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Diesel maintenance.

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stevo as b4
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PostPosted: 23:47 - 08 May 2018    Post subject: Diesel maintenance. Reply with quote

This is probably a question for Polar Bear and anyone else on here that's worked on boats, off shore, power generation etc.

Why on big boats/ships and generators, do they spend so much time faffing around with time intensive maintenance. By this I mean taking running engines apart to replace an injector that flows a bit less than the others, or climbing inside crankcases to wipe out the used oil stains, and taking bearings apart to measure for wear every five minutes?

In my mind these are big fuck off engines that spin slowly and arnt exactly stressed to the point of approaching max piston speeds, or pressure charged to the limit of the head gaskets all the time.. I do get that they are big engines that are a bit expensive to buy or replace if you fuck one up, but I've always thought it's a bit anal or looking for work like the Army do, when a yearly oil change and set of filters would probably be more than sufficient.

Do they do all this because failure would be life/death like pumping out mines for example? Or do they do it all in the name of efficiency? I watched a program about building a new container ship with big MTU engines fitted. They had a shit ton of sensors, telemetry links with the factory and cylinder by cylinder monitoring like you might expect on a 1000bhp Nissan Skyline engine. The argument was that one cylinder not running as well as the others costs £XXXXX which on such a big engine/ship would be a considerable amount of unnecessary operating cost.

I get than in the military they'd probably clean/strip/polish everything all the time, for an excersise or something to do, but in commercial industry? I just think that huge plant machinery built big, strong, and heavy could look after itself a bit more.

Hell even 40tonne trucks don't get this much attention and maintenance, and in haulage down time is money to probably a much greater extent.
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G
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PostPosted: 00:02 - 09 May 2018    Post subject: Re: Diesel maintenance. Reply with quote

stevo as b4 wrote:

Hell even 40tonne trucks don't get this much attention and maintenance, and in haulage down time is money to probably a much greater extent.

One 40t tractor unit can be very quickly replaced by another.

Complete guess, but I would expect for insurance reasons there's more impetuous to stick to manufacturer guidelines on a big ship for similar reasons to the above - rather than it being one 40' worth of cargo, it's many hundreds of 40' loads of cargo that are going to be delayed with missed maintenance, or worse outcomes.
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Polarbear
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PostPosted: 01:04 - 09 May 2018    Post subject: Reply with quote

Wow, a question and a half................. Laughing A Teffers job.

Firstly, it might seem like every 5 minutes but remember, a ships engines are running pretty well 24 hours a day, 7 days a week so if you have a 10 cylinder engine and the injectors have to be totally overhauled every 10000 hours that is 1 injector every month and a half. Then if they start failing (normally a fluctuation in exhaust temperature) it can increase the fuel consumption quite drastically so have to be done pretty well straight away. Add in other things, valve inspections, liner wear, etc. etc. and so you plan to do a complete unit ( 1 cylinder)while the ship is in port. That is head off, new valves, injectors, rings and check bearing and liner wear. It takes about 12 hours if everything goes right.

When I was at sea on the biggest supertankers we were burning 160 tonnes oif fuel a day at full speed. They are actually more efficient now but 100 tonnes a day is still the sort of consumption on the biggest boats. Fuel costs are around $500 per tonne so a ship can burn $50000 of fuel a day. You are under huge pressure to keep the plant running at it's most efficient.

Fuel consumption you can see is a really big thing and with modern ships the telemetry is sent automatically and continuously to the owners and the engine manufactures so any deviation from the norm, well you better have a good reason or a plan to rectify it before the superintendent phones you in the morning. I know because I've been on both ends of that telephone call. Laughing

Then you have Flag state and classification society. That's the country the ship is registered under, UK, Panama, Liberia etc. and Lloyds, BV, American Beaureau of shipping and others who give the ship the classification to sail. They certify every thing from the smallest valve to the largest bit of machinery and stipulate the maximum time it can be used for before opening up for inspection. They also stipulate when the ship has to be dry docked for inspection, usually every 2.5 or 5 years depending on the ships age.

And insurance. Insurance costs on a big ship are horrendous. Everything must be done to the manufacturers specifications and times or failures that impact on the delivery or result in damage will be argued by the insurance to be void if the planned maintenance is not kept up to date. The penalty clauses with a late cargo delivery can run into millions which are claimed back from the insurers, and yes, they are as big bastards as every other insurance company Laughing

One last point - The engineers are on the ship whatever so the manpower costs do not come into it. A ship has to carry a minimum compliment so the owners have no qualms about slave driving their engineers!

Gone are the days when I first went to sea when just getting anywhere was pretty miraculous Laughing
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weasley
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PostPosted: 08:32 - 09 May 2018    Post subject: Reply with quote

Just to add that even though the engines turn "slowly", the pistons can still reach the same speed as in your bike. A practical maximum piston speed is around 25m/s - because of the long stroke, these engines often get near that, even at a few hundred rpm (depending on engine design). And there are immense forces pushing through the piston rod and conrod to the crankshaft. The cost of failure is high and as Polarbear says, you have crew right there.

I used to inspect marine engines during port visits; often I would ask the chief engineer to have a piston pulled out to rate its cleanliness. I had to take the piston, do an objective rating of its condition (this is no quick task) and then hand it back to the engineer for refitting without delaying the departure of the ship, which would have cost my company if they were late leaving. Often the piston was almost too hot to handle.

And as a tangent, I always like telling people that the cylinder head nuts on these engines are tightened by hand. Very Happy
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Polarbear
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PostPosted: 08:47 - 09 May 2018    Post subject: Reply with quote

weasley wrote:
Just to add that even though the engines turn "slowly", the pistons can still reach the same speed as in your bike. A practical maximum piston speed is around 25m/s - because of the long stroke, these engines often get near that, even at a few hundred rpm (depending on engine design). And there are immense forces pushing through the piston rod and conrod to the crankshaft. The cost of failure is high and as Polarbear says, you have crew right there.

I used to inspect marine engines during port visits; often I would ask the chief engineer to have a piston pulled out to rate its cleanliness. I had to take the piston, do an objective rating of its condition (this is no quick task) and then hand it back to the engineer for refitting without delaying the departure of the ship, which would have cost my company if they were late leaving. Often the piston was almost too hot to handle.

And as a tangent, I always like telling people that the cylinder head nuts on these engines are tightened by hand. Very Happy


The old ones were as I expect you know, using a bloody great sledge hammer to do them up!

Modern ones with hydraulically stretched or heated bolts, where's the fun in that. Laughing

One other thing for people that are not familiar with large marine engines, the big, slow speed engines can have bores of around a meter +, we aren't talking small here. everything is way to big for manual handling and you stand inside the cylinder to take liner wear measurements.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRAySAa_jxDfgeIJqbqtSiOROOsVpnBv6kvrupTZbvEV5xnGfQlzA
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weasley
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PostPosted: 13:27 - 09 May 2018    Post subject: Reply with quote

Polarbear wrote:
weasley wrote:

And as a tangent, I always like telling people that the cylinder head nuts on these engines are tightened by hand. Very Happy


Modern ones with hydraulically stretched or heated bolts, where's the fun in that. Laughing


That's more what I was getting at - stretch the stud, lightly spin the nut down by hand, then release the stud, job done.

Biggest engine design in use I believe is 98cm bore. I think one of the big two (Wärtsila-Sulzer or MAN B&W) had a 108cm bore engine on the books but nobody ever ordered one.

I used to be in charge of developing oils for these engines, although I have also worked with 4-stroke ("trunk piston") diesel and gas-fuelled engines. I used to love visiting ships for engine inspections... landfill stationary gas engines, less so.
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WishayKillie
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PostPosted: 13:54 - 09 May 2018    Post subject: Reply with quote

Polarbear wrote:

The old ones were as I expect you know, using a bloody great sledge hammer to do them up!

Modern ones with hydraulically stretched or heated bolts, where's the fun in that. Laughing

One other thing for people that are not familiar with large marine engines, the big, slow speed engines can have bores of around a meter +, we aren't talking small here. everything is way to big for manual handling and you stand inside the cylinder to take liner wear measurements.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRAySAa_jxDfgeIJqbqtSiOROOsVpnBv6kvrupTZbvEV5xnGfQlzA


Makes the "wee" Wartsila 16V32's we have seem even smaller Laughing , although there are 6 of them.

I worked over in SHI in Korea between '15-'17 and used to see the big slow speeds having the mega blocks of the hull built around them for the 18000TEU box boats getting built at the time, that was an impressive site.
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dydey90
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PostPosted: 20:03 - 09 May 2018    Post subject: Reply with quote

I’ve never worked on a ship but I’m a maintenance engineer so I can appreciate the focus on preventative maintenance. If you suddenly shit a piston in the middle of the Atlantic, you’re going to be a sitting duck unless you carry enough spares to get going or you somehow manage to get a replacement shipped out. Literally, shipped out Laughing

I’ve done plenty of strip-and-inspect jobs where parts have been replaced for the slightest reason because the cost of breakdown in any plant will quickly outstrip the cost of the parts in minutes.
Also, how long is a ship generally docked for to load or unload? Because the engineers will want to use any of that time to drop on to anything that needs doing.
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Polarbear
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PostPosted: 22:27 - 09 May 2018    Post subject: Reply with quote

dydey90 wrote:
I’ve never worked on a ship but I’m a maintenance engineer so I can appreciate the focus on preventative maintenance. If you suddenly shit a piston in the middle of the Atlantic, you’re going to be a sitting duck unless you carry enough spares to get going or you somehow manage to get a replacement shipped out. Literally, shipped out Laughing

I’ve done plenty of strip-and-inspect jobs where parts have been replaced for the slightest reason because the cost of breakdown in any plant will quickly outstrip the cost of the parts in minutes.
Also, how long is a ship generally docked for to load or unload? Because the engineers will want to use any of that time to drop on to anything that needs doing.


In my industry, LNG transportation, the accepted maximum turn round time in port is 24 hrs.

Container ships can be much less than that, even when unloading a full cargo.
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MCN
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PostPosted: 00:28 - 10 May 2018    Post subject: Reply with quote

World Shipping, Bulk Cargo and Bulbous Bows.

At one time ships were designed to be more efficient by installing a bulbous bow. It made the water flow around the hull better as the ship pushed through the seas. Drag and stuff.

The use of bulbous bow has now been reversed.

The reason is that many ships now sail to a fixed schedule and so there is not as much of a rush to get from port to port and cruising speeds have been reduced. The reduced speed means the bulbous bow now costs money to push through the waves.

They cost so much that savings can be made by removing the bulbous bow and reverting to 'conventional' pointy bows.

https://www.marineinsight.com/naval-architecture/nose-jobs-for-ships-reasons-behind-retrofitting-bulbous-bow/

ANd things are not pulled apart on a whim coz the maint crew have nothing better to do.
If a ship loses power in the middle of the ocean, whilst manoeuvring at a harbour or in bad weather it can become very expensive or catastrophic.
So stuff that we know fails (from history) is serviced well before a predictable time of failure or when other shit is in bits to do other, unrelated work. If the covers are off for one thing then it is prudent to replace other things to negate a need to go to all the bother of ripping it apart to do it later.

Aaaaand... The 1st rule of the sea is that if it can fail it will fail. Shocked

Boats Rock.
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stevo as b4
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PostPosted: 17:32 - 10 May 2018    Post subject: Reply with quote

Thanks for the information and education.

There's quite a bit more to it all then than my first thoughts, and I get that doing pre-planned ahead of the max service life maintenance not only makes sense now, but costs less than a missed delivery, unscheduled port time, a ship needing recovery or a sunken ship and dead crew. Maybe it's similar in that respect to aviation engine life and maintenance/inspection programmes then?

I read that the newer generation of electronic controlled big engines are actually much more maintenance intensive and are expected to be worked on much more often than old simpler engines too. I suppose when efficiency and cost is the most overriding factor, like in any industry or competitive market today, saving money through maximised efficiency is a huge importance.

I also overlooked both the amount of use/hours these big engines have and so how quickly major service intervals come round. And then there's the fact that say a boat engine is under much more constant high load and percentage of power and rpm, than a car engine that only really sees tiny bursts of full load in acceleration over its life or on a Top speed run etc. Even aviation engines are under much less constant load when at cruise altitude I guess than a boat motor, especially on a displacement hull?

I think I was thinking of trawler fishermens mentally, of where spending a load of money on a running engine is at odds with catching as much as possible and having a good wage. I guess a trawler captain/owner would be told to feck right off if he told his crew their 2weeks wages from being battered in a force 10 storm would be used to do a bit of planned engine maintenance. Laughing
Maybe if it was to buy bigger nets and more gear so they might catch or process alot more fish then they might not mind so much.
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MCN
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PostPosted: 15:58 - 11 May 2018    Post subject: Reply with quote

Big boat (and most generator) engines do OK on full load.
The load is almost constant so there are less accelerating/decelerating forces which cause wear.
Constant load is good for an engine if within designed limits.
Loads over 60% good.
Under 50% bad.
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