Underground » Detection and Prevention of Fires and Explosions
This project consisted of two phases. The first phase of this project sought to determine the feasibility of using non-destructive testing methods to evaluate the strength of ventilation control devices (VCDs) to withstand the required overpressures. The second phase critically evaluated recent technical changes, made by overseas testing authorities, to destructive type testing of VCDs to facilitate the design of a local facility.
The project set out to assist the evaluation of ventilation control devices for the purposes of compliance with the Queensland regulations and to ensure maintenance of the structure's integrity. There was a serious need for the establishment of a VCD testing station within Australia, as the only place where the full range of VCDs could be tested was in overseas galleries. Testing of ventilation control devices has, and continues to be undertaken, at significant cost and effort on the behalf of manufacturers while at the same time there is no established method whereby the integrity of devices already installed in the mine can be tested.
Due to the change in the legislation as well as the development of newer destructive methods throughout the world, the paradigm under which this project started, changed significantly after March 2001. This led to alternative methods of destructive testing being considered. During the period of the project the need arose for different performance criteria for other ventilation controls devices apart from seals to be investigated as well. These studies led to the establishment of a draft standard that specified different post-explosive performance criteria than that which was originally specified. All of these changes led to the need for the non-destructive testing of ventilation control devices.
In evaluating the possible methods of non-destructive testing, it was found that the most suitable method would be one that would provide an image of the internal conditions of the structure, as well as one that would give a comparative estimate of the material strength of the components of the structure. Such methods are capital intensive and require a high level of skill from the person that does the measurement. This makes the use of such equipment a costly exercise. Simpler and more cost effective methods were identified that could be used to determine the conditions of a structure although not at the same level as the imaging methods. Meanwhile, work conducted at the Lake Lynn facility in the United States as well as in South Africa, has proven the viability of innovative methods for the destructive testing of seals and other ventilation structures at low cost. The important outcome of this research work, is the understanding that for most practical designs of VCD, as long as the pressure is applied for a sufficient period of time, at least a few tens of milliseconds, it does not matter if it is hydraulic, pneumatic or explosive. These proven methods can then be used to specify a test facility design that could be used in Australia to test both high and low strength ventilation control devices.
A surface facility is preferred due to the flexibility would afford as well as the ability to be sited more favourably with regard to the required infrastructure. For one-off testing the use of an underground cavity has not been discounted but this option is not seen as an alternative to the surface facility. There appears to be at least two attractive approaches to the design of such a test facility. These are a freestanding installation, or an extension to the current TestSafe Explosions Gallery (Londonderry NSW). A freestanding facility has the advantage of flexibility of location. An extension to the TestSafe Gallery would have a cost advantage due to the utilisation of existing infrastructure and experienced VCD testing staff. Either design could enable test pressures to be applied via a range of methods.
The anticipated cost of such a facility could be up to a half a million dollars. Although it would generate considerable safety and economy benefits to the Australian mining industry, it is doubtful if the full cost of erecting such a facility could be recovered solely from testing charges.
It is foreseen that by using this specification and refining it to suit the site-specific requirements a cost affective alternative to overseas testing could be established in Australia.