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Aiming at the problem in measuring the nonuniformly distributed pressure generated by the pipe belt conveyor when conveying raw coals, a hexagonal adjustable pressure measuring device for the idler group is proposed. The dynamic model of the pipe belt conveyor clamping-type roller group is established. In order to simplify the calculation process of mechanical analysis, the modal analysis is carried out to determine the factors which will influence the pressure. The pipe diameter and filling rate are selected as the key control factors by the sensitive analysis of pressure of the pipe belt conveyor clamping type roller group. An adjustable diameter-type supporting roller group experiment device is self-designed, and the dynamic pressure change of the roller group and each roller pressure are tested. The results show that the average error between the simulated and tested values of the pressure of the idler group at different filling rates is 7.3%; the theoretical and simulated values of the pressure of the idler group are in good agreement with the experimental values. The study provides a theoretical basis and experimental reference for the design and application of pipe belt conveyors.

Nowadays, countries around the world are shifting towards a development model highlighted by green ecology and low carbon [

The conveyor belt of the pipe belt conveyor is guided by the idler [

However, many of the above studies were just focused on the no-load conveying of the pipe belt conveyor, but the conveying of raw coal and other materials was not taken into account. In this paper, a pressure testing device for the hexagonal adjustable idlers was proposed to solve the difficulty in measuring the nonuniformly distributed pressure generated by the pipe belt conveyor when conveying raw coals. Moreover, a mechanical model of the bottom-type idlers of the pipe belt conveyor was established. Then, the sensitivity analysis on the factors influencing the pressure of the idlers was completed to reduce the workload of the mechanical analysis of the idlers. The main control factors were then found based on the weighting to be the pipe diameter and the filling rate. Finally, the conclusions of the theoretical analysis were verified through a series of simulations and tests.

The 16.7 km pipe belt conveyor developed by the project team in 2019 has been successfully applied, as shown in Figure

The pipe conveyor.

As shown in Figure

Clip-type bottom roller material element diagram.

The conveyor belt’s total pressure _{i} (

It can be concluded from the aforementioned equations that idlers of the pipe belt conveyor are subject to three forces, including belt lateral pressure _{li}(_{ci}(_{gi}(

As can be seen in equations (_{b}, width of the conveyor belt

In engineering design, design sensitivity is often defined as the derivative of structural response obtained by design calculation with respect to a design variable. That is, a structural response represents structural response function _{i} at a specified design point _{i}:_{i}. The absolute value of _{i}; the greater this value is, the more sensitive to _{i} the function _{i} must be very small. However, in practical application, difficulties in changing different design variables by same values vary, while difficulties in changing optimization variables by same percentages are basically the same. For example, when the material density is large and the pipe diameter is small, changing the material density by 0.1 is easier than changing the pipe diameter by 0.1. Therefore, this paper proposes the concept of pressure weight of idlers and takes this weight as the basis for optimizing parameters.

For any multivariate differentiable function, the following equation can be derived using Taylor’s expansion:

The partial derivative term in equation (

After the weight vector _{1}, _{2}, … , _{n})^{T} is defined to make it become the percentage of function value corresponding to any one variable to total function value, the weight can be expressed as

In optimization design, the pressure of idlers is usually the implicit function of various optimization design variables and can be expanded according to equation (

As can be seen in Figure

Simulation diagram. (a) Sensitivity of the structural parameters on the pressure of the roller group. (b) Weight of the structural parameters on the pressure of the roller group.

The analysis results show that the variable that has a great effect on the pressure of idlers is pipe diameter and material filling height. Therefore, final optimization variables are determined to be pipe diameter and material filling height (filling rate).

The difficulty of separation of raw coal and mixed gangue after mining is increased due to the nonuniform particle size. Therefore, it is necessary to crush a large amount of raw coal and gangue before transportation by the pipe belt conveyor. In general, a jaw crusher can be used to crush large coal gangue to 18–48 mm [

Simulation process.

Tables

Pressure value of the roller group at 60% filling rate.

150 mm | 180 mm | 210 mm | 240 mm | |
---|---|---|---|---|

Measuring area no. 1 | 49 N | 58 N | 73 N | 107 N |

Measuring area no. 2 | 30 N | 40 N | 69 N | 79 N |

Measuring area no. 3 | 17 N | 19 N | 18 N | 20 N |

Measuring area no. 4 | 9 N | 12 N | 13 N | 15 N |

Measuring area no. 5 | 7 N | 11 N | 19 N | 30 N |

Measuring area no. 6 | 38 N | 65 N | 74 N | 131 N |

Pressure value of the roller group at 75% filling rate.

150 mm | 180 mm | 210 mm | 240 mm | |
---|---|---|---|---|

Measuring area no. 1 | 69 N | 72 N | 103 N | 132 N |

Measuring area no. 2 | 29 N | 41 N | 70 N | 79 N |

Measuring area no. 3 | 10 N | 49 N | 52 N | 60 N |

Measuring area no. 4 | 17 N | 19 N | 40 N | 51 N |

Measuring area no. 5 | 14 N | 21 N | 30 N | 35 N |

Measuring area no. 6 | 51 N | 60 N | 97 N | 139 N |

This test was set up on a self-designed hexagon pressure testing device with adjustable pipe diameter, which consists of 6 linear feed guides, 6 pressure sensors, 1 external eight-way signal transformer, and 1 eight-way paperless recorder, as shown in Figure ^{3} and thickness of 4 mm.

Test device. 1, pressure transducer; 2, linear feed guide; 3, conveyor belt; 4, bracket; 5, signal transmission line.

During the test, signals of 6 pressure sensors were detected within 150 mm∼250 mm of pipe diameter at no load, 60% or 75% filling rate, and full load. Then, the pressure sensor’s signals under different pipe diameters were obtained with the paperless recorder and computer, and the relevant data were processed with signal processing software [

Schematic diagram of experimental test. 1, pressure transducer; 2, conveyor belt; 3, linear feed guide; 4, signal processor; 5, paperless recorder; 6, PC.

Six pressure sensors’ signals at no load, 60% or 75% filling rate, and full load were researched and analyzed by processing the test data with MATLAB numerical analysis software, as shown in Figure

Pressure diagram of the roller group under different pipe diameters: (a) no load, (b) 60% filling rate, (c) 75% filling rate, and (d) full load.

Figures

The pipe diameter is set at 150 mm. Table

Comparison of simulation and test results.

Pressure simulation (N) | Pressure test (N) | Error (%) | ||
---|---|---|---|---|

1 | 60% | 49 | 54 | 9.1 |

75% | 69 | 70 | 1.5 | |

2 | 60% | 30 | 32 | 6.7 |

75% | 29 | 32 | 9.4 | |

3 | 60% | 7 | 7 | 0 |

75% | 10 | 11 | 9.1 | |

4 | 60% | 9 | 10 | 10 |

75% | 17 | 19 | 10.5 | |

5 | 60% | 8 | 9 | 11.1 |

75% | 14 | 15 | 6.7 | |

6 | 60% | 38 | 40 | 5 |

75% | 51 | 56 | 8.9 | |

Average error | — | — | 7.3 |

From Table

Pressure comparison of theoretical, simulation, and test rollers.

In this paper, a pressure testing device for the hexagonal adjustable idlers was proposed to solve the difficulty in measuring the nonuniformly distributed pressure generated by the pipe belt conveyor when conveying raw coals. Moreover, a mechanical model of the bottom-type idlers of the pipe belt conveyor was established. Then, the sensitivity analysis on the factors influencing the pressure of the idlers was completed to reduce the workload of the mechanical analysis of the idlers. The main control factors were then found based on the weighting to be the pipe diameter and the filling rate. Finally, the conclusions of the theoretical analysis were verified through a series of simulations and tests. The specific conclusions are as follows.

The mechanical model of the pinch-bottom idler group of the circular pipe belt conveyor is established by using the microelement method. In order to reduce the workload of mechanical analysis of the idler group, the sensitivity analysis of mechanical model of the idler group is carried out, and the pipe diameter and filling rate are obtained as the main controlling factors of the pressure of the idler group.

Self-designed test is used to simulate the stress of the hexagonal roller group, and the force distribution of the hexagonal roller group and the dynamic force diagram of the hexagonal roller group under different filling rates are obtained. Comparing the force simulation value with the test value of the hexagonal roller set shows that the average error between them is only 7.3%. The research provides theoretical reference and experimental basis for the design of raw coal conveying of the circular pipe belt conveyor.

The data used to support the findings of this study are available from the corresponding author upon request.

The authors declare that there are no conflicts of interests regarding the publication of this paper.

Shuang WANG conceptualized the study; Shuang WANG and Deyong LI formally analyzed the results; Shuang WANG and Kun HU obtained the funding; Deyong LI wrote the original draft.

This research work was supported by the National Natural Science Fund Project of China (grant no. 51874004), Nature Science Research Project of Anhui Province (grant no. 1908085QE227), and Graduate innovation fund of Anhui University of Science and Technology (grant nos. QN 2018101 and QN 2018116).