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

IACS UR A3 Pull, 30-Minute Duty, 2-Minute Overload, Brake Holding, Wildcat Torque & Drive Power

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

Turn chain diameter, grade, anchorage depth and chain breaking load into the windlass loads that matter. Calculate IACS-style continuous pull, deep-water correction, short-term breakout pull, brake and chain-stopper holding loads, physical suspended anchor-and-chain load, wildcat torque, electric or hydraulic drive power, recovery time, foundation load and candidate windlass fit.

Chain Cable & Anchorage Basis

The IACS UR A3 continuous-duty pull is calculated from chain diameter and grade, with an additional depth term above 82.5 m. Enter the certified minimum breaking load for the actual chain cable because brake, stopper and supporting-structure checks depend directly on MBL.

Chain cable diameter

Chain grade

Certified chain minimum breaking load

Use the chain certificate / applicable class value. This tool does not infer MBL from diameter.

Maximum anchorage depth for windlass sizing

Anchor mass

Chain mass in air

kg/m

Submerged weight factor

% of air wt

Hawse / mechanical lift efficiency

Used only for the physical suspended-load cross-check. UR A3 continuous-pull coefficients already embed their own assumptions.

Additional physical breakout / seabed release load

Number of anchors hoisted simultaneouslyUR A3 continuous-pull basis assumes one anchor is raised at a time.

Brake, Chain Stopper & Foundation Arrangement

Chain stopper arrangement

Custom brake holding factor

% MBL

0 = use IACS arrangement basis: 45% with chain stopper fitted, 80% without one.

Chain stopper design factor

% MBL

Foundation / support custom factor

% MBL

0 = auto: 45% for windlass with independent stopper, 80% if no stopper or stopper attached to windlass.

Candidate Windlass

Continuous pull rating

Short-term overload pull rating

Brake holding rating

Chain stopper rating

Rated chain recovery speed

m/min

Installed prime mover rating

Wildcat / cable-lifter pitch diameter

Gear reduction ratio

Transmission efficiency

Candidate retrofit / purchase cost

Vendor / Windlass Candidate Register

Compare candidate windlasses against the same chain-cable requirement. Brake, pull, speed and prime mover kW are evaluated independently so a large motor does not mask a brake or gearbox limitation.

Candidate	Cont. kN	Overload kN	Brake kN	Stopper kN	Speed m/min	Prime mover kW	Wildcat dia m	Gear ratio	Trans eff %	Cost

Prime Mover & Drive Sizing

Drive type

Nominal chain recovery speed basis

m/min

Short-term overload speed fraction

% nominal

Prime-mover service margin

Electric motor efficiency

Electric system voltage

V 3-phase

Power factor

Hydraulic pressure

bar

Hydraulic overall efficiency

Annual anchoring / weighing operations

Shipboard electricity cost

$/ kWh

Engineering Readiness

Chain certificate / MBL confirmedDiameter, grade and minimum breaking load match the chain actually installed or specified. Anchor mass / type confirmedAnchor mass and any non-standard HHP / SHHP arrangement are included in project review. Brake setting / holding test basis availableBrake condition, lining, adjustment and holding capacity are verified rather than assumed from motor size. Chain stopper arrangement / rating confirmedIndependent versus windlass-attached stopper configuration is reflected in the structural load path. Windlass foundation / deck support checkedSupporting structure and fasteners are reviewed for the applicable operating load path. Class / OEM design basis identifiedCurrent class rules, windlass certificate, chain / anchor data and shop / onboard test requirements are mapped into the project.

Engineering screening only: This tool is not a class-approved windlass calculation, brake test, chain-stopper design, deck-foundation strength assessment, chain-cable certification, anchor selection, hydraulic-system design, electrical protection study or OEM guarantee. IACS Unified Requirements are minimum requirements and individual class societies may apply additional or more stringent provisions. The 2026 SOLAS anchor-handling-winch regime is a separate subject and does not apply to a ship's own bower-anchor windlass merely because it handles the vessel's anchors.

Reference basis: Current IACS UR A3 Rev.1 (June 2019) covers anchor windlass design and testing. Its core windlass sizing framework includes a 30-minute continuous-duty pull derived from chain diameter and grade, an additional depth term beyond 82.5 m, at least 1.5× continuous pull for a short-term breakout period of at least 2 minutes, and a nominal chain recovery speed of at least 0.15 m/s. Brake and supporting-structure load cases depend on whether a chain stopper is fitted and how it is arranged. Verify the current rules of the vessel's class society for procurement and approval.

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