High Depth Dredging Solutions from Dragflow

Deep-sea and high depth dredging is a new emerging trend in the dredging market. Deep sea exploration represents a huge technical challenge, where critical hyperbaric conditions and maintenance needs play an important role on the overall success of a project.

Dragflow is a world leader in this field with dredging solution up to 300m of working depth and several successful projects with dredging depth above 100m. Dragflow High Depth Solutions include: high depth dredging pumps, high depth cutter heads and high pressure water systems, oil hoses umbilicals, hydraulic spooler for hoses management and specific hydraulic power pack for long oil lines and off-shore conditions.

The company has been involved in the production of submersible dredge systems for more than 25 years. A business that begun in the early 80′ specifically for coastal protection along the Italian and European costs, thanks to the passion of the people and engineers working in the company, has rapidly evolve into an international recognized partner for the most challenging deep sea dredging projects.

Why approaching deep sea projects with submersible pumps

Efficiency factor: Dredging and solids reclamation are energy intensive operations. The main challenge for manufacturer of dredging equipment is to developed efficient machines that can reduce use of energy and thus contain the operating cost of projects together with reduced fuel emissions.

Dragflow has been fully concentrated on submersible dredge pump technology since the beginning: the presence of a double blade agitator together with pump suction directly in contact with the material make Dragflow pumps able to move slurries with solid content up to 70% by weight. Higher solid concentration means concentrate the energy to move solids instead of water, it means possibility to work with smaller diesel engines and reduced discharge pipe diameters. The results is a considerably reduced operating cost and fuel consumption per cubic meter while keeping total daily production at the same level of bigger size suction pumps.

Usability factor: The submersible pump due to its own heavy weight can be position into the water thanks to the use of a crane and a steel cable. This solution permit to work any depth without limitations. Dragflow has also introduced an innovative double cutting system that do not create any problem of rotation when pump is working even if it is only suspended by a single cable.

Components of a High Depth Dredging System

High Depth Pump and Cutter: The core of any dredging system is the pumping unit. Dragflow has developed a line of hydraulic and electric pumps for high depth applications. High depth pumps and cutters are equipped with a pressure compensations system that permits to compensate the external water pressure with the oil pressure inside the pump.

Pump and cutters compensators are studied for the maximum dredging depth and carefully mounted to guarantee equivalent internal and external pressure of the dredging system. A specific hydraulic system mounted on the pump avoids abrupt interruptions of oil flow to the pump and cutter thus protecting the motors and pump’s internal components thanks to a slow reduction of RPMs.

High Depth Cutting Systems: As previously illustrated the dredging system can be combine of a compensated double cutting system, this permit installation of cutter heads also in deep-sea project without risks of making the pump spin around. Additional cutting power can be installed thanks to a compensated high pressure jet-ring system. This latter is composed of a Dragflow compensated high head hydraulic pump and a usual jet ring frame.

Oil Hoses reels and umbilical: In high depth projects it becomes crucial to have an efficient and flexible system to bring hydraulic power to the dredging system. A traditional oil line, for projects with working depth higher than 30m, may results too exposed to the risk of being damaged but also very complicated to handle. These may result in a huge oil leakage into water and a long down-time to replace hoses.

Umbilical systems are ideal to combine safety and usability. They consisted of a set of oil hoses twisted around a sacrificial rope, that absorbs all the strains and shocks, and covered by a protective canvas. To proper handle umbilical line Dragflow has developed a line of custom made hydraulic reels that can be controlled from main power pack (also via wireless controls) and that are equipped with an automatic brake for descending operation and automatic recovery for ascending operations. Hydraulic reels are provided of rotating junctions and rotating base frame for easier installation on existing barges.

Hydraulic Power Packs: High depth hydraulic dredging system requires an efficient and reliable Power Packs. Specifically Power Packs for high depth are:

• designed to have separate oil circuit for pump and cutters in order to permit high flexibility during operations and avoid to stop the pump in the case that cutters are stopped due to presence of rocky
  layers;
• equipped with assisted descent of the pump and cutter that enters into action when “automatic” mode is selected on the power-pack;
• oil boosters and oil compensators to avoid cavitations during fast start-up of hydraulic pumps;
• equipped with a sound proof canopy “all weather” resistant or built-in into container style enclosures;
• prepared with wireless remote control to improve usability and operator’s safety or with 3G wireless connection to send and store operational parameters into remote servers. This latter functions permits to managers in remote offices to have a real time idea and an historical view of how the system is performing.

Future developments

Dragflow expansion into the high depth dredging sector has lead to an increased research and development of new products. Dragflow ability to deliver world-class high depth dredging equipment is due to the dedication, expertise and creativity of its people across disciplines spanning from mechanical, structural and hydraulic engineering to production and quality control.

The latest studies in high depth equipments are concentrated in the development of trenching systems for installation of sea-lines or outfalls in soft, medium compact, ground and for pipes with size from 500mm to 1500mm. Trench system will include 4 suction and reflowing pumps, 4 milling cutters, 4 submersible water jets pumps and 1 or 2 water-ballast systems.

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August 29, 2014