Underground » Maintenance
The risk of serious injury resulting from the uncontrolled release of high pressure hydraulic fluids is of ongoing concern in the longwall operations as there have been several fatal accidents and number of near miss incidents reported over the last 20 years. All mines must recognise the hazards associated with high pressure fluids and manage these hazards appropriately, as per:
- The Coal Mining Safety and Health Regulation 2001, S80 Fluid above and below atmospheric pressure; and
- The Mining and Quarrying Safety and Health regulation 2001, Part 10 Plant Generally.
In addition, individual mine's safety and health management system needs to identify all aspects of safely managing a high pressure fluid system. NSW MDG 41 - Guideline for Fluid Power System Safety at Mines is a valuable reference tool for developing site management plans and strategies.
This project is part of an ongoing ACARP research program aiming to assist the industry in risk management of longwall hydraulic system uncontrolled release of high pressure fluids. By way of background, the work program for ACARP project C17020, “Performance Based Specifications for Longwall Hose Assemblies” completed in 2012, included pressure measurements in longwall hydraulic circuits at Newlands Northern Underground (NUG) and Mandalong mines over a period of about one month. The results of these measurements revealed the presence of anomalous and significant pressure spikes in some longwall hydraulic circuits of Caterpillar shields at Newlands Northern Underground (NUG) mine . No such spikes were recorded at Mandalong.
It is important to develop a good understanding of the conditions under which these over pressurisation events can occur in practice. The industry monitors for the C17020 have therefore recommended that additional work be undertaken to investigate the pressure spikes seen in the NUG circuits. It was also agreed that the hydraulic system and operational data monitoring programs be expanded to encompass other underground longwall faces with different aged equipment and from other different hydraulic OEM's.
Due to the number of different equipment designs and ages needing to be monitored, it was proposed that this project be carried out in stages, with stage 1, aiming to define hydraulic pressure history profiles and remedial actions for over-pressurisation issues found in the monitoring programs for the three most common longwall systems used in Australian operations. The longwall systems proposed to be considered for Stage 1 were:
- Joy longwall system at Angus Place mine;
- Caterpillar longwall at Oaky Creek North mine;
- Caterpillar longwall system retrofitted with Tiefanbach electro-hydraulic control system at Newlands Northern Underground mine.
As result of Newlands Northern Underground mine being closed down and Angus Place mine placed on care and maintenance, site access and support with the monitoring program had to be sought from alternative sites. Carborough Downs mine operating Nepean/Inbye longwall system fitted with Tiefenbach electro-hydraulic system and Springvale colliery operating Joy longwall system agreed to host the monitoring programs.
Whilst this report has been primarily written to address some of the needs/issues associated with hydraulic systems used in longwall mining operations, its findings may be applicable to other underground and surface mining applications. The key findings and recommendations arising from this investigation are extensive and well documented in the report. The full report is of real value to all those running long walls.