Bringing a dredge ship up-to-date

A major building products supplier needed to update a number of dredging ship discharge systems. The existing DC drives were obsolete and the control algorithm did not give precise control, resulting in long discharge times and unpredictable control of the discharge buckets. Implemented during the ships’ annual maintenance in dry dock, the overall project included:

• New Process PLC
• Replacement of 4 DC winch drives
• Replacement of conveyor invertors and soft start units
• Re-cabling of communications network
• New fibre optic communications link between control room and bridge
• New operator stations
• New absolute encoders for each winch
• Remote support for the ships’ engineers

 

Our Solution

Iconsys designed and built a drive system utilising ABB DCS800 DC drives for the winch control, with Vacon AC drives for speed-controlled conveyors and ABB soft starts for the remaining conveyors. The system was integrated using a Siemens S7-300 PLC based multiprocessor control system.

Maintenance and operator stations used touch screen HMIs. Remote I/O stations from the Siemens ET200M & ET200S range minimised re-cabling work. Other networks used included Ethernet and Profibus. Remote access for support of the system and ships’ engineers was via a 3G network. New operator control stations incorporated HMI screens for control stations within the ships and conventional push button control for control stations mounted on deck.

 

Results

• Production expectations exceeded
• Reduced discharge times by up to 33%
• Safety improved due to the reduction in broken winch cables and “flying” discharge buckets.

 

Client Feedback

The ship captains were delighted with the process improvements that have reduced discharge times by up to 33%. Improved control has allowed the ships to meet and exceed production expectations, giving high utilisation. Safety has also improved due to the reduction in broken winch cables and ‘flying’ discharge buckets.