Ship launching using rubber inflatables, or commonly known as airbags, is a very popular vessel launching method, particularly in Asia. Besides, many shipyards are using it for ship repairs where the “rubber airbags” (or “belons” in Indonesia) are used to facilitate the haul-ins of ships by winch. The use of such inflatables may seem to be pretty simple and straightforward, yet many are still not convinced of its safety due to accidents like this:
To get a bit more perspective, we spoke with Kevin Ang, a regular gCaptain reader from MAX Groups Marine, a Malaysian company that is promoting the airbag launching method all over the world, particularly in America & Europe. We were advised that accidents such as the one pictured above are misleading as it is an execution failure rather than a product failure.
The following are some of Kevin’s insights about airbag launching and how to ensure success, rather than a catastrophic and embarrassing failure.
1) Identifying the type, size & weight of the vessel before you launch.
It is surprising that many take this step of granted. Main factors like types, sizes, vessel weight, working height (distance between the hull of the ship and ground) affects your choice of airbags. The main structure of vessel is vital in determining the placement of the inflatables too. Many fail due to the ignorance of such details as they think that airbag launching is a “one-size-fits-all” technique.
2) Type, length and number of airbags have to be chosen carefully.
There are many types of airbags. They are different in number of rubber layers, rubber quality, strength of the layers etc. The dimensions of rubber inflatables in terms of diameter, length and layers determine its lifting/bearing capacity. It is highly advisable that a weight contingency should be taken into consideration as a safety margin so that the inflatables will have a longer lifespan in the long run because they are used well within their lifting capacity. Extra airbags for mobilisation proposes should also be considered. MAX also uses an in-house built software to check the type, length and number of inflatables proposed.
3) Ground structure/ slipway has to be free of sharp objects and preferably, a small degree slope.
First and foremost, a hard ground is a must to have a safe and successful launching. The suitability of the launching area must be considered and steps taken to prepare it. Although some launch their vessels on soft ground, it is not worth the risk and is not advisable. Additionally, the launchway must be free of hard & sharp objects like sharp metal plates, big stones etc. These may damage the rubber launching bags during launching.
4) Slipway Winch to provide pulling force needed.
A slipway winch is needed to hold the vessel in place (prevent it from slipping into the water) during the placement of airbags. Slope angle, weight and type of ships should be carefully considered to determine the winch capacity. A choice of electric winch or hydraulic winch also depends on the facilities of the shipyard and the aspects of its usage.
5) Determine the accessories needed for ship launching using airbags.
Accessories like pulley blocks, shackles, steel wire rope and MAX’s innovative Quick Release Shackle may be needed. The types of accessories and volume depends on the situation.
6) Determine whether a slow launch or quick launch.
Some inflatable launchings are done by releasing a quick release shackle (the connection between the winch & the vessel) and the vessel is allowed to slide into the water facilitated by gravity. However, for trickier situations, a slow launch may also be practised. This is where the winch slowly releases the rope and the vessel is allowed to slide slowly. For slow launches, the balance of the ship is ensured so if at any point of time it falls out of balance, the winch will be immediately stopped and corrections can be made.
7) Rubber inflatables are versatile
Aside from ship launchings and used to facilitate pulling vessels out of the water, these rubber inflatables can be used to mobilise heavy structures like caissons, floating jetties and other equipment. Moreover, it is very commonly used in marine salvage projects where it is used to float or lift. Many shipyards are pleased that aside from using these rubber airbags for their ships, they are able to use them for other purposes as well. This versatility has served them well.
8) Cost advantage due to flexibility.
Launching using rubber inflatables have relatively lower costs, especially upfront investment. The most interesting aspect is its “scalability”. Many ship repair yards in Asia prefer this method as they can increase their ship repair capacity whenever they want and not be restricted by say, the dimensions of the dry docks they own.
With the above tips in mind, launching with rubber airbags is a viable option for vessels ranging from smaller-sized barges, tugs, or even larger-sized chemical tankers and cargo ships of up to 10,000 gross tons.
The following video shows the successful launch of an anchor handling tug here:
And an 8,600 ton cargo ship:
Want to learn more? Visit Shiplaunching.org