OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

tban the present Classification Society guidelines. This is because Classification Society guidelines base
che mooring equipment on the IACS equipment numeral. While trus is a good basis for anchoring
equipment, it does not adequately rellcet the transverse loads imposed upon a restrained ship.

The formulae for oil tankers are based on formulae (9) and (13) and assume that the maximum
longitudinal force occurs in the ballast condition and the maximum transverse force at the aft per-
pendicular in tbe full load co nditjon. TIle validity of this assumpijon should be checked by use of
the formulae listed in Section 2.4.1.

2.6.1 Mooring Restraint Requirements for Oil Tankers above 16 kDWT

2.6.1.1 Wire systems

Spring li nes:

S )( MBL = 1.992 An + 0 .369(0. 01 L.~p + L.op)

Breast lines:

BR x MBL = 1.476 ALF + 1.291 TLllP

Where:

S total Dumber of spring lines

BR total number of breast lines

MBL = minimum breaking load of each line in kN

T maximum (summer) vessel draft

Assumptions:

(22)

(23)

(a) Environmental conditions <.:orrcspond 10 the standard criteria outlined in Section 2.2. Maximum

forces on the sbip are derived by formula (9) for the longirudinaJ direction and by formula (13)

for tbe transverse direclion.

(b) The moori.ng layout follows good moori.ng principl~ (as per Seclion I). A layout efficiency

factor based upon experience WiUl good layouts has been used.

restraint capability of line group

'Efficiency·' =

max. load in anyone line x no. of lines in group

Line groups are broken down into spring lines, forward breast lines and aft breast lines.

One hundred percent efficiency would represent equal length breast l.ines al 90° to the longit udinal

axis of the ship and equal length spring lines parallel to the longitudinal axis, all in the horizontal

plane.

The following cfficiencies are assumed:

Spring lines 0.90 = 90%

Breast (jnes 0 .70 = 70lrfo

(c) All mooring lines are of steel.

(d) The maximum al.lowablc tension in anyone line is 55% of the mlnlmum breaking load of the

line, and the winch brake.~ must be capable of holding this load.

(e) Spring and breast lines are arranged symmetrically about midships so that the forward number

of lines is equal 10 the aft number.

(f) The minimum draft of oil tankers corresponds to the lMO draft, which is approximately

0 .02 Lop + 2.0 m.