Comms wins valve actuator contracts in Netherlands

The ability of Rotork electric valve actuators to fulfil preferences for different open control system technologies has helped to secure two innovative and environmentally responsible contracts

The ability of Rotork electric valve actuators to fulfil customers' preferences for different open control system technologies has helped to secure contracts at two innovative and environmentally responsible projects in the Netherlands.

In the first, the actuators incorporate Foundation Fieldbus connectivity with a Fisher Delta V DCS (distributed control system) for the supervision of a pioneering district heating scheme in the Westpoort area of Amsterdam.

Designed by the utility company Nuon, the "Afval is Warmte" scheme provides 'clean' heat using steam produced from a municipal rubbish incinerator that would otherwise be wasted.

The incinerator provides steam to run generators that supply electricity to the local grid.

The waste steam from the generator now passes to the new plant where it heats the water in a large holding tank.

A closed loop circuit from the tank distributes hot water to local companies to provide economical heating for offices and factories.

Currently around twenty companies are included in the scheme, but the number is expected to increase to over 125 by 2004.

Rotork has supplied IQ actuators with factory fitted Foundation Fieldbus cards to operate Adams butterfly valves on the "Afval is Warmte" scheme.

A short distance away, Rotork IQ actuators with Profibus connectivity are employed at a large scale pollution clean-up project in the Ketelmeer (Kettlelake), at the mouth of the River IJssel, a distributory of the Rhine.

The River IJssel carries particles of silt, sand and clay which settle on the Ketelmeer floor.

This sediment contains waste material from factories along the IJssel and the Rhine - including heavy metals, PCBs and PAHs - which over time has built up into a thick layer of contaminated sludge that is threatening to reach the area's ground water.

The pollutants are bound to the clay and not the sand or water.

Therefore the beaches along the Ketelmeer and the water itself are not polluted.

However, the floor of the lake is polluted, and this sludge must be dealt with to protect both human and wildlife health.

The Government authority Rijkswaterstaat studied clean-up methods and carried out numerous tests before deciding that it would have to be carefully collected and permanently stored where it can do no harm.

As there is nowhere to put the sludge on the surrounding land, Rijkswaterstaat designed a unique scheme whereby a huge clay-lined pit, or depot, surrounded by a 10 metre high dyke, has been built in the middle of the Ketelmeer itself.

The depot is one kilometre in diameter, 45 metres deep and capable of storing 23 million cubic metres of sludge.

Once the entire Ketelmeer has been cleaned up, the filled depot will be permanently sealed with layers of clay and sand and converted for recreation and nature reserves.

A scheme of this ambition and scale involves a host of diverse pumping and pipework plant, valves, flowmeters and instrumentation to successfully and precisely dredge the polluted silt from an area equal to the size of nearly 6000 football pitches.

In addition, 7 million cubic metres of silt from other areas is being shipped in for treatment and storage.

This silt is transported to the depot through more centrally controlled pipework, including plant to add water if the silt is too dry and separators to remove any sand content for use in civil engineering and building.

The entire operation is controlled from a centralised control room within the new administration facility built on the IJsseloog Island beside the depot.

A Profibus two-wire network provides control and monitoring communication between the DCS and field equipment, including the Rotork actuators, which control the movement of the water and silt throughout all the transporting and processing stages.

Profibus was elected as an economical and efficient means of accurately collecting the large amount of diverse operating data necessary to ensure that the plant is functioning correctly, and to identify potential problems before they cause any disruption.

Rotork IQ actuators have an enviable reputation for operational reliability in harsh and exposed environmental locations, such as those at the Ketelmeer lake.

In particular, the actuators' IP68 watertight and temporarily submersible double-sealed enclosure design provides permanent protection to the comprehensive solid state diagnostic information gathering and storage circuitry, including connectivity cards.

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