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18Maritime Reporter & Engineering News Bollard pull is derived from a trial where the towline is connected to a bol- lard and the power settings are increased to MCR (Maximum Continuous Rating).The tension in the towline is then meas- ured by a calibrated and certified load cell. ?Sustained bollard pull?, ?maximumstatic bollard pull? and ?maximum bol-lard pull? are derived from the measured continuous tension. To conduct the re- quired measurements during bollard pulland escort trials MARIN Trials & Moni- toring has recently expanded its meas- urement equipment. The range of avail- able load cells has now been extended to have a capacity of 250 tonf. Additionally, the new load cells are equipped with wireless, high range data transmissionand a Moving Base Real-Time- Kinematic GPS? system has been ac-quired to record the horizontal towline angle during escort trials. This system consists of two Real-Time- Kinematic GPS receivers working in a Rover/ Base setting. One system is placed on the escorted vessel and the other on the escort tug. In this way the track and the heading of both vessels are recorded as well as the towline angle. This is important real time information todetermine the maximum steering forceobtained. During both bollard pull andescort trials the developed shaft power of the tug is derived from the shaft torque and rpm measured by MARIN?s SMART system.ESCORT NOTATION TRIALS To receive a Class ?escort tug? notation the maximum steering force that can beproduced by the tug on the vessel, as well as the time it takes to swing from board to board, have to be established. For this purpose escort trials are conducted wherethe escort tug is connected to the stern ofa large vessel. While the vessel maintains course and its pre-set speed, the tugswings sideways to produce the maxi- mum steering force on the vessel. The time required to achieve maximum steer- ing force from one side to the other isalso measured.COLUMNEYE ON DESIGNBollard Pull & Escort Trials at MARIN MARIN carried out an extensive array of tests for bollard pull & escort trials and it boosted its offering with new dedicated equipment. About the AuthorHenk van den Boom is manager at theTrials & Monitoring department of MARIN, the Maritime Research Institute Netherlands. MARIN offers simulation, model testing, full-scale measurements and training programmes, to the ship- building and offshore industry and gov- ernments. For more information: [email protected] / www.marin.nl MR March 12 # 3 (17-24):MR Template 3/6/2012 12:34 PM Page 18