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QUESTION 9.1.4

Strength compatibility of lines, tails and joining shackles

Oil, Chemical, LPG, LNGDocumentation

What is being checked

The inspector is checking whether every line, tail and joining shackle, including spares, is compatible with the vessel's Ship Design MBL and mooring-system working load. Certificates and the MSMP must demonstrate the required design break-force and safe-working-load relationships.

Ready onboard

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DESIGN BASISShip Design MBL and mooring-line WLL are clearly stated in the MSMP.LINESEach mooring line has an LDBF within 100-105% of Ship Design MBL.NYLON LINESWhere applicable, nylon line strength is specified on a wet break-tested basis.TAILSEach synthetic tail has a TDBF within 125-130% of Ship Design MBL.SHACKLESEach joining shackle has an SWL equal to or greater than the WLL of the lines in the system.CERTIFICATESManufacturer product certificates are available for every item in service and every spare.INVENTORYThe loose-equipment list agrees with the physical inventory and certificate values.SPOT CHECKSeveral tabulated LDBF, TDBF and SWL values have been independently checked against original certificates.

Practice questions

Answer aloud, then open the preparation point.

1What is the vessel's Ship Design MBL, and where is it stated?

Use the vessel’s approved procedures, records and fitted-equipment instructions. Demonstrate the evidence rather than giving only a general answer.

2Show how the acceptable LDBF range for this line was checked.

Use the vessel’s approved procedures, records and fitted-equipment instructions. Demonstrate the evidence rather than giving only a general answer.

3Why is the required TDBF higher than the Ship Design MBL?

Use the vessel’s approved procedures, records and fitted-equipment instructions. Demonstrate the evidence rather than giving only a general answer.

4For a nylon line, is the certified break force based on wet or dry testing?

Use the vessel’s approved procedures, records and fitted-equipment instructions. Demonstrate the evidence rather than giving only a general answer.

5Show that this joining shackle's SWL is not below the mooring-line WLL.

Use the vessel’s approved procedures, records and fitted-equipment instructions. Demonstrate the evidence rather than giving only a general answer.

6Select one spare item and trace its certificate and strength values.

Use the vessel’s approved procedures, records and fitted-equipment instructions. Demonstrate the evidence rather than giving only a general answer.

Where an observation may arise

MSMP

Ship Design MBL, WLL or the loose-equipment list is absent or unclear.

CERTIFICATES

Product certificates are missing for any in-use or spare line, tail or joining shackle.

LINES

A mooring line has an LDBF below 100% of Ship Design MBL.

TAILS

A mooring tail has a TDBF below 125% of Ship Design MBL.

SHACKLES

A joining shackle has an SWL below the WLL of the mooring lines.

MISMATCH

The inventory or summary table does not agree with the product certificates or physical items.

Master's practical note

Prepare one simple strength table from the certificates, but never rely on the table without checking the originals. The most common confusion is comparing unlike terms. Ship Design MBL, LDBF, TDBF, WLL and shackle SWL serve different purposes and do not need to carry the same number. The relationship between them is what must be correct.

Equipment boundary and references

Equipment boundary: Strength values must be taken from the approved MSMP and original manufacturer certificates. Do not convert or infer values from rope diameter, appearance or a generic table.

References

OCIMF Mooring Equipment Guidelines, Fourth Edition, sections 5.2.1, 5.8.2 and 5.8.4.1
Vessel Mooring System Management Plan
Manufacturer product certificates

Last reviewed: 2026-08-11