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Old 2nd June 2019, 07:42   #1
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Default Man, Machine and Water - A brief introduction to Marine Engines

Prologue
Imagine riding a vehicle which can develop 25,000 horses of power! How would you feel? Imagine the engine of this vehicle has 6 to 9 or even 12 cylinders, each of which is around 1 meter in diameter. And finally imagine what could be the mileage of the vehicle or that famous question of Indians, "kitna deti hai?" Well, I can say it consumes only 60,000 liters per 24 hours of ride.

Yeah, most of you must have guessed it and for those who haven’t, I am talking about an engine which propels the large crude oil tanker or large container ship, and I am privileged to ride in one almost every day. Well, not literally everyday, but at least when I am working.

By the way 25,000 BHP is equal to 18 MW of power and 1 MW of power is enough for 400-900 homes. I rest the math on your hands. :-D
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Flash-Back (some history. Errrrr...sorry, I don’t like it too)
Ever wondered how the petrol / diesel we fill in our cars or for that matter even imported cars comes to our country? Ever pondered when you see large containers moving on a truck - where they came from and where they are going. Well, that's how most of the heavy / large and bulky goods are moved across states, country and continents. Yeah, it is by ships. There are dedicated ships for that, car carriers, crude oil carriers, petroleum product carriers and reefer carriers as well. That's how we import some fruits from other parts of the world.

Shipping or carriage of goods by water, has played a significant role in the development of human society over the centuries. Shipping has been a crucial link by which commercial relationships have been established between widely separated parts of the world.

It is often the least expensive way of moving large quantities of goods over long distances. The existence of reliable water transportation has been a key to the economic and political well-being of most nations throughout history. For example, the merchant fleet of Great Britain during the industrial revolution was instrumental in the growth of that nation as a world power. Same way the shipping industry has evolved by leaps and bounds over the past lets say 40 years. OK OK, that’s enough.

Flash-Forward (yeah….)
Nowadays, it is very common to find a large ship which can carry millions of barrels of crude oil or million of tons of bulk cargo like coal, rice grain or even iron ore. These large floating metal juggernauts can move at a speed of 16 knots or 30 KMPH. Yeah, this is a very slow speed if you are on land and you may get fined in some countries if you drive at this speed. But, with the amount of cargo they carry, to develop this kind of speed, it requires special kind of machinery or technology.

The Engine (The Power House)
I am sure you must have seen above image and I am sure you have checked out and compared it with a standing man. What, was there one? OK, I will give you one more chance of a sneak peak again (I remembered the Invisible Gorilla prank. No, you don’t know? Check it out on YouTube).

That’s the sheer size of the engine and once you see the above image, it is not required to describe the engine by height and weight. That’s the power house which drives or rather propels the ship.

There are different types of marine engines - internal Combustion engines, steam engine and gas engines to name few. Herewith, I would like to talk or narrate about my ship's engine - the internal combustion engine. It's time to check out some real pictures finally.
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In generic terminology, if I can say, then, the engine is a 6-cylinder, 2-stroke, turbocharged cam-less or electronically controlled engine or 6S70ME-C engine. The maker of engine MAN B&W, no its not typo error, its B&W and not BMW. The above picture shows a bird's eye view of the engine, whereby one can see 6 units of 6 cylinders.

The piston of the engine is 70 cm or 700 mm in diameter. As this a super long stroke engine, the piston is connected to the crankshaft via a piston rod. The below picture shows the piston and piston rod assembly which is 2.5 m long and weights 2400 kgs.
Man, Machine and Water - A brief introduction to Marine Engines-1c.jpg

Some interesting details of engine
There is no ignition key nor starting motor for this engine. The engine is started with the help of 30 bar compressed air or 430 PSI for those who can relate with PSI. Some of you may be curious to know, how compressed air can start an engine. The compressed air is sent to those cylinders whose piston is at the top (TDC). By this, the engine starts to turn and once it attains nominal RPM, the diesel (fuel) is injected into the cylinders, it is similar to hand cranking of old engine-driven pumps. I’m sure some of us used them for irrigation purposes. Once the engine is running at an RPM when fuel can be ignited, slowly the RPM is raised.

The engine can be run on 4 speeds or lets say 4 gears (no, there aren’t any gears). Dead slow, slow, half and full ahead (forward) and similarly dead slow, slow, half and full astern (reverse). The maximum RPM of this engine is 90. That is why these are called super long stroke, slow speed engines.

Mind you, there is no brake for this engine. We have to control the speed according to the distance to be moved and vice versa. So, to maneuver the ship, it takes special skill and those specialized people are called captains of the ships. It takes years of knowledge and experience to handle and maneuver these gigantic ships, some of them even measuring 400 m in length. Imagine turning a 400 m ship on a tight river bend, that too with no brakes. Phew! On top of that, you have to keep in mind wind force, water current and what not.

Now, if the Captain navigates the ships, who does the maintenance or in automobile terminology servicing of the engine?. Yeah, ….. This is where our expertise come into the picture and we are The Marine Engineers. We can strip apart the engine and can assemble back with help of some special tools and off-course, experience!!!!.

More about the Engine
I will not go into very detailed technicality of the engine, I will try to relate the same to the automotive engines. Similar to an automotive engine, this engine has a set of ancillaries, which are required to run the engine without any problem. Fuel oil pumps, engine cooling water pumps, engine cooling water cooling system, lube oil pump and system and so on and so forth.

Fuel used in the engine is called heavy fuel oil, which is a byproduct of crude oil. So, to have to inject the fuel into the engine, it has to be heated to a temperature of 130 C and raised to a pressure of 350 bar. Some of the engines have a system similar to common rail diesel injection (CRDi), where the pressure of the fuel is increased to 1000 bar and above.

Engine cooling pumps pump the fresh water into the engine and help in removing the heat generated by combustion. This water is in turn, cooled by another system, which acts as a radiator in automotive engines.

We follow a strict maintenance or service routine and all the spares parts are always stocked for emergency usage. The maintenance routine is followed as per the number of hours of usage. For example every 16,000 hours of running, a complete de-carb of the engine is carried out. Every 8,000 hours, fuel injectors are opened up and cleaned or renewed as necessary.

Epilogue
There are many machines running in sync for a ship to go from point A to point B. If I start telling about every one of then, I won't be knowing where to start and where to stop and it would be boring for some or maybe all .

I hope you all liked the brief introduction to marine engines. I will try to compile one post for every machine in the near future.

P.S. I have been following Team-BHP for more than a decade now, but this is my first post. Hope you all enjoyed it. Any comments for improving the post will be welcome and I apologize if I have made any mistake.

Last edited by Aditya : 3rd June 2019 at 11:43. Reason: Typos, grammar, spacing. Max 2 smileys per post. Please familiarize yourself with the forum rules
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Old 2nd June 2019, 08:41   #2
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Default re: Man, Machine and Water - A brief introduction to Marine Engines

We want more. We want more. Please tell us more about the bridge, the engine room operations, the ship and please post as many photos as you can. Lovely.
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Old 2nd June 2019, 09:48   #3
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Default re: Man, Machine and Water - A brief introduction to Marine Engines

Cool. Would be interested to know more about the Turbo in these engines. What kind of rpm and boost do they run? What is the boost plumbing? One more question, what is the compression ratio of these engines?
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Old 2nd June 2019, 10:30   #4
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Thanks for the concise-yet-informative post. As someone who works on heavy-duty diesel engines, I can relate to many points explained by you. These giants are pretty different from the conventional on-road automobile engines, though they share the same fundamental characteristics. And yes, the fact that these monstrous engines run on a different version of crude oil is something new to me, as I always thought these ran on diesel.

I had always wondered how these super-long-stroke engines could be started up using conventional starting methods; thanks for clarifying that doubt.

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Old 2nd June 2019, 13:22   #5
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Cool. Would be interested to know more about the Turbo in these engines. What kind of rpm and boost do they run? What is the boost plumbing? One more question, what is the compression ratio of these engines?
The Turbocharger revs at 12000 RPM at full load and makes as much as 3 bars of pressure. But as these are super long slow speed engines the efficiency of the the turbocharger is poor at low loads. So to assist in good combustion additional blowers are provided. These are called Auxiliary Blowers and are driven by the electric motors. Once the engine or the turbocharger starts to develop good pressure then these motors cut out.

These engines doesn't have inlet valves rather they are provided with ports at the bottom of the liner where by the combustion air is let in to the cylinder when the piston uncovers the ports.
Compression ratio of these engines varies from 12 to 18 and for our engine it is 13.2
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Old 2nd June 2019, 14:24   #6
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Originally Posted by MJ@Mariner View Post
The Turbocharger revs at 12000 RPM at full load and makes as much as 3 bars of pressure. But as these are super long slow speed engines the efficiency of the the turbocharger is poor at low loads.

Thanks for this thread, really enjoyed reading it. I am a former merchant (Chief) engineer . My first vessels had these low speed two stroke engine. Later I moved to mostly medium speed engines on ocean going tugs and AHTs.
You might want to recheck the numbers on the turbo chargers. Those revs and pressure were a lot a LOT lower in my days.

What position/rank are you currently holding?

Jeroen
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Old 2nd June 2019, 15:27   #7
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Default re: Man, Machine and Water - A brief introduction to Marine Engines

Hello MJ@Mariner. Thanks for the post about Marine Diesel Engines (concise yet informative). I was sailing on Crude Oil Tankers (the engines were generally 6S70MC-C, ME-C was under development) and have shifted to DP Offshore Vessels (Dive Support) a few years back. It was an amazing experience working on Big Diesel Engines. On Offshore Vessels, it more of watch-keeping and less of maintenance (only emergency) as the Vessel is on hire and cannot afford to have any down-time. All the pending maintenance is carried out during the Port call which is usually once in a month.
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Old 2nd June 2019, 15:41   #8
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Originally Posted by Jeroen View Post
Thanks for this thread, really enjoyed reading it. I am a former merchant (Chief) engineer . My first vessels had these low speed two stroke engine. Later I moved to mostly medium speed engines on ocean going tugs and AHTs.
You might want to recheck the numbers on the turbo chargers. Those revs and pressure were a lot a LOT lower in my days.

What position/rank are you currently holding?

Jeroen
Hello Sir,

Confirm that the revs and the pressure is correct. I understand these figures may not have visioned before, let's say 20years back, but now a day's these figures are very common.
Infact I've sailed on engines developing 50000BHP which has 2 Tubocharges reving at these speeds.

I am sailing Chief Engineer too on Crude oil change Tankers. Good to know there are some Mariners in the group.
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Old 2nd June 2019, 16:04   #9
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MJ@Mariner.
Lovely post. Well written & explained.

Could you share more information about the ME-C series. How different are they to conventional Main Engines. What are their advantages & shortcomings. Special precautions to be taken, if any.
I donít have any experience on these engines hence the query.
Thanks.
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Old 2nd June 2019, 16:45   #10
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Originally Posted by Ithaca View Post
MJ@Mariner.
Lovely post. Well written & explained.

Could you share more information about the ME-C series. How different are they to conventional Main Engines. What are their advantages & shortcomings. Special precautions to be taken, if any.
I donít have any experience on these engines hence the query.
Thanks.
The nomenclature E in ME-C stands for Electronic. The standout difference being there is no cam or cams in this engine. Main job of the cam is timing of the operation, be it injection of fuel, be it exhaust valve opening or be it starting and reversing the engine. So all these jobs are now controlled electronically.

Main Advantage of these engines are they are super informative. They pass on so much information to the user we can accurately check the health of the engine.
The engine has an online power measurement system which measures the Pmax, Pcomp and Pmep. Once these parameters are known and analysed the engine can be tuned online.

Lets say, one of the unit is developing less power, based on above parameters the engine can be easily balanced. Hope I am not going too technical.
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Old 2nd June 2019, 20:19   #11
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Thank you for the reply. Detailed & informative.
This is a fascinating concept - shall try to read more about this.
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Old 2nd June 2019, 20:36   #12
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Originally Posted by MJ@Mariner View Post
Prologue
In generic terminology if I can say, then, the engine is 6 Cylinder, 2 stroke, turbocharged cam-less or electronically controlled engine or 6S70ME-C engine. ...The engine is started with the help of 30bar compressed air or 430PSI for those who can relate with PSI.
The engine can be run on 4 speeds or lets say 4 gears ( No, there arenít any gears).
What sort of clutch connects the engine to the propeller. I assume when this giant engine is being started with compressed air it is de-clutched from the propeller shaft and then as it starts to run on its own it is clutched in and the ship starts to move. How large & heavy is your propeller.
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Old 2nd June 2019, 21:27   #13
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Confirm that the revs and the pressure is correct.
What would be the impeller diameter of these turbos?

Regards
Sutripta
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Old 2nd June 2019, 22:22   #14
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What sort of clutch connects the engine to the propeller. I assume when this giant engine is being started with compressed air it is de-clutched from the propeller shaft and then as it starts to run on its own it is clutched in and the ship starts to move. How large & heavy is your propeller.
Sorry to jump into the post.

Narayan Sir, the Main Engine of large ocean going cargo ships and tankers of all types is directly coupled to the propeller via an intermediate shaft that connects the flywheel of the main engine to the tail shaft on which the propeller sits.
Intermediate shaft usually is balanced on one or more intermediate shaft bearings.
The tail shaft is housed in the Stern tube with seals in the forward (Engine Room) and aft side (Sea Side) to prevent sea water entering the stern tube which is filled with Lube oil.

Below is a representative photo of the entire assembly from main engine to propeller.
The picture attached below has more than one intermediate shaft bearing but usually just one suffices since the main engine is in the after most part of the engine room.

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This is how the Tail shaft is sealed.

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Propeller is directly coupled to the main engine, the propeller rpm is always the ME Rpm.


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Old 3rd June 2019, 00:44   #15
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Hello MJ@Mariner,
Thanks for this thread. Welcome to team bhp forum. I am also sailing as a Chief Engineer on Vale max VLOCs 4 lakhs ton vessels. Sailing mostly on Wartsila Sulzer 7RT-flex Engines since 10 years. I can see lot of marine engineers in this forum.

Venkatesh.H
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