(Avoiding defining what a short fall is). The squishiness in short falls probably reduces the Impact load by 50%. and some of us might have the delusion that that models us well, but I don't. The human is modeled as a collection of steel weights. If it is a human being caught, the squishiness of the human is not accounted for. If I say the catch was made in 0.1m, I get one answer, but if I say 0.2m, the answer I get is probably half that. There are calculators available to estimate the Impact Load, but you have to enter numbers into the calculator which you probably don't know. Which is useful for comparing ropes, but not for much else.īut in the real world, Fall Impact loads are difficult to get a handle on. Climbing rope designs are tested for the Impact Load they generate in a standardized test fall (a UIAA fall), which is about the worst fall one would expect (to survive) in the field.Thus when you buy a climbing rope, there is a number in its specifications that tell you what the rated Impact Force is on this rope, under extremely specific conditions, when new.

If you are taking a fall of significant length, you want to be falling on a dynamic climbing rope, which has a carefully engineered stretch to it so that the Impact Load is minimized. It is a hard number to measure, but it can be measured with proper equipment. This is a very difficult number to calculate. More rigorously, we state a single number which is the highest force generated in the catch.

The Fall Impact Load is the force generated by an object falling and then being caught by a rope, cable, lanyard, etc. The rapid links we are talking about use 5X, so they are 5 times stronger than the WLL stamped on the side.

The lowest I have seen is 5X, and I am told some items might use 10X. But you would have to know the Safety Factor used for that specific item, which can vary. The Safety factor takes account of what kind of loads are created on the item in reality when you lift your aged sportscar using a crane. Manufacturers provide a Minimum Breaking Strength (MBS) which is the load that you can apply to the device without it breaking - though the load needs to be applied in exactly the way the item was tested.įor any specific item, the MBS can be calculated from the WLL or SWL by multiplying by the Safety Factor. IF your crane operator is a real crane operator and not your cousin Vinny who saw how to do it on YouTube.Ĭlimbing gear is rated using an entirely different system. If the WLL is 750 kg, and you need to lift your Lotus Europa Special (mass=740kg) out of the display case with a crane, you can use this item in the chain. It is a claim that under specific normal industrial lifting conditions, this item can be used (in a specific manner) for lifting a load up to the rated weight. WLL and SWL (working load limit and Safe Working Load) are two systems for rating hardware (and software) for industrial use. which covers the subject of carabiner specs and what they mean in detail and very clearly.) (Some people will want to start is this post by Richard Delany at Rope Test Lab: Carabiner Specifications Question - Can someone explain the difference between safe working load and fall impact load? Or are they the same? CHAPTER ONE - SOME BACKGROUND NOMENCLATURE EXPLANATION

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