Hello Mr. Tore,
From Aaron...
"To the best of my understanding, based on the engineering reports and archival documents, the exhaust line remained, generally full of water. To what extent I do not know. The backpressure generated by the diesel engines kept the water at bay as the exhaust gasses were expelled. This is why it was so very important to close the shutoff valve at the end of snorkeling otherwise the water flushed back to the engines, forced toxic gasses into the engine room and could flood the engines."
Some of that doesn't make sense... If you stopped the diesel engine and failed to shut the schnorchel exhaust shut-off valve, then you could flood the engine. However, I don't see the toxic gasses into the engine room under that scenario.
Starting the Diesel engine for schnorchelling:
I imagine that you keep shut the external diesel exhaust valve, drain and open the internal diesel exhaust valve, and open the main exhaust valve (port or starboard) for blowing. Now, we have air filled pipes up to the schnorchel shut-off valve. At this point, you are setup for blowing the schnorchel exhaust mast that is full of water (about 8 meters high).
If we start the Diesel engine on air and monitor the exhaust pressure gauge for blowing the ballast. When the pressure gets to .5 kg/cm2, we open the schnorchel exhaust shut-off valve and switch the diesel engine to fuel (Start). Then bring the engine up to speed while clearing the schnorchel exhaust mast of water. Hopefully, when the hot exhaust gases hits the compressed air and it expands in the exhaust pipe system, it push the water up and out of the schnorchel mast exhaust pipe, and not cause exhaust safety valve in the diesel room to open...
Does this sound reasonable?
Regards,
Don_