Hyflo is the sole South African distributor of pneumatic equipment from the Japanese company SMC.
The product range includes linear positioners used for proportional control in the process and instrumentation industries. SMC supplies linear or rotary positioners working on a variety of electrical input signals.
Hyflo recently supplied linear positioners to a coal mine. Grade sorted coal is washed and then redirected accordingly depending on who the customer is.
A pneumatic control system
Because of the danger of fire in coal mines, pneumatic equipment was called for. Hyflo was commissioned to design and build a control system meeting this requirement. The design included electro-pneumatic regulators (ITVs), micro-mist separators, filters, regulators, pneumatic linear positioners, cylinders, reed switches and solenoid valves. The air line preparation equipment was housed within IP65 enclosures. The linear positioners were mounted directly onto SMC pneumatic cylinders, along with reed switches and solenoid valves where required. Based on the signal given by the central PLC to the ITV panels, the stroke of the cylinder rod was monitored and positioned accordingly.
Dust problems
During commissioning and operation a problem arose when fine coal dust kept building up within the barrel of the positioner, negatively affecting its performance. On a coal mine it is critical that downtime be kept to a minimum and as a result replacement positioners are ordered frequently.
An innovative boot
Hyflo responded by adapting the positioner for extra protection. Using a concept developed on Australian coal mines, a special clip and boot were designed to fit over the sliding surface of the linear positioner to seal the exposed barrel. The clips and boots are sourced locally. The result is that all exposed parts are protected from dust to a far greater degree, even when extended.
The new design increases the life span of the linear positioner and reduces maintenance costs. Assembly is done directly by Hyflo and by using local materials, delivery times are improved.
This innovation is applicable to the coal, sugar and copper industries and any other industry exposed to dust where linear positioners are required.
Electro-pneumatic regulators and linear positioners
SMC’s standard type linear positioner, series IP200, is suitable for remote positioning or stroke regulation of dose units, pumps, gears, drives, velocities, proportional apertures of valves and many other applications. The smoothness of movement of these cylinders, in combination with the positioner system, leads to precise positioning. Hysteresis is less than 1% of the total cylinder capacity. The 20 to 100 kPa signal pressure acts directly on the servo positioning system in such a way that a modification or change in this pressure is transformed immediately into a movement of the piston. Zero point and span adjustment is easy and simple. Standard strokes are available up to a maximum of 500 mm. A special option of Viton seals is also available for operation at elevated temperatures.
Where the linear positioner may be exposed to excessive vibration, causing ‘hunting’, all of SMC’s pneumatic positioners can be controlled manually, locally or remotely through its range of precision regulators or electrically through ITV regulators. The electro-positioners are available as a range featuring different input signal options and different monitor outputs.
For more information contact Nicky Hall, Hyflo, +27 (0)11 386 5836, [email protected], www.hyflo.co.za
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