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Damen Pumps on Dredge Michel DSR Aid Aggregate Dredging in French Waters

Piriou Shipyards delivered a 2,300 cubic meter (3,000 cubic yard) trailing suction hopper dredge, fitted out with Damen dredge pumps and related equipment, to the French sand mining contractor CETRA in September.

The hopper dredge, named Michel DSR (Michael Da Sousa Reis), will mine sand and gravel off the Brittany coast and transport it throughout France’s Loire estuary. The vessel is a prime example of Franco-Dutch cooperation in dredge building, said a Damen representative.

The twin-screw hopper dredge is fitted out with a single starboard-side 600 mm (23.6 inch) trailing pipe with integrated submerged dredge pump. The vessel is 85 meters long, 15.85 meters wide and has a dredging draft of 5.98 meters. The bridge and the accommodation are located aft. The seven-person crew accommodation is fully air conditioned. The pump room and the engine room are located in the forecastle, near the hull suction inlet. Two 1920 kW Caterpillar propulsion diesel engines produce a speed of 13 knots.

The vessel was designed to dredge up to 40 meters (131 feet) deep.

To optimize efficiency and generate high mixture concentrations, a Damen model OBP6055LD dredge pump on the dragarm is direct-driven by a 600 kW electric motor. The jet water-assisted California type drag head was chosen because the mining activity concentrates on relatively coarse sand and gravel meant for the building industry. The trailing pipe is remotely operated by three gantries and their hydraulically driven winches. The draghead winch wire runs over a swell compensator managing a maximum four meter swell.

The versatility of the ship shows in the unloading systems, which can be accomplished by direct pump-out of by an excavator mounted over the hopper.

The in-board Damen dredge pump, type BP6055HD, is installed for self discharging the hopper cargo using the longitudinal self-emptying system along the hopper with hydraulically-operated Damen dredge valves as suction channel doors. The 1800 kW high pressure dredge pump has wear resistant wet parts and a mechanical shaft seal, and efficiently pumps the diluted cargo to either the side coupling or the bow coupling. The side coupling was designed to fit land-based counter couplings in various ports. The 600 mm (23.6-inch) bow coupling unit is installed for pumping ashore on several existing floating pipe lines.

When the dry discharging system is used, the vessel does not require any port infrastructure. The Caterpillar excavator, type 385C, is based at coaming level and runs over rails located along the sides of the hopper. During dry discharging it moves slowly forward, depositing dry hopper cargo in the funnel which moves along the port side conveyor belt. Another conveyor belt, turned aft during transit, is now directed over the bow or side to deposit the gravel on quay.

The hopper dredge is fitted out with Damen dredging instrumentation and dredging automation. The performance of the dredge pumps is closely monitored using the data from the vacuum and pressure sensors, plus the detailed production data from the radioactive density meter and the magnetic inductive velocity meter. The position of the trailing pipe is monitored by the Suction Tube Position indicator using data from inclinometers on the trailing pipe hinges. The course of the hopper loading process versus time is shown on the Load and Draught system, fed by data from the bilge mounted pressure sensors.

The Michel DSR, named after the owner’s family, was commissioned in July. After its satisfactory sea trials and dredge trials the vessel was handed over to CETRA. The vessel began its productive life from its homeport Saint Nazaire and is now continuously delivering building materials to many French ports along the Atlantic coast.
CETRA (Compangie Européenne de Transports de l’Atlantique), based near the French Atlantic coast is a specialized wholesaler in building materials. The company owns one other hopper dredge. The dredges are used to win sand and gravel off the French Atlantic coast, and to transport it to various locations along this coastline. The company, member of the CADDAC group, was founded in 1975 and is fully owned by the De Sousa Reis family.

French shipbuilding and repair yard Piriou is based in Concarneau on the southern Brittany coast. The yard has built more than 300 vessels during 45 years of business, and the Michel DSR is their first experience in dredge newbuilds. Their main areas of operation are medium-sized vessels with high added value, such as ocean going tuna seiners, fishing vessels and towing and offshore service vessels.

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