Improving fire safety and asset loss control in mining: Evaluation and development of a video based fire detection system

Abstract

The overall results of this research addressed the question of how increased time for mineworkers to evacuate mines prior to the onset of untenable fire conditions is achievable. Additionally, improved asset loss control for underground mining is feasible through the successful development of Video Based Fire Detection (VBFD) in mining, as it provides more information earlier for mine fire fighters to intervene in the growth and spread of fire, therefore maintainable coal production is achievable. VBFD may also be used to activate automatic fire suppression systems. VBFD is an emerging volume type smoke detection technology that utilises Closed Circuit Television (CCTV) cameras to capture and analyse real time video data for the purpose of smoke recognition. VBFD technology performance was compared with the performance of fire detection methods currently used in underground coalmines to determine whether valuable improvements to fire safety and asset loss control could be made. Increased available safe evacuation time for mineworkers and a longer available time to extinguish fires earlier in their growth stage were considered the primary measures of success. The scope of this research included three main studies: a. Proof Of Concept (POC) tests; b. Detailed Experiments; and c. Field Testing. The initial trials successfully demonstrated the capability of VBFD to detect small coal fires associated with fixed plant installations in a low light simulated mine environment. Encouraged by these findings, detailed experiments were developed and subsequently applied at the Safety In Mines Testing and Research Station (SIMTARS) experimental facility at Redbank, Australia. The experimental plan involved 54 individual fire test experiments that recorded the level of Carbon Monoxide (CO) concurrent at the VBFD alarm activation time. Sensitivity analysis was undertaken by varying the air velocity over the fire source, which affected the smoke plume shape. The other component of the sensitivity analysis involved variations in light levels aimed at testing the VBFD smoke detection sensitivity. The data were subsequently analysed to identify trends in the detection response of both the CO sensors and the VBFD. Some of the tests carried out exceeded the capability of the VBFD system, which was an important aspect in the research and the evolving capability of video smoke detection. The experimental fire characteristics were subsequently replicated numerically using Computational Fluid Dynamics (CFD) so it could be used in this research to estimate the evacuation response of mineworkers under more onerous fire conditions, which could not physically be undertaken in an operational mine. A following VBFD field study was proposed to review and utilise the results of installation commissioning data and maintenance testing of a VBFD system at an operational underground mine environment. The purpose of this field-testing was to inform the underground mining industry of limitations that may exist in terms of the VBFD reliability in service, such as potential maintenance issues. During the period of the subject research the Australian resources industry moved from being in a position to readily facilitate and support minor external unfunded research projects within its underground mine assets, to its current position where it was no longer willing or able to assist. As a result of the lack of a trial VBFD system in an underground mine, the subsequent field study opportunistically considered the reliability and performance of VBFD in a very similar and related environment, however this facility was not an underground mine, but a South African coal fired power station. The results of the reliability testing of 360 VBFD devices over a 12 months’ period showed that VBFD was very reliable. Future VBFD research might address two aspects. Firstly, VBFD may be used to detect flames or smoke. Whilst coal handling plant fires typically manifest during their early stages of growth as smouldering fires, other fixed plant fires have the potential to produce flames from the outset. Underground refuelling stations and transformers exhibit this phenomenon, so flame detection capability is possible and should be explored. In this research, VBFD CCTV cameras were of a very basic functionality. They were simple, relatively low cost devices operating in the visible light spectrum only. Secondly, the use of high resolution “mega pixel” cameras with the capability to operate in very low light levels should be researched. It was found that VBFD offers considerably faster response to visible smoke plumes than other forms of fire detection currently used in underground coalmines. In terms of VBFD reliability, it was more resistant to contamination from mine pollutants than typical commercial ‘point type’ photoelectric or ionisation smoke detectors. It was shown in the research that significant improvements in fire safety and asset loss control in underground mining can be made through the application of VBFD for early fire detection of fixed plant fires.