What you need to know to realize an Extended Dry Docking (EDD)

Stefan Molenaar

Every ship owner has to deal with it: a dry dock. The SOLAS requirements dictate that all merchant vessels must complete an inspection of the hull in a dry dock twice within a five year period and the intermediate survey must not be more than 36 months. This includes maintenance of the hull, propeller, rudder and other parts which are immersed in water and are normally inaccessible by ship staff at regular sailing period. Ship owners start planning their dry docking activities several months before the schedule date, because these activities take a lot of preparation and are relatively expensive. You often see that ships have to take a totally different route for a suitable dry dock place, as most of the time the desired facility is not available when needed. This is most common with larger vessels.

Extended dry docking (edd)

There is a possibility to extend your docking period with a special program that all major classifications societies have, called the “Extended Dry Docking” or EDD scheme. Under this extended dry docking program, ships have a privilege to extend their dry docking period from 5 to 7.5 years. This means that ships under this special program get the maximum dry dock interval of 7.5 years by replacing certain dry dockings by In-Water Surveys (IWS) which are carried out by approved diving companies. Did you know we also have the possibility to run under water service on our seals during In-Water Surveys?


For more information you can read our blog: ‘In-water surveys instead of Dry-Docking’

Why EDD?

By extending the docking period your ship will stay in water for a longer time. One of the major advantages is that the availability of the vessel for business will be increased. EDD also brings ships an extensive flexibility and savings in docking costs.




If you want your vessel to be considered for EDD, you have to undergo In-Water Surveys. Nonetheless only ships with solid results are allowed to continue the extended dry docking Program. To ensure safety and quality during the extended dry docking period, each classification society has its own requirements for a ship. Several conditions for a vessel to be allowed under this program are:


  • EDD is only available for general cargo ships, container ships and multi-purpose dry cargo vessels. Ships such as passenger and tanker vessels and those subjected to Extended Hull Survey Program (EHSR) and Enhanced Survey Program (ESP) cannot apply for extended dry docking.
  • Corrosion protection is a strict requirement if you want to be considered for EDD. Only ships with high quality underwater coating are allowed to this program.
  • The age of the ship is a very important factor during acceptance for extended dry docking. Desirable is a ship younger than ten years and particularly a ship that is between the age of zero and five years. Older ships can be considered for EDD depending on the ship type, flag stage, classification society and other design and operational factors.

More information

Tips before you dry dock!

Even though your vessel may be qualified for the EDD program, ship owners will always have to deal with dry docking to keep their ship safe. As said before, every day in dry dock and every delay costs a great deal of money. It is our observation that proper preparation for the work to be performed, can significantly shorten the elapsed repair time. Proper preparation enables our technicians to get down to work quickly and safely. Here are eight tips to prepare for the arrival of a service engineer.


Supreme® aft seal

  1. Install a scaffold on which our technician can work safely
  2. Have the shipyard remove the rope guard and carefully spray the outside of the seal box clean
  3. In case of regular maintenance, the shipyard can drain the sleeve in advance
  4. To be able to mount the seals in situ, the technician requires 230V on the scaffold

Finally, naturally you will want to keep the new seals clean. For this reason make sure that no other work that causes dust is being performed in the vicinity. For example spraying, sandblasting, grinding and welding work. Preferably schedule these activities prior to the installation of the new seals.

Supreme® forward seal

  1. Make sure that the seal can easily be reached by our technician. Ample space is required for the technician, as well as the tools. This is the only way to achieve an optimal result.
  2. Remove any floor plates and sections. At the same time, make it possible to disassemble them for future maintenance
  3. Give due consideration to draining the small tanks and the sleeve. Make sure that everything is clean
  4. Provide for a 230V cable near the seal


What is the best way to prepare for a service job? Find out more in our blog!

Cost savings due to proper planning

With proper preparation your work here is half done. Proper planning combined with proper preparation saves you money. Experience shows that in some cases proper planning can result in cost savings of up to 30%!


Going into dry dock? Our Supreme Ventus® and Supreme Athmos® can play an important role in making your vessel environmental friendly. If you would like to engage our service engineers to support and assist you during your upcoming maintenance, we are there for you! Lagersmit provides 24/7 support with its global network.

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