Unexpected ice formation in areas of restricted flow has caused problems in the past, viz. the loss of the nuclear powered attack submarine USS Thresher (SSN-593) in 1963.
"Thresher had probably suffered the failure of a join in a salt water piping system, which relied heavily on silver
brazing instead of welding; earlier tests using ultrasound equipment found potential problems with about 14% of the tested brazed joints, most of which were determined not to pose a risk significant enough to require a repair. High-pressure water spraying from a broken pipe joint may have shorted out one of the many electrical panels, which in turn caused a shutdown ("
scram") of the reactor, with a subsequent loss of propulsion.
The inability to blow the ballast tanks was later attributed to excessive moisture in the ship's high-pressure air flasks, which froze and plugged the flasks' flowpaths while passing through the valves. This was later simulated in dock-side tests on Thresher’s sister ship, USS Tinosa (SSN-606). During a test to simulate blowing ballast at or near test depth, ice formed on strainers installed in valves; the flow of air lasted only a few seconds. Air driers were later retrofitted to the high pressure air compressors, beginning with Tinosa, to permit the emergency blow system to operate properly."
