Hi-Track/SEBS Continuous Haulage System

This project set out to redesign the Scott enclosed belt system (SEBS), in conjunction with the HiTrack support system, for underground coal mine applications. This project focused on three primary objectives:

· To develop a Fire Resistant and Anti-Static (FRAS) belt formulation adequate for underground coal transportation;

· To engineer the 400 series SEBS to operate on a reduced diameter discharge drum; and

· To engineer the 400 series SEBS to operate on a reduced diameter tension wheel.

A methodology was invoked to address each of these objectives in parallel and then to tie them together by incorporating them into a working demonstration system as a means to prove the systems longevity with the modifications made.

Results from engineering the belt segments to handle a smaller diameter discharge drum and tension wheel suggested that by altering the J-Section design a tighter diameter was achievable. Initial works began to construct both a small scale cyclic test jig and a larger scale test system to prove the modifications. Whilst no long term system or high cycle testing eventuated, the workshop static testing was successful.

Results from FRAS testing a number of iterations of polyurethane (PU) were not successful. Whilst there was a great deal of confidence from the PU supplier and other industry experts, the likely formulations were successful in passing only four of the five FRAS test components.

Given the unsuccessful FRAS results, a stop was placed on the project and further guidance from ACARP sought. It was decided to continue the project using the remaining budget with modified objectives. The new objectives became:

· Develop a rubber variant of the Scott enclosed belt from a known FRAS rubber compound in a 160 series (given that a 160 series system was available to trial the rubber);

· Trial the rubber belt variant to evaluate if FRAS rubber was a viable alternative to PU.

Nepean Rubber was engaged to assist with development of the required moulding, process and selection of rubber. A 160 series belt was successfully manufactured.

A set of ten belts were installed into an "around the clock" operational system in Melbourne. Four of the ten belts were manufacture with re-enforcing similar to the PU belt design and the remaining six were manufactured without any re-enforcing as it was believed this would be more reliable and exhibit more desirable performance characteristics.

Immediate results revealed that the four belts without re-enforcing displayed excessive elongation. This elongation is a problem for the Melbourne based system as it has (by design) restricted travel on its tension wheel mechanism. It is believed that elongation would not be as critical if the system had been built with a larger travel. However these four were removed and the six re-enforced belts remained in the system.

At the time of writing this report the six re-enforced FRAS belt segments have been successfully in operation for six months. The visual condition of these belts looks good compared to PU belts of the same age. There are some notable characteristics that differ from the PU belt product that effect the performance of the belts in the system. Belt elongation variation with temperature effects the overall elongation of the system and can create issues with the system in Melbourne due to a limited tension wheel travel. Rubber belt co-efficient of friction appears to be higher than PU and can cause belt segments to track (to a greater extent than the PU) on rollers that are not correctly aligned. The spreading and reforming of the rubber belts at the load station and discharge station appears smoother and quitter than PU and there is very little creasing of the belt at the tension wheel when compared to PU.

None of these characteristics prevent the system running and it is speculated that the less desirable characteristics could easily be eliminated by further tuning the rubber formulation. It is still noted that these characteristics would need to be taken into account if moving to implementing a new system with entirely rubber belts.

To progress this work the following steps could be considered:

· Take no further action; or

· Develop an 400 series belt based on the learnings from the smaller 160 series FRAS belt and the work done in engineering the belt segment to accommodate tighter operating diameters;

· Undertake official FRAS certification of the 400 series FRAS rubber belt variant;

· Construct a short above ground 400 series system that contains the smaller diameter components and a series of turns and gradients that can be used to a) confirm the scaled principal of an 400 series FRAS rubber belt and b) longevity test the 400 series FRAS rubber belt;

· Construct a program to trial an 400 series FRAS rubber belt underground.