|This is a short extract from “OCIMF’s RECOMMENDATIONS FOR SHIPS’ FITTINGS FOR USE WITH TUGS”
We recommend all interested to purchase the book from OCIMF since there is a lot of important information.
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Escorting is becoming a widely used method of risk management at various ports and harbours worldwide. It is usually, although not exclusively, used for tankers. It differs from the normal use of harbour tugs in that the escort tug is in attendance and may be made fast (active or tethered escorting) for an extended distance, with the escorted vessel making way at speeds of typically 5 to 12 knots.
The usual purpose of escorting is to assist the tanker in the event of steering and/or propulsion failure. Within the limits of tug safety, the escort tug can take the way off the tanker, alter its heading or both. Crucially, it can slow the tanker down so that it becomes easier to control.
It is important to note that with the escorted vessel underway, and the tug applying a towing force at an angle to the ship's heading, the water flow against the hull and the tug's own displacement will generate hydrodynamic forces. When combined with the propulsion forces these may give a resultant (steering) force in the towline far exceeding the static bollard pull of the tug.
Safe Working Loads (SWLs) are expressed in metric tonnes rather than the technically correct unit of force Newtons (N) to avoid conflict with recommendations contained in Mooring Equipment Guidelines.
(Note: I metric tonne force = 9.81 kilo Newtons).
Recommendations for the Tanker Owner Recommendations for the Tanker Owner
Tankers over 20,000 dwt but under 50,000 dwt to provide:
Tankers of 50,000 dwt and above to provide:
The following recommendations assume that the strong point is not incorporated in the Emergency Towing Arrangement. In such cases: