Energy Absorber (EA) Lanyard/ Tear webbing lanyard:
We are aware of Lanyards & Full body harness (FBH) that are utilised for work at height to ensure the safety of worker. The basic components are anchorage, full body harness & connecting element (lanyards).
A concept of EA lanyard got its recognition so as to reduce the impact on worker’s body, which is spontaneously exerted on the body as it stops (kinetic energy=0, velocity=0) after a free fall locked by anchoraged lanyard. Its objective is to keep the impact below 6KN. Above 6KN, the internal parts of human body gets damaged and may be fatal, which is due to fall arrest and not by hitting the ground on free fall.
Now the questions are:
What is the mechanism of EA?
What is the minimum impact required to activate EA?
When will the threshold impact be attained?
When do you require EA?
EA is a Tear webbing (layers of webbing overlapped & stitched). The free fall leads to conversion of kinetic energy to potential energy (PE), as the fall locks/arrests through anchorage lanyard. This PE creates heavy impact & leads to high tension on connecting element. Now, the whole impact initiated by PE will be exerted or transferred to the victim. Here, we have to keep the impact less than 6KN to avoid internal injuries.
If we connect a tear webbing (EA) between the FBH & Rope lanyard, then the impact due to PE will cover EA lanyards also. As soon as the impact gets above 2-3KN, stitches between the overlapped layers of EA break in a sequence to initiate deceleration leading to non-occurrence of sudden fall arrest. This deceleration keeps the impact upto 2-3KN which is the threshold for tear webbing to get released & thus final impact doesn’t reach 6KN.
The mentioned threshold of 2KN for activating EA can be attained if a 100KG body connected to FBH & anchorage lanyard gets a free fall of 2 meters (W=mgh). This is one of the conditions. One other condition may be, 70KG body connected to FBH & anchorage lanyard gets a free fall of 3 meters. Oops, in India we neither use 3 meters layard nor we recommend a 100KG guy to work at height.
If we keep anchoring the lanyard hook over our head with our weight of 70KG, the maximum impact on us & the anchorage systems will not be more than 1.4KN. This energy will not lead to activation of energy absorber.
Now, the consumer, customer & safety incharge has to technically assess, that do they really require EA lanyard by putting in extra cost, when their worker has a weight less than 80KG with a lanyard length limited on 2 meters.
*This article does not recommend to avoid use of EA layards. It advises to use EA where it is practically required.
VIDEO FOR ANCHORING LANYARD:
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