One of the things we have noticed about new guys from 'school' is that they don't seem to be taught the correct way to rig a messenger line. It isn't their fault, they just haven't been taught it - I'm willing to bet there are some commie instructors who can't rig this correctly either - those that can
do and those that can't
teach eh?
'Messengers' are used to tranfer tools/equip etc to the diver via a 'downline'. Although we work with multi-million dollar hardware the 'downline' is very simple technology - it goes to the jobsite and is made secure so all that the diver requires can be sent along it - every commercial job uses one or a variation of it. The 'messenger' is used to lower and recover whatever the diver needs. Now, simple it may be but if you get the rigging wrong you can seriously foul-up a downline and should this happen at a point too shallow for the sat divers to reach and too deep for the air diver... well, you've created a major f*^K-up and people ask superintendents like me "why the fcuk is this job taking so long?" and I book whoever is responsible on the next crew-boat ashore. The school of hard knocks for sure.
My ruff drawing shows 2 messengers on a downline , the first one has a single shackle rigged to the d/line with tools hanging off it - its a F*^k-up waiting to happen. It may work fine in 5 -7m of water but any deeper and there's more than a chance that as the load slides on the d/line it will begin to spiral with the lay of the rope until there's so many wraps around the d/line it eventually stops. Unfortunately, this also means that when you try to recover the messenger to start again - hey presto - it won't fcuking budge! "Oh wot a silly boy I am," you say to yourself. Also, the tools etc hanging from the running shackle by their lanyards can and will take their own twists around the d/line and then the running shackle lands on top of 'em and jams it all in a bag of snot. When there's a $150,000-a-day vessel waiting on the divers you don't want everyone looking at
you 'cos you messed-up with a piece of string!
The second method shown is the
only correct way to run a messenger - with a 'tag-line' of 300mm to 700mm between d/line and messenger. Ideally the 'working shackle' which holds whatever you're sending should be a bit larger and heavier than the 'running shackle' - the other way round and you may get the 'spiralling' again (though the running shackle needs to be large enough to do its job - run freely). Look at the drawing and you see that the rigging forms an '
L' shape... a K, Y or jelly shape won't do. This rig also applies when you want to send a ropes-end (ie, a 2nd downline) - always add the 'tag-line' and save yourself a lot of grief. Make-up a permanent messenger rig (with 3-part safety shackles if possible), don't use it for anything else and it'll be ready every time you need it.
I hope it all makes sense
