The Art of Dredging

Dredging and shipping

Operating hydraulics during shiprepairs

A hopperdredger (or cutterdredger) in drydock can be a real hazard for drydock personel and ship’s crew.


These ships are equipped with large gate- and butterfly valves, often with a diameters of 1 meter or more. These large pipes are opened up for repairs and everybody has easy access to the inners of the piping system.

Further, a hopperdredgers’ bottom has dumping doors, and selfdischarging doors, pretty large in size (think 4x4 meter on average for a bottomdoor), heavy weight, and remotely operated from the wheelhouse, and it’s all hydraulics.




Onboard "Gerardus Mercator"  we were always bothered by the idea that somebody got sliced in two by a gatevalve, or crushed by a bottomdoor.

It’s a real possibility: during repairs you need to actuate these doors and valves almost daily.

Hydraulic systems must be blocked -preferably- in more than one way, to avoid any wannabe to operate hydraulic systems.


So -to keep things on the safe side- we made ourselves a procedure:


An engineer is assigned as “hydraulics engineer”.

Talk hydraulics, talk to him. 


He has the overview of the complete hydro-system; he knows what is disconnected, blinded, open, and out of order due to ongoing repairs.


All actuating of hydraulics has to have approval of the captain, nobody is allowed to move a single valve.


We do not operate hydraulics without the repairyard knowing it.  

We discuss the operation of hydraulics during daily meetings with the  shipyard. 


For the actual operation of a valve or door: we proceed as follows:


  • Short briefing with electrican, “hydraulics engineer", chief mate and captain. We discuss wether actuating is possible, considering that parts of the electrical and/or hydraulic system are disconnected, due to repairs, and considering power limitations in drydock.  We prepare a list of all hydraulic cilinders to be actuated.
  • Chief mate goes to the dredgedesk in the wheelhouse. 
  •  Hydraulics engineer to Engine Control Room (ECR)
  •  Electrician goes online in the ship’s main PLC and blocks all hydraulic components ith use of dedicated software on a laptop). When he’s ready, no valve or door can be moved without his intervention in the PLC.
  • Captain goes to the first valve or bottomdoor to be actuadted and ensures that the area is clear.  (Mostly you'll find some shipyard welders sleeping in pipes, halfway trough a gatevalve, or painters having a nap under a bottomdoor
  • And all of the above crew communicates with each other through UHF walkytalky, on the same freequency. (UHF is better than VHF for this purpose, because it penetrates easily steel bulkheads.)
  • When all and everybody of the crew is in place, the captain calls to actuate the first valve or door, then:

Ø       hydraulics engineer switches the appropriate hydraulic pump on

Ø       electrican deblocks the valve/door in the PLC

Ø       chief mate actuates the valve/door

Ø       captain calls that valve/door is actuated, moves, and stops in the required  position

Ø       elec blocks valve/door

Ø       engineer switches off hydraulic pump



·          And so on, every step again, for the next valve or door to be actuated


    The chief mate keeps an eye on the list of hydraulic users to be actuated.

   If the captain blunders (calling on the wrong bottomdoor numbers or mistaking port from

   starboard, as it happens) the chief mate calls it a misunderstanding and stops everything until things are clarified.


   Mistakes do happen.


   Things can be pretty confusing on the dockfloor.




When walkytalky  communications break down, everyone involved has the order to stop actuating immediately and block all the hydraulic systems until communication is restored.



(Normally we use mobile phones as backup comms).




Outboard valves have emergency closing systems.

These systems have to be blocked or disconnected in drydock, to ensure that the valves are not untimely operated.


This safety procedure differs from ship to ship; some ship have a continuously pressured hydraulic (ring)line.

With that kind of system it's wise to take of solenoids from hydraulic cilinders, and / or use ballvalves in the hydraulic line.


A safe procedure must be ship-specific.

The procedure onboard "Gerardus Mercator"  may be a pain in the ass; we need four crewmembers to actuate a cilinder.


But better to be be safe than to be sorry.



Marc Van de Velde





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