CANTON, Mich., Dec. 1 /PRNewswire/ -- Underground mining is an explosive business. To ensure that workers and machines are not exposed to unnecessary risks, special safety concepts are in place to keep explosive hazards in check. In conjunction with the Swedish mining machine manufacturer Sandvik Mining and Construction, Pilz has developed the first ultra robust PSS control system, designed with the principles for integrated explosion safety.

Spray systems prevent dust explosions

Roadheaders made by Sandvik Mining and Construction are used in underground mining to excavate coal and salt. Rotating cutter heads on the front of the machine excavate the material, creating a large amount of dust which can cause a dust explosion. A water-based spray system on the machine is designed to prevent this by binding the dust particles. The spray system must be permanently monitored to ensure reliable operation while the cutter heads are operating.

Until now the spray system on the cutter heads has been monitored using digital flow and pressure sensors. With the new concept from Sandvik, analog sensors measure flow rate and pressure, while a PSS control system evaluates the results. Due to the hardness of the material, both the drilling device and the machine must be able to withstand particularly strong vibration. The PSS control system is also exposed to these stresses, so it was important to find a "vibration-free" solution.

Robust PSS control system monitors water pressure and flow rate

Pilz modified an existing PSS control system with digital and analog inputs to make it suitable for use in mining. The rugged version is temperature-resistant and vibration-proof. The components are bonded and therefore "vibration-free". This helps to counteract wear. As a result, the control system meets the high shock and vibration requirements. The PSS control system is installed on the roadheader in a flameproof enclosure.

The spray system must operate reliably to guarantee safety underground while the roadheader is in use. Consequently, water flow rate and pressure must remain within certain limit values. The PSS control system uses a calculation formula to constantly establish and compare limit and operating values. If there are any deviations the control system signals to stop the cutting motor that drives the cutter heads.

Sandvik and Pilz worked closely in developing the new control system. The safety concept and technical design were planned and implemented in the hardware at the customer's end. In accordance with the customer's specifications, Pilz generated the software for the PSS control system. The safety functions were verified during joint tests on the machine. The excellent cooperation kept the development time short. The first prototype was able to go into testing after just a few months.

SOURCE Pilz Automation Safety

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