On Fri, 27 Sep 2013 21:06:13 +0300, injipoint
wrote:



It's my understanding that nuclear subs are powered by steam
turbines which generate electricity for the electric motors that
run the propellers. The steam for the turbines comes from the
heat of the fission reactor. Lower a few more fuel rods and it
doesn't take but a few minutes for the core to heat up and the
cooling water temperature rises along with it.

Not sure but I think it might take longer. I know they take time
to lower the power, like a day or about that but I don't know enough
about the process to know the start up bit.

I was a USN boilerman on a DDG.
Some years ago, but here's how it worked than.
Nuke or oil-fired is the means to generate steam in boilers.
Whether nuke or oil, steam is steam. Boilers is where it all starts.
Steam powers turbines. For main propulsion, generators, and
auxiliaries like pumps and forced draft blowers feeding the boilers.
Steam also powers evaporators to produce fresh water.

Lighting off a cold boiler is the only lengthy process. Took about
2-3 hours on my ship, but since boilers were only "cold iron" in a
safe port like Norfolk, Va, they are normally hot and ready and
powering the ship even in port. Not much steam demand when not
propelling the ship, so they are basically idling.
When cold iron in a "safe" port, electric cables and fresh water lines
are hooked up to the ship.
You need electricity to go from cold iron to a hot boiler.
We could probably go from cold iron to "full hot" in less than an
hour, but it's better to bring up heat/pressure slowly to avoid heat
and expansion shock, so we always took a measured pace, firing only
one of the boiler 5 burners.

Nowadays steam is dead - except for nukes. As far as I know non-nukes
are now all gas turbine, diesel, turbo-diesel, etc.

Here's how it works with a steam-powered ships like injipoint
observed. I'll use my DDG as an example, but there won't be much
variance. Just replace rod movement for "burners."
In port a forward and aft boiler are hot and running on one burner
each. Each fireroom has 2 boilers, but normally only one is hot.
Running all boilers at full power gains very little extra speed.
Boilers have scheduled maintenance even underway, and often the idle
boiler is open and not operational for this reason.

The forward fireroom feeds steam to the forward engineroom main
turbines. That runs the starboard shaft.
Aft runs aft and port shaft.

Even on my ship built in 1961 most boiler controls were automatic.
Feed water, oil pressure, etc.
The main "humans" operating the boilers were the burner man and the
console operator. Operating pressure was 1275 psi.
Others on various fireroom watch stations monitored temps and
pressures, and were ready to take action for "casualties."
When steam demand began dropping pressure, the burnerman manually
pushed in another burner, and lit it by pulling down the oil control
valve.
Oil on a burner was either shut or wide open.
The console operator had little to do except adjust oil pressure when
demand was low, and adjust "excess" air, to avoid stack smoke.
But the console also provided an overview of many systems.

So you leave port on maybe 2 of the 5 burners, with low oil pressure.
Say you're doing 4 knots. The skipper wants to avoid a bottom
structure by backing one screw. Not sure about how the ship is
actually controlled, but I've seen this many times.
He sends a telegraph command to the engineroom powering that shaft.
Can't remember if that comes to the fireroom simultaneously, or the
engineroom repeats it.
Full astern. The engineroom cranks opens their main throttle, and
starts pulling steam. In the fireroom a full astern bell means the
burnerman pushes in and light all burners as fast as he can, because
all hell will break loose. As steam pressure drops, everything winds
up to maintain pressure, It's like banshees screaming. Forced draft
blowers, feed pumps, oil pumps, air flow, burners burning, steam
flowing.

There are limits. The engineroom throttleman isn't supposed to take
pressure below 1120 psi. That's the prescribed pressure for boiler
shutdown. At sea there's no electricity except that provided by
steam. You need the steam to run the pumps to restart the boilers.
I've seen it get close, and a couple times warned the throttlemen I
was going to shut it down. They listened.


My ship was designed for ASW, so we spent a lot of time chasing Soviet
subs. We were armed with nuke ASROC missiles.
Top speed was 27 knots. We were 4500 tons.
But she was geared for ASW, so she would squat and gain speed pretty
quickly when you opened the throttles. No roostertail, but a pretty
massive stern hump.
http://www.navsource.org/archives/05/01003.htm
That says top speed 33 knots. Maybe with 4 boilers and overload
burner tips. Never did that when I was aboard for 3 1/2 years.
1964-67. Flank speed was 27 knots. We would usually measure speed
by screw shaft "turns," not knots. I never heard more than 27 knots
mentioned, and can't remember the turns, maybe 40-50 max.

Going from 1/3 ahead to full to flank is the usual speed progression
of ships. If not done abruptly, there's no real excitement.
From dead to flank is a lot of action and noise.
From flank to full astern or vice versa is hectic, but only done in
open sea during "exercises."
It's been a long time, but my memory says port maneuvers were the
"scariest." From full astern to full ahead repeatedly.
Of course I couldn't see what was happening from the fireroom, but my
imagination always said we about to run something down or hit a dock.

Sorry if this is "too much information."