Idler Rolls Research Articles

Belt Rotation in Pipe Conveyors: Failure Mode Analysis and Overlap Stability Assessment

Pipe conveyors provide sustainable solutions for environmentally sensitive or topographically complex powdered and bulk-solid handling processes; however, belt rotation is among the most critical failure modes of these equipment, influencing engineering, operational, and maintenance activities throughout the conveyors’ lifecycles. Position changes in the overlap are mechanical responses to uneven contact forces between the vulcanizing rubber belt and the idler rolls, owing to the highly nonlinear process of the belt folding from a trough to a tubular shape, and no method for quantifying the belt’s stability is currently available. In this study, we analyzed the failure mode of belt rotation and proposed a linearized model of an overlap stability index to evaluate the resilience of the overlap position through a case study of a short-flight curved pipe conveyor. Our proposal considers an interference model between the simulated torque of a curved flight in a pipe conveyor and the calculated torque of its equivalent straight flight by using kernel-smoothed density functions. It is adapted to incorporate adjustment factors for the filling degree based on simulations, the effect of the overlap in the forming force of the belt, the remaining useful life of the belt, and the coefficients of friction between the belt back cover and the idler rolls due to adhesion and hysteresis. An application was developed to calculate the belt’s rotational holding torque and rotary moment by processing real operational data, simulated contact forces, and the relevant equipment parameters. This analysis identified the reduced transverse bending stiffness and increased belt tension forces as the root causes for position changes with a loss of contact in the upper idler rolls of curved flights 10, 13, 15–16, and 17. The contributing factors included spots of augmented contact forces during the initial stages of the belt lifespan in curved flights 15–16, which presented unstable conditions due to increased opening forces, with an OSI of 0.8657. Furthermore, we proposed corrective and preventive action plans, an optimized replacement interval for the belt, and recommendations for design changes according to the relevant standards.

Abrasive wear resistance of idler roll polymeric materials

Idler rolls are an integral part of belt conveyors. Recently, steel idler rolls have been replaced with polymeric ones in low to middle load applications, bringing several advantages due to the polymer’s lightweight and low abrasiveness in the conveyor belt. However, using polymeric material for high load application brings challenges, particularly presenting similar structural and abrasion resistance to steel. This work puts forwards a methodology using a rubber-wheel tribometer to evaluate the abrasion resistance of polymeric idler rolls in their most severe operating condition (halted idler roll) and defines a threshold limit based on the results obtained with steel idler rolls. The methodology was applied to 07 different polymeric materials. To further understand materials abrasions resistance, scratching tests were performed, and the main wear mechanisms, verified by scanning electron microscopy (SEM) and abrasion factor (FAB), were discussed along with the material properties. The main conclusions are: i) some polymeric materials present abrasion resistance similar to steel rolls; ii) the wear micromechanisms, verified by SEM and FAB, are good indicators of abrasion resistance of the materials but insufficient because they do not include temperature and fatigue effects resulting from multi abrasive events; iii) the additive fillers significantly altered the abrasive resistance of materials, although they do not change the material properties significantly.

Research in placement of measuring sensors on hexagonal idler housing with regard to requirements of pipe conveyor failure analysis

In order to ensure ecological transport without failure requirements for the transport of bulk materials by continuous conveyor systems, careful attention should be given to the proper shape of the conveyor belt which is provided by positioning the idler rolls in the idler housing of the pipe conveyor. This paper presents the research on idler housing contact forces (CF) at the cross-section of the loaded conveyor belt filled up to 37.5% and 75%, resulting in a multiple linear regression model in the form: CF = β0 + β1TF + β2M + ε, where TF is the tension force and M is the material filling volume. Based on it, the relative changes of the contact forces were subsequently processed. From the analysis obtained, the position of the most suitable placement of the strain gauge contact force sensors on the idler rolls is proposed, in view of the timely detection of the warning values for failure analysis.

Research about influence of the tension forces, asymmetrical tensioning and filling rate of pipe conveyor belt filled with the material on the contact forces of idler rolls in hexagonal idler housing

Reliable operation of the pipe conveyors requires continuous monitoring and evaluation of their selected indicators. Asymmetrical tensioning of the conveyor belt is the serious negative and undesirable operational situations. There is still remaining without answer one important question, namely it is the question whether such improper kind of the tensioning is able to cause changes of the contact forces and in such a way also to influence negatively the processes of conveyor belt wearing or if the asymmetrical tensioning has a relevant impact on the contact force values. The main task of this article is to analyse relations among the tension force values, asymmetrical tensioning and filling rate in the cross-sectional area of the piped belt, which is filled with the material, with regard to the values of the contact forces that are acting on the individual idler rolls arranged in the hexagonal idler housing of the pipe conveyor.

Prediction of contact forces on idler rolls of a pipe conveyor idler housing for the needs of its online monitoring

Pipe conveyors are currently widely employed in continuous transport of raw materials. Contact forces on idler rolls of an idler housing represent an important parameter to be monitored in the process of online operational monitoring. Operational tension force cannot be reached during the experimental research performed on laboratory conditions with regard to construction of the testing equipment. It is impossible for the current experimental rig. The main objective of the manuscript is to monitor dependences of contact forces on tension forces in individual idler rolls of a pipe conveyor idler housing. The manuscript output is in form of contact forces’ prediction for respective idler rolls for two more rates of tension forces and two cases of measurements: with and without material load.

Experimental research on condition monitoring of belt conveyor idlers

Belt conveyor systems are widely used in bulk material handling and transport applications. Within a belt conveyor, depending on its distance, there can be tens of thousands of idler rolls which face random failure. However, condition monitoring solutions for belt conveyor idlers is underdeveloped. This is because the choice of monitoring parameters is still arbitrary. This paper aims to investigate which parameters can represent technical condition of idler rolls for the purpose of condition monitoring. A belt conveyor test rig is developed in laboratory. Temperature and vibration sensors are applied to monitor idler rolls induced with different types of failures. Patten of temperature evolution and RMS level of vibration are extracted from the signal and analysed. It is concluded that temperature measurement at roll shafts is a straightforward and effective manner for condition monitoring of belt conveyor idlers.

Online monitoring of pipe conveyors part II: Evaluation of selected operational parameters for the design of expert system

Abstract Online monitoring of pipe conveyors operation is a key condition to their operational reliability. According to Molnar et al. (2016), the parameter to be used for evaluation is the change of contact forces on the idler rolls of hexagonal idler housing of a pipe conveyor. However, the statement itself is not enough for online monitoring purposes. Evaluation criteria in form of evaluation gauge enabling the identification of processes occurring in the conveyor belt need to be set followed by adequate measures taken afterwards. The paper aims to review the courses of contact forces at various tension forces since these are the parameters convenient for tracking of pipe conveyor operation. For better independence of results and conclusions, the measured values are transformed with the use of min/max method of standardization and then modified by moving averages. Experimental tests are evaluated with the use of basic statistics methods, correlation and regression analysis. The outputs include analysis of contact forces and time dependence, contact forces and tension force dependence for two different measurements, with and without material.

Measurement and simulation of the bulk solid load on a conveyor belt during transportation

This article presents findings from a research program to investigate the interaction between bulk solids and a conveyor belt during transportation. The research involved measuring and simulating the loads acting on a conveyor belt during transportation for a number of bulk solid materials and belt sag ratios. Laboratory experiments and simulations on a moving belt conveyor were undertaken, where the pressure acting on the surface of the belt due to the interaction with the bulk solid was measured for the first time using Tekscan® pressure sensors. The experimental results are compared to existing theoretical methods and to simulations undertaken using the Discrete Element Method (DEM). Good correlation between the measured experimental data and the simulations was found, with the outcomes leading to improved methods to calculate loads on conveyor idler rolls and increased accuracy in predicting the energy loss due to the bulk solid flexure.

The indentation rolling resistance of spherically profiled idler rolls

The energy loss due to indentation rolling resistance in a conveyor belt system can account for up to 60% of the total power usage. It arises due to an asymmetric pressure distribution as a viscoelastic belt cover is indented by a rigid idler roll. This causes a retarding moment on the idler roll, dependent on the load, speed, idler diameter and the properties of the conveyor belt cover. As pouch conveyor systems become more prevalent in industry, the supporting structure, and thus the indentation rolling resistance of such systems is of importance. These designs typically employ curved belt profiles, or spherical idlers in order to aid belt tracking and closing. From this, a spherical indentation into a generalised Maxwell backing is modelled, and compared with experimental values. In addition to this, the strain dependency across the contact is investigated.

Rotating Resistance of Belt Conveyor Idler Rolls

The primary function of idler rolls in a belt conveyor system is to support the conveyor belt along its length. Predicting the cumulative resistance of idler rolls is vitally important in calculating the belt tension and therefore power requirements of a system, particularly on long overland conveyors where there are typically more than one thousand idler rolls per kilometer of belt. The rotating resistance occurs due to the friction of the rolling elements in the bearings, the viscous drag of the lubricant, and the friction of the contact lip seals. This paper provides theoretical methods to calculate each component of the rotating resistance and describes an apparatus designed to measure this resistance force under simulated operating conditions.

Measurement of a pipe belt conveyor contact forces and cross section deformation by means of the six-point pipe belt stiffness testing device

This paper presents an experimental study that investigated the influence of major pipe conveyor parameters, such as pipe diameter, belt width, transverse bending stiffness, line mass and position of the belt overlap on the load distribution between the individual idler rolls, as well as the ability of the belt to form a stable pipe. The measurements were conducted using a static six-point pipe belt stiffness testing device. The results confirmed that bigger pipe diameters require higher bending stiffness to ensure the belt forms a stable pipe. The pipe diameter can be changed by either varying the length of the overlap, or by selecting a different belt width and keeping the ratio pipe diameter versus the belt width constant. More flexible belts require larger overlap for stable pipe shape. If the ratio belt width versus pipe diameter is constant for all manufactured belt widths, higher stiffness is needed for wider belts.

Monitoring of dependences and ratios of normal contact forces on hexagonal idler housings of the pipe conveyor

Contact forces, which are induced due to a reciprocal contact between the conveyor belt and forming idler rolls during a current operation of the pipe conveyors, are influencing the operational characteristics of these conveyors significantly. Despite of frequent application of the pipe conveyors, the question of contact forces is neglected relatively. This paper analyses closely the contact force values and their dependence on tensional force in order to identify mutual relations taking into consideration the selected factors.

Influence of tension force asymmetry on distribution of contact forces among the conveyor belt and idler rolls in pipe conveyor during transport of particulate solids

Contact forces among the conveyor belt and conveyor idler rolls are playing an important role because they are relevant factors during transport of particulate solids by means of the pipe conveyors. The contact force values are influencing significantly the global operational characteristics of the given transport system. There are changing force conditions in the conveyor belt during transport of material using the pipe conveyors. From this reason it is necessary to investigate and to analyse an impact of the conveyed particular solids on the contact force values. There is described in this article an influence of the transported material (i.e. particulate solids) on the contact force values in combination with their asymmetry during conveyor belt tensioning. There were investigated five measuring points loaded with a symmetrical and asymmetrical tensioning of a specimen section of the pipe conveyor transport belt, using the Friedman test. The Friedman test was calculated separately for the factor asymmetry with setting of tension force and separately for the factor tension force with setting of asymmetry.

Analysis of asymmetrical effect of tension forces in conveyor belt on the idler roll contact forces in the idler housing

This paper analyses an impact of asymmetrical tension forces, which are occurring in the conveyor belt, on the contact forces in the guiding idlers. It describes causes of an increased wear-out of the conveyor belts due to an asymmetric tensioning of the transport belt. There were investigated five measuring points loaded with a symmetrical and asymmetrical tensioning of a specimen section of the pipe conveyor transport belt, using the Friedman test for the factor of asymmetry. The tension force determines also changes of the contact force layouts in the individually investigated idler rolls. A newly developed method was applied in order to identify states of the particular experimental phases for the process of the transport belt tensioning and relaxation. This method is based on differences of the contact force time behaviours. It is possible to present a hypothesis, taking into consideration the obtained results that a side slipping of the running conveyor belt is caused by the tension force asymmetry also on the real operational conditions.

Mathematical models for indirect measurement of contact forces in hexagonal idler housing of pipe conveyor

This article presents creation and verification of linear regression models intended for prediction of the pipe conveyor belt contact forces on the idler rolls in the hexagonal idler housing. This problem is solved for using the method of indirect measurement, which enables to specify other required parameters with certain desired calculation accuracy on the basis of one monitored parameter. There is defined an initial hypothesis, which consists in assumption that it is possible to determine the contact forces in all other guide idler rolls according to detection of the contact force in one guide idler roll. The obtained models are corresponding with real operational conditions. The main advantage of these models consists in a fact that they have been created according to the real experimental measurement. The results presented in this paper are useful for the real practice because they enable to arrange such position of the guide idler rolls in the hexagonal idler housing, which is easy accessible not only with regard to the mounting of it, but also taking into the consideration safety, as well as which is suitable for installation and service of the measuring equipment.

A regression model for prediction of pipe conveyor belt contact forces on idler rolls

The paper presents design and verification of regression models for prediction of pipe conveyor belt contact forces on idler rolls. Their advantage is in the fact that they have been created according to the real experimental measurement. The obtained models correspond with real operational conditions. The concept of the experimental rig at the Technical University of Košice is designed so that it represents 8m long section of pipe conveyor. The conveyor belt is an object with action of tension force and at the same time it takes the initiative in the contact force formation. Several criteria have been used to verify the presented regression models. The tensioning force 9000, 12,000 and 15,000N have MPE of prediction error less than 5%. About 120,000 measured values have been processed during the evaluations which correspond to approximately 15,000 results from experimental measurements.

Calculating the Flexure Resistance of Bulk Solids Transported on Belt Conveyors

AbstractBelt conveyors are used extensively in the mining and mineral processing industries to transport bulk solid. As industry demands arise and conveying technology improves, belt conveyor installations are becoming progressively longer and belt speeds significantly faster. With longer conveying distances it becomes increasingly important to accurately calculate the motion resistances at the design stage, with the view of minimising these resistances to improve the efficiency of the installation. The motion resistances that occur along the length of the conveyor are known as the main resistances and include the belt and bulk solid flexure resistance, the rotational resistance of the idler rolls and the indentation rolling resistance of the conveyor belt.

Cross-Sectional Shapes of Corner Zones of Hexagonal Steel Pipes Formed by Extroll-Forming Mill with Expanding Inner Idler Rolls

To improve the cross-sectional shapes (outer curvature, wall thickness change) of the corner zones of hexagonal steel pipes (168.0, 170.0 and 173.0 mm wide, STK400) formed by an extroll-forming mill, an expanding-type forming tool with six idler rolls is introduced into the groove of No. 1 grooved rolls to impose peripheral bending on the portions of the round pipes (outer diameter D0 = 190.7 mm, wall thickness t0 = 4.6 mm) that correspond to the corner zones of the finished products. Characteristics of the cross-sectional shapes of the corner zones of the hexagonal pipes are investigated with respect to the nose radius of the inner roll and the degree of corner bending by the inner rolls, and compared with the results obtained by conventional extroll-forming. The results show that a hexagonal steel pipe with a small outer radius at each corner zone can be manufactured using a pair of inner idler rolls with a small nose radius.