Bollard Pull

Bollard pull is the zero speed pulling capability of the tug. It is a measure of the usefulness of the ship in a stranding scenario or in holding a large tanker or aircraft carrier off a lee shore. Bollard pull figures, like horsepower, may be open to interpretation. Ideally, bollard pull is tested when a tug is built and certified by one of the classification societies. Bollard pull tests are also sometimes performed after major engine overhauls. Tug owners whose tugs have been tested usually provide a copy of the certificate attesting to the bollard pull figure. Bollard pull, like horsepower, is a selling point for tugs and is sometimes overstated. For instance, there are rules of thumb for converting propeller power (shaft horsepower) to bollard pull, such as one ton pull per 100 horsepower for a conventional propeller or 1.2 to 1.5 tons pull per 100 horsepower for a propeller fitted with a nozzle. The owner may save the cost of a bollard pull test and simply apply one of the factors to convert propeller power to bollard pull without ever knowing what the real figure is. It is unlikely that the owner would ever select a conservative conversion factor. European owners generally report bollard pull in their literature and reputable salvage tug owners are generally able to produce a certificate to document the test. American owners and the worldwide offshore oil support industry, on the other hand, rarely report bollard pull. When they do, the figure may not have been validated by a test. Horsepower is probably a more reliable measure among ships of these types.

Links
IMO Bollard Pull Testing Procedure

Marine Engineers Blog

Marine Survey Practice

ABS Guidelines for Bollard Pull Test Procedure