Question (from a layman) about torque

The Jag belonged to a friend. It had the same weight, engine displacement, and cylinder count (6) and as my father's '50 Dodge sedan. Not much similarity beyond that.

Jerry

Thanks to Steve and everyone else for the sound counsel.

As a Navy vet myself, I don't mind the sea stories either. ;-)

- Scott

On boats (submarines), we too had to run the turning gear. But the drive shaft was much shorter and sag wasn't much of an issue. Steam turbine rotor bending was more the concern, due to uneven heating (cold condenser below, and sealing steam applied to the shaft's labyrinth seals). If completely 'cold', like from an IMA or overhaul, we had to run the oil for a day or so just to warm it up to the minimum for jacking (90 F IIRC, for 2190 turbine oil). Then put the turbine/gear on the the 'jack' for four hours before bringing steam into the engine room and applying steam to the shaft seals, or warming the engine.

Lubrication on relatively small turbines (just a couple of ton rotors) is a matter of just having low-pressure oil supply and letting a dry shaft 'ride up' one side of the journal. It quickly pulls a film of oil under the shaft.

Large commercial turbines (on the order of 50 ton) also have 'lift pumps'. Along the with the low-pressure lubricating oil, a 'lift pump' supplies high pressure oil (>100 PSI) to a special port in the lower half of the bearing sleeve. It is enough pressure to force an oil film under the shaft, even when it isn't turning. So prior to first starting the turning gear, the lift pumps are used to 'break free' the shaft from the bearing sleeves. Quite often, once the shaft is turning (with the turning gear), the lift pumps can be secured as the oil film around the shaft is then enough to allow continued turning with the small motor.

daestrom

On Sun, 19 Nov 2006 18:24:50 GMT, "daestrom" proclaimed to the world:

I appreciate you posting this. My main duties involved the instrumentation and controls of both the boilers and main engines, but my rate was boiler tech. The shop I worked in had both boiler tech and machinist mates. The main engines had very little controls. I am sure this is the same with your sub. I did a lot of work on subs after I got out of the Navy and worked as a private contractor. The steam cycle remains the same as did the turbines which used the power produced by whatever source, be it conventional or nuke. Anyway, I was hesitant to post any info on main bearing lubrication with sketchy memory. Jerry spends late nights checking all my facts.:-) (Just kidding Jerry. I appreciate every question you pose.) Anyway I vaguely remember the lift pumps and decided not to mention them fearing I might not be accurate. Thanks for filling in the details. Do you remember what the lift pump pressures were?

I remember one time where the labyrinth packing was damaged by someone incorrectly jacking. I also remember uncoupling the main shaft so we could jack the turbine while the shaft was down.

You don't happen to remember how big the shafts were on the sub, do you? I remember on tridents and the sea wolf, the shafts appeared to be much smaller. It seems a little silly today but this might still be classified. Which class of sub did you serve on?

Commercial turbine lift pumps run about 100 psi (relief set for 120). But they're positive displacement (little versions of a typical 'gear' pump), so the exact pressure depends on the weight of the shaft and the temperature/viscosity of the oil.

We had it 'both ways'. The main reduction gear output could be disconnected from the shaft so the turbines/gear could be jacked without turning the shaft (a big-a__ clutch). Then each turbine shaft had a 'hard' coupling that could be disconnected between each turbine and the gear (port-starboard main turbines fed one reduction gear). That was in case a turbine was damaged, you could spin the shaft from the opposite turbine at reduced bells.

Don't know if it was ever classified, I'm sure the hp rating was. As I recall, they were only about 18" to 20" across, much smaller than your carrier version (and shorter too). The trickiest part of them was the seals, we didn't use 'packing gland' type, but the 'mechanical seal' type in order to adapt to changing depth/sea-pressure.

Tridents? SeaWolf? HA!!! Luxury liners!! Try 'boring holes in the ocean' in 'Permit' class. Yes, those are the ones with *miles* of seawater piping and were originally named 'Thresher' class. ("fast and black, and never come back")

daestrom former EMC(SS)

...

I remember Thresher being lost, and I remember how surprised some experts were when she was ultimately found nearly intact. I recall a seminar at which it was claimed that she was probably scattered in small pieces over a wide area. "... never came back." Were there other losses?

Jerry

On Tue, 21 Nov 2006 21:11:30 GMT, "daestrom" proclaimed to the world:

I never even got to see any of those subs except along the docks at the sub piers sitting near the old diesels. I guess they were built to last without much repair. ;-)

And those luxury liners were not so luxurious when ripped apart in dry dock, particularly since I was there to work on storage tank level indicator/controls. They would never tell me what "CHT" stood for. It must be classified. (LOL) I figured it must be "Chocolate Heaven Tank" from the looks of what was left in the tank when we got to it. To tell the truth, I also worked on a lot of other stuff too.

"Collection and Holding Tank" If the odor didn't provide a hint, there mist have been some powerful chemicals, too.

Jerry

On Tue, 21 Nov 2006 19:03:39 -0500, Jerry Avins proclaimed to the world:

I know what it stands for Jerry. It was a joke.

And actually it stands for Collection, Holding and Transfer tank.

On Tue, 21 Nov 2006 19:30:37 -0500, Paul M proclaimed to the world:

And I forgot to add this. Smell was not a problem because the tanks were always cleaned and disinfected before I ever got into them. This was not true at most of the WWTPs I worked at later. I watched this Indian guy take off his shoes, socks and pants and wade knee deep on a strut in the top of a aeration tank once at a small private plant. He asked me to wash him down with a garden hose afterwards.

It's the straight-faced ones that always take me in. I should know better. When I do it, people often get put off, not amused.

Jerry

On Tue, 21 Nov 2006 22:32:57 -0500, Jerry Avins proclaimed to the world:

I'm not put off at all. I find you refreshingly simple in your logic and insistence of accuracy. That IS a compliment, BTW. You can be the straight man in my act! :-)

On the older boats, we didn't mess around with such 'euphenisms'. They were called 'sanitary tanks', but were far from 'sanitary'. (why *is* it that sewers for human waste are called 'sanitary', seems a complete perversion of the term :-)

daestrom

"Sanitary" as opposed to open ditches, flinging it out the window, etc.

Pete Keillor

Because it was more sanitary than chucking it onto the street from a second story window?

Cheers Trevor Jones

The Ministry of Truth strikes again ...