Critical design characteristics of quality quick release hooks

Authorship

Trelleborg Marine Systems (TMS)

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The time for disputing the value of quick release hooks (QRH) is long gone; decades of successful applications have proven their worth over traditional bollards. But with so many hook manufacturers and suppliers vying for market share, the debate over what makes a quality QRH is still very much in the minds of port operators.

And so it should be. The hooks will need to secure millions of dollars of vessel and cargo and deliver other benefits such as efficiency and safety. The last thing a port operator needs is a system that can’t meet these requirements, resulting in lost time and money and perhaps damage to the vessel and injury to the mooring crew.

Unfortunately, not all hook manufacturers have the experience to deliver quality and reliability, and recent examples of hooks releasing under load without warning shows that when selecting a hook for installation, the experience of the manufacturer needs to be considered.

At first glance any hook will provide somewhere to attach a mooring line. The performance of a QRH must therefore be evaluated by the extra features that deliver functionality above the basic requirement. After 30 years of development and working closely with port operators, Australian QRH manufacturer Trelleborg Harbour Marine has identified several small but critical areas of design that make a large difference to the performance of a QRH unit.

Protected release mechanism
As the name suggests, the primary function of a quick release hook is to enable the mooring line to be quickly and easily released. Most hook designs achieve this with a mechanism usually constructed of cables and levers. If this mechanism is damaged, the hook may not release the mooring line at the moment the jetty operator commands. This means the jetty crew needs to intervene, which defeats one of the primary purposes of the QRH: a quick release.

Prudent design will put the release mechanism within the hook side plates, which will protect it from damage when swinging hooks collide. Mechanisms that are on the outside of the side plates risk damage that can put the hook unit out of action. As a secondary benefit, containing the mechanism within the side plates eliminates protrusions that can entangle the messenger line. For the same reason, all fasteners, pins and grease nipples should be recessed into the side plates.

Positive hook locking
The temptation of a hook that resets automatically after release can be hard for jetty operators to resist, but these systems carry with them the risk that the hook may not lock positively. If that happens, the hook may open under load and release the mooring line unexpectedly. Because this is most likely to happen when the mooring line is first loaded, jetty and vessel crew close to the mooring line may be in danger of injury if it releases without warning.

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