New IMCA Guidance on Underwater Air Lift Bags
The International Marine Contractor’s Association (IMCA) have recently clarified and strengthened the guidance on the operation of underwater air lift bags. Alf Leadbitter, Dive Training Authority at The Underwater Centre, explains the need behind the recent changes to the Guidance on Open Parachute Type Underwater Air Lift Bags.
Air lift bag use: clarification needed
Alf says, “The clarification was first recognised as being needed by commercial diving schools, as students could not read the document and then write a plan for using air lift bags. IMCA also recognised the need, as engineers were asking for clarification on diving jobs from around the world. The misunderstanding was mainly concerning drawings, although some confusion was in the writing.’
‘A second concern was raised by the manufacturer that bags were being returned with damage caused by the inverter line. This led to some tests being carried out which concluded that the force in the inverter line was far greater than originally thought. There was no way of calculating the force as many factors were involved, and an agreed Minimum Breaking Force (MBF) of 1.5 times the lifting capacity of the bag was recommended for both the attachment points and the inverter line.
‘New drawings were then provided by Alan Melia, Offshore Diving Manager at Global Energy, and the changes to the guidelines were subsequently agreed at the working group, of which I was a member with other interested parties.”
While the new guidelines give clearer guidelines on the use of air lift bags, The Underwater Centre has been using air lift bags configured the correct IMCA way for many years; air lift bags are commonly used by commercial divers, therefore training in the use of air lift bags is included as standard in our commercial diver training packages.