Rick wrote:



Recips don't require as great a vacuum as a turbine to operate at their
peak efficiency. Plant efficiency without the turbine would drop
considerably as the energy in the recip exhaust would be lost to heating
the sea.



I see you agree with me, the steam would be bypassed to the condensor.
But I'm puzzled by your statement that recips don't need as great a
vaccum for peak efficiency. Isn't thermodynamic efficiency directly
related to the inlet and outlet pressures -or do you mean that most
reciprocating engines run at higher outlet pressures?

Cheers

DSK wrote:

Rick wrote:

One could reasonably assume that the plant was designed to accomodate
the loss of the turbine and the condenser could operate at the vacuum
required to allow full power from the recips.


Sure, but for how long? It's a liner, designed to maneuver with the aid
of tugs. Warships have far greater ability to steam in maneuvers, but at
the cost of efficiency & space. A liner has to make money.


At that time the reliability of the turbine was in question so that the
plant was designed to run without it indefinitely. If I recall, the
bearings proved to be a problem on a sister ship.

Cheers

Rick wrote:

DSK wrote:

Rick wrote:

One could reasonably assume that the plant was designed to accomodate


Sure, but for how long? It's a liner, designed to maneuver with the
aid of tugs.


As long as it takes to fix the problem. The condenser is large enough to
handle the steam flow required to produce full rated power. 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.

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. Our
plants are optimized to operate at a continuous maximum power and steam
flow. Anything less is taking life easy on plant at the cost of a slight
increase in brake specific fuel consumption. There are many factors
involved in how fast we go for how long that have nothing to do with the
engine.

... Plant efficiency without the turbine would drop considerably as
the energy in the recip exhaust would be lost to heating the sea.

Right... and this is why I think it would be difficult to maintain
vacuum if you ran without the turbine for any length of time.


The relationship you imply assumes the condenser was sized to require
the use of the turbine ... that simply is not the case. The turbine
allowed the recovery of waste heat at full power. Their is a subtle
relationship between the efficiency of the recips and the cutoff
settings used when operating with and without the turbine online. If
cutoff is extended, as it might have been when turbine was online, the
recips produced greater power but at less efficiency than when cutoff
was shortened so as to allow maximum expansion in the engine.

Maximum expansion of minimum steam (short cutoff) comes at the cost of
wide temperature variations and condensation and re-evaporation withing
the cylinders which is avoided at high speeds and extended cutoff which
leaves more energy in the steam for the turbine to extract.


Don't you think that if the throttleman overdid the reverse steam, it
could damage the crosshead bearings, or the shaft couplings and/or
line bearings, or maybe fold up the prop? Other ships lost prop blades
and so forth at times. The Olympic class props had the blades bolted
to the hub so that the pitch would be adjustable (the ship had to be
in drydock for them to adjust it).


Don't know why it should. The crosshead bearing only "feel" the side
thrust imposed by piston rod movement relative to the connecting rod and
that is a function of load.

Line bearings don't know or care what direction the shaft rotates.

The torque on the shaft instantly changes from driving the prop to being
driven by the prop the instant the throttle is closed. The inertia of
the rotating shaft is absorbed by impeding the inlet of steam from the
throttle to the cylinder. When the force of the steam exceeds the force
of the piston being driven by the shaft inertia the engine will reverse.
The throttle is not opened wide at the same instant that reverse is
selected ... give the operator a little credit for knowing how to
operate the engine. The time involved is very short though, you do not
have to wait until the shaft stops rotating all by itself.

Ships still shed blades and even break shafts ... even though the props
and shafts are designed to function under torgues and stresses that the
engine would never be able to deliver under any and all concievable
conditions of normal or emergency operation.



Please take it easy on Doug. He's our resident propulsion engineer. His
knowlege is second to none. But seriously, a good accurate post IMO.
Often HP steam was bled to the LP cylinders to start big marine steam
engines? Do you do you do that on your tug?

Cheers

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

Nav wrote:
... It was Doug who said there was no bypass valve.

I didn't say anything of the kind, you clown.

Go back and re-read my posts. I said that a turbine will not be stopped
by opening a bypass valve, which is what you claimed was the summ &
total of how to reverse the Titanic's engines.


... He
seemd to think it was stopped by just closing a valve -but where he
thinks the steam from the main engines would go is anybodys guess.

Do tell.


While the inlet was subatmospheric,

In other words, under a vacuum... as I said.


.... the steam would still be passed to
the condensor whose pressures were even lower. I think it's also pretty
sloppy to call the inlet prssure to a turbine a vacuum. Don't you guys
traditionally use mmHg for near vacuum pressures?

It was you who is quoting a psia figure and confusing it with psi.

DSK

Nav wrote:
I still say the inlet pressure was 9psi!

You can say whatever you like.

...Care to admit I was right?

Why? You're not. Like I said... go and ask somebody else, or look it up
yourself. I've given you plenty of references if you can't possibly
believe my answers.

DSK

An apology would be in order, but isn't really expected.



Nav wrote:
Yes it is -from you! I said the inlet pressure it was 9 psi to correct
your statement that the inlet was at vacuum. You then said I was wrong
and it was 11psi.

No, I did not, Navsprit... or is it Navjax?



You are busted.

For what, proving that you're blabbing about things you don't
understand... again?

DSK

Nav wrote:

I think it's also pretty
sloppy to call the inlet prssure to a turbine a vacuum. Don't you guys
traditionally use mmHg for near vacuum pressures?

We sometimes us inHg and sometimes we use psia, depends on the
shipbuilder and machinery supplier. It is reasonable to assume a metric
ship displays mmHg ... makes no matter as far as operation is concerned.

It is hardly "sloppy" to call inlet pressure the condenser a vacuum. It
is engine exhasut and as long as it is less than atmospheric it is a
vacuum.

Condenser pressure is engine exhaust pressure for engineering purposes.
We determine condensate depression and other operational factors by
calculating condenser vacuum based on exhaust temperature.

Rick

Nav wrote:
At that time the reliability of the turbine was in question so that the
plant was designed to run without it indefinitely.

Oh really? Perhaps you can produce a reference to that?

Doesn't matter, steam turbines had been in service for some years
before. It wasn't an issue of reliability *at all*. The issue was cost.
The Royal Navy subsidized the construction of the Mauretania and the
Lusitania, both of which were in service several years before the
Olympic & Titanic were designed. Another smaller issue Harlan & Wolff's
relative inexperience with an all-turbine plant of that size.


... If I recall, the
bearings proved to be a problem on a sister ship.

Care to produce a cite on that? Or did you just pull that out of thin
air, like almost everything else you've said so far in this thread and
many others?

Next you'll be claiming that you know more about the Constit... oops, I
mean the Titanic's steam plant than anybody else!

The real question: why am I bothering to attempt a discussion with such
a loony-tunes?

DSK

Rick wrote:
We determine condensate depression and other operational factors by
calculating condenser vacuum based on exhaust temperature.

Here's a good homework question for Navvie/Navjax/Navsprit:

Define "condensate depression" and explain it's significance in steam
plant operations.

DSK

DSK wrote:

Nav wrote:

... It was Doug who said there was no bypass valve.


I didn't say anything of the kind, you clown.

Go back and re-read my posts. I said that a turbine will not be stopped
by opening a bypass valve, which is what you claimed was the summ &
total of how to reverse the Titanic's engines.


Isaid nothing about summ and total. the first act in stopoong the
turbine was to open the bypass valve. Ask Rick he really knows about
steam plants. Let me remind you of what you said in your usual sneering
tone:


"Please tell me what ships you've steamed where the engine could be
stopped by "opening a steam bypass valve." Also please tell me where the
steam is bypassed to... are you suggesting dumping main steam directly
into the condenser? "


Another point I'd like you to explain is how do you stop the engine and
not the shaft. Push in the clutch, maybe?



It was you who is quoting a psia figure and confusing it with psi.



No confusion at all. The pressure is exactly as I stated it. It was you
who claimed that the oiperating pressure was 11 psi(a). (Which is wrong
anyway you look at it). All I was doing was quoting data that you said
was wrong because somehow you know more about the Titanic plant and how
it works than anyone else. Strange that you don't know that steam bypass
vlaves are standard in multiple engine plants... Maybe they never let
you run the engines on the ship you served on.


Cheers

Rick wrote:
Well, in the mode and condition which I described, I KNOW that the
engines can run indefinitely without exceeding the condenser capacity.

OK. I'm a bit surprised to hear that, since it's definitely not true of
most plants I know about. Otherwise loss of condenser vacuum wouldn't be
given such a prominent place in the drill book.


... 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.

Well, that's what I meant. You're taking that balance very much for
granted. "Under some conditions, reduced power operation may be
required" is definitely true, but an understatement IMHO. Sometimes you
have to shut down and start over, to restore vacuum!

Run that by again ... "compression" of the shaft? I would love to see
the figures on that one ...

Sorry about that.... got it backwards... in stopping the shaft against
the momentum of the ship, the shaft would be in tension... not going to
produce much axial load that way! Make that strain on the couplings, not
the line bearings ;)

BTW I wonder why our brilliant Navspritjax didn't catch that mistake?

Interesting discussion, thanks for joining in.

Fresh Buckets O' Steam
Doug King

Nav wrote:

Often HP steam was bled to the LP cylinders to start big marine steam
engines? Do you do you do that on your tug?

Steam was admitted directly to the condenser via a "snifter valve" in
order to raise vacuum enough to allow smooth starting, never heard of
admitting drum pressure steam to the LP, it would sure jerk the poor
engine around.

My tug has a very large for its power and quite elderly diesel. I only
operate other people's steamboats for a living.

Rick

DSK wrote:
Nav wrote:

At that time the reliability of the turbine was in question so that
the plant was designed to run without it indefinitely.


Oh really? Perhaps you can produce a reference to that?

Yes. http://www.dellamente.com Here you a

"Harland & Wolff were quite limited technically, with only their own
experience to draw on. They were aware of the power and economy the
turbine offered, although still unsure of its reliability, and chose to
play it safe ..."

Or is this another site that knows less than you about the Titanic?


... If I recall, the bearings proved to be a problem on a sister ship.


Care to produce a cite on that? Or did you just pull that out of thin
air, like almost everything else you've said so far in this thread and
many others?


Good lord. Are you seriously suggesting that turbine bearing failure did
not occur in that era? I'd say that your behaviour is exposing your true
nature quite nicely -just for the record.

Cheers

Nav wrote:

But I'm puzzled by your statement that recips don't need as great a
vaccum for peak efficiency. Isn't thermodynamic efficiency directly
related to the inlet and outlet pressures -or do you mean that most
reciprocating engines run at higher outlet pressures?

Reciprocating steam engines alternately see cool steam and hot steam on
the same end of the cylinder. As the steam expands during the stroke it
cools. As it cools, it cools the cylinder and some of it may condense on
the cylinder walls.

When steam is admitted to the previously exhuast side some of it
condenses immediately then reevaporates as the cylinder temperature
rises again. This phenomenon is exaggerated at the low pressures and
temperatures associated with greater vacuum. The thermodynamic
efficiency of a recip steam engine is limited due to this effect.

That is why steam turbines like superheated steam and exhaust into the
greatest vacuum obtainable. The only place we want steam to condense is
in a condenser and the only place we want to evaporate feedwater is in
the boiler.

Rick

DSK wrote:

Rick wrote:

We determine condensate depression and other operational factors by
calculating condenser vacuum based on exhaust temperature.


Here's a good homework question for Navvie/Navjax/Navsprit:

Define "condensate depression" and explain it's significance in steam
plant operations.


Good lord. How childish. No wait, it's a genuine question right? Well
Doug, it's a temperature difference that is impoertant to overall
thermodynamic efficiency which can be defined as P/Qh-Qc. For a steam
plant, the steam temperature and it's dryness fraction times the mass
flow rate determine heat fluxes in that equation.

Yes Doug, I did freshman thermodynamics. Did you?

Cheers

DSK wrote:

Rick wrote:

Well, in the mode and condition which I described, I KNOW that the
engines can run indefinitely without exceeding the condenser capacity.


OK. I'm a bit surprised to hear that, since it's definitely not true of
most plants I know about. Otherwise loss of condenser vacuum wouldn't be
given such a prominent place in the drill book.

Drill book?

What drill book?

Cheers

Rick wrote:

Nav wrote:

Often HP steam was bled to the LP cylinders to start big marine steam
engines? Do you do you do that on your tug?


Steam was admitted directly to the condenser via a "snifter valve" in
order to raise vacuum enough to allow smooth starting, never heard of
admitting drum pressure steam to the LP, it would sure jerk the poor
engine around.

Well it was bleed only. I looked and found this description:
http://www.johnforester.com/Maritime/SEB2.htm

"When the engineer needs to start the engine, and it won't start just by
opening the throttle valve, he can open either of these bypass valves to
let a little steam into the valve chests of the other cylinders just to
get the engine moving. Once it is turning, he then closes the bypass
valves to stop wasting high-pressure steam in the low-pressure cylinders. "

Cheers

Rick wrote:
otnmbrd wrote:

Interesting .... thanks. I would have thought, considering the mass
involved that you would have had to reduce "ahead" steam first, prior
to "pulling one lever".

Sorry, I neglected one point of your post because it is so much a part
of normal or emergency operation as to require no thought ... of course
the throttle is closed prior to changing direction, no marine steam
engine is routinely started at full throttle. The shaft speed may not
change much when and as the throttle is closed rapidly but closing the
throttle is part of the sequence of operation.

Rick


Thanks. That was/is the point I was looking for.

otn

Nav wrote:

Good lord.

That may not be the response you were looking for ...

You guys have fun, it is time to bow out of this one.

Rick
USCG Chief Engineer
Steam/motor/gas turbine

DSK wrote:

OK. I'm a bit surprised to hear that, since it's definitely not true of
most plants I know about. Otherwise loss of condenser vacuum wouldn't be
given such a prominent place in the drill book.

Loss of vacuum is a show stopper ... loss can occur for any number of
reasons unrelated to engine operating conditions ... and most often has
nothing to do with what the engine is or was doing. There is a reason
the vacuum guage is the largest and placed squarely in view of the engineer.

Well, that's what I meant. You're taking that balance very much for
granted. "Under some conditions, reduced power operation may be
required" is definitely true, but an understatement IMHO. Sometimes you
have to shut down and start over, to restore vacuum!

The balance is taken for granted, at a given vacuum I can remove a given
amount of heat ... removing a given amount of heat will produce a given
vacuum for a given steam flow, it is very simple, don't put any more in
than you can remove. Loss of vacuum equates to a loss of power in a
steam plant, it's like putting a potato in an exhaust pipe, if you can't
get the potato out quick enough the engine stops ... no magic there.
There is no need to "shut down" if you completely lose vacuum,
everything shuts down all by itself ... especially if you are relying on
SSTG's for electrical power. Have been faced with losing vacuum many
times but have never seen or heard of having to shut a plant down in
order to restore it ... most vacuum comes from the condensation of steam
in the condenser so stopping all that steam from entering is the worst
thing you can do.

Rick

Nav wrote:
... Let me remind you of what you said in your usual sneering
tone:


"Please tell me what ships you've steamed where the engine could be
stopped by "opening a steam bypass valve." Also please tell me where the
steam is bypassed to... are you suggesting dumping main steam directly
into the condenser? "

And, as Rick confirmed, "opening a steam bypass valve" does not stop a
turbine. You have to open steam to the reverse element.

In other words, you were wrong, Navvie.



Another point I'd like you to explain is how do you stop the engine and
not the shaft. Push in the clutch, maybe?

And I'm still waiting for an answer on that. Did the Titanic have a
clutch? How many large steamships have clutches such as you were talking
about in an earlier post?




No confusion at all. The pressure is exactly as I stated it. It was you
who claimed that the oiperating pressure was 11 psi(a).

No, that's not what I said, which is why you're not producing another
exact quote.

.... you said
... you know more about the Titanic plant and how
it works than anyone else.

Actually, I never said any such thing at all. You must be confused....
again....



... Strange that you don't know that steam bypass
vlaves are standard in multiple engine plants...

Actually, they aren't. There is no bypass from the HP and/or IP turbine
directly into the condenser in any plant I've ever steamed, naval or
civilian. So, there may be many plants out there with such valves, but
they're certainly not standard.


... Maybe they never let
you run the engines on the ship you served on.

Maybe. Wanna bet? Oh wait, you don't pay when you lose. Never mind.

DSK

Nav wrote:
Yes. http://www.dellamente.com Here you a

"Harland & Wolff were quite limited technically, with only their own
experience to draw on. They were aware of the power and economy the
turbine offered, although still unsure of its reliability, and chose to
play it safe ..."

Or is this another site that knows less than you about the Titanic?

It conflicts with what I've read about the design parameters laid out
for the Olympic class ships and discussion between Bruce Ismay (do you
even know who he is without Google?) and Lord Pirrie. I suggest you look
further. An excellent start would be to ask the question directly on the
Encyclopedia Titanica engineering forum.

I don't think you will, because I don't think you're interested in the
answer. You seem to be more interested in Jaxlike posturing and posing.
Certainly, a person with training in naval architecture would be able to
figure out prop slip, and would probably know where to find a good
reference to condensate depression.

DSK

Rick wrote:
The balance is taken for granted, at a given vacuum I can remove a given
amount of heat ... removing a given amount of heat will produce a given
vacuum for a given steam flow, it is very simple, don't put any more in
than you can remove.

Simple in theory, complicated in practice.

... Loss of vacuum equates to a loss of power in a
steam plant, it's like putting a potato in an exhaust pipe, if you can't
get the potato out quick enough the engine stops ... no magic there.

Exactly. That is what I've been getting at all along. If vacuum starts
going down, you have to start redcing steam in.


There is no need to "shut down" if you completely lose vacuum,
everything shuts down all by itself ... especially if you are relying on
SSTG's for electrical power.

Sure, but hopefully you don't let it get that far.

...Have been faced with losing vacuum many
times but have never seen or heard of having to shut a plant down in
order to restore it ... most vacuum comes from the condensation of steam
in the condenser so stopping all that steam from entering is the worst
thing you can do.

Never had a condenser get a slug of air from the glands? Never flooded
the hotwell when a condensate pump craps out?

Anyway, if you keep dumping too much steam into a condenser as it loses
vacuum, it can get really hot and make it difficult to restore vacuum
without shutting down and starting over with the air ejectors.

I make no bones that most of my experience, and all my training, was in
the Navy, which practices these things regularly and tends to run all
drills out to their end point. It looks to me like we agree on many
things but have widely different experiences in widely different plants.

Regards
Doug King

Define "condensate depression" and explain it's significance in steam
plant operations.


Nav wrote:
Good lord. How childish. No wait, it's a genuine question right? Well
Doug, it's a temperature difference

Right.

Where?

I mean, between which two points in the steam cycle?

... that is impoertant to overall
thermodynamic efficiency which can be defined as P/Qh-Qc.

How else could it be defined, in more everyday terms?

... For a steam
plant, the steam temperature and it's dryness fraction times the mass
flow rate determine heat fluxes in that equation.

Yes Doug, I did freshman thermodynamics. Did you?

Yep. But your answer is mostly gobbledy gook to me. What's a dryness
fraction? Are you saying that condensate depression relates to degree of
superheat?

Rick can you make any sense of this?

DSK

DSK wrote:

Yep. But your answer is mostly gobbledy gook to me. What's a dryness
fraction? Are you saying that condensate depression relates to degree of
superheat?

Rick can you make any sense of this?

You both have really muddled and overcomplicated the issue.

Condensate depression is simply the difference in temperature between
the temperature at which steam will condense at the pressure existing in
the condenser and the temperature of the condensate in the hotwell.

Too much cooling (beyond about 10* below condensation temperature) means
that BTU's are needlessly tossed overboard and must be replaced by
burning expensive fuel.

Rick

Rick wrote:
You both have really muddled and overcomplicated the issue.

All I did was ask the question.


Condensate depression is simply the difference in temperature between
the temperature at which steam will condense at the pressure existing in
the condenser and the temperature of the condensate in the hotwell.

Absolutely & precisely correct.


Too much cooling (beyond about 10* below condensation temperature) means
that BTU's are needlessly tossed overboard and must be replaced by
burning expensive fuel.

Yes.... although the Navy cares less than they should about fuel
economy. We used to shoot for 5 degrees.

Here's a fun thought... let's list all the unexpected things found in
main condenser headers. How about a case of beer (unfortunately mangled
& empty)?

Fresh Steam
Doug King

DSK wrote:


No confusion at all. The pressure is exactly as I stated it. It was
you who claimed that the oiperating pressure was 11 psi(a).


No, that's not what I said, which is why you're not producing another
exact quote.



Ok you asked for it:

Nav:
Wot no bypass valve? Where did the steam go Doug -into the vacuum at the
tubine inlet? Bwhahahahhahaha!! You are such a clown. The inlet pressure
was 9psi -it's on all the web sites describing the engineering -or are
they wrong too?

DSK:
Actually, they are. The design (according to Harlan & Wolff, who should
know) called for inlet to the turbine at ~ 11 psia. So, if you grant
them 9psi *a* then they're not far wrong. Or are you now going to claim
that the condenser ran at 3 psi ... even back then, hotwell pressure was
usually given in mmHg... hint hint... "

Kblam!

Cheers

DSK wrote:



... For a steam plant, the steam temperature and it's dryness fraction
times the mass flow rate determine heat fluxes in that equation.

Yes Doug, I did freshman thermodynamics. Did you?


Yep. But your answer is mostly gobbledy gook to me. What's a dryness
fraction? Are you saying that condensate depression relates to degree of
superheat?



You claim to have done freshman thermodynamics in engineering and you
don't know what the dryness fraction is? How strange. Perhaps you had
better look it up -'cos I know nothing! Try a google and you'll learn
some freshman engineering on steam plants.

Cheers

Rick wrote:

DSK wrote:

Yep. But your answer is mostly gobbledy gook to me. What's a dryness
fraction? Are you saying that condensate depression relates to degree
of superheat?

Rick can you make any sense of this?


You both have really muddled and overcomplicated the issue.


It's Dougs fault. He always does this (asking ever more arcane
irrelevant questions) when when he's painted himself into his corner of
ignorance. He goes on and on until he finds something that you can't be
bothered to answer and then he'll jump around the playground claiming he
scored some point. I can see he's trying to do it to you now...

Cheers

otnmbrd wrote:

Some comments interspersed

DSK wrote:

DSK the marine propulsion expert wrote:

In any case, the ship was going full speed, the loss of the prop
stream across the rudder would not reduce the rudder's effectiveness
very much.


This is probably most notable, in my experience, with variable pitch
props, but you can and will experience it with fixed pitch. You slow the
rpm of the prop and it tends to mess a bit with the smooth flow of
water past the rudder, reducing effectiveness until hull speed reduces
to rpm speed. (personal observation).


Yep, my point exactly. Wonder why he's never noticed it?

Cheers






Nav wrote:

http://www.dellamente.com/titanic/engines5.htm



Interesting web site. Thanks for the link.

It does contain a number of inaccuracies, though.


"Regardless, most scenarios agree steam to the turbine would have
been cut off. While this had little effect on the ship's forward motion,



???

The central turbine was about 35% ~ 40% of the ships forward power.
How is it going to have "little effect on the ship's forward motion?"

Or do they mean that shutting off steam to the turbine would not have
produced significant stopping impulse? That would be much more correct.


They might be thinking that the mass of the ship will keep things moving
with a gradual reduction in speed, not readily apparent in the time
frame of this collision.


They also don't appear to know how the reciprocating engines were
reversed.


... it deprived the rudder of the steady, forceful stream of water
necessary to turn a ship of that size.



???

A steady stream of water goin 22 + knots is not "forceful"?


It's forceful, but definitely not as forceful



... Several sources claim the rudder on the Titanic and her sister
ships was too small. If that was indeed the case, shutting down the
center turbine would be the last thing you would want to do in an
emergency."



The "rudder too small" claim is total malarkey. The Olympic was the
same design and had a long service career, with a reputation of being
a good handling ship.


Disagree. Rudder technology has come a long way. Although I don't doubt
that the ships may have been considered good handling by many of the
day, there are many possibilities which could have improved the
"overall" rudder effectiveness, though whether this could have saved the
day, is pure conjecture.



Hmm, seems to agree with me?



Sure. It's incorrect and based on assumptions when accurate data is
readily available.

Speaking of which, have you worked out the prop slip for the Olympic
class ships yet? Data readily available, all you need is the prop
pitch, top speed, and top speed rpm.


Slip is a variable ..... changes from day to day, based on a number of
factors.


... My yacht steers well without propwash because it's rudder, in
comparison, is huge... My point is that, most power vessels can have
much smaller rudders because they use the propwash to significantly
increase rudder effectiveness. It's standard naval architecture.



At low speed, sure. At full speed, the prop stream does increase
rudder effectiveness but I'd say that it's not "significant."
Judgement call, I guess... certainly your vast experience in handling
large steam ships and your claimed naval architect training give you a
big advantage here.

DSK


Would disagree. Prop wash is a very important contributor to rudder
effectiveness at all speeds .... put a ship's engine on "stop" ....
trust me, your effectiveness decreases rapidly.

otn

That's about all folks. I'm getting pretty tired of Navvie's BS.

Nav wrote:
Ok you asked for it:

Nav:
Wot no bypass valve? Where did the steam go Doug -into the vacuum at the
tubine inlet? Bwhahahahhahaha!! You are such a clown. The inlet pressure
was 9psi -it's on all the web sites describing the engineering -or are
they wrong too?

So, here you are quoting yourself making several wrong claims, with a
bwahaha and calling names besides.



DSK:
Actually, they are. The design (according to Harlan & Wolff, who should
know) called for inlet to the turbine at ~ 11 psia.

Know what this "~" means?


... Or are you now going to claim
that the condenser ran at 3 psi ... even back then, hotwell pressure was
usually given in mmHg... hint hint... "

So you didn't get the hint, have no clue what Rick & I have been talking
about.

Now you pretend that you never claimed the exhaust and the condenser
aren't under vacuum, along with shirking all the other bogus statements
you've made.



Kblam!

Is that the sound of you dropping what few marbles you used to have on
the floor? Goodbye, Navsprit.

Cheers!
DSK

DSK wrote:

Nav wrote:

Yes. http://www.dellamente.com Here you a

"Harland & Wolff were quite limited technically, with only their own
experience to draw on. They were aware of the power and economy the
turbine offered, although still unsure of its reliability, and chose
to play it safe ..."

Or is this another site that knows less than you about the Titanic?


It conflicts with what I've read about the design parameters laid out
for the Olympic class ships and discussion between Bruce Ismay (do you
even know who he is without Google?) and Lord Pirrie. I suggest you look
further. An excellent start would be to ask the question directly on the
Encyclopedia Titanica engineering forum.

I don't think you will, because I don't think you're interested in the
answer. You seem to be more interested in Jaxlike posturing and posing.
Certainly, a person with training in naval architecture would be able to
figure out prop slip, and would probably know where to find a good
reference to condensate depression.



Now THAT'S posturing!

Cheers

Nav wrote:

I don't think you will, because I don't think you're interested in the
answer. You seem to be more interested in Jaxlike posturing and
posing. Certainly, a person with training in naval architecture would
be able to figure out prop slip, and would probably know where to find
a good reference to condensate depression.


That is a bit unfair, Nav, prop slip is all over the board (+ or -)
depending on weather, load, currents and any number of things effecting
the hull ... even down to how good the helmsman is.

Rick

Rick, I didn't write that -Doug did.

Cheers

Rick wrote:
Nav wrote:

I don't think you will, because I don't think you're interested in
the answer. You seem to be more interested in Jaxlike posturing and
posing. Certainly, a person with training in naval architecture would
be able to figure out prop slip, and would probably know where to
find a good reference to condensate depression.



That is a bit unfair, Nav, prop slip is all over the board (+ or -)
depending on weather, load, currents and any number of things effecting
the hull ... even down to how good the helmsman is.

Rick

Nav wrote:


otnmbrd wrote:

Some comments interspersed

DSK wrote:

DSK the marine propulsion expert wrote:

In any case, the ship was going full speed, the loss of the prop
stream across the rudder would not reduce the rudder's
effectiveness very much.



This is probably most notable, in my experience, with variable pitch
props, but you can and will experience it with fixed pitch. You slow
the rpm of the prop and it tends to mess a bit with the smooth flow
of water past the rudder, reducing effectiveness until hull speed
reduces to rpm speed. (personal observation).


Yep, my point exactly. Wonder why he's never noticed it?

Cheers

Some things you notice on ships, you may not notice on boats, and vice
versa. Also, these effects can vary greatly in their intensity and it's
not a "given" that it will happen to a noticeable degree in all cases at
all times. BG One of the things which makes boat/ship handling so much
fun.

otn

DSK wrote:

That's about all folks. I'm getting pretty tired of Navvie's BS.

Nav wrote:

Ok you asked for it:

Nav:
Wot no bypass valve? Where did the steam go Doug -into the vacuum at
the tubine inlet? Bwhahahahhahaha!! You are such a clown. The inlet
pressure was 9psi -it's on all the web sites describing the
engineering -or are they wrong too?


So, here you are quoting yourself making several wrong claims, with a
bwahaha and calling names besides.



DSK:
Actually, they are. The design (according to Harlan & Wolff, who
should know) called for inlet to the turbine at ~ 11 psia.


Know what this "~" means?


... Or are you now going to claim that the condenser ran at 3 psi ...
even back then, hotwell pressure was usually given in mmHg... hint
hint... "


Yes, aren't you gald I told yiou that? But are you sure it's mmHg and
not inHg?


So you didn't get the hint, have no clue what Rick & I have been talking
about.

Now you pretend that you never claimed the exhaust and the condenser
aren't under vacuum, along with shirking all the other bogus statements
you've made.


No, I was the one who told you what the operating pressures were and
which you (of course) said was wrong. Your first post questioned whether
I knew how the turbine would be stopped (by closing a valve?). I told
you that the turbine would not be stopped by just closing a simple valve
(as that would also stop the main engines). So, this all started by my
saying a bypass valve would be opened, a point which you have finally
come to accept as _having_ to be true -despite your sneering and claims
to be an expert on the Titanic. In fact I've done nothing but post
factually correct statements and every one of them has been refuted and
attacked by you.

Perhaps you can explain why a self proclaimed marine propulsion engineer
with freshman thermodynamics and 20 years experience has never heard of
the term "steam dryness fraction" or recognise the equation for the
efficiency for a heat engine? I think I know why but I'd like to hear
your explanation.

If I "shirk" your questions it's because there are irrelevant to the
issue under discussion and anyway that's a very childish game (it's
called "I know something you don't").

Cheers

DSK wrote:


Actually, they aren't. There is no bypass from the HP and/or IP turbine
directly into the condenser in any plant I've ever steamed, naval or
civilian. So, there may be many plants out there with such valves, but
they're certainly not standard.


Well I guess this company for one never sells any?

http://www.emersonprocess.com/fisher...ditioning.html

Doug please try to engage your brain. In a plant where multiple engines
are used there has to be a way of taking one of them off line without
trashing steam flow in the whole plant right? Think about what happens
when a generating turbine trips! You can't just close the turbine inlet
valve as the boiler pressure would skyrocket. What you do is open a
bypass valve. In big plants you may also inject water to cool the steam
(it's pressure is dropped by adiabatic expansion after the valve) and
thence to the condenser.

If you have a plant where one engine takes the steam from another and
you want to drop the second off line you first open a bypass valve. So,
that's all, why did you even argue about it with me?


Cheers

DSK wrote:
Actually, they aren't. There is no bypass from the HP and/or IP
turbine directly into the condenser in any plant I've ever steamed,
naval or civilian. So, there may be many plants out there with such
valves, but they're certainly not standard.


Nav wrote:
Well I guess this company for one never sells any?

http://www.emersonprocess.com/fisher...ditioning.html

Thanks for one good laugh today. Did you read the description of these
valves? Did you just type "turbine bypass" into Google and grab the
first link that came up?



Doug please try to engage your brain. In a plant where multiple engines
are used there has to be a way of taking one of them off line without
trashing steam flow in the whole plant right?

Are you under the impression that a set of HP, IP, and LP turbines, all
geared to a common shaft, are considered "multiple engines"? What you're
talking about is a main steam loop.

A main steam loop has to supply power to propulsion engines (turbine or
whatever), feed pumps (recip or turbine), SSTG (do you what that stands
for?), and also feeds steam into auxiliary systems through pressure
reduction control valves & sometimes via desuperheaters. Some systems
have forced draft blowers on main steam also, but most FDBs are on an
aux loop.

A main steam loop is laid out similar to a firemain loop... the idea is
to supply all stations with redundant paths, so that you can isolate any
part of the system and still keep the rest running. Each section and
each piece of equipment will have stop valves and/or guarding valves.
Your "bypass valve" is for something else entirely.

... Think about what happens
when a generating turbine trips! You can't just close the turbine inlet
valve as the boiler pressure would skyrocket.

Why? Do you not have combustion controls down there? Or even firemen
that can stay awake on burner watch?


... What you do is open a
bypass valve.

That depends on the plant.

... In big plants you may also inject water to cool the steam
(it's pressure is dropped by adiabatic expansion after the valve) and
thence to the condenser.

That's not what is done on any marine plants I ever heard of, or for
that matter, any stationary ones. It would be incredibly wasteful of
fuel. Hey Rick, you following this?


If you have a plant where one engine takes the steam from another and
you want to drop the second off line you first open a bypass valve. So,
that's all, why did you even argue about it with me?

I'm not arguing, I was trying to explain some of the basics of what
likely happened when the watch officer on the bridge of the Titanic
tried to dodge that iceberg. Since this discussion has wandered so far,
I've mostly been laughing at you... trying to explain 'condensate
depression' with an integral, and confusing HP & LP turbines for
"multiple engines." Thanks for the laughs, Navvie.

DSK

That's not what is done on any marine plants I ever heard of, or for
that matter, any stationary ones. It would be incredibly wasteful of
fuel. Hey Rick, you following this?

No, have just got home a few minutes ago,brought a boat down from Alaska
and am now on my way to the airport to fly to Lauderdale for the
superyacht show ...

The only place water gets injected into the steam is in an attemperator
just before the evaporators. I cannot think of any single more wasteful
exercise than adding water to steam for any reason other than to cool
the steam going to an evaporator feed water heater running on live steam
rather than bleed steam.

Rick