Excavation at Sea

Turck’s QR24 encoders enable the wear-free detection of rotation on electric winches for the Reimerswaal trailing suction hopper dredger

A hopper dredger excavates sand and gravel from the sea floor and transports it to its hold. One of the world’s largest trailing suction hopper dredgers with a dry discharge system is the Reimerswaal. The electronic controls and installation of the ship comes from the Dutch electrical engineering company eL-Tec Elektrotechnologie BV.

The central suction pipe is extended and guided by three steel cables that are wound in and let out using electric winches. Three encoders on the winches detect the unwinding and winding of the steel cables on the Reimerswaal. Two other encoders are mounted on the cable winches that lower and raise the two spud poles at the fore and aft of the ship.

Frequent failure of magnetic encoders

Previously, all five winches were fitted with magnetic encoders with an integrated Profinet interface. However, the encoders had to be replaced frequently due to mechanical faults. The high seas are an inhospitable environment for electronic components.

“Four out of five encoders failed within a year,” as Sander Lensen, programmer at eL-Tec, described the wear. Lensen must know. During servicing, he and his colleagues repeatedly had to assign an IP address to the new encoders and teach the devices.

Wear-free and plug-and-play

“The new encoder had to be wear-free and enable the replacement of encoders to be carried out by the technical personnel on the Reimerswaal themselves,” Dick de Vries, head of the service department at eL-Tec, describes the central requirements for a new encoder. “We therefore looked for an encoder that doesn’t have any mechanical connection to the winch shaft and is permanently sealed. For this there was only one encoder, and it comes from Turck.”

Profinet interface and SSI output

EL-Tec now uses the absolute version of the QR24 contactless encoder with an SSI output. The Profinet interface was implemented using the Ethernet gateway from Turck’s BL20 modular I/O system. The encoder is connected to the gateway via an SSI input card. This makes the solution plug and play enabled. The ship’s crew could easily replace the encoder themselves in the event of a fault. The gateway stores the Profinet address and a new encoder could be put into operation without any additional parameter setting required. This option would not be possible with an encoder with an integrated Profinet interface. “If the solution becomes established permanently, we will also be using the QR24 in other projects. Up to now it looks pretty good.”