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Wednesday, October 23, 2019

Maritime Logistics Professional

August 25, 2016

The Importance of Correctly Fit Bulldog Grips

Tony Watson, Risk Assessor at UK P&I Club, advises on the correct application of bulldog grips in order to minimize damage to cargo.
 
Bulldog grips are commonly used for the securing of project cargo, both under and below deck. They are also  used on ships on mast stays and crane wires, although swaged connections are now more common.
 
The single most predominant factor associated with the failure of cargo lashings is the incorrect application of bulldog grips. Failed lashings can result in significant damage to cargoes, and can also pose significant risk to the wellbeing of crew members and the safety of the ship.
 
The Club’s Risk Assessors note that stevedores and shipyards should consider the following:
  • The saddle part of the bulldog grip should be applied to the “live” load bearing wire, whereas the U bolt goes around the “dead” tail:
  • A useful way to remember this is by using the mnemonic “never saddle a dead horse”.
  • Another good “aide memoire” is Saddle / Stressed, U / Unstressed.
  • The distance between the grips is important and should be about six times the rope diameter; not significantly more or less.
  • The length of the tail is also important and should be greater than five times the rope diameter.
  • The tail should be whipped or bound to prevent it unravelling.
  • The number of grips used depends on the diameter of the wire but at least three should be used for wires up to 19mm.
  • It is important that the tightness of the nuts is checked periodically as the grips have a flattening effect on the wire, resulting in a reduced grip. 
Various tests were carried out several years ago which showed that a perfectly made up hard eye around a thimble will hold at 90 percent to 100 percent of the nominal breaking load (NBL) of the wire before slipping and/or fracturing. If the grips are reversed, (contrary to the often expressed opinion that “it makes no difference”) the wire will fail at around 50 percent NBL.

By using only two grips (instead of the recommended three), even correctly applied, the wire would slip at around 60 percent NBL reducing to 50 percent when reversed or staggered. With one grip, these figures were 25 percent (correct way around) and 18 percent (reversed).

The correct method of fitting bulldog grips is hardly ‘rocket science’ but the majority of those seen on board are, in some way, incorrectly fitted. Proper supervision in the builder’s yard should ensure that these are initially fitted correctly. Equally, stevedores/lashing gangs should be supervised and instructed to correct improper lashings.
fracturingU.K. P&I Club