Bollard Pull Tests

 

What is a bollard pull test?

As opposed to ground vehicles, the horsepower rating of a watercraft engine is insufficient determining how powerful a ship-assist tug is. In order to certify a ship-assist tugs as fit for service, it’s power output must be measured. The power output of a tug determines the pull or towing force it is capable of applying. The power output is measured by performing a bollard pull test.

How is a bollard pull test performed?

The power output of a ship-assist tug is best described as “thrust developed at zero speed”. In order to meet the requirements of their specialized operation, tug propulsion systems are designed for maximum performance at zero speed in the forward direction. To simulate conditions in which a tug is expected to operate, the tug is tethered to bollards (short steel structures commonly used for mooring ships to the pier) and a load cell is placed on the tethering line. The tug applies tension to the tethering line while the load cell measures the applied load. Having been tethered, zero speed and maximum output is possible.

For reliable results, bollard pull tests should ideally be performed in deep water, far from the mouth of a river on a calm day with minimum traffic. Currents or strong winds can potentially falsify readings. In order to ensure that the force is only generated by the interaction of the propeller and surrounding water, sufficient distance should be provided between the tug and pier wall. Rudder angle should be close to zero degrees; it is important to keep conditions as static as possible. Engine power and heading should remain constant and the test should continue until the reading on the load cell settles on a near-constant value for reliable measurement.

Eilon Engineering’s Ron Crane Scales™ dynamometers are particularly suited for performing bollard pull tests. Their small dimensions and light weight make them ideally portable and easy to handle during test preparations. Built-in data logger and PC output options simplify test verification. IP67 environmental sealing protects the load cell from accidental immersion in water. Availability of multiple displays make it possible for both the captain and test engineer to view dynamometer readings simultaneously allowing for greater control during the test.
 

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