DURBAN – The navy has successfully tested a new escape system for crew in a damaged submarine in waters up to 100m deep.
When the class 209 type 1400 submarines were delivered from Germany, the initial two-man escape procedure was found to possess a serious fault. The system called for two men at a time to enter the submarine tower and ascend the ladder leading to the outer hatch, one standing above the other.
Wearing a special suit and breathing gear, they would wait for the tower to be flooded, after which, in theory, the hatch would be opened and they would make their escape to the surface. The built-in buoyancy of the suit would aid in this respect. The tower would then be refilled with air ready for the next two escapes.
Unfortunately, it was discovered that as the tower was flooded, the man on the lower end of the ladder was forced upwards by the air in his suit, causing both men to become stuck at the hatch opening.
The SA Navy has been working on this problem since 2009 with Armscor, the Institute of Maritime Technology and the CSIR and has developed a system known as Tess (tower escape safety system) that enhances the original method, but includes a mechanical rail system to the inside of the tower.
Each submariner hooks himself onto this rail, one below the other. As the tower floods the rail system keeps each man fixed in position, despite the air in their suits wanting to force them upwards.
One by one they are then released by means of a hold-trigger and release mechanism linked automatically to the opening of the tower upper hatch.
Even if the submariner is unconscious this system will work automatically. The procedure takes from three to 10 seconds for both submariners to surface from a depth of 10m.
The cycle is then repeated until the entire crew has evacuated the boat.
The navy recently carried out a full test of Tess off Simon’s Town, using the submarine SAS Manthatisi. The successful test was conducted at a depth of 20m with two submariners reaching the surface where navy divers were waiting to further assist them.
The SA Military Health Service Institute for Maritime Medicine is also involved with this development in planning and providing medical support due to the risks associated with quick ascents, such as barotrauma (decompression sickness), hypothermia or carbon monoxide poisoning.
The navy says the successful completion of the Tower Escape will now be an additional requirement to qualify as a submariner.