STANDARDS bodies and legislative branches are continually investigating and working on establishing what the minimum levels of safety are to ensure the integrity of the whole system.
For the user the challenge is understanding what equipment and information works for them.In height safety, connectors must meet the same strength requirements as any other piece of the system they are a part of.
Most hook (snap hooks and karabiners) manufacturers design their hooks to the North American standards (ANSI & CSA) or the European standard (CE).
As such the strength requirements of most hooks actually exceed the requirements outlined by AS/NZS 1891.1 of 15kN and meet the strength requirement of 22.2kN (ANSI & CSA requirement).All hooks manufactured to these standards will be marked with the strength rating so that the user can make an informed selection and ensure that their hook is not in fact the weakest link.
The greatest hazard associated with hooks is the question of compatibility.The compatibility of hook to "D" ring (harness or anchorage connector) becomes critical if there is a possibility of the gate coming into contact with the "D" ring and causing roll out, the accidental disengagement of the hook during a fall or normal operation.
This possibility has prompted virtually every standards body in the world to require locking gates on both snap hooks and karabiners.Locking mechanisms have continued to evolve and simple latches and screw gates have made way for user-friendly trigger mechanisms and autolock (double action and triple-action) gates.
The advances in locking mechanism technology have been a subtle balance of increased safety with useability.For example the development and continual acceptance of autolocking gates on karabiners has strongly been resisted within the fire brigades, technical rope rescue and rope access communities.
This resistance stems from the realisation that when a karabiner is used as a connector within a travelling haul system it can potentially rub against structure and the locking mechanism on the gate can be rolled open.
Once open a karabiner loses a significant amount of its strength (up to 2/3 in some instances).Even with the development of triple action karabiners the argument continues.
Unless users are highly trained and practice on a continual basis, the use of technical rope systems are not recommended.Common hazards associated with screw gate karabiners are that if the user forgets to screw the gate closed we have a non-locking hook.In addition, the orientation of a screw gate is very important.
If our goal is to keep the systems used simple and easy to learn, rope systems and screw gate karabiners are unwarranted.
With the intention of keeping systems simple and safe, the selection of the right hook must take into account the ability of the worker to use the hook.
When the connector that is connected and disconnected on a regular basis (for example between lanyard and anchor point or self-retracting lifeline and harness) functionality must be considered.
In an application where the load is applied on the spine of a hook, there is little question that a snap hook is easier to use and provides the exact same strength and safety of a karabiner with equal rating.
A 22.2kN karabiner with a double-action gate matches the safety requirements and strength of a similar triple-action hook but has the advantage that most workers can easily open the hook with a single hand.The triple-action hook requires the use of both hands for all but the most practiced worker as the action of moving the barrel up prior to twisting requires the worker to put a finger inside the karabiner as leverage.
Selecting the right hook for the task is very important, but so is the issue of compatibility of hook and anchor point or "D" ring.Simply using a locking hook (snap hook or karabiner) does not guarantee compatibility.The rated strength of any hook is along its major axis (the spine) of the hook.
All proof loading (the static pulls test on a hook to approximately 2/3 its breaking strength) and destructive testing (to establish its tensile strength) is from end to end.The weak point on a hook is in fact its gate.
Currently there are only two industrial standards worldwide which identify a strength requirement for a hooks gate.ANSI and CSA in North America require that the gate on a hook be tested with a static load applied to the face and side of the gate.The gate must be able to withstand a minimum of 1.0kN to the face and 1.5kN to the side of the gate with a maximum of 3mm deflection under load.
Given that AS/NZS 1891.1 requires that the design of a shock absorber must reduce the force of a fall to below 6kN, if there is any possibility of having the gate impact on the anchor point, the possibility of forced rollout exists regardless of the type of locking mechanism.Testing for compatibility, the ability to get pressure on the gate, becomes the real decision; which hook is more about the application and suitability to the job.
Choosing the right tool for the job requires the right information that comes with experience and training.
* Emmett McGregor is marketing and technical support manager with Capital Safety Australia .