Mooring Rope Selection


Can anyone please tell me how to choose a mooring rope. The problem is as follows:

A ship has to be moored at mid sea. The ship will be moored to 4 mooring buoys with one rope each. Each ropes will be tied to a separate bollard on the vessel.
I know the maximum environmental force that will be acting on the ship. Can anyone please tell me how to decide which wire rope will serve the purpose? Will my maximum environmental force = minimum breaking load of the wire rope?

Thanks a lot folks

No. The mooring line size is not just the max environmental load for the ship. I recommend a mooring analysis if this is a large ship (90+ m). Without knowing your specific location and regulatory jurisdiction, I can’t say specifics. But here is some general advice from past cases where I specified mooring lines.

  1. Use the OCIMF Mooring Equipment Guidelines. Make sure to get the latest edition.
  2. If you are exposed to open waters, be sure to consider the ship’s momentum due to wave action. That usually adds to more than the total environmental load.
  3. Be sure your environmental loads are for the worst case scenario. OCIMF recommends a wind speed of 60 knots and a current of 0.75-3 knots, depending on current direction.
  4. The vertical angle of your mooring lines will make a big difference. This is considered the line efficiency. Anything over 30 deg is very inefficient and will require larger mooring lines.
  5. For steel cables, the calculated load on each mooring line can be no more 55% of the lines minimum breaking strength.

Read this article on gcaptain newsletter today and you will at least know what to choose as rope material:

ropeguards variety.jpg

And never forget the correct acessories:blush: