ballistics. reminds me of why we did some things

for all you nukes that entered the fleet after about say, 77 or 78, the warmup procedure for the mains was pretty cut and dried.

ever wonder why you exercised the throttles before cutting in steam to the headers?
when i was a baby nook machinist mate, we warmed the mains by cutting in gland seal with the mains on the jacking gear, pulled a vacuum in the condenser, and then secured the jack. next you slowly rolled the turbines in the astern and the forward directions, never "slamming" the steam to the nozzle block. this allowed the turbine rotor shaft to warm evenly, reducing the likelihood of a bowed rotor, and subsequent failure of that component.

in 77 or 78, at the piers in ballast point, the haddo and the haddock were tied up one in front of the other. i don't remember which was in front. the aft boat was getting ready to get underway. they had brought the reactor up, bypassed and warmed the steam headers, and were getting ready to warm the mains. the throttle boy whipped the throttles open in the astern direction (as was appropriate), spun them shut, and slammed them open in the ahead direction. the trick was to reverse steam flow before the turbines got over 50 rpm, so as to not cause the screw to turn and take a bite. nice things, reduction gears. they let you get max efficiency out of the turbine at several thousand rpm, with the screw only turning in the hundreds. max efficient speed for both. well, bad things can happen when you start slinging steam turbine throttles without allowing for proper warmup.
as the turbine speed reversed from astern to forward, the throttleboy slammed the throttles back to the astern direction. i know that was common throughout the fleet. i'd watched it done on several boats. something about throttleman prowess to be able to goose the turbines bigtime, without putting way on the boat. usually this isn't a problem.
usually.
unless you slam them around and the throttle linkages stick. like they did. guess what happens when a submarine, tied to the pier, suddenly gets a full head of steam dumped into the turbines? aayup. the aft boat lurched forward hard enough to tear the cleats loose topside, and slammed into the screw of the boat ahead of it. so what do you get? two disabled submarines, one with the bow looking like my mom's car when she drove into a lightpole in the grocery store parking lot, and the other with a completely toasted screw, shaft seals, and main thrust bearing.
to add insult to injury, the cleat that was torn loose? it's trajectory took it some 250 feet, to come crashing back to earth via the forward boat's skipper's windshield.

so now you know why the throttles are exercised before bringing steam down the headers.

posted by bothenook @ 3:13 PM