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Author Topic: Diesel Engine Lubricating Oil  (Read 1544 times)

peter.dwight

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Diesel Engine Lubricating Oil
« on: June 25, 2010, 05:54:01 PM »

Greetings friends..
A question that went through my mind is what equipment and provisions are on board ship for maintaining and checking the quality of the lubricatiing oil. I know that a lot of it is carried and of course engines run days and weeks on end so how is it cleaned and maintained?
Looking forward to hearing from you.
Regards.
Peter.
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Shipmate60

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Re: Diesel Engine Lubricating Oil
« Reply #1 on: June 25, 2010, 09:21:34 PM »

A small sample is taken from a sample point from thye runni9ng engine and when at room temperature a series of tests are carried out on the sample.

Bob
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peter.dwight

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Re: Diesel Engine Lubricating Oil
« Reply #2 on: June 25, 2010, 09:30:19 PM »

Greetings Bob.
Thanks for the reply. What means are used to clean the oil? I dont think you would change a cartridge as per the family car. I would imagine that some sort of centrifugal filter would be used.
I look forward to hearing from you.
Regards.
Peter.
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Shipmate60

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Re: Diesel Engine Lubricating Oil
« Reply #3 on: June 25, 2010, 09:46:25 PM »

We do have cartridge filters with a pressure differential gauge on it when the pressure reaches a pre-determined pressure they are changed over.
These are used in parallel with a clean filter ready to use by changing some valves.
The Fuel system is the same too.
Some of the larger engines do run "Glacier" filters which are small centrifuges and filter paper to trap the larger particles.

Bob
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boatmadman

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Re: Diesel Engine Lubricating Oil
« Reply #4 on: June 25, 2010, 10:42:07 PM »

Lub oil condition is maintained by continual use of a centrifugal purifier that spins out impurities and moisture. Impurities, (carbon usually) manifests itself as a black deposit in the purifier bowl, which needs regular cleaning. Moisture is dumped into a drains vessel as the centrifuge runs.

This is a common process also used in shore based industry, including large power stations.

For the longer term condition of the oil, samples are taken and analysed in labs, results dictate whether 'freshening' or a total oil change is required.

Ian
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Bunkerbarge

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Re: Diesel Engine Lubricating Oil
« Reply #5 on: June 26, 2010, 04:30:34 AM »

When you get up to full size marine diesels you will almost certainly find some sort of centrifugal purifier capable of handling somewhere in the region of five tons of oil per hour.  As has been said this is a mechanical process that centrifuges out carbon deposits and moisture but there can be other impurities held in solution.  The detergent qualities of the oil degrade with time but in larger engines the replenishment of the oil as it is burned usually maintains this property.  Depending on the size of the engine and the load you could be looking at a couple of hundred litres of oil per day as a normal and acceptable consumption.  Then oil is therefore never changed and when a major service is undertaken the oil is transferred to a seperate tank and circulated through the purifier during the overhaul process before being returned to the engine when the work is completed.

On board facilities can keep a track of basic properties such as moisture content and viscosity which goes down when contaminated with diesel fuel or up when contaminated with heavy fuel or carbon deposits.  Larger vessels may well utilise regular oil analysis services provided by the oil manufacturer which can give much more in depth information and can detect the smallest quantities of such things as metals, which may well indicate wear of certain components.

Some oil analysis programs may well be quite comprehensive and include such equipment as side thrusters, stabilisers, hydraulic power packs etc. as well as the main engines, and some vessels may even use a portable purifier to clean the smaller systems on a rotational basis.

Just to give you an idea a medium speed diesel engine of 16,000 bhp could contain in the region of 20 tons of oil in it's lubrication system.  The engine itself will also have numerous lube oil filters mounted on it as well, possibly of an automatically backflushing type which operates on the system lube oil pressure.
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boatmadman

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Re: Diesel Engine Lubricating Oil
« Reply #6 on: June 26, 2010, 08:14:43 AM »

The conditioning and maintenance of the lub oil varies with its application.

At my work, a large industrial gas turbine of about 230,000 hp, the lub oil system is very simple. There are two filters and thats it.

When on a shutdown, we move a portable centrifuge to the vicinity and run that.

We do take samples for analysis, and occasionally change the oil, maybe every 5 years or so, but that depends on degredation.

Of course, it has to be appreciated that lub oil in a diesel engine will pick up more contaminants than in a turbine due to the design and characteristics of the engine. Also, the mechanical loading of the oil in a reciprocating engine's bearings will be much greater than that of a purely rotational engine, resulting in shorter life.

Conversely, the bearing cooling requirements the oil is exposed to in a large turbine may be considerably higher than those of a large diesel. In the example given, the hot end bearing at full load is supporting a shaft running at 540 deg.c

Ian
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peter.dwight

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Re: Diesel Engine Lubricating Oil
« Reply #7 on: June 27, 2010, 05:47:47 PM »

Greetings.
Thank you all for the received information. I did not realise that oil consumption was so high. It does make sense that constant replenishing would help to maintain the oil quality. It is always the case that there more to these things than you might imagine.
Kindest regards.
Peter.
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tobyker

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Re: Diesel Engine Lubricating Oil
« Reply #8 on: June 27, 2010, 08:55:35 PM »

20 tons of oil! Thank God Royal Enfield never put that much in - our sheds would have been washed away. Another interesting thread - thanks for the info chaps.
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