It is important to state that a left hand lay rope and a right hand lay rope MUST never be joined together unless the jointing mechanism is prevented from rotating, otherwise the rope will be allowed to un-twist together, which may have a significant effect on the integrity of the ropes, and could result in failure of the rope. There are two particular situations/arrangements where a left hand and/or right hand rope combination may be considered beneficial;
To prevent rotation of load – Twin rope operating systems (Overhead hoists, Grabbing systems, Container handling cranes, etc.) are generally designed to utilise one left hand rope and one right hand lay rope. When lifting a load both ropes will be subjected to an axial load and will try to un-twist, but since the ropes have been spun in different directions during manufacture one rope will trying to un-twist in one direction whilst the other rope will try to un-twist in the opposite direction, the two ropes therefore acting against each other to prevent/minimise rotation of the load.
When spooling a rope – Tension is generally applied to ropes whilst they are being spooled on to a winch drum and this tension will try to rotate / untwist the rope and therefore it is preferable to have the rope rotating up against the previous wrap of rope to minimise ‘gapping’ between the adjacent wrap of rope particularly on the bottom layer. Therefore, to achieve this, depending if the rope is anchored on the left or right hand side of the drum or the rope is being spooled under-wound or over-wound will determine if, a left or right hand lay rope should be utilised.