Submarine Escape Trunk Cofferdam

Support equipment is not lesser equipment

An escape trunk is the route by which a crew leaves a submarine in an emergency. A cofferdam is the temporary watertight structure that makes work on it possible: it seals off the area so people can work on the trunk without the compartment flooding.

That makes it easy to treat as secondary, and it is exactly the category where under- engineering causes the most damage. The cofferdam is not the valuable item; the submarine and the people working around it are. It also has to hold through an operation that cannot simply be paused and restarted.

What the design has to account for

Not just the seal. Support structures like this are defined by the awkward cases:

• The seal has to hold under a real pressure differential, not an assumed one
• Access matters: a structure that seals correctly but blocks the work is useless
• Handling and rigging loads while the structure is placed, which are often worse than the static condition
• Repeatability: this is a fixture, and it has to seat the same way every time

That is analysis, not estimation, which is why it starts with our licensed professional engineers rather than at a weld bench.

How it is built

Structural steel fabrication by certified fabricators, on fixture tables we designed and built ourselves. Welds inspected in process. Where a cut edge will be highly stressed, waterjet leaves no heat-affected zone for a crack to start in.

Related work

HPS builds a range of Navy and Air Force support equipment, including HH-60 aircraft maintenance stands, submarine ventilation hatch houses, a cradle system for the T-38 Talon, and maintenance stands for the Army’s helicopter fleet.

More on defense fabrication.