LONGWALL UNDERGROUND COAL MINING
Hydraulic high pressure pumping system is widely used in any longwall underground coal mines. High-pressure pump stations are used to provide hydraulic power to hydraulic roof support. The medium is usually emulsion with 95/5 mix of water and raw oil. The full pump system typically comprises of multiple pumps. Pumps will be started in sequence and on-demand. A pressure transmitter will be fitted at the delivery line to give a pressure signal to the pump control system to determine pumps starts/goes idle. Each of the pumps is equipped with unloading valve which reacts to a pressure setting and diverts the flow either to the delivery line (high pressure) or back to the tank (low pressure).In addition to providing hydraulic power to roof support, pump systems are also using to provide pressurised water underground for the use of dust suppression and equipment cooling.
ENERGY SAVING TECHNOLOGY
Variable Frequency Drive (VFD)
Fitting variable frequency drive usually has a great payback on mining system due to the amount of energy can save as well as also the other economical benefit will VFD can give in a mining 24/7 application.
A low demand of flow is usually seems on a longwall hydraulic system due to the fact the majority of roof support movement is very minor and predictable. Based on a real data, 95% of the operation time system is running at below the maximum flow which system can produce, with the around 30% of the time the unloading valves are unloaded. This mean pumps on the systems are pumping back to the tank at the majority of the running time on a fixed speed system/configuration. By fitting VFDs, the pumps can slow down to minimum speed when there are less demand. VFDs will adjust to motor speed to match the flow requirement. VFDs equipped pump system is able to maintance a relatively constant pressure which will reduce the pressure spike in the system, and in turn reduce tear and wear and maintenance cost.
Parallel Pumping
Due to technology limitation, VFDs will not be able to quick enough to response a sudden flow demand or drop. RMI Pressure Systems has therefore introduced an advance control philosophy of parallel pumping, which means all pumps on the system are running with VFDs and at the same speed. Multiple pumps act together as ‘one big pump’ which reacts to the flow demand. Such control philosophy will reduce the requirement of quick reaction from the VFDs by sharing across the multiple pumps on the system. A real parallel pump solution can then realised with the benefit of energy-saving.
Hydrofinio has developed an energy-saving and benefit calculator which will show the potential saving as well as the payback period for your specific application and parameter. Contact us now for more information.
RMI also innovated more advanced technology in energy saving such as ODIN and Agilis. Click here for more information about RMI Pressure Systems.