How they make propeller shafts on large vessels like ocean liners or aircraft carriers waterproof considering the intense water and mechanical pressures that come into play?

Question

It seems like a grommet-type seal would fail in no time. Also, looking at an image of one of the propellers for the Queen Mary, it hit me that this is decades old, and would have to go to dry dock to be serviced, and there is no way they are doing that so… How is that even possible? I’d figure dry rot would set in somewhere along the way.

In: Engineering

Answer 1

We can also swap in a new seal while the ship is in the water!

Modern sealing arrangements have a air bladder we can fill that closes off the sea to seal passage. We then remove the old seal and push the spare seal down the shaft into place and secure it.

Drop the air pressure out of the bladder check for leaks and start up the engine again.

We normally carry one spare seal on the shaft and while there are split seal you can install we always prefer the single piece ones.