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Old 4th June 2019, 22:11   #31
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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Originally Posted by Jeroen View Post
That gave sufficient air capacity to start another auxiliary engine, bring it on the grid and start up the rest of the systems. Quite interesting trying to figure out how to start up an, unknown to us, engine room!

Jeroen
Looks challenging, so small or big, every engine requires compressor air to start.

The job is really not for the faint-hearted
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Old 4th June 2019, 22:28   #32
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Looks challenging, so small or big, every engine requires compressor air to start.



The job is really not for the faint-hearted

Yes, mind you, the Diesel engines in our lifeboats were all full manual:

decompression lever and a handle to crank the engine.

Quite tricky and many mariners have suffered the consequences with broken wrists and or worse.

On my very first trip as an apprentice engineer I was responsible for maintaining the two life boat engines. Which meant starting them a few times every month. I got pretty good at it. It certainly helped me getting to terms with kick starting my Royal Enfield 1974 Bullet!

You get the timing wrong and they will bite you!

Jeroen
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Old 4th June 2019, 23:10   #33
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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Der MJ@Mariner,
How compressed air(450psi) is produced? is there a compressed air tank?
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Originally Posted by adi.mariner View Post
Hello T1000. There are Air Compressors which compress the Air to 30 Bar (450 psi) required for starting the Engine. Mostly they are of the reciprocating type (Piston inside Cylinder).
Other than those, there are Air Compressors which compress the air to around 7 bar (101.5 psi) which is required for Control Systems and other Auxiliary Systems on-board.
Regards.
And
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Originally Posted by MJ@Mariner View Post
Hi T1000, As explained by fellow BHPian, there is tank or technically called air reservoir which holds 30 bar compressed air for immediate use.
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Thank you for the detailed response.
Is there a diesel engine or an electric motor that powers the air compressor. What happens if the air reservoir gets empty.
As answered by adi.mariner & MJ@Mariner, There are usually a pair of air bottles that store the compressed air for starting Main and Auxiliary engines.
One of the bottles will be in use and the other is topped up and kept isolated for use only in case of emergencies.
The main air compressors will continually top up these bottles and that operation is controlled by pressure switches that initiate starting and stopping of the air compressors automatically.
Additionally, Maritime law requires every sea going vessel to have a spare Emergency air compressor and an emergency air bottle of a smaller capacity.

The Main Air compressors reciprocating equipment which are electric motor driven.
Again a vessel will always have two of them. Have seen only one vessel with 3 Main air compressors in my life.

MAIN AIR COMPRESSORS USUALLY FOUND IN ENGINE ROOMS.
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Some proactive owners provide a separate compressor - usually an Atlas Copco Screw Compressor - to take care of low pressure air requirements which are capable of providing air upto 9 bar.
This compressor has its own air bottle which is continually topped up by that stand alone compressor.
This low pressure air is tapped for the control systems in the engine room, service air requirements in the engine room and on deck.
The ship's gangway is also operated by an air motor supplied air from that deck air.
This equipment is continually on and this helps reduce the operating hours of our main air compressors since air above 8 bar is normally not required for normal shipboard operations.

THE LOW PRESSURE COMPRESSOR MOST PROACTIVE OWNERS PROVIDE
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I hope I have answered your query.

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Originally Posted by Jeroen View Post
The procedure was as follows:
Quite interesting trying to figure out how to start up an, unknown to us, engine room!
Jeroen
What Jereon Sir has elaborated here and performed by him during an emergency is now standard practice when we are sent to the ship yard to get new ship ready for take over by the owners.
The test is called Dead Ship Test. Carried out during the sea trials.
It is the time taken by the vessel to go from zero power & no equipment working to establishing all required power, filling up the main air reservoir and giving one kick to the main engine and the main engine firing on fuel.
This is timed and is certified by classification society.
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Old 4th June 2019, 23:20   #34
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

Nice thread. Took me back few years.
An ex Marine engineer myself here. Didn't sail long enough to be a chief engineer. Quit during my Class 2.

However even though I left the sailing, it could not take the Marine world away from me.

Now I sell stuff to the Marine industry.

I still remember my first step inside the engine room as a junior engineer on a chemical tanker owned by SCI in 2006. I was greeted by the sight of the Second engineer inspecting the crankcase during a Main engine decarb. The engine in question was a MAN B&W 6S60MC. Was fortunate enough to get a main engine decarb on every vessel I sailed. It's such a pleasure to work on these Giants!
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Old 6th June 2019, 18:00   #35
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Originally Posted by Jeroen View Post
That gave sufficient air capacity to start another auxiliary engine, bring it on the grid and start up the rest of the systems. Quite interesting trying to figure out how to start up an, unknown to us, engine room!

Jeroen
Also. its a challenge to do it in a completely dark environment without any electricity

A design question,
If the propeller rpm is around 90, then why cant a hydraulic motor power the propeller.

Won't it make the propulsion system simple?

Last edited by Gannu_1 : 6th June 2019 at 18:40. Reason: Back to back posts merged. Please edit your previous post if re-posting within 30 minutes. Thanks.
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Old 6th June 2019, 19:41   #36
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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Also. its a challenge to do it in a completely dark environment without any electricity

A design question,
If the propeller rpm is around 90, then why cant a hydraulic motor power the propeller.

Won't it make the propulsion system simple?
Is there anything simpler than a direct connection to the crankshaft? A hydraulic motor would require a hydraulic pump that is driven by the engine. This will be big, heavy and much less efficient than a direct coupled propeller.
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Old 7th June 2019, 10:36   #37
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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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.
Now that's hitting a ton on debut! Fantastic write up. Thank you so much for the effort to write this. Your passion for the topic really shows. Kudos.
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Old 7th June 2019, 13:15   #38
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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The test is called Dead Ship Test. Carried out during the sea trials.
It is the time taken by the vessel to go from zero power & no equipment working to establishing all required power, filling up the main air reservoir and giving one kick to the main engine and the main engine firing on fuel.
This is timed and is certified by classification society.
I could be wrong, but I do not think it was part of the classification in my days.

But it does take a lot of time to start up from a dead ship. A lot of it depends on how things were shut down to start with. On diesel which use heavy oils, it is important that the engine(s) have been switched to regular diesel long before shutting down. The heavy oil, depending a bit on specification requires heating to 80-100oC just to be able to pump it properly.

On the ships I sailed, heating was done mainly by means of steam. So although a diesel ship we still had a proper boiler as well. In fact it was what was known as an exhaust gas boiler. So the exhaust gasses from the main engine could be diverted through the boiler in order to heat it. Pressure was relative low, I seem to recall 6-8 bars, and it was just saturated steam. Good enough for heating.

When the main engine was not providing sufficient quantity of exhaust gasses, (shut down or running at low RPM) the boiler would be fired traditionally with burners.

The problem with these salvage jobs was that everything had been shut down whilst still running on heavy fuel. So once we had restored electrical power, the next thing is really to fire up the boiler and start heating the fuel lines and day tanks. Very often you will end up having to take valves and filters apart to clean them out. Very dirty very messy job.

Starting up a dead ship after it was shut down properly will still take several hours. When it was not shut down properly, it could take a lot longer.

Steam (turbine) drive ships usually take a lot longer to start up.

Are exhaust gas boilers still used on modern vessels, or are we using thermal oil boilers (usually electrically powered).?

Jeroen
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Old 7th June 2019, 22:21   #39
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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I could be wrong, but I do not think it was part of the classification in my days.
But it does take a lot of time to start up from a dead ship. Jeroen
Dead Ship Test is carried out during sea trials. Here unlike the case you described, the vessel is not a dead ship.
It is a fully functioning ship. All Aux Engines are firing on Heavy oil. The Aux Boiler is on Auto. All machinery are functioning including purifiers, air compressors and other cooling pumps.
The main power and emergency power is tripped to perform the test.

Quote:
On the ships I sailed, heating was done mainly by means of steam. So although a diesel ship we still had a proper boiler as well. In fact it was what was known as an exhaust gas boiler. So the exhaust gasses from the main engine could be diverted through the boiler in order to heat it. Pressure was relative low, I seem to recall 6-8 bars, and it was just saturated steam. Good enough for heating.
Starting up a dead ship after it was shut down properly will still take several hours. When it was not shut down properly, it could take a lot longer.
Are exhaust gas boilers still used on modern vessels, or are we using thermal oil boilers (usually electrically powered).? Jeroen
Most sea going merchant vessels still use the economiser to generate steam using exhaust gases from the main engine while at sea.
And all ships have Aux Boilers or Donkey boiler to complement the steam generation from the Exhaust Gas Economiser.

As you have rightly pointed out, starting a dead ship takes a long time provided you have enough Diesel oil and requisite permissions from the owners and the charterers to burn up this diesel oil to restore normal operations to the vessel.

Have asked a few colleagues - Dead Ship Test is still being carried out by classification society on new buildings at sea trials.

And Jeroen Sir, one thing that may surprise you - due to stringent pollution norms nowadays, we carry out air cleaning of the economiser and not the normal water washing of the economiser as was prevalent till early 2010s.
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Old 8th June 2019, 10:36   #40
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

Thanks MJ for the thread.
Being a mechanical engineer and working on gas turbines for 10 years, I found this thread very interesting. Please keep the thread rolling.

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Old 8th June 2019, 19:12   #41
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Not a mariner but I remember big czechoslovakian generator sets which we used in industry in Faridabad. These giants, to me, generators of 750 kilowatt used compressed air to start. They ran on LDO or furnace oil.

As others said what introductory thread.

Last edited by sudev : 8th June 2019 at 19:13.
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Old 9th June 2019, 06:07   #42
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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Nice thread. Took me back few years.
I was greeted by the sight of the Second engineer inspecting the crankcase during a Main engine decarb. The engine in question was a MAN B&W 6S60MC. Was fortunate enough to get a main engine decarb on every vessel I sailed. It's such a pleasure to work on these Giants!
Most probably we are going to carry out de-carb of couple of main engine units in few days provided we get millions of people and authority. Now a days it is very difficult to get the permission to carry out job on the main engine. As per the regulations engine to be ready all times at port, so no chance of carrying out the job in port.
Most of the port authority don't allow to carry out jobs in their waters as well when in anchor. If everyone allows the charterer doesn't allow.
Ab bolo kaise kare and kab,

If we happened to the de-carb, I shall take some pictures and compile a post here on this thread. It takes about 12hours to carry out the decarb.

However, the units in question here required piston (piston crown) change, so time for overhaul maybe more.
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Old 9th June 2019, 22:49   #43
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Default Re: Man, Machine and Water - A brief introduction to Marine Engines

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Most probably we are going to carry out de-carb of couple of main engine units in few days provided we get millions of people and authority.
However, the units in question here required piston (piston crown) change, so time for overhaul maybe more.
Which port is the vessel in.
How many spare crowns do you have.
Piston crown changing and pressure testing is a whole day job in itself.
All the best.
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