Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

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; , TU Delft / 3mE / TT / LT.