Anchor Pattern (Mooring)

An anchor pattern is the designed array of anchors, chains, and wires that holds a moored mobile offshore drilling unit (MODU) or construction barge on station, typically 8 to 12 lines spread symmetrically about the unit. The pattern is sized for the design environmental load (wind, wave, current) with a target factor of safety on line tension under intact and one-line-damaged conditions per IMO MODU Code (Res. A.1023(26)) and class rules such as DNV-OS-E301. Anchor-handling tugs run, set, and recover each leg; spread mooring is the alternative to dynamic positioning for station-keeping.