5.1 Relative merits of parachute-type lift bags
Open parachute underwater air lift bags have the open bottom design. So can use it for any water depth operation. Can use it to lift objects or sunk vessels from any water depth. It is more safety.
The material of air lift bags is PVC coating fabric. So it is lightweight easy to operate. Meanwhile, it only has one lifting point. So it is easy to install. And it has vast working agree. Don’t like the enclosed cylindrical airbags have to use horizontally.
5.2 Application of parachute underwater lift bags
Generally, the salvors can use open bottom air lifting bags at any depth for marine salvage or re-floatation objects from the seabed. Because the open bottom design makes the operation more safety. Thus, this parachute lift bags is one kind of all-purpose inflatable buoyancy units. Especially, can use it for the scuba diving lift bags, marine salvage bags, boat lift salvage, shipwreck salvage, and float bags salvage.
Herein, we list some common application.
- Deepwater salvage
- Ship salvage buoyancy support
- Shipwreck salvage
- Static buoyancy support
- Commercial and military use
- Subsea rigging
- Military equipment lifting
- Floating bridge supports
- Inflatable pontoons
- Extra buoyancy for pipe and cable
Also, and raising work, the parachute underwater airbag lifts have two general types – static and dynamic:
- Static lift – this is where an air lift bag is secured by hold-back rigging and used as a single lift point, commonly known as a “skyhook”. The air lift bag has very positive buoyancy. But it is directly restrained to anchor points. Thus, the lift bag is fixed and the load is free to move vertically with the use of a suitably approved lifting device;
- Dynamic lift – this is where the air lift bag is used to lift the load directly, typically for the movement of loads between locations. The parachute lift bag and the load tend to be close to neutrally buoyant with a system of restraints in place. In such instances, the lift bag and load should move together.
You can refer IMCA D 016 – Rev.4 “Guidance On Open Parachute Type Underwater Air Lift Bags” to know more information. Or see our other related articles.
In one word, every kind marine salvage airbags have its special own application. According to the project condition, the salvor should choose suitable marine salve bags.