Sylt, Germany's most northerly and exclusive island in the North Sea, is exposed to continuous attacks from the sea. Despite all (passive) defence measures in the past, parts of the sand beach are swept away on every storm tide. So for some years a further, active strategy has been employed: during the summer months, sand which has been eroded by the storm tide is replaced by reclaimed washed sand.
Suction dredgers with a loading capacity of 17,000 m3, using a lateral sucker, collect sand from the sea bed down to 70 m depth (title drawing) and deposit it via a pipeline onto the beach. The 1,200 kW submerged pump in the suction pipe is supported by a booster pump on board: two speed controlled asyn-chronous motors of 2,600 kW each (photograph) are installed in tandem for flushing the sand-water mixture onto the land.
The actual speed sensing of the tandem drive is performed by a HUEBNER incremental encoder HOG 16 equipped with double scanning of the incremental disk for the two frequency converters. Its HeavyDuty technology particularly matches the tough operating conditions
In picture:
Incremental Encoder
HOG 16 with double scanning
in operation.
