running one engine when you have two

Third/get you home engine

I believe that Marlow in its 70/78ft range had an option of a smaller third engine as a get you home - low speed cruise unit 6/7.5Knts.

We were aboard one, a few years ago in Canada over four or five days fishing, the owner used the option frequently to add range and for fishing speeds. When running on this option it was very quiet, almost no vibration.They claimed it almost doubled their range above low speed on the twins.

I had never seen this before when twin engines were already installed - knew about the "wing" engines used in Nordhaven.

What interested us was the engine was in a totally seperate compartment accessed from the swim platform with its own fuel tank,additional fuel was available from the main tanks with independent filtering in line at the push of a lever.

A nice feature was the feathering prop on that shaft.

If I remember the additional cost of the feature was then about 150K

Seemed a good idea to me when time is not the issue.

Accessed from the swim platform? The last Marlow I was on, the swim platform was a ballast tank. It wasn't meant to be one but it flooded when the boat got wet.

It would make me very nervous to have anything inside a Marlow swim step.

MTU 16V 4000 M93L with ASD-18L

We are getting closer. But the ASD-18L seems to be a very rare species and both the 12V 4000 M93L and the 16V 4000 M93L are heavy iron in regard to the 2000 series.

If you compare the weight and total power of the different setups, the solution with the 3 x 16V 2000 M94 looks like the best relation between weight, power, size and most likely price for a 100 ft boat with Arneson drives.

Comparison of the complete powertrains:

3 x MTU 16V 2000 M94 with ZF gear and 3 x ASD-16, 7.800 total Hp and 34.395 lbs dry weight.

2 x MTU 12V 4000 M93L with ZF gear and 2 x ASD-18, 6.230 total HP and 53.254 lbs dry weight.

2 x MTU 16V 4000 M93L with ZF gear and 2 x ASD-18, 9.230 total HP and 60.176 lbs dry weight.

And this calculation does not include the increased weight of the hull for the stronger and heavier engines. The last version surely belongs into a bigger boat. Because of the published numbers, the last version of the powertrains could theoretically propell a Mangusta 165 in a triple configuration. Would be interesting to know, wheather this performance setup would work.

Sometimes, it is better to use all three engines of three; rather than using one.

The RMS Titanic power arrangement is an interesting read:

RMS Titanic - Wikipedia, the free encyclopedia

Note: scroll to Power

You're talking about steam power. Turbines are efficient with steam when run at their optimal RPM's.

Talk'n engines, as in the Thread title, running one engine when you have two.

Thought it an interesting read, that's all.


P.S.- Turbines are efficient with steam, especially if additional steam is not required for their use.


P.P.S.- Since you seem to have some idle time, please explain how the new expansion canal project in Panama will accomodate the newly built transport ships. Feeling stumped? Welcome to the club.


Hint to problem:

new canal width = 54.86 m

most new boat beams = 56.4 m and 58 m

Thread = http://www.yachtforums.com/forums/y...er-ports-container-shipping-technologies.html

Post = http://www.yachtforums.com/forums/y...ntainer-shipping-technologies.html#post188957

Steam turbines

One time in my life, I have been in an engine room with multiple running steam turbines. On a German Navy DDG Class Missile Destroyer during an combined air / navy exercise. I was detached to the ship as a liason officer for that exercise. One of the Chiefs was a friend of mine and at times without air activity, I spend part of my off duty time with him in the engine room.

Ambivalent experience, I must say. Very powerfull, great power to weight ratio (if you do not count the boilers but they were not in the engine room), very reliable but awful for the personel working in that room. I know, the engine room of an destroyer can not be compared with one of those mighty liners like the old Queen Mary or the United States and working in the military is not a soccer game but it was awfully hot, noisy and everbody was always afraid of leaks in one of those numerous tubes and hoses. The high pressure, ultra hot steam was supposed to be invisible and could have cut a person in half when walking trough it. Warning signs "Be aware of steam" were all over the place. I can tell you, the young Lieutenant was a bit scared .

But it was impressive to see this ship doing speeds above 30 Kts and evasive maneuvering like a PT boat during simulated air attacks. Very effective weapon system. But these American built ships had awful quarters for the normal sailors. Then I understood their saying "Join the Navy, see the worst"

The times for steam turbines as prime movers for the merchant navy are over because of their low effiency. Ironically, their revival was caused by the demand for more energy efficiency in ship propulsion. Today they are used for waste heat recovery of hot exhaust gases on large 2-strokes and gas turbines. With all means of wast energy recovery on the latest large 2-strokes, the specific fuel consumption of those engines is down to 150 g / KW / h and the overall effiency above 50 %. On special transports, where the cargo has to be heated during transport, the TE can go up to 80 %.

Can't imagine how dangerous that environment was for those servicemen. My marine engineer colleague tells stories of carrying a broom extended forward as they traversed the machinery spaces during commissioning on some steam powered ships, and had the rare event of seeing that broom head disintegrated by vaporized steam as he held it - a sober realization that could of been him except for the 4-5 feet of "broom security" .......

Panama is a third world country. So they are building the new canal to accomodate ships built in.......you know the 1990's.....LOL

Hi,

You might want to look at Exhaust Gas Boilers or Economisers.

These are not turbines and are generally used to provide energy savings in the form of pre heating of Boiler Feed Water and maybe the Evaps.

There are no doubt still some steam turbine driven LNG Tankers around, these being able to run on their own boil off.

Steam turbines

Yes, you are correct but they use the heat almost completely. Aft turbos with generators, heat exchangers to produce steam for generating electricity or geared to the shaft and boilers to generate process heat for preheating HFO or whatever.

On LNG carriers steam turbines used to be very common. As far as I know, one or the other of this type of ship is still under construction in Korea.

The new types under construction or developement either use dual fuel piston engines or combined dual fuel gas turbines and steam turbines (for waste heat recovery). The high EGT of more than 600 degrees centigrade of modern gas turbines leaves so much heat energy behind, that it can perfectly be used both for the production of steam for propulsion and process heat for boilers. The great advantage of dual fuel engines for LPG carriers is the possibility of using fuel oil when proceeding with empty cargo tanks towards their loading ports and using boil off gas on their way to their destinations, when the cargo tanks are full.

But all is under the same idea. Do not let any kind of energy go unused through the funnel $$$$$. It is purely based on costs. Smaller LPG or flammable gas carriers use dual fuel piston engines, the VLC and bigger LPG carriers use gas turbines. Boiling water to produce steam, in order to drive a turbine as prime mover has the lowest overall efficiency of all, except for nuclear powered vessels. But the time for nuclear powered merchant vessels seems to be over (Savannah and Otto Hahn) at least in the capitalistic world. So, Russian nuclear icebreakers do not count .