Calculation Of Anchor Hold Power And Strength Of Mooring Lines&Fenders Required For Crude Oil Transfering At Anchorage

With the fierce competition in the shipping market,an increasing number of large-size oil tankers,such as VLCC and ULCC,are being put on the shipping market to reduce transportation costs.However,restrained by the depth of channels,most ports cannot meet the requirement of discharging operation for such very large ships,hence pre-off-loading is additionally required for completing discharging.The main way of the pre-off-loading is crude oil transfering at anchorage.It is inevitable for the transfering to bear the load of wind,wave and current,so it is essential to slack the adequate anchor chains,arrange sufficient mooring lines and fenders to resist the impact force coming from the wind,current and wave for preventing ship's dragging,departing and bumping.This paper studies how to determine the length of the anchor chain,and the type and quantity of the mooring lines and fenders.Firstly,the calculation method of the loads imposed on the ship by wind,wave and current is presented.Then the paper shows the calculation formula of anchor holding power and give the calculation of the length of the chains required to be paid out to against the above loads by way of example,during this process,the typical crude oil transferring pattern in Shandong Province Laizhou port is taken as the example for carrying out the calculation of loads coming from the wind,current and wave in accordance with relevant math models and parameters,it is explicitly shown for the analysis method and arithmetic process of the calculation of the length of the anchor chains to be paid out.At the end,the paper shows the arithmetic method to determine type and quantity of mooring lines against wind,wave and current and the fenders to absorb the berthing energy of catcher boat,and complete the calculation of the strength of mooring lines and fenders required by way of example of the crude oil transferring work in Laizhou Port.And the paper provide the automatic calculation procedures for quick calculation of the chain length and the amount of mooring lines and fenders base on Microsoft Excel.The methods and procedures concerning of calculation of anchor hold Power and strength of mooring lines&fenders required for crude oil transfering at anchorage in this paper can be served as references for actual practices and risk accessing process.The conclusion of the paper can be referred by the relative oil tank for applying the anchor chain length,mooring lines and fenders.