2 Stroke

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Turbo
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2 Stroke

Postby Turbo » Sat Jul 17, 2010 1:07 pm

Hi,

Thanks for the help before, I've been at sea for a while actually but got my EOOW Motor oral this Friday.

I'm pretty happy with most of the material now but.. some very simple questions that I am struggling to find answers to because I've never actually physically seen the items in question. (I'm transferring from Royal Navy - Submarine, so very different.) Never got time off work to do an oral prep either unfortunately.

1. With respect to the 2-Stroke Diesel, will I be expected to know about Dual Fuel Diesels and their cycles?

2. I'm confused about the Scavenge Belt - what actually is it?
The Scavenge auxiliary blowers - are they constantly running? Are they simply motors turning fans in the scavenge inlet?

When the Scavenge fire procedure mentions firing a portable fire fighting appliance into the Scavenge Belt? (Or use the fixed one)

3. Why do you have to increase lubricating oil into the cylinder in the event of a Scavenge Fire?
I'm guessing it's because you have to take it to it's slowest running speed and lub oil pump driven from crankshaft? I just don't get why that particular cylinder needs it because you're only isolating the fuel? (Sorry if it's a basic question but would appreciate clarification)

4. Do the large two stroke engines have a turbo fitted to each cyclinder exhaust? Or a common exhaust with one turbo?

5. What temperature do the double bottomed storage tanks keep HFO? Are these still steam coils?

6. Does the boiler fuel come from the same settling tank as the Diesel or are they seperate tanks?

7. How often is the fuel transferred from the storage tanks to settling tanks? I understand the service tanks/day tanks hold 24 hours worth of fuel? are there float switches that automatically transfer the fuel between tanks or is it done daily?

I think these questions are so simple that's why I can't find the answers!

I hope someone can help me out and I appreciate any help.

Thanks.

Turbo

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D Winsor
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Re: 2 Stroke

Postby D Winsor » Sun Jul 18, 2010 3:57 pm

If you had more time you could find the answers to most of your questions in any good Marine Diesel Book such as Reed's Marine Diesel Engines
Considering you are short of time I will attempt to answer some of your questions.

1 Duel fuel engines should not be a problem because most slow speed engines burn either diesel or blended fuel up to 380 centistokes.

2 The scavenge trunk is a single space that all the cylinder liners pass through at the level of the air inlet ports. Combustion air is usually supplied by an engine driven mechanical type blower such as a roots blower which could be supplemented by a single or double turbochargers on small high or medium speed engines such as a Detroit Diesel. The auxiliary scavenge blower you spoke about is used on large cross head engines to supply sufficient combustion air to get the engine started after which the blower is shut off. Depending on the size of the engine 1 to 4 large turbochargers may be fitted to supply air to the engine. On an engine with multiple turbo chargers usually 1 turbo will driven by the exhaust gases from 3 or 4 cylinders but can supply air to all cylinders if required.

3 The oil referred to in this question is cylinder oil not crankcase oil. On large 2 stroke engines and some large 4 stroke engines the piston rings are not lubricated by oil from the crankcase but through a separate cylinder oil lubrication system. In order to lubricate the piston & rings, oil is injected though injectors called quills mounted in the cylinder liner at varying times of the stroke.
When a scavenge fire occurs it burns off the oil residue that lubricates & protects the bottom of the piston and the liner therefore the amount of cylinder oil must be increased to reestablish a lubricated surface for the piston rings to run on and prevent seizure

4 answered in question 2

5 It depends on the grade of fuel being stored diesel fuel does not require heating, blended fuel is usually stored at approximately 40 to 45 deg C. The fuel is kept warm with steam passing through coils in the tanks.

6 The boiler fuel can be supplied from the same tank as the main engine or could have it's own tank

7 Depending on the size of the settling tanks fuel is transferred once a day usually at midnight and put in service supplying oil to the day tank at noon giving 10 to 11 hours for water and other impurities time to settle out before going through the purifier.


I hope this info helps
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

Turbo
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Joined: Tue Apr 06, 2010 5:41 am

Re: 2 Stroke

Postby Turbo » Tue Jul 20, 2010 7:13 am

Thanks very much for the information, I really appreciate it.
I have got Pounders Marine Diesels book but I heard someone referring to the Scavenge belt and I immediately thought of an actual 'belt' and was confused about where or what it was!

Is the engine room log book filled in hourly or once per watch?
I have a copy of a log and which parameters are to be written on it but I am not sure where you would log things such as starting machinery or stopping it, events that may happen engineering wise?
In the Navy we have an Engineers log where events are recorded and time but also log sheets? Is it the same?

Thanks again,

Turbo

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JK
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Re: 2 Stroke

Postby JK » Wed Jul 21, 2010 1:13 am

Your engine room log is filled out once a watch with machinery readings.
There is a space for writing starts and shutdowns and other bits of info of legal importance.
It can not be written in pencil, you cannot blot things out, they have to be lined out and initialed and you can't tear out pages to start over when you spill coffee on it-a hanging offense with most Chiefs I sailed with.
Saying that, other specific machinery may have readings done more frequently and have a log sheet beside it, to be filled out on rounds. Then you have your oily bilge book, ballast transfer record, boiler treatment log sheet, LO consumption sheet and whatever else a specific ship and regs deem important.

Turbo
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Re: 2 Stroke

Postby Turbo » Wed Jul 21, 2010 1:29 am

Thanks JK, just clearing up the final bits and pieces now before Friday.
Thanks D Winsor also, I'll let you know how I got on.

Cheers,

Turbo

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Big Pete
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Re: 2 Stroke

Postby Big Pete » Thu Jul 22, 2010 5:18 am

Good luck turbo!!!

Big Pete
It is always better to ask a stupid question than to do a stupid thing.

Turbo
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Joined: Tue Apr 06, 2010 5:41 am

Re: 2 Stroke

Postby Turbo » Fri Jul 23, 2010 5:30 am

Hi guys,

Many thanks for all the help, I passed the EOOW oral this morning, I know only the beginning but a big relief that now I can leave the RN and hopefully find employment on a merchant ship... This site has been a great help in studying too.

Thanks again,

Turbo

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JK
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Re: 2 Stroke

Postby JK » Fri Jul 23, 2010 6:12 am

Congratulations.
You're right, it is the first but biggest step.

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The Dieselduck
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Re: 2 Stroke

Postby The Dieselduck » Sat Jul 24, 2010 11:38 am

Yes indeed, congrats.
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