Sometimes overlooking little things can have a huge impact. In this specific case the lifting arrangement was to lift 85 tons bowthrusters which were bolted down to a 22.5 ton support frame. The frame itself was supported by a 4-leg wire rope bridle sling, while the bowthruster was supposed to hang in a single leg wire rope sling. Well, if you do that the single leg wire rope sling will start to unlay itself by untwisting causing the entire arrangement to start to spin around its axis. Complications arose because the bowthrusters had to be installed under water so any unexpected movement of the load would be an unwelcome event to the divers!

The solution was to use a Twin-Path® Extra sling. Why?
a) The Twin-Path® Extra sling does NOT rotate under load
b) The sling was small enough to hook up to narrow hardware
c) The elongation characteristic is similar to wire rope

After the production of this sling we performed repeated elongation tests at various loads to exactly determine the elongation this sling would have in actual service. This data was then used to set the wire rope rigging so when the entire thruster assembly was hoisted, the wire rope and the Twin-Path® Extra sling shared exactly their proportionate load. As an extra bonus we even wrapped the Twin-Path® Extra sling with a special underwater reflective tape so that the divers were able to locate the slings immediately in the murky harbour water.
Barge transporting all of the thrusters ready for underwater installation.
Here you can see the frame supported by wire rope and the thruster itself hanging in a Twin-Path® Extra sling attached to the top of the thruster.