MEG4 requirements of Mandal Fairlead Shackle
OCIMF丨MEG4 丨HMSF丨Mooring Lines丨Joining Shackles
Date: January 27,2021
Author: Mark Song
5.8.4 Connections
Tails are generally connected to mooring lines either through the use of mechanical connecting devices (i.e. joining shackles) or directly with the use of a cow hitch. Each method has specific considerations ,as outlined below.
5.8.4.1 Connection devices
Tails can be connected to both steel wire and HMSF mooring lines using a connection device. Connection devices are normally made of meta l. If alternative materials may be considered , follow the guidance in section eleven.
There are several manufacturers of joining shackles and currently there is no standard value for the safety factors between SWL and minimum yield strength or Ultimate Tensile Strength(UTS) failure values. However,most manufacturers will supply connection devices that have a safety factor of three ,i.e. a breaking load that is three times the SWL.This is a greater safety factor than is used for lines. The SWL of joining shackles should always be equal to,or greater than ,the WLL of the lines in the mooring system ,so that the SWL will never be exceeded within the working load range of the lines to which they are attached. Although WLL values for wires and synthetic lines are slightly different (55% and 50% of ship design MBL respectively)
it is not intended that joining shackle manufacturers or ship operators attempt to match the SWL of the shackle to the WL L.In the absence of a standard value for safety factors,a minimum safety factor of three is recommended. Deviations from this should be considered in the context of the overall mooring system design to minimise the risk of connecting device failure.
When the D/d ratios provided by the connection device are below those recommended by the tail manufacturer,the connector should be orientated so that the smaller diameter pin is connected to the mooring line and the larger diameter sheave or spool is connected to the tail.Since mooring tails are of a larger diameter than main lines,this helps connect the larger fitting end to the larger rope.
Users should consult with both the line and shackle manufacturers when necessary to ensure the proper orientation is used and the fitting does not create unacceptable fatigue on the line or tail.Connection devices should be inspected regularly as part of the LMP and discard criteria established and documented. Connection device inspections should normally include visual inspection,dimensional verification and periodic NDT inspection.
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