At the BMA Saraji Coal Mine in Central Queensland, workers were in need of a reliable dosing system to keep their wash bays and workshops clean. Slip hazards were the biggest concern with personnel having no option but to carry large amounts of detergent across the premises. With occupational health and safety a top priority, the mine was in desperate need of an effective solution.
Kelair was brought in to design a self-contained galvanised dosing skid that could be installed on-site and connected to raw water supply lines. As there was no perfect pump package able to be used, the system had to be built from scratch and the pump outsourced. This meant working with suppliers to find the right type of pump and associated equipment for the job.
According to Chris Thomas, Sales Engineer at Kelair, “The previous setup at the mine meant that workers had to manually collect detergent from a large containers and take it to where it was needed.
“Not only was this a slip hazard if any detergent was spilled, it also meant that workers were entering potentially dangerous areas of the mine to deliver detergent without having authorisation.”
Skid measurements and challenges
According to Mr Thomas, two identical skids were proposed for the site and have recently been installed. Planning of the skids involved a lot of collaboration between Kelair and Saraji operators and engineers as well as strict adherence to guidelines and standards.
“Mine sites have a lot of operation and safety regulations - sometimes up to 80 pages of requirements to sift through. Because of this, we had to be very specific about our design to ensure that it adhered to all requirements,” said Mr Thomas.
As per site requirements, detergent needed to be automatically added to the raw water line at a maximum concentration of 30 per cent detergent to 70 per cent water. The design of the skid also had to ensure that the unit could be easily bypassed without interrupting the raw supply if required.
“The concentration rate of detergent to water needed to remain constant even when the raw water flow rate varied from 0 L/sec to a maximum flow rate of 2.5 L/sec. This means that the maximum injection rate is 0.75 L/sec when using the unit.
“Making sure that the skid performed exactly to these measurements during testing took a lot of consideration and expertise,” said Mr Thomas.
Everything also needed to be incorporated into the one unit, so coming up with a perfectly performing system from scratch was a challenge.
“Halfway through testing we also had to redo some of the electrical components that weren’t functioning properly. However, Kelair’s ability to quickly solve the problem due to their sound technical knowledge and good support base meant that time delays were at a minimum.”
The complete system included a control panel, flow meter and associated valves and switches, as well as a pressure release valve on the positive displacement pump.
The skids ended up being 1.5m high, 1.7m long and 0.75m wide, and weighing about 175kg each.
The following are the list of requirements of the skid as documented by the Saraji Mine:
- The system needs to have both an automatic and manual mode. The automatic mode injects automatically depending on the flow rate. The manual mode allows manual and adjustable dosing in the unlikely event the flow meter malfunctions or is not communicating to the controller properly.
- Manual mode also allows for the transfer of detergent from the main tank to an alternative vessel or location via the secondary discharge point.
- Pump protection is required in the form of pressure shut off, pressure relief and no flow protection.
- In manual mode, the pump runs continuously while nozzles and taps will be turned on and off randomly.
- A delay is required in the system so the pump does not shut off when a nozzle or tap is closed but allows a delay before shutting off.
- This will be achieved by adding an adjustable delay to the pressure switch and while that delay is in effect, the pressure shall be relieved via a pressure relief valve and circuit feeding back into the main supply tank.
- The pressure switch will triggered once a pressure of 875 KPa is reached and a delay of 15 minutes shall be displayed. Once the 15 minute delay has elapsed the pump shall turn off automatically.
- A mechanical pressure relief valve set at 950 KPa will also be fitted on the discharge side of the pumps as a backup for the pressure switch or for relief when the pressure switch is timing out.
- The pressure build up in the system shall not exceed 1050 KPa whilst the skid is relieving.
Kelair was chosen for the job due to their past experience and success with similar dosing skids.
According to Mr Thomas, Kelair consistently uses high quality materials and ensures that each of their projects are completed to a high standard within a good time frame.
“The site managers at Saraji were very happy when they saw the finished product. They were happy with the way it functioned, and also liked the way it looked and the materials used.”