The stiffer the lifeline the less the sag, but when a person falls and the lifeline has to save the person’s life then it’s much better to have a decent amount of sag otherwise the forces in the lifeline become absolutely massive and stress on the end anchors unmanageable.

Best advice- don’t buy these from “on-line” stores, or from people working with a glossy foreign brochure. You need to see actual design calculations of the loads and resulting stresses.   

ZIPPY’S STRESS METER

ZIPPY’S STRESS METER

Like Zippy says – “The more sag the better!”  But the lifeline must still prevent the person from hitting the ground. So, it’s better to get this designed by a competent person / organisation. http://www.wahs.co.za