Equipment Number
Abbreviation: EN
Class-society-calculated dimensionless number that sets the required size + weight of anchors + chains + windlass + mooring equipment.
Regulatory detail & full definition
Equipment Number is calculated from displacement + windage area + freeboard per each classification society's rules (broadly consistent). The resulting number is looked up in a table that prescribes the anchor mass, chain diameter + length, tow-line + mooring-line breaking loads, and windlass capacity for the ship. Ships with EN outside the standard table (very large tankers, LNG) require special engineering analysis.
Authoritative source: IACS Publications ↗
Related
Source: IACS UR
High confidence
Editorial confidence: how we grade.