International Conference on Trends in Industrial and Mechanical Engineering (ICTIME'2012) March 24-25, 2012 Dubai
Design and Development and Calibration ofan On-board Weighing System for an Industrial Wheel Loader A. F. Kheiralla, Abbas Eltigani, Mohamed Musa, Ahmed Osman Elzaki,Mohamed Hamed the weight that a truck is carrying. The weight of the payload, including the weight of the truck, is measured by first driving the truck onto the weighbridge; this weight is referred to as the gross weight. To obtain the weight of the payload (the net weight), the tare weight (the weight of the empty truck) must then be subtracted from the gross weight. Worldwide various weighing system have been design, developed, and patented. Buckingham and Franklinville [2]patented weighing apparatus for lifting equipment. Their invention related to generally lifting mechanism having apparatus for weighing lifted loads and more particularly for weighing loads on forklift trucks. Wise et al. [3] developed load weighing system for lift trucks and the like. Their invention relates to hydraulic weighing scales and more particularly to a hydraulic weighing system for installation upon a fork lift truck or the like to enable a load to be weighed at the same time as it is lifted by the truck fork. Bradley [4] patented deformation responsive weighing apparatus for measuring applied loads. His system comprised a straight, longitudinal bar of uniform circular cross section which was elastically deformable in response to loading, the bar being retained by bar supporting members adjacent to the end of the bar. Statweigh India Pvt. Ltd. [5] commercialized on-board weighing system for wheel loaders and on-board dumper weighing system (GUARD–53) which consisted of a very high capacity pressure transducer fixed to the inlet port of the vehicle's lifting cylinder. Chromium in the Sudanwas first reported in the occurrences of Pod form chromite early in the 1930s. Small-scale mining of the ore has been in progress since the 1950s. At present Sudan produces around 40 000 MT of chromite annually. One of the most target areas for chromium, according to their potentialities, available information and access was Ingessana Hills Area. The Ingessana Hills area of the Blue Nile State lies about 80 km SW of Ed Damazin, the state capital. The location of the Ingassana area, the good infrastructure, and the rich Savanna-subtropical climate encourage investment and may lead to an ore successful mining industry in the future. In the Ingassana Hills area the mining company mining chrome ore in the form of large blocks with concentration up to (5060%) and is exported directly. The wheel loaders are essential for quarries, transfer stations, mines and remote sites at Ingassana, Blue Nile to perform loading cycles. The practice involve loading trucks with filled parcels ranging in capacity from 1 to 1.5 MT after
Abstract—Thispaper presents thedesign, development and calibration of an on-board weighing system for an industrial wheel loader to provide on-the-go weighing for trucks. The system sensing elements were based on three locally made load pins transducers replaced the existing pins between the wheel loader arm and the bucket. The design concept of the transducer was based on longitudinal uniform circular cross section pin which is elastically deformable in response to load from bucket. Each pin is being fixed by pin supporting members of wheel loader arm adjacent to the ends of the bar. A load applying member from the bucket is located on the pin between the pin supporting members. Electrical resistance strain gauges were mounted on pin load and arranged into a full bridge constant current, and interfaced to data acquisition system via host computer. Statics calibrations test on the pin load transducer showed high accuracy of linearity between applied load and output volt with coefficient of correlation (R2) equal to 0.993. The transducer measurement accuracy are within acceptable range limit with measurement errors no more than 0.7% and 1% of the measured magnitudes under static and dynamic measurements, respectively. Based on the obtained results, it is recommended that the developed weighing system should be incorporated on the wheel loader and to be field tested in the actual harsh mining environments.
Keywords —Data
acquisition system; Strain gauges; Wheel loader;
Weighing system.
I. INTRODUCTION
T
CREDIBLE weight system is essential for any industry using the measurement of weight as a benchmark for sale of a product.Weighing systems can take several forms but the most common design includes one or more load cells that support a platform, a junction box, and a weigh controller. When a weight is applied to the platform, a portion of the load is transmitted to each load cell. Each load cell sends an electrical signal to the weigh controller via the junction box which sums the signals from a number of cells. The weigh controller converts the summed signals to a weight reading [1]. One of the most common weighing systems used in the bulk transportation industry is the weighbridge. Weighbridges are used throughout the world as a way of quickly assessing Abdelmotalab F. Kheiralla is the Head of the Agricultural Engineering Department, Faculty of Engineering, University of Khartoum, P. O. Box 321, Sudan (phone: +249-923212871; e-mail:
[email protected]). Abbas Eltigani, andMohamed Hamed are with the Agricultural Engineering Department, Faculty of Engineering, University of Khartoum, P.O. Box 321, Sudan(E-mail:
[email protected]). Mohamed Musa, Ahmed Osman Elzaki are undergraduate students of the Mechanical Engineering Department, Faculty of Engineering, University of Blue Nile. P.O. Box 143, Elrosseris, Sudan.
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International Conference on Trends in Industrial and Mechanical Engineering (ICTIME'2012) March 24-25, 2012 Dubai
that they were transported to Port Sudan and shipped outside for export. The type of loading task varied between different sites and between different machines at the same site. The loading cycles tended to be long in duration, usually between 5 to 10 minutes carrying weight of 2 MT to 3 MT including the bucket. To date there are no onboard weighing system incorporated to wheel loaders for loading trucks with this valuable chromium ore. For contractors with multiple remote sites or operators with remote location weighing system can store and record the data for loaders. On-board weighing system for a mining wheel loader to provide on-the-go weighing for trucks in Ingassana mines is badly needed. Such system allows loader operators to successfully and accurately load trucks to needed capacity eliminating load adjustments and safe money and time compared to the stationary weighing system. Especial weighing system need to be developed to allow loader operator with accurate load needed without stopping the loader or bucket to capture weight. This optimizes the amount weighted during loading and reduces trips to a central scale, consequently avoids costly under-loads and materials loss due to overloads.
The objective of this paper was to design, develop, and calibrate an on-board weighing system for a mining wheel loader to provide on-the-go weighing for trucks. The works involve: - To design and develop a load pin transducer to be incorporated between wheel loader arms and bucket. - To calibrate and validate the developed load pin transducer via data acquisition system and host computer on a loading frame in the laboratory. II. MATERIAL AND METHODS A. General Description This chapter describes the design and development and calibration of an on-board weighing system for a mining wheel loader to provide on-the-go weighing for trucks. The proposed system sensing element was based on three locally made pins transducers replaced the existing pins between the wheel loaders and the buckets and interfaced to data acquisition system on-board of the wheel loader. Fig. 1 depicted the common practice of wheel loader while loading the trucks with chromium parcel. Fig. 2 depicted the location of the replaced pins on the wheel loader.
Fig. 1 Typical industrial and mining wheel loader during loading practice
Fig. 2 The proposed location of the load pin transducer on the wheel loader
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International Conference on Trends in Industrial and Mechanical Engineering (ICTIME'2012) March 24-25, 2012 Dubai
The Overall criteria of the proposed on the–go weighing system for the industrial and mining loader were: - The load pins transducers are locally made. - Pins transducers are completely integrated to the wheel loader - The system can be easily moved from loader to loader. - The system allows loader operators to accurately load trucks, rail cars or vessels to optimum capacity, - The system eliminate load adjustments at the outbound scale - The system gives perfect solution for straight weighing applications where only weight information is required. - The simple read-out provides in the real time plus data handling capability. - The weighing system is dynamic allowing loading with high accuracy without stopping the loader or bucket to capture a weight. - This optimizes the amount weighed during loading, reduces trips to a central scale, and avoids costly underloads and material loss due to overload.
Fig. 3 Dimensions of the proposed pin transducer (All dimension in mm)
B. General Description of the System The on-the-go weighing system for industrial and mining wheel loader was based on three load pin transducers replaced the existing pins that where attached between wheel loader arms and the bucket. The design of the transducer was based on longitudinal uniform circular cross section pin which is elastically deformable in response to load from bucket. Each pin is being fixed by pin supporting members of wheel loader arm adjacent to the ends of the bar. A load applying member from bucket is located on the pin between the pin supporting members. Electrical resistance strain gauges are mounted on the pin to measure the deformation of the pin, and measuring circuitry detects the changes in electrical properties of the strain gauges caused by loading to provide a measurable response indicating the magnitude of the load. These strain gauges are arranged in a full bridge circuit and interfaced to the data acquisition system. Fig .3 illustrates the principal dimensions of the load pin transducer. Fig .4 illustrates the arrangement of loading pin between support and loading member for calibration. The block diagram shown in Fig .5 illustrates the load pin transducers and its associated data acquisition system.
Fig. 4 Load pin transducer arrangement between support and loading member for calibration
Lower left Transducer
C. The Load Pin Analysis and Design: The design formulae of the load pin were originally based on analytical equation extracted from Hearn [6].Consider the load pin as a uniform beam, of flexural stiffness EI, and length L, which is fixed to both end supports C and G (Fig 6). Suppose a concentrated vertical load W is applied to the beam at a distance afrom C. If M C ,and M G ,are the restraining moments at the supports, then the vertical reaction is at Cis as follows (Hearn : 𝑎𝑎
1
𝑎𝑎
Data logger
1
Host computer
W �1 − � + (𝑀𝑀𝐶𝐶 − 𝑀𝑀𝐺𝐺 )W �1 − � + (𝑀𝑀𝐶𝐶 − 𝑀𝑀𝐺𝐺 )(1) 𝐿𝐿
𝐿𝐿
𝐿𝐿
𝐿𝐿
The bending moment in the beam at a distance z from C is therefore𝑧𝑧
