Steam vs Diesel RPM in (Heavy) Weather

Interesting point, we have pitch shedding on the blades on our Voith tugs but haven’t considered what would happen on our ASDs. As it is 0730 on Sunday here, will spend the rest of the day resisting the urge to log into work and read the Rolls Royce manuals…:slight_smile:

Most of my ships in the RAN were steam turbine and, as we never sailed at full power other than for trials for very short periods, there was always more readily available. The bridge ordered the revolutions and that was provided as ordered. Cruising speeds were usually well below 50% power for a destroyer or frigate 12 -16 knots. 50% power (one boiler connected, say) was sufficient for 24 knots. Double that power to get to 30.

I can’t say I ever noticed RPM variations from the bridge. There was no instrumentation for that anyway.

I can certainly vouch for the responsiveness of such steam plants. I was navigator of a destroyer where the Captain lost it a bit during berthing in Sydney. He had the con after I had set the ship up on a standard final approach. For reasons only he knew, he gave three “full” ie emergency engine orders in succession in a minute or two - full astern both, full ahead both and full astern both. I had never seen a “full” before and the first was impressive, the second absolutely spectacular stopping the ship in less than a quarter ship length from about 10 knots astern, and I reckon the third totally gob-smacking stopping the ship in 10 feet from about the same speed ahead and causing some sailors on deck (and probably below) to stumble. By the time I persuaded him to stop engines and settle down, all safeties were lifted, steam was screaming out and nobody could hear a thing, The stokers had the boilers at well over full power by the second manoeuvre and reaction time was instant.

Oh the joys of 50,000 shaft horsepower at the fingertips! Never seen it since unfortunately.

Having sailed through the different positions aboard steamships (and motorships for that matter), have had great occasion to experience different operational behaviors in heavy weather…

Of course I will be referring to only geared turbine vessels- it is largely dependent upon the type of turbine control system- the older, hand operated nozzle control valve systems operated with a maneuvering valve (normally opened wide at Departure) and the turbine controlled by the combination of nozzle control valves opened. This was basically a constant steam flow setting- the RPM would fluctuate according to loading, but the steam flow essentially remained constant… A speed limiting hydraulically actuated governor system through a series of hydraulic relays and control valves would close in on the throttle when a preset rpm was exceeded… Some (not all) incorporated an overspeed governor which would “trip” the throttle linkage when reaching a preset rpm (Shutte & Koerting) while others had a separate overspeed tripping device…

On GE ITC (Integrated Turbine Control) the control system would maintain the rpm set point according to either the Bridge or Engine Room control lever- and basically maintain that rpm (or attempt to) and thus constantly vary the steam flow. It was highly inadvisable to operate in heavy weather in Bridge Control…There was of course a “rough weather” setting (in the control cabinet originally) which would damper out the error signal and thus the system response- by offset and limiting functions; but it in real heavy weather we would usually be at full ahead maneuvering as opposed to above it… These systems were known to have electronic as well as mechanical overspeed shutdowns…

I have never sailed aboard a steamship with CPP…Would be very interesting to say the least!

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good info here, great replies. I was reminded of cleaning the sight glasses, so old i had to make new gaskets out of something. Was also reminded of the Chernobyl disaster as I’ve just finished a well documented book about how that went down. quite the story!!

Thanks for your comments… I also have read extensively on this subject, especially careful reading of INSAG-1 and INSAG-7. The positive/negative void coefficients and quotients, also the “neutron poisoning”… The manual withdrawal of the control rods certainly didn’t help…Good reading… All about sufficient time for the emergency generators to start and come up to operating voltage…Poor procedures, non-existent safety culture, inherent design errors and massive complacency…

i was amazed at how fast the reactor went critical. they had only 2 or 3 rods in as I recall and producing a min. amount, like 200 i think? then BLAM, that was it!

Yes., Positive Void Coefficient- the RBMK direct transfer reactors were a nightmare- graphite moderator rods…

The whole thing was started because they wanted to find a way for the generator set to continue supplying power to the emergency coolant loop pumps after a turbine trip… back then the emergency generator startup, voltage buildup and on line timing for just the emergency services was too slow. First they changed out the rotary amplifier voltage regulators with static shunt inverters… still too slow, so they changed the exicters and upgraded the SSI’s…

The "final"test was supposed to take place in daytime- instead of on the Mid to Eight Watch… people weren’t following procedures and allowed the mW thermal to decay down to about 12%… In a panic they attempted to raise the output- by pulling 90% of the Control rods- including Manual rods which were NEVER supposed to be withdrawn… Couple this with the fact that the main coolant loop pumps were secured for the test… What essentially happened was a steam explosion which lifted and shattered the 1000 ton upper biological sheild… OUCH!