IACS UR A3 Continuous Pull, 2-Minute Overload, 9 m/min Hoisting, Brake Holding, Wildcat Torque & Prime-Mover Power

Anchor Windlass Pull, Chain Load, Brake Holding & Motor Power Sizing Tool

Turn chain diameter, grade, anchorage depth and certified chain breaking load into the windlass loads that matter. Calculate IACS UR A3 continuous pull, deep-water correction, short-term breakout pull, brake holding load, chain-stopper / foundation load path, wildcat torque and minimum prime-mover power. Advanced mode adds a physical anchor-and-chain lift cross-check, custom class factors, electric or hydraulic drive sizing, recovery time and vendor-candidate comparison.

Data type
Currency
Currency selection changes display only. No exchange-rate conversion is performed.
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Need much more depth? Click Advanced above. Add the physical anchor-and-chain load cross-check, custom brake / stopper / foundation factors, overload speed, electric or hydraulic drive sizing, recovery time and candidate windlass comparison.

Fast Windlass Sizing Screen

Simple mode uses the IACS UR A3 ordinary-stockless-anchor pull formula and requires the actual chain MBL for brake / stopper checks. UR A3 assumes one anchor is raised at a time.

mm.
kN. Use the chain certificate / applicable class value.
m. UR A3 adds a depth term above 82.5 m.
m/min. IACS UR A3 minimum mean hoisting speed is 9 m/min.
m.
% from prime mover to cable lifter.
% above calculated continuous drive power.
kW.

Pull & Physical Load Basis

kN. Used only when Custom is selected.
kg.
kg/m.
% of air weight.
% for physical suspended-load cross-check only.
kN physical cross-check allowance.
m submerged / suspended.

Brake, Stopper & Foundation Factors

Leave custom factors at 0 to use the IACS arrangement basis. Brake is 45% MBL with a chain stopper fitted or 80% without. Chain stopper is screened at 80% MBL. Foundation operating load is 45% with an independent stopper, otherwise 80% when no stopper is fitted or the stopper is attached to the windlass.

% MBL. 0 = automatic IACS arrangement basis.
% MBL. 0 = 80% when a stopper is fitted.
% MBL. 0 = automatic arrangement basis.

Prime Mover & Drive

% of nominal chain speed during breakout.
%.
V, 3-phase.
bar.
% pump-to-cable-lifter drive basis.
rpm for indicative reduction-ratio calculation.
m for recovery-time display.
Selected currency / kWh.

Candidate Windlass Register

Compare pull, overload, brake, stopper, speed and prime-mover rating independently. Candidate names are not submitted to Ship Universe Tool Data.

CandidateCont. kNOverload kNBrake kNStopper kNSpeed m/minMotor kWWildcat mCost

Engineering Readiness

Bower-anchor windlass screening only: this tool is not a class-approved windlass calculation, chain-cable certificate, brake test, chain-stopper design, deck-foundation assessment, shaft / gear stress analysis, electrical protection study, hydraulic-system design or OEM guarantee. The 2026 SOLAS anchor-handling-winch regime is a separate subject; a vessel's normal bower-anchor windlass should not be treated as an offshore anchor-handling winch merely because it handles the ship's own anchors.
Reference basis: Current IACS UR A3 Rev.1 (June 2019) requires a windlass prime mover to provide continuous pull for at least 30 minutes. For ordinary stockless anchors to 82.5 m, Zcont1 is 37.5d² N for Grade 1, 42.5d² N for Grade 2 and 47.5d² N for Grade 3, with d in mm. For deeper anchorage, Zcont adds (D - 82.5) × 0.27d² N. Short-term breakout pull is at least 1.5 × continuous pull for at least 2 minutes, and mean chain-hoisting speed is at least 0.15 m/s. Brake holding is 80% of chain MBL without a stopper or 45% when a stopper is fitted. Supporting hull operating load is screened at 45% MBL for a windlass with an independent stopper and 80% when no stopper is fitted or the stopper is attached to the windlass. IACS requirements are minimum requirements and class societies may be more stringent. IACS UR A3 · IACS Recommendation 10 · ClassNK support-structure example
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