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Concepts

Capsize Girding

A tug capsize caused by the towline pulling the tug broadside or stern-to the direction of load, overwhelming its righting moment. The tug is "girded" — caught by its own towline and unable to recover.

Definition

A tug capsize caused by the towline pulling the tug broadside or stern-to the direction of load, overwhelming its righting moment. The tug is "girded" — caught by its own towline and unable to recover.

Mechanism

  1. Tug is towing or assisting a large vessel
  2. The lead of the towline shifts to a beam or stern angle (perpendicular or near-perpendicular to the tug's heading)
  3. The lateral force from the towline exceeds the tug's transverse stability
  4. The tug heels rapidly and capsizes — often within seconds
  5. Crew have little or no time to respond or release the hook

Why it happens

  • Tug gets out of position relative to the towed vessel
  • Large vessel changes course or speed unexpectedly
  • Tug operator cannot release the towhook in time
  • Towhook release fails (see Towhook Failure)
  • Poor communication between tug and pilot

Key risk factors

  • Conventional towing hooks without automatic or quick-release mechanisms
  • High bollard pull relative to tug's beam (more power than stability)
  • Confined waters limiting the tug's maneuvering room
  • Operating in a position where the towline can sweep aft

Accidents linked to this concept are grouped by vessel type.

Tug (55)

Other (2)