[BlackBeard]

Hello Everybody,

Since there was interest shown towards this topic and there already exists threads on Marine Diesel Engines on the forum I am making one regarding the working of a Marine Steam turbine, YES they do still exist!

Marine Steam turbines are the primary means of propulsion on board LNG carriers though they are rapidly going obsolete with the advent of gas burning diesel engines. Most LNG carriers built pre 2015 were with steam propulsion. The generators on board are also steam turbine driven called Turbine Generators with Diesel generators as a back up.

Most would want to know why is steam still being used as a means of propulsion at this day and age. It is only because of the nature of the cargo carried on board LNG carriers i.e Liquefied Natural Gas - Methane.
The cargo keeps continuously evaporating, technically called boiling off and this needs to be controlled. The BoG produced is 0.1% when the ship is in Ballast condition & 0.15% when she is loaded. This percentage is of the total cargo carrying capacity of the ship in CBM.

What better way than burn the gas and produce steam to propel & power the ship?

A brief overview of the process flow is as follows: Both the boilers are MITSUBISHI MB-4-KS

1) BoG generated is sucked by a compressor and sent to a heater. (-130C to 40C)

2) From the heater it is sent to the boilers for burning after mixing with pre-heated air.

3) The heat produced inside the boiler is used to further produce super-heated steam.

4) This superheated steam is used for the turbines (propulsion & power).Auxiliary steam is used for heating purposes.

5) The exhaust steam is condensed in a condenser and re-used, so its a closed loop system.


Boiler Front view.


Boiler Local Control Panel


Boiler Top looking towards ECR - Engine Control Room


PORT Boiler Burner


STARBOARD Boiler burner

[BlackBeard]

The Main steam turbine is a KAWASAKI UA-360 Cross compound, impulse, double reduction geared marine turbine output rated at 23757 kW / 32300 PS

The HP turbine - 4860 rpm, 10 stages
The LP turbine - 3222 rpm, 8 stages AHEAD, 2 stages ASTERN
The Propeller - 84.8 rpm

The reduction gear is a tandem articulated, double reduction, double helical type.
1st reduction pinion - 1st reduction gear - 2nd reduction pinion - Main gear - propeller shaft - Propeller

The thrust bearings are located in the forward side of both LP & HP turbines.

Main turbine overview


Main turbine looking from PORT side


Main turbine looking from STARBOARD side


EMERGENCY manoeuvring panel/station

[Jeroen]

Thanks for sharing, very interesting. I am a former merchant navy chief engineer. Although I have sailed on just about all types of vessels, never on a steam powered!

On diesel engine ships we did have auxiliary boilers, mainly for heating heavy fuel, lub oil, accommodation and sometimes (liquid) cargo. Always saturated steam.

I have visited a few steam vessels over the years. Very different from diesel driven.

Is the “boiling off” sufficient when under full power/steam. Can you mix the gas with other fuel as well. Do you use marine diesel or heavy fuels in case of no or insufficent boil off.

A good friend of mine spend a year as an apprentice on the then steam powered container vessel Nedlloyd Decima. Twin boilers, twin turbines. About 81000 HP which would give her a top speed of about 30 knots!

I visited my friend onboard in Rotterdam. Absolutely massive engine room!

A couple of years they ripped out the boilers and turbines. Put two slow speed 2stroke engine in, about 50000 HP. Which gave her a speed of about 21 knots.

Quite a few other steam container vessels were converted. All due to the high price of oil.

As a rule of thumb, if you want to double the speed of a (full displacement) vessel you need to install 8 times the horsepower. (Speed = HP to the power 3)

And HP is almost linear with fuel usage. In theory the boiler/turbine had a higher efficiency than a diesel. And the boilers could use the most awful (and thus cheap) heavy fuel.

Also, in those days the maximum HP from a marine diesel was quite a bit lower than today.

So in many cases the steam boiler turbine lost out to the more efficient diesel engine over time.

These LNG carriers are probably some of the last proper steam ships in existence, apart from some vintage museum steam ships.

Jeroen

[BlackBeard]

Originally Posted by Jeroen

Is the “boiling off” sufficient when under full power/steam. Can you mix the gas with other fuel as well. Do you use marine diesel or heavy fuels in case of no or insufficent boil off.
Jeroen

The NBoG (Natural Boil off Gas) is insufficient when doing full speed (18.5/19 knots). There are 2 options either force the Boil off by using a forcing vaporizer if on Gas only mode or use VLSFO (Very Low Sulphur Fuel Oil) or MDO (Marine Diesel Oil), the latter is known as dual mode wherein fuel and gas are burnt simultaneously inside the boiler, usually this mode is used during manoeuvring close to the coast, narrow channels and during harbour pilotage.

I forgot to mention about the Turbine Generator.
Type: Mitsubishi Multi-stage, single cylinder condensing turbine
Rated output: 3450 kW
Turbine rated speed: 10036 rpm
Generator rated speed: 1800 rpm
Reduction gear: Helical single reduction gear
Gear ratio: 5.576


Turbine/Turbo Generator

[Thad E Ginathom]

Amazing stuff!

Do you guys remember all this detail about the ships you've crewed on? Or do you keep a personal (or official?) log?

[BlackBeard]

Originally Posted by Thad E Ginathom

Amazing stuff!
Do you guys remember all this detail about the ships you've crewed on? Or do you keep a personal (or official?) log?

Some we remember for the others we have access to data from the ship & colleagues. There are more meticulous individuals who do maintain logs.

[Jeroen]

Originally Posted by Thad E Ginathom

Do you guys remember all this detail about the ships you've crewed on? Or do you keep a personal (or official?) log?

I don't think I remember everything. You do remember names of the ships you sailed on. But even crew members' names after 35+ years is becoming more and more difficult.

I am on several FB groups, dealing with the various companies I worked for. So that is a good way of staying in touch, sharing a lot of old photographs and some old memories. Mind you, the really good stories I have yet to read on FB!

I have my old seaman's book still. So I can always check names of ships and the period I sailed on them. Unfortunately, it is incomplete. I thought I lost it, so I got another one, which I lost as well. Only for the first one to turn up when I was cleaning up an old cupboard.

Jeroen

[BlackBeard]

The above is the arrangement of the propeller shaft from the main gear end to the propeller itself the slope is unique never seen it on diesel engine ships, they are almost always straight.



This is the location of the turbine looking ahead, the curved lines are the ships hull curvature

[Jeroen]

Originally Posted by BlackBeard

The above is the arrangement of the propeller shaft from the main gear end to the propeller itself the slope is unique never seen it on diesel engine ships, they are almost always straight.

[

Very interesting. Never seen anything like this on a large merchant ship.Any idea why they had this arrangement? Something to do with the size of the main gear housing?

Jeroen

[venkat_partha]

Amazing. This post gives me a peek into the world of bulk cargo shipping, and more interestingly, into the engine room.

And, by the way, how do you keep it so neat?

[Ithaca]

Excellent thread, BlackBeard Garu.
Since I did my exams in India and did not opt to qualify for the steam ticket, i missed out on sailing on LNG steam ships. I did not venture away from the VLCC, Aframax & Oil Chem trade for most part of my career.
This thread is an eyeopener for folk like me who are fascinated with the world of LNG Steam ships.
As a fourth Engineer, i did have the opportunity to sail on a VLCC which had a turbo-alternator. As soon as we left port, the turbo-alternator was put into service and the aux diesel engines put on standby. The level on noise pollution does come down significantly when only the Main Engine and turbo-alternator are in service at sea.

Originally Posted by venkat_partha

And, by the way, how do you keep it so neat?

Ships have two motormen and maybe a wiper who are assigned decks (floor for the layman) by the second engineer. It is the duty of the motormen and wiper to keep their area clean, usually sweep and mop the deck once a week as a routine.
And before a vessel arrives at port, the second engineer gets the staff to compulsorily mop all the decks.
Depending on the owner's budget, the vessel's decks and machinery are painted once a year at a minimum - done to keep the engine room looking clean and keep the staff busy.
This adds to the visual cleanliness of the Engine Room workspace.

[dragon_booster]

Nice thread!! Why they don't consider retrofitting existing steam-powered vessels with more modern propulsion systems?

[BlackBeard]

Originally Posted by Jeroen

Very interesting. Never seen anything like this on a large merchant ship.Any idea why they had this arrangement? Something to do with the size of the main gear housing?

Jeroen

Could it be due to the tapered bore of the helical gears in the GB?

Originally Posted by venkat_partha

Amazing. This post gives me a peek into the world of bulk cargo shipping, and more interestingly, into the engine room.
And, by the way, how do you keep it so neat?

Steam ships do not have much of oil leaks compared to a motor ship, also as rightly stated below workspaces are kept neat and tidy.

Originally Posted by Ithaca

Excellent thread, BlackBeard Garu.
Ships have two motormen and maybe a wiper who are assigned decks (floor for the layman) by the second engineer. It is the duty of the motormen and wiper to keep their area clean, usually sweep and mop the deck once a week as a routine.
And before a vessel arrives at port, the second engineer gets the staff to compulsorily mop all the decks.
Depending on the owner's budget, the vessel's decks and machinery are painted once a year at a minimum - done to keep the engine room looking clean and keep the staff busy. This adds to the visual cleanliness of the Engine Room workspace.

Thanks & correctly stated.

Originally Posted by dragon_booster

Nice thread!! Why they don't consider retrofitting existing steam-powered vessels with more modern propulsion systems?

Cost, It will be Prohibitively expensive to cut open the hull and remove existing machinery & install new ones not to mention the price of the new machinery!

[handsofsteel]

Originally Posted by Jeroen

These LNG carriers are probably some of the last proper steam ships in existence, apart from some vintage museum steam ships.

Jeroen

You probably did not consider warships while penning this down sir!

A few interesting facts for the laymen in this forum:-
1. The huge aircraft carriers (nuclear powered) are all basically steam driven with a closed loop steam system. Steam is generated in these using the energy from the reactor.
2. Apart from these, there are numerous frigates/ cruisers in existence world over (I admit numbers are dwindling though) in which the prime movers are LSFSHFD powered boilers and steam turbines.
3. In WW II, there were ships (Prince of Wales being the most famous example) with 8 main turbines capable of achieving 36+ kts of speed.
4. In the days of yore, steam ships would be tasked with producing a smokescreen around a formation of ships once the enemy was sighted to obfuscate the targets. This was achieved by blowing soot accumulated in the tube nests and by burning extra fuel. However, one had to be very careful as extra fuel could even explode the burners.
5. FFO (Furnace Fuel Oil) burning boilers were the worst in terms of soot generation. Operating these would leave you looking like a coal miner at times.
6. The boiler operators were some of the hardiest men around. Temperatures in these compartments would normally be 54-56 deg C and often reach 70 deg C (in the event of steam leaks).
7. The British built ships, unlike the American ones which were welded throughout, had flanged pipes leading to lots of leaks during operations. Superheated steam being invisible, leak detection was done by a variety of methods and always with the utmost care as it could burn you.
8. The process of flashing up a boiler (and shutting it down) would take 24 hours.
9. Steam propelled ships have lesser underwater noise than any other ship (diesel/ Gas turbines).
10. The efficiency of the steam plant (practically 36-39%) and the low cost of fuel (low grade fuel could also be burnt), made them very popular.

[BlackBeard]

Originally Posted by handsofsteel

4. In the days of yore, steam ships would be tasked with producing a smokescreen around a formation of ships once the enemy was sighted to obfuscate the targets. This was achieved by blowing soot accumulated in the tube nests and by burning extra fuel. However, one had to be very careful as extra fuel could even explode the burners.

10. The efficiency of the steam plant (practically 36-39%) and the low cost of fuel (low grade fuel could also be burnt), made them very popular.

"Soot blowing" is still done when the boiler is using fuel instead of gas but for safety reasons.

Efficiency is certainly an issue with the steam plant hence the shift to gas fired diesel engines with the advent in newer technology.