Mooring Rope Ultra High Molecular Weight Polyethylene Fiber

Specify the line by its Line Design Break Force (LDBF), which should be 100–105% of the ship design MBL; a tail’s design break force should be 125–130% of the ship design MBL. Give both figures on the requisition, with the circumference or diameter, length, eye at one or both ends, and whether the tail is supplied with the line.^[3][4]

HMPE must be kept to a minimum bend radius or compressed fibres are overloaded. In the Bahamas Maritime Authority casualty, the manufacturer’s minimum equipment-to-line diameter ratio was 15:1 and fittings had less than half that; the lines with the largest wrap on roller fairleads failed first. When ordering a new diameter or make, ask the supplier for the minimum D:d ratio and check it against the ship’s fairleads, rollers and bitts.^[2]

The catalogue lines name a specific branded rope. If an equivalent HMPE 12-strand from another maker is acceptable, say so, and ask for the LDBF on the certificate so the offers compare.^[3]

MEG4 gives the method for calculating required mooring line strength and its relation to equipment working load limit and maximum winch pull. The Bahamas Maritime Authority points to MEG4 as a reference for any mooring arrangement using HMPE, and to the OCIMF/SIGTTO Guide to Purchasing High Modulus Synthetic Fibre Mooring Lines.^[5][2]

The winch brake is the main protection of the mooring system: it should render above the lines’ working load limit but before any component fails, and the render point should be clearly marked for the crew.^[2]

HMSF ropes have very specific stretch and snap-back characteristics that need to be considered; synthetic ropes give little or no audible warning before they break. The Code of Safe Working Practices asks for objective retirement criteria and certificates kept on board and linked to each line.^[1]