Valve actuators pass Estonian test

Rotork's representative in Estonia has completed the second part of an unusually demanding project on belt conveyor systems at two of the country's power stations.

Working with Rotork's specialist retrofit valve actuation engineers, Bahr Pump OU, Rotork's representative in Estonia, has completed the second part of an unusually demanding project on belt conveyor systems at two of the country's power stations.

Situated at the city of Narva, the Eesti and Balti power plants are the world's largest generating stations to use oil shale as the energy source.

Balti also provides a centralised heat and hot water supply for Narva as well as process steam for industry.

In this application there are no valves.

Instead the actuators are used on diverter mechanisms that feed crushed oil shale to the power stations' bunkers.

The oil shale, which has the physical properties of very soft brown coal, is fed along the belt conveyors, creating a very dusty environment that is continuously sprayed with water jets and hosepipes.

In addition, the conveyors are positioned on top of the bunkers in areas where the temperature is very high, ranging from 30C in winter to 50C in summer.

The combination of dust, water and high temperature overwhelmed the Russian electric actuators originally installed, some of which had been covered in plastic bags in an attempt to keep them running.

In contrast to the Russian actuator's old-fashioned design, the Rotork IQ actuator - with its double-sealed watertight enclosure and "nonintrusive" setting features, enabling switch setting without removing electrical covers - is well equipped to resist the demands of the application during installation, commissioning and operation.

Even so, the stations' owners, the Estonian National Energy Company, demanded a full year's satisfactory operation from the first phase of Rotork actuators installed before they would sanction phase two.

Bahr Pump OU originally installed 18 IQ20/IW4 gearbox combinations, with linkage designed by Rotork retrofit engineers to provide the correct combination of torque and speed to meet the 10-second, quarter-turn operation required to move the diverter plates in and out of position.

All these actuators survived their 12 month probationary operating period without any breakdowns, enabling the National Energy Company to order a further 16 units with confidence.

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