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The efficient operation of the longwall roof support system directly affects the safety and productivity of the mine; any downtime on the system in such a diffi- cult operating environment would be counter-productive. The reliable perfor- mance of these systems is essential if the mine is to maximize output and see a return on investment. Due to the high pressures required to operate the roof support structures, the pumps use a reciprocating piston princi- ple, usually powered by a mid-sized elec- tric motor. A reciprocating pump discharges liquid by changing the internal volume of the pump and uses non-return valves (NRVs) at both the inlet and outlet ports of the pump. Typically, these pumps can produce 1,000 bar in pressure, in this application they will typically be operating at around 350 bar. The major benefit of the reciprocating pump is that it produces a fixed volume of fluid displacement at a given speed and provides a constant flow, regardless of pressure. This fundamental design is ben- eficial to control the pumps by a variable speed controller, which allows accurate control of the output pressure. For appli- cations requiring increased flow rates, one or more pumps can be added in parallel to the original to produce the desired flow rate at the same pressure rating. It is important that the pump design incorporates the necessary safety features, including a safety relief valve to protect against a dead-head situation, when the system demand for flow has stopped, causing the pressure to rise instantly. The safety valve should be designed to allow the entire pump capacity to flow, while the opening point should be set at 10% above the operating pressure. In addition, the pipework associated with the safety relief valve should be properly sized to ensure adequate flow conditions. For high-pressure applications, recip- rocating pumps offer additional benefits as the design offers greater mechanical efficiency, which means that a smaller prime mover can be used and less energy is consumed. By carefully selecting the correct motor and matching it to the pumping system, a more efficient combi- nation can be created, resulting in lower total cost of ownership. Achieving an efficient design is one thing, but making it reliable for a mining application as well requires a higher level of development. This requires a certain degree of "over-engineering," using mate- rials and design concepts that may exceed the original specification, but which will afford a much greater level of reliability. In heavy industries, such as mining, building something to last can make the difference between catastrophically expensive down- time and ultimate profitability. RMI Pressure Sys- tems supplies reliable high-pressure pump- ing systems. The com- pany also has a policy of continuous devel- opment of energy effi- cient products, which has led to the intro- duction of the O D I N (On Demand Intelligence) control system. This system uses a range of data supplied from equipment used in the process of long- wall mining and uses it to calculate the changes in demand for hydraulic fluid before they occur. In this way, ODIN can modulate the pump speed and change the flow and pressure characteristics to meet demand in the most responsive way possible. www.rmipsl.com Wear Liners Alloy Steel International's new Arcoplate- Super Alloy has attained respectable per- formance goals, according to the manufacturer. It has an alloy overlay range from 6 to 20 mm thick. Impact resistance, abrasion resistance and a low coefficient of friction make it possible to attain optimum results in abrasion resis- tance, according to Alloy Steel. It has been used for hopper liners, dozer blades and dump bodies. Miners are getting 50,000 hours of wear life on dozer blades. The manufacturer claims the installation is quick, price competitive and virtually maintenance free. The wear life on dump bodies has increased by 200% to 300%. www.alloysteel.net Diesel Tank Cleaner Tank contamination, also known as "algae," is a biomass that has formed an agglomeration of microorganisms in which cells adhere to each other on the tank surface or at the fuel water interface. These adherent cells are surrounded by a shield of extra-cellular polymeric sub- stance (EPS). This biomass protects the bacteria from biocides and most other additives. Technol 246 is a problem-spe- cific fuel additive that will penetrate and dissolve the biomass rapidly and solve the filter plugging problem. As little as 8 oz will treat up to 275 gallons, where a gallon will treat up to 4,000 gallons. www.dieselcraft.com 58 www.coalage.com February 2015 p r o d u c t n e w s High-pressure Pumps for Longwall Roof Supports High-pressure pumps, such as the S500 from RMI, provide hydraulic power to the roof support systems.