An armoured face conveyor (AFC) is a chain conveyor, which is used in the longwall mining process to transport material from the coal face. The integrity of the AFC chain is a critical factor in determining the reliability of the AFC and maintaining the efficiency and profitability of a longwall mine.
This thesis argues that the dynamic behaviour of an AFC drive has a significant influence on the tension in the AFC chain, and is therefore critical in determining the reliability of the chain and the entire AFC system. There are currently two drive types widely used to power the AFC; the fluid coupling and the controlled slip transmission (CST) drives. This thesis explores the dynamic behaviour of both drive types and their effect on chain tension using a computer model of the AFC. This work was undertaken in two parts.
The first part involved the development of the equations of motion of common AFC components, such as the asynchronous motor, fluid coupling, gearbox, CST, chain sprocket, and the chain assembly. The equations governing the forces applied to the chain and the process of loading the extracted material onto the AFC, were also developed.
In the second part of this thesis the dynamic model of the AFC was implemented on a computer program. The computer simulation was used to study the performance of the fluid coupling and CST drives under different loading scenarios. Inter alia, it was found that:
1. Critical performance parameters of the model can be found using a series of system identification tests, which can be carried out on the target system in one shift.
2. After these system identification tests have been performed, the model is a good predictor of the steady-state behaviour of the target system.
3. The dynamic behaviour of the drives has a significant effect on chain tension when the load applied to the chain rapidly increases.
4. When the chain is jammed, the CST drive produced lower chain tensions than the fluid coupling drive.
5. To prevent adverse chain tensions during a chain jam, it is necessary to fit the fluid coupling drive with a torque limiter.
6. The fluid coupling and CST were both effective in limiting the torque applied to the motors when a large developing load (i.e a blockage) was applied to the chain.
It was found that the tension applied to the chain by both drive types, was a result of the torque applied by the motors and the inertia of the drive components. For a fluid coupling drive that is not fitted with a torque limiter, the inertia of the drive components contributed significantly to the total tension in the chain.