That Old-Time Southern Engineering

[samfp1943]

BaltACD

Locomotive left a shop yesterday after having 2 power units replaced - caught fire today inside a tunnel.  Great shop work - have to check those fuel line connections.

 

My question is a general one: Over the last year or so, I have noted on a number of passing BNSF's  GE locomotives, burned places slightly over halfway back on the engine housings.

  These spots range from roughly a couple of feet in diameter, to several that seem to have brned the paint off a large portion of the engine hood,[ on the mostly, left sides of the engines.]   I had always thought that thses might have been a result of turbo failures, since they seemed to be in the area near of the exhaust stack.

BaltACD's statement referencing the problem of an engine fuel leak, prompts me to ask:

Are these fires very frequent?

How much of a problem are they? 

Are they most a problem on the GE's?

Do the engines carry any kind of crew-activated fire suppression equipment?

Thanks

 

[Wizlish]

Some of this was already addressed: GEs have high-pressure fuel in lines that can fracture and spray.  I do not know how many turbo lube failures involve either primary or secondary breach of the lube line, but engine oil pressure would do a pretty good spray from a crack, and the pressurized engine compartment might neatly carburete the flow...

I will however sit back and listen to the railroaders with first-hand experience cover what they have observed the problems to be.

[Electroliner 1935]

BaltACD.

That is a fantastic video of the Titanic's massive propulsion system and put together in such a clear story. And it confirmed my assumptions about how a triple expansin engine would be built. Thanks. I had seen a triple expansion Corliss water pump at the Cincinnati water works during a field trip and it was a three cylinder unit. 

I also liked the way they ended the video. Clever. But so sad for the hard working crew. 

[M636C]

I was distracted by work and was unable to answer this in time.

The cylinder arrangement on Diamantina was the same as the Titanic, just a smaller engine, developing 2750 shaft horsepower on each of two shafts. The Frigates had no exhaust turbine, of course.

Thinking back, I was familiar with these engines because I'd been billeted on a sister ship Culgoa in Sydney in 1969. Culgoa was just an accommodation ship but clearly a couple of junior engineers were going to check out the machinery spaces at the first opportunity.

The US Navy built 100 ships to the same design as the UK and Australia (and I think with the same engine) as Patrol Frigates (PF). The class PF was revived in the late 1970s for a new class of escort, called the PF-109 which after some changes of designation became the FFG-7 class with which I am also familiar.

By coinicidence before reading further in this thread, the Navy's Principal Marine Engineer and I were discussing the Titanic with a staff engineer.

I believe the Titanic exhaust turbine may have played a role in the collision with the iceberg. As indcated in the video, the turbine did not reverse and was stopped during manouvering. When the Titanic went astern on sighting the iceberg, the turbine stopped. This meant that there was a stopped four bladed screw immediately ahead of the rudder, upsetting the flow over the rudder and reducing its effectiveness.

If the ship had just turned without going astern, it may have been able to clear the iceberg, since the rudder would have been in the thrust flow from the turbine's screw.

Of course, it is most unlikely that the deck officers on the bridge at the time would have understood much of the ship's engineering, even if they'd been on the similar "Olympic" before.

M636C

[Wizlish]

M636C

I believe the Titanic exhaust turbine may have played a role in the collision with the iceberg. As indcated in the video, the turbine did not reverse and was stopped during manouvering. When the Titanic went astern on sighting the iceberg, the turbine stopped. This meant that there was a stopped four bladed screw immediately ahead of the rudder, upsetting the flow over the rudder and reducing its effectiveness. If the ship had just turned without going astern, it may have been able to clear the iceberg, since the rudder would have been in the thrust flow from the turbine's screw.

The screw of the Parsons turbine would almost certainly have been 'windmilling' after shutdown, and while this would have an effect on rudder integrity it shouldn't have been any more effect on rudder integrity than that of the cavitation or vortices it produced with the turbine power.

Far more likely that the turbulence of the abruptly-reversed main screws produced lower-than-expected actual counterforce, and the deceleration would give lower rudder authority.  In a very real sense if the turbine had been arranged to provide power in reverse it would have created similar cavitation and turbulence directly ahead of the rudder... but this might not have been the 'bad thing' so many people assume, for a different reason.

I don't think there is much argument that if the rudder had been thrown over (and perhaps one of the two engines slowed or reversed to give differential thrust) the ship would have missed the iceberg handily.  But there is some argument that if the ship had way taken off her but had actually collided with the iceberg more 'head on' (instead of grazing along the side and popping out all those rivets) she might not have sunk at all, or in any case would have lived long enough for some of the other large ships to reach her and transfer passengers.  (In that calm sea it would have been almost surely possible to come alongside even if the Titanic were down by the head and taking water...)

In a sense all this is 'second guessing' and armchair hindsight.  Would I have power-steered a brand new ship and injured heaven knows how many passengers (or broken the dining-room crockery) ... and had little excuse to show, because without the disaster of the ship sinking with such a massive loss of life, it's just Schettino ship handling.  And it's difficult to gauge high-momentum collisions or effects ... if anyone has seen the video of the LRC that almost hit a local freight on camera, you'll see one of the train crew bail out a couple of seconds 'early' -- he looks like a fool, but he couldn't tell from the relative accelerations what the effect was going to be.

[wanswheel]

[BaltACD]

wanswheel

Rudders are for controling forward motion - backward, not so much.

[Wizlish]

BaltACD

Rudders are for controlling forward motion - backward, not so much.

But we're not talking about 'backward motion', we're talking about steering when the ship is moving forward but propwash is making the rudder's action less effective.  One specific point about the design of the turbine screw on Titanic was its sizing and placement to leave a considerable amount of the rudder 'unaffected' by its action when providing power, and this is part of the earlier discussion about the effect of the prop when the turbine lost input steam during the 'crash reverse' of the two engines.  There was no 'backwards' involved at any point during Titanic's striking the iceberg...

[BaltACD]

Wizlish

BaltACD

Rudders are for controlling forward motion - backward, not so much.

But we're not talking about 'backward motion', we're talking about steering when the ship is moving forward but propwash is making the rudder's action less effective.  One specific point about the design of the turbine screw on Titanic was its sizing and placement to leave a considerable amount of the rudder 'unaffected' by its action when providing power, and this is part of the earlier discussion about the effect of the prop when the turbine lost input steam during the 'crash reverse' of the two engines.  There was no 'backwards' involved at any point during Titanic's striking the iceberg...

Still appears to be very little rudder for whole lot of ship.  Forward or otherwise.

[Wizlish]

BaltACD

Still appears to be very little rudder for whole lot of ship. Forward or otherwise.

You don't need that much for hydrodynamics.  But yes, one of the reported things about Titanic involved her low-speed authority and her 'suction' tendency toward other ships.  I'd also suspect that putting the rudder 'hard over' would effectively stall it on a ship with this mass, particularly if it were already 'overloaded' or turbulent/cavitating water were washing up into the induced region of low pressure... these things aren't just plates stuck at an angle to deflect water flow...

Here is the rudder on the United States for comparison:

I think it is well-known that 'most' of the steering authority on twin-screw ships is achieved with the screws and not with the rudder, however.  Implicit in the 'missing the iceberg' scenario as I understood it was 'back on one engine' with the other kept partially or fully AHEAD, and speed used to give additional rudder authority (not held 'hard over', either), rather than trying to get way off the ship in an impossibly short time.

Looking forward to Leo Ames on the tech of this subject.