute the CERCHAR
test on a flat surface and should be held firmly in the vise clamp for no-slip grip
during the test. The rock specimen has a maximum width of 150 mm (6 in.) and
height of 76 mm (3 in.).
The rock samples used were sandstone, basalt, limestone, granite,
dolomite, and shale. The sandstone was collected from San Juan, Batangas. The
basalt and granite were from Mabini and the shale, limestone, and dolomite were
the operating load, operating time, operating speed and testing length. Six rock
samples were tested under 50 Newton, 70 Newton and 90 Newton operating load.
The speed used in testing were 300 rpm, 800 rpm and 1300 rpm. Each rock type
was tested under three different load and three scratching speed. The time it took
for the pin to reach the 10 mm standard distance was recorded as the operating
time. Upon evaluating the results, the parameters obtained were as follows; (a) the
operating load of the apparatus was 70 Newton; (b) the operating speed was 1300
RPM.
Diameter of tool wear and CAI values were the parameters included in the final
testing.
The results obtained using the apparatus were compared according to the
reference ranges of values of different kind of rocks according to Thuro et al. (2007)
The study provided an operational manual and maintenance manual for the
The process for the development of this study was first, the researchers had
to conceive the required knowledge about rock properties; second was the
development stage where they created a proposed design layout then automate
the new CERCHAR abrasion apparatus for rock abrasion considering proper
system components; next was the identification of different parameters that were
essential to the study on the said objectives. After fabrication, it was followed by
The output of this research was to automate the CERCHAR Abrasivity Index
(CAI) apparatus for measurement of rock abrasion with an operation manual that
would serve as a guide for proper use of the CAI apparatus. The operating
provcedures were derived based on the standard test method for laboratory
ASTM D7625. The automated CAI apparatus adopted the mechanisms to produce
reliable results.
of the prototype. Each system components were analyzed to meet the material
Dolomite, and Shale. Basalt is the hardest while the Shale is the softest. The rock
samples were cut into cubical shape to allow scratching on flat surface and to be
were the operating load, operating time, operating speed and testing length. Six
rock samples were tested under 50 Newton, 70 Newton and 90 Newton operating
load. The speed used in testing were 300 rpm, 800 rpm and 1300 rpm. Each rock
type was tested under three different load and three scratching speed. The time it
took for the pin to reach the 10 mm standard distance was recorded as the
operating time. Upon evaluating the results, the parameters obtained were as
follows; (a) the operating load of the apparatus was 70 Newton; (b) the operating
conduct the final testing to determine the diameter of tool wear and CERCHAR
Abrasivity Index (CAI) using a camera module. Six different rock types were
examined under three trials. The following results were obtained: For Basalt, the
average wear diameter produced by the pin was 0.3707 mm and CAI value of 3.7;
for Sandstone, the average wear diameter was 0.2520 mm within 6.65 s and an
average CAI value of 2.5 mm; for Andesite, the average wear diameter was 0.2517
mm, scratch time of 6.52 s and CAI value of 2.5; for Limestone, the average wear
diameter, scratch time, and CAI value was 0.1722 mm, 6.42 s, and 1.7,
respectively; for Dolomite, the average wear diameter was 0.1470 mm, average
scratch time of 6.30 s, and an average CAI value of 1.5; for Shale, the average
wear diameter was 0.0771 mm, average time of 6.10 s, and an average CAI value
of 0.77.
6. The higher the applied load, the higher the produced CAI will be.
Selection of the static load to be used in final testing was based on the consistency
of results at varying speed that satisfies the reference values. Effect of testing
length variation on CAI was also examined on six rock samples with dissimilar
hardness. It was observed that the significant amount of pin wear occurs at the
first 5 mm of the testing path. Only a slight quantity of wear was produced after the
standard distance of 10 mm. For Basalt, 63% of the pin wear occurred in the first
5 mm, both 69% for Granite and Sandstone, both 65% for Limestone and Dolomite,
7. Operation manual has been developed and provided for the future
works. The manual includes the step by step procedure starting from the
preparation of the sample up to the testing proper. Safety mechanism was also
conclusions:
2. By cutting the rock samples into cubical shape and maximum width of
150 mm (6 in.) and 76 mm height (3 in), the testing was successful and
the pin with hardness HRC 55 was more stable during scratching. The
rock sample was held firmly in place and can be easily fitted into the vise
clamp.
operating load and operating speed. Wear diameter and CAI values vary
from the applied load and scratching speed. The scratching time
depends on the operating load and the operating speed and also
increases the scratching time also increases. The harder the rock
sample the longer it takes for the pin to reach the standard scratching
distance of 10mm.
4. The diameter of tool wear and CAI values of rocks depend on the
samples.
5. When compared to the reference values, the CAI values were able to
satisfy the ranges of all six rock samples. Therefore, applied load of 70
N and 1300 rpm scratching speed were applicable to all the six rock
samples.
6. The applied load and scratching speed greatly affect the CAI produced.
increases. The significant amount of pin wear was produced at the first
5 millimeters of the testing length. The test on the effect of testing length