Mooring Line MBL, Tension & Recoil Energy Calculator

MOORING • MBLSD / LDBF • WLL • PEAK TENSION • STORED ENERGY • FITTING LOAD

Mooring Line MBL, Tension & Recoil Energy Calculator

Screen a mooring line against Ship Design MBL, installed Line Design Break Force and working-load limits. Estimate dynamic peak tension, effective strength after user-entered retention factors, elastic stretch, stored strain energy and optional tail contribution. Advanced mode adds winch/fitting checks, retention losses, scenario stress and tension-energy sensitivity.

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Need winch brake, fairlead resultant, condition loss or scenario stress?Click Advanced above. Simple uses the MEG4/IMO reference WLL percentages and a linear 0.5 strain-energy factor.

StrengthWLL & LDBF utilization

LoadStatic → peak tension

EnergyMain line + tail

Line Strength & Operating Load

Use vessel-specific approved values where available. Under MEG4 terminology, “rope MBL” is replaced by MBLSD and LDBF.

Line typeDefault reference WLL: 50% synthetic, 55% wire.

Ship Design MBL (MBLSD)kN

Installed LDBF / certified break forcekN

Measured / static line tensionkN

Dynamic tension allowance% added to static tension.

Main line loaded lengthm

Main line elongation at peak tension% of loaded length.

Optional tail LDBFkN. Enter 0 if no tail.

Optional tail loaded lengthm

Tail elongation at peak tension%

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Advanced adds strength-retention, winch/fitting checks and stored-energy modeling.Use manufacturer load-extension data and approved vessel limits where available. The energy factor lets you move beyond the default linear 0.5 approximation.

Design Strength & Working Load

Line type

Ship Design MBL (MBLSD)

Installed LDBF

WLL basis

Custom WLL% MBLSD; used only when Custom selected.

Condition strength retention%

Bend / D:d strength retention%

Additional strength retention%

Tension, Winch & Fitting Load

Measured / static line tensionkN

Dynamic tension allowance%

Winch brake setting / load limitkN

Applicable fitting resultant-load limitkN

Line direction change at fittingdegrees. Resultant = 2T × sin(angle/2).

Main Line Stored Energy

Main line loaded lengthm

Main line elongation at peak tension%

Main line energy integration factor0.5 = linear load-extension approximation.

Optional Mooring Tail

Tail LDBF / certified break force

Tail strength retention%

Tail loaded lengthm

Tail elongation at peak tension%

Tail energy integration factor

Mooring Review Checks

These checks do not change the calculations. They flag inputs that should be verified before operational use.

Line certificate / LDBF verifiedUse the installed line certificate and manufacturer documentation. Mooring arrangement plan reviewedConfirm MBLSD, fittings and approved limits. Current line condition assessedWear, abrasion, heat, contamination and retirement criteria. D/d and lead geometry checkedConfirm bend severity against manufacturer guidance. Winch brake setting verifiedUse test/maintenance records, not nameplate assumptions alone. Snap-back risk assessment currentStored energy does not define a safe standing distance.

Tension Stress Cases

Sensitivity cases scale static tension and effective retained strength. Energy sensitivity assumes line stiffness inferred from the entered base elongation, so use manufacturer load-extension curves for detailed engineering.

Case	Static tension ×	Dynamic allowance Δ pp	Strength retention ×

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