Designing the mooring system


    Overview

The inputs of the system are the K of the mooring system and the concept that was chosen using the MCA. The output the proceeds into the fatigue testing. The overview is below.

    Input

-Concept from MCA
-K

-anchor limitations (the amount of force that one anchor can hold)
-wind wave and current direction (directional rose Of all the environmental forces)
-classification rules (classification societies have minimum requirements for mooring systems)

    Output

-Design

In the design phase the concept design of the mooring system is combined with the K requirements from the strength calculations

The only variables that are left are the number of lines and anchors, the diameter of the lines and the limitations/size of the anchor loading capacity. 

These variables lead up to one spread system with anchor size and line diameters. 

A few examples for spread systems are:

3x2, 3x3, 3x4, 4x2, 4x3, 12 equidistant


The direction of the environmental forces will in first instance be decisive for mooring in 3 or 4 directions.

The anchor capacity and the line diameter options decide if there are 2, 3 or 4 wires needed, together with the classification rules. This visa versa interaction between anchor and lines is shown in the tree with the double arrow. Besides that the direction of the environmental forces controls a major part of the spread type, the anchor and wire interaction control the major part of the amount of wires, the last important subject is the redundancy. It has to be checked how much the mooring system can handle with one line broken. This will generate a loop within the design box, to optimize the configuration for these three inputs.

This all combined creates the mooring system which can then be tested for fatigue. 

There are two feedbacks, one from the fatigue calculation if that proves to be insufficient. 
And one from the model test if that shows any deficiencies in the mooring system.

The preliminary design has now been done. This would in principle be enough. However, most of the mooring systems should be tested to see if all the design steps have been followed correctly. Furthermore it should be checked to see if the mooring system will stand the test of time.