A Simple Method for Estimating the Driving Resistance of Rubber Conveyer Belts by Using a Self-traveling Roller

Transcription

1 Applied Mechanics and Materials Online: ISSN: , Vol. 330, pp doi: / Trans Tech Publications, Switzerland A Simple Method for Estimating the Driving Resistance of Rubber Conveyer Belts by Using a Self-traveling Roller Shinya KINOSHITA 1, a, Kazuya OKUBO 2,b and Toru FUJII 2,c 1 Graduate student of Doshisha University, Kyoto, Japan 2 Department of Mechanical Engineering, Doshisha Univ. 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto, Japan a dtl0340@mail4.doshisha.ac.jp, b kokubo@mail.doshisha.ac.jp, c tfujii@mail.doshisha.ac.jp Keywords: conveyor belt, simple estimation method, driving resistance, carrier roller Abstract. The purpose of this study is to provide a simple method for estimating the driving resistance of rubber conveyer belts. The driving resistance of a rubber belt running on the carrier roller was estimated by a resistance force acting on a roller moving on the rubber conveyer belt while the belt was fixed on an aluminum channel. Four types of conveyor belts were tested to confirm the present technique is useful for grading rubber conveyer belts from a viewpoint of energy dissipation on the carrier rollers of the conveyer system. The effects of normal force acting on the roller and driving speed of the roller on the resistance force were investigated. Four belts were fabricated with different rubber types of rubber, respectively. It was confirmed from the experiments that the estimated resistance force varied with respect to the rubber characteristics, which was consistent to the experience from the existing belt conveyer systems for energy consumption. The resistance force of the carrier roller increases with an increase of roller speed. It also decreases when a lower damping rubber is used while the belt rigidity does not affect the resistance force when low resistance rubber is used. The proposed method is applicable to estimate the total energy loss of rubber conveyer belts on the carrier rollers. Introduction Rubber belt conveyer systems are widely used in the world as a massive transportation system [1,2]. Belt conveyors are, in most cases, the most cost-effective solution to handle bulk material mass flows over short and medium conveying distances [3]. The use of conveyors can decrease the workload in mines considerably, reduce investment in capital construction, shorten construction periods and generate marked social and economic benefits [4]. Due to their advantages, belt conveyors are also used in other industries, such as in natural resource processing, smelting, cement and lime production, pulp and paper productions, sea and river ports, civil engineering, agriculture, sugar factories, power plants and others [5]. In late years, a large size of belt conveyor for long-distance transportation was needed by increasing distance of mining site. The power loss of the belt conveyor system increases with an increase of the distance of it. Then, the power loss becomes the most important issue for long distance conveyor belts. The energy loss of the conveyer belt is directly related to the driving resistance occurring when passing the carrier rollers. Generally, the driving resistance related (=the power loss) is evaluated at the belt convery site under the belt conveyer operation because any substitutive test methods have not been well established in laboratory scale while some methods may have been focused to reduce the power loss. A simple method for evaluation of the driving resistance of conveyor belt, other words, resistance force acting on a carrier roller is required in the laboratory. The purpose purpose of this study is to provide a simple method for estimating the driving resistance of rubber conveyer belts. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-08/04/16,22:09:36)

2 Applied Mechanics and Materials Vol Testing Machine and Specimen Testing Machine. The driving resistance (=resistance force) occurs when the rubber belt runs over the carrier roller. If the belt is completely elastic, no energy is theoretically dissipated on the roller as long as no slip occurs. Due to some energy loss occurs if the belt rubber has viscoelastic deformation characteristics due to hysteresis. The resultant resistance force parallel to the belt running direction acts on the carrier roller. Therefore, the reaction force of the carrier roller is measured, and simultaneously the resistance force can be estimated. In the practical conveyer system, carrier rollers are fixed, and the rubber conveyer belt is moving on the roller while payloads are transported. Instead of the running belt, a carrier roller is moving on the belt while the belt is fixed on the flat plate. Details are given below. Specimen. Commercially available conveyor belts were used in the study. Fig.1 shows the dimensions of rubber belt samples used. Rubber belts consist of rubber and canvas. They have three plies. Four types of canvas conveyor belts were used. Belts types and their differences are shown in Table 1. Nominal hardness for rubber was used to identify the belt rigidity, Standard (A60) or High (A65). Two different types of rubber were used, designated by the terms Normal resistance and Low resistance. Fig.1. Dimensions of the rubber belt Table 1: Types of belt specimens. No. Rubber rigidity (JIS K6253) Resistance 1 High rigidity (65A) Normal 2 High rigidity (65A) Low resistance 3 Standard rigidity (60A) Normal 4 Standard rigidity (60A) Low resistance Testing Machine. Fig.2 shows the schematic view of the testing equipment to estimate the driving resistance due to the carrier roller. In this method, the driving resistance is determined by the resistance force acting on the testing roller moving on the rubber conveyor belt. The rubber belt is fixed on an aluminum channel while the guided roller is put on the rubber belt. The testing roller used here is consistent to the carrier roller of belt conveyers. To drive the device, a length of wire is attached to the plate on which two rollers are fixed. One is the testing roller while the other one is the guiding roller to keep the moving device parallel to the belt. It is pull by using an electric motor. Two stain gages were glued on both side surfaces of arms of the roller support. Those strain gages genrate the signal proportional to the resistance force. The contacting normal force to the roller is applied by a diaphragm air cylinder fixed on the plate, which corresponds to the conveyer load. An arbitrary normal force can be applied to the belt by adjusting the air pressure. The resistance force is measured while the moving device is constantly traveling on the aluminum channel. The roller speed was altered from 0.9 to 1.91 mm/min. The diameter of two steel rollers is 89.1 mm. The distance between two rollers is 150 mm.

3 276 Materials Engineering and Automatic Control II Fig. 2. Schematic view of a self-traveling roller device. Condition of Experimental Table 2 shows the test condition when different types of belts were tested. The roller speed was set to be constant and 0.9m/s. The contacting normal force was applied 31.25N. Table 3 shows the test condition when the contacting normal force was altered from to 41.75N. The roller speed was set to be constant and 0.9m/s. The test condition was shown in Table 4 when the roller speed was altered from 0.9 to 1.91m/s while the normal force was set to be constant and 31.25N. The sampling frequency for the data acquisition system was 5kHz. The normal force variation with respect to time was also measured to assure it was constant during test. At least three tests were conducted for each test condition. Table 2: Test condition when four belts were used (Test 1) Contacting normal force [N] Roller speed [m/s] Type of rubber belt Normal rigidity (Normal & Low resistance) High rigidity (Normal & Low resistance) Table 3: Test condition when the contacting normal force was altered (Test 2) Contacting normal force [N] Roller speed [m/s] Type of rubber belt 10.25, 20.75, 31.25, High rigidity (Normal & Low resistance) Table. 4: Test condition when the roller speed was altered (Test 3) Contacting normal force [N] Roller speed [m/s] Type of rubber belt , 1.15, 1.53, 1.91 High rigidity (Normal & Low resistance) Results and Discussion Resistance Force Variation Due to Belt type. Fig. 3 shows the comparison of resistance force among four rubber belts (Test 1). It is found from the figure that the resistance force for both low resistance belts (specimens No.1 and 3) were smaller than those of normal belts (specimens No.2 and 4) in spite of difference in rubber rigidity o the belt. These results show that the performance of the rubber conveyer belts for over-all resistance force due to belt driving could be well evaluated by the present method. Namely, the difference in power loss performance among rubber conveyer belts can be ranked. The total driving resistance may also be estimated by using the measured resistance force. Under this test condition, the belt rigidity would not be sensitive to the resistance force as long as low resistance rubber is used.

4 Resistance force acting on the roller [N] Resistance force acting on the roller [N] Applied Mechanics and Materials Vol Fig. 3. Difference of driving resistances of four types of belts. Influence of Contacting Normal Force on the Resistance Force. Fig.4 shows the variation of resistance force with respect to the contacting normal force obtained from Test 2. It is obvious that the resistance force increases with an increase of normal force for both cases. However, the resistance force increment with respect to the normal force is more significant for the normal rubber belt than the low resistance rubber belt. Consequently, the resistance force reduction ratio, shortly relative ratio which is the ratio between two resistance forces decreases at high normal forces. The relative ratio curve with respect to the normal force is downward convex, but more than 15% reduction in driving resistance force is obtained at 41.75N of the normal force, which means we may expect 15% power saving when this belt is used for long distance belt conveyers. In order to identify the performance of rubber conveyer belts for driving resistance, an appropriate contacting normal force should be applied to the roller for the test when the proposed method is used Fig. 4. Relation between Fig.4 Relation driving between resistance driving of two resistances different of two type different belts and type normal belts and contacting force normal contacting force. Influence of Roller Speed on the Resistance Force. Fig.5 shows the variation of resistance force with respect to the contacting normal force obtained from Test 3. It is obvious that the resistance force increases with an increase of resistance force for both cases. The resistance force increment with respect to the roller speed is same tendency. Consequently, the resistance force reduction ratio, shortly relative ratio which is the ratio between two resistance forces constants at high roller speed.this result shows that the resistance force is estimated by the proposed method without depending on the relative velocity between roller and belt.

5 Resistance force acting on the roller [N] 278 Materials Engineering and Automatic Control II Roller speed [m/s] Fig. 5. Relation between resistance force of two different type belts and roller speed Fig.5 Relation between resistance force of two different type belts and Conclusions roller speed. 1. The difference of driving resistance of conveyer belts caused by the carrier roller can be compared by the proposed method consisting of the moving roller when different type belts are used for the conveyer. 2. The proposed method is applicable to estimate the total energy loss of rubber conveyer belts on the carrier rollers. 3. The resistance force at the carrier roller increases with an increase of roller speed. It also decreases when a lower damping rubber is used. The belt rigidity little affects the resistance force when the low resistance rubber belt is used. 4. The resistance force increases with increasing the contact normal force as well as the roller speed. References [1] Krystyna Czaplicka: Eco-design of non-metallic layer composites with respect to conveyor Belts, Materials & Design, Vol.24 (2003), issue 2, pp [2] I. S. Lowndesa, S.A. Silvestera, D. Giddingsb, S. Pickeringb, A. Hassanb, E. Lester: The computational modelling of flame spread along a conveyor belt, Fire Safety Journal, vol.42(2007), issue 1, pp51-67 [3] HOU You-fu, MENG Qing-rui: Dynamic characteristics of conveyor belts, JOURNAL OF China University Of mining &Technology, Vol.18 (2008), issue 2, pp [4] Hou Youfu, Xie Fangwei, Huang Fei: Control strategy of disc braking systems for downward belt conveyors, Mining Science and Technology (China), Vol.21 (2011), issue 4, pp [5] Dariusz Mazurkiewicz: Analysis of the ageing impact on the strength of the adhesive sealed joints of conveyor belts, Journal of Materials Processing Technology, Vol.208 (2008), issue 2, pp

6 Materials Engineering and Automatic Control II / A Simple Method for Estimating the Driving Resistance of Rubber Conveyer Belts by Using a Self- Traveling Roller /