Connected systems offer cost savings in quarries and mines

Cost savings in quarries and mines

Saving energy generally means making an investment in equipment and many operators use payback periods to justify the expenditure. So, what do you address first and where do you go for further optimisation and cost savings?

Trevor Herbert, Business Development Manager for Mitsubishi Electric Automation Systems Division addressed the British Aggregates Association (BAA) recently. He outlined the opportunities available for practical energy and cost savings using today’s smart connected automation systems.

Quarries and mines depend on electric motors for powering fans, pumps, conveyors, crushers, winches, hydraulic power packs etc. They vary in size and importance from large machines critical to site safety and operations to smaller ones for basic plant processes such as dust suppression and surface water control. Some of these could be contributing more towards energy and general cost saving.

Installing a variable speed drive to a low power drive can save money, and payback period depends on the application. ROI figures improve with larger machines and higher duty cycles, particularly for fan and pump applications. The middle size range of electric motors offer more potential for larger savings. There are still lots of mechanical damping assemblies in use on pumps and fan motors that are very inefficient.

Says Herbert “We recently fitted a VSD to a pumping system with a header tank and basic on/off feedback loop control. Its manual control valve was almost closed as no one was available to keep adjust it when demand changed. Fitting a VSD optimised for pump control saved 78% of energy used and paid for itself within six months.”

The biggest energy savings will usually be on the largest motors, although it’s rare now to find a big 200kW plus unit without an effective VSD installed. Yet, this is where the advantage of better plant visibility and smart connected automation are crucial.

Cost savings with smart condition monitoring (SCM)

Intelligent VSDs like Mitsubishi’s FR-A800 offer onboard PLC functionality that works with the SCM delivering savings by reducing unplanned downtime. Herbert outlined several instances of major pieces of rotating equipment that had failed due to the harsh operating conditions.

SCM is suitable for retrofitting to most plants and monitors data from sensors on the equipment. By comparing parameters such as power, temperature, vibrations etc. with levels established from normal running flags warnings to plant operators. SCM installation costs will vary, but a plant survey provides a good indicator for most installations. Installing SCM is always cheaper than the cost of capital equipment failure and loss of production.

A Smart Condition Monitoring solution is often a low-cost investment and very quick and easy to install. It helps if there is a local Mitsubishi Electric inverter to plug the sensor straight-in using an Ethernet cable. Otherwise, a simple boxed local control and networking solution based on our automation equipment is available and simple to install.

Besides condition monitoring the health of the machine, it can also feed-back energy usage data. From that point users can start to watch and record electrical efficiency to calculate other key metrics such as OEE. This is where the benefits of a ‘connected’ site from an automation point of view starts to pay dividends.

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