C.R.J. Versteegh
Design of a belt scraper test facility
Masters thesis,
Report 2006.TL.7041, Transport Engineering and Logistics.
Material escaping from belt conveyor systems is an everyday occurrence in
many plants. This 'fugitive' material arises as spillage or leakage at
transfer points. Left unchecked, fugitive material creates a drain on
conveyor efficiency, productivity and profitability. One of the methods to
minimize the amount of fugitive material is the application of special
engineered belt cleaning equipment. During the years, multiple belt cleaning
systems have been developed, but a universal belt cleaner, that performs
well and maintenance free for a long period in every condition, is still not
developed.
More insight and knowledge in the key parameters of belt cleaning system can
be used to improve the functioning of the future designs. In industry,
however, key parameters like belt speed, loading conditions or moisture
content of the bulk solid material change inherent to the industrial
process. This frustrates effective research on belt cleaning systems, and
gave motivation for Prof. A. Roberts of the Australian based 'Centre of Bulk
Solid & Particulate Technology' (CBSPT) of the University of Newcastle, and
B. Law of the Australian based engineering company 'ESS Engineering Services
& Supplies' (ESS) to start a research project, that concerns the
performance of belt cleaning equipment, with particular interest in belt
scraper equipment that is used in the Australian coal handling industry. The
first step in this research project is to design, manufacture and commission
an experimental test facility that enable the measurement of the performance
of belt scraper systems in respect to their wear rate and cleaning performance.
This test facility is developed in cooperation with Delft University of
Technology, Faculty Mechanical, Maritime and Materials Engineering, Section
Transport Engineering and Logistics. This research project starts with an
analysis of different aspects from literature concerning key parameters
influencing the performance of belt cleaning system. The design of the test
facility is split in three phases. First, a conceptual design is established
through the formulation of criteria extracted from literature. In this phase
design tools, such as morphological schemes, multi criteria analysis and
sensitivity analysis are applied. Second, the conceptual design will be
translated into a structural design that is manufactured. Third, a
commissioning phase will define if the test facility performs according to
the established criteria, and possible modifications will be implemented.
Finally, a number of test series will completed the first step of this
overall research project. This research project was done in the research
environment of TUNRA Bulk Solids Research Associative, which is situated at
the University of Newcastle, Newcastle, NSW Australia.
This test facility allows for the independent control of key parameters
enabling research opportunities that are not possible in industry. The test
facility also provides the possibility to determine the optimum solutions for
specific operating conditions found in industry. Costumers have the
possibility to simulate their particular operating condition. This research
project will be concerned with research to the performance of belt scraper
system, with special emphasis on the cleaning performance and wear rate of
belt scraper. The test facility is initially setup for underground coal mine
conditions. The bulk solid material, that is processed, is coal in wet,
slurry like, condition.
The basic design of the test facility consists of three main systems. First,
the belt conveyor system that transports bulk solid material from A to B by
rotating an endless rubber belt over two pulleys. The belt has a carry
strand where the bulk solid material is loaded on, and a return strand that
takes the belt back form the discharge area to the loading area. Second, the
belt scraper system that removes adhered bulk solid material from the carry
strand of the belt. These belt scrapers are basically a number of blades
adjoined on a shaft and connected to a tensioning device that presses the
scraper blades against the belt surface. This system contains two scraper
types that are positioned consecutive against the belt surface near the
discharge area of the belt conveyor system. The primary scraper is the
workhorse of the two and removes mainly coarse material. The secondary
scraper is very effective in removing the fine "left-over's" of the total
amount of adhered carryback material. Third, a recirculation system that
collects the scraped off bulk solid material and subsequently distributes
this material again on the belt of the belt conveyor system. The key
components of this system are a storage bin that is positioned underneath
the belt cleaning system and collects the bulk solid material. A slurry
pump, connected to the storage bin, transporting the bulk solid material
upwards to a bin that is positioned above the conveyor system and distributes
the bulk solid material back on the carry stand of the belt.
The cleaning performance of a belt scraper is measured by the amount of
carryback on the belt surface after it passed the belt scraper. This level
is measured using a semi-automatic carryback gauge. This carryback gauge
scrapes off the residual carryback. The carryback removed is weighted and
presented as a carryback value per unit of belt area. The wear rate of the
belt scraper blades is measured by weight loss in a set time interval.
During a blade wear test the blades are periodically removed from the test
facility, cleaned and dried. Subsequently the loss of weight and the
dimensions of the contact area of the blade are measured. This contact area
is used to calculate the contact pressure between blade and belt. Other
system variables such as belt top cover wear, belt temperature, particle
size distribution and moisture content of the bulk solid material are
monitored either continuously or periodically within the test facility. This
test facility provides the possibilities to test different blade scraper
designs with different operating conditions like varying belt speeds,
moisture contents, different bulk solid material or different belt types.
The results of the carryback test series performed with primary scrapers
correspond with other results found in literature. No conclusions on the
result of the blade wear test series on the primary scraper are presented at
this stage. The poly urethane primary scrape blades that were tested are
hygroscopic, and during the test series the blades were not sufficiently
stabilized for temperature and humidity disrupting correct weight measurements.
A major degradation of the recirculating bulk solid material was found. This is
caused by the pump's high number of revolutions in combination with the limited
volume of the recirculation system. This can be largely overcome by installing
a larger pump that provides more displacement with reduced pump revolutions,
and a periodically replacement of the bulk solid material.
With this project the first step of design, manufacture and commissioning of
a test facility that enables testing on the performance of belt scraper has
been completed successfully. For further research it is advised to setup an
extensive test program that allows for the measurement of the performance of
different types of belt scrapers. Also the blade dynamics have to be included
in this test program.
Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2006.10.22;
logistics@3mE.tudelft.nl
, TU Delft
/ 3mE
/ TT
/ LT.