BHP Billiton Mitsubishi Alliance (BMA) have engaged Dowdens Pumping & Water Treatment's Mackay Branch to deliver a specialised Modular Underground Dewatering System at their Broadmeadow Coal Mine, located approximately 200km South West of Mackay, QLD.
The Broadmeadow Underground Coal Mine is a 'Top Coal Cave Longwall Punch' mine located approximately 30km from Moranbah. Located on BMA's Goonyella open cut mine lease, the Broadmeadow Mine was established in late 2003 and feature's BMA's first application of punch longwall mining - a highly efficient underground technique utilising an existing open cut pit for longwall panel access. Broadmeadow Mine delivered a number of synergies between BMA's underground and open cut operations, including utilisation of the existing Goonyella coal preparation plant capacity, increased flexibility to respond to market demand, improved reliability of supply for customers and optimisation of product quality through selective blending.
The Modular Underground Dewatering System (MUDS) was designed / manufactured and installed by Dowdens Mackay to optimise further development of BMA's Broadmeadow mining operations by improving on-site dewatering efficiencies. The MUDS has been utilised in developing Broadmeadow panels 12 & 13, and will help to advance mine site progression for the entire life of operations. The main objective of this project was to provide a unique, custom built air / electric pump system to improve Broadmeadow's dewatering efficiency. This was achieved through the automation of pumping systems supplied and lowering any ongoing maintenance requirements - thereby saving site operator input, lowering air / power consumption and reducing the need for BMA to further invest in dewatering pump systems.
Dowdens were engaged during the concept phase of this project to provide input and engineering advice to help BMA overcome the many operational challenges this site presented. With intimate product knowledge and via extensive direct consultation 2 unique transportable Quick Docking System (QDS) Fish Tank Dewatering POD designs were developed. Capable of operating under 1,000V power, these modular POD systems required the ability to remain operational during regular power outages, utilising the limited underground supply of compressed air. Each pump station needed considerable storage / retention capabilities (5,000L per POD) and the capacity to operate seamlessly 'in-sequence' thereby delivering zero overflows onto roadways even during loss of underground power.
The composition of the water derived from the mine's development process posed its own transportation challenges with a high water content ratio of rock, coal, trash and coal fines. A solids management system consisting of various sieves, hoppers and tank agitation components was developed and tested to ensure the coal fines and inflow management system was capable of continuous operation, whilst also delivering simplified maintenance and cleaning procedures.
The coal fines and inflow management system was designed with the ability to:
With the negotiations finalised, Dowdens proposed the fabrication of 2 Teams of 4x Dewatering PODs. Each Team is led by the newly designed 5m³ EXD QDS transportable roadway POD. 3x additional specially modified 4m³ Elliptical PODs (a combination of EXD & IP66 rated) are then positioned at strategic intervals along the panel as main gate development advances.
Dowdens Pumping & Water Treatment was successful in BMA's tendering process due to:
After a successful tendering process Dowdens team of engineers and draftsmen immediately began analysing the recovered Crinum mine 4m³ POD design. After much consideration, a plan was established to incorporate all new specifications and functionality required whilst retaining as much of the existing structure as possible, saving both fabrication time and money. This design was carried over to the new generation 4m³ Elliptical PODs.
The Narrow Gauge 5m³ Lead POD had to utilise every inch of its restricted underground foot print to facilitate the 5,000L capacity and extra-large solids screening hopper. All work access steps and ladders were designed to be stowed away to avoid contact by passing machinery. All equipment was to be readily accessible to operators, even while positioned hard against the roadway rib. The complete set of design drawings were completed within 5 days and construction began immediately ensuring delivery was made within BMA's tight project deadlines.
Specially equipped 1,000V electric motors were incorporated in the build to operate custom made hard-metal centrifugal pumps - primarily selected for water transfer between PODs operating 'in-sequence'. The Cast Iron WILDEN T15 Air Operated Double Diaphragm Pump was selected to serve as the auxiliary system for its robustness and relatively small weight-to-flow ratio. The lower weight and lower capital cost of the T15 allowed two pumps to be incorporated into each pump station to serve in duty / standby, or duty / assist mode if required.
A pneumatic control system provides seamless switching between air and electric pumping modes. Non-powered level controls allow maximum tank differential between the air pumps 'on & off' functions saving air consumption. Potential overflows are prevented by a pneumatically operated, inflow regulating valve. Each of the POD inflow manifolds are equipped with 4 auxiliary 50mm pump inputs to integrate localised pumping to the 'outbye' system. Custom built electrical control panels incorporate all EX'd field devices providing temperature, pressure, flow & fault communications via a PLC to the site Citect system. Area lighting and visual pump status indicator lights can be positioned remotely ensuring clear viewing from the mines underground roadways.
Dowdens Pumping & Water Treatment design philosophy for this project was: Cost Effectiveness - Current Best Practice - Ease of Installation - Simple & Effective Plant Operation - Plant Reliability & Reduced Ongoing Maintenance.
Modular Underground Dewatering System's Key Components are listed below: