DSK wrote:
I don't think so. There's a volume/temp relationship involved. If you
put steam at a higher pressure & temp into the condenser, at some point
you are going to exceed it's cooling capacity.
Well, in the mode and condition which I described, I KNOW that the
engines can run indefinitely without exceeding the condenser capacity.
... The circulator pump moves more water than is required to remove
the heat leaving the turbine. Reduced power operation might have been
required, just as modern plants - even military plants - but there is
no time limit associated with that condition.
???
What part of steam plant operation and construction elicited the "???" ?
Most condensers and circpumps have a larger capacity than required for
normal operation up to a sea temperature around 85* F. Under some
conditions of sea temperature and load, reduced power operation may be
required to match condenser capacity. Once the balanced is achieved
there is no time limit to operation.
AFAIK there's a time limit, either you regain vacuum and resume steaming
normally, or you don't... and you restrict steam into the engines until
you either have to shut down or you regain vacuum.
Warships have far greater ability to steam in maneuvers, but at the
cost of efficiency & space. A liner has to make money.
I don't believe wasrships have any exclusive claim to maneuverability
... that statement applies equally to a warship or a merchant plant.
No, but warships are designed & built with far less regard to cost and
far greater regard to increased capacity. No merchant ship is ever going
to give up the tonnage & space for such a power plant. For example, a
Fletcher class destroyer's hull was about half filled by it's boiler &
engine rooms.
The Fletcher is smaller than most merchant steamships so of course the
plant takes up a larger proportion of the hull volume ... hardly a
reflection on plant capacity or maneuvering traits.
Right. But you're assuming that the condenser was enough oversized to
accept all the additional energy from the steam normally extracted by
the turbine.
Not at all, read my posts.
Suppose you took a somewhat more modern plant and installed a pipe from
the crossover into the LP exhaust trunk, shunting exhaust from the HP or
IP turbine directly into the condenser. That would be a similar
situation... and I'm thinking it would be difficult or impossible to
keep vacuum. But after reflection (as I said in my last post), I'm also
thinking it wouldn't matter so much with the Olympics because they would
only have to do this for a short time.
We carry just such a pipe. It is made precisely for use in case a LP
turbine casualty occurs and allows HP turbine exhaust to go directly to
the condenser. No big deal, just reduce power to maintain the vacuum
required for the auxilliaries and carry on for as long as it takes.
Just exactly the same way Titanic would operate if the turbine was
unavailable.
Wouldn't stopping the engine against the force from the prop potentially
create greater loads than normal forward operation?
Don't know why it should, steam is compressible.
True, but they care a *lot* about compression on the shaft, which is
going to produce axial forces. If you're trying to stop the prop against
the force of water going by, it seems to me you could generate at least
as much compression as if you are trying to accelerate the ship.
Run that by again ... "compression" of the shaft? I would love to see
the figures on that one ...
But there's more than just shaft inertia involved here... there's the
inertia of the whole ship driving the prop.
Not to seem too cynical but I have to ask if that is the source of the
shaft compression that is going to effect the line bearings ...
I dunno about "all concievable conditions"... that sounds really
expensive! And remember, back in 1912 engineering metallurgy had not
advanced as far.
Yes, it is and always has been expensive. All conceivable conditions are
often met and/or exceeded on ships over their life of steaming around
the world essentially non stop for a quarter century or longer.
Rick