Engine question ??

Understood.
Do big generators use any kind of pre-oiler?
We were always careful to start at low idle and slowly apply load.

The ones I have dealt with did not and had no pre heating. With the C18's I got the flash file adjusted so the wind up to operating RPM was within Class requirements. They have run really well and done 20,000 hrs before major overhaul.

I got the idea to reduce the acceleration rate while sitting outside a watering hole and part of the scenery was a yacht being tested at a shipyard my attention was drawn to the puffs of black everytime a genset started.

CAPTJ - How many big generators have you actually started? Class require a genset to be fully operational in a lot less than that time frame.

And what does Robertoman consider big? I suspect it's more along the line Capt J is talking than that you normally deal with. I talk to people who consider 8 kw large, we think of 90-100 kw as being large, and I'm sure to you they're small. I've never even seen one 200+ kw.

This is what I would call a big Genset



This is the normal size and type of Genset we normally deal with, if not working with HFO fuel



I believe this is the size of Genset you think KIWI is dealing with



And this is what I would call a small Genset. Sorry Eurotrash, I know .



And this little banger can not be mistreated. He runs on almost anything that burns. But without a soundshield, he will mistread you, especially your ears. The good old Faryman single cylinder diesel. But almost all small marine generator producers are still using this engine. And for the hardcore user, their is an air cooled version without soundshield. That is more painfull than Jimmy Hendrix and Meat Loaf together.

In the commercial world:

HFO fueled Gensets are either started on MGO/MDO and then switched to preheated heavy fuel oil or preheated externally prior a direct HFO start. They normally run continuously and the Chief has enough warning time to tread them properly.

MGO/MDO Gensets in continuous operation are given a warm up phase prior applying load on them. But modern engines can accept medium loads directly after startup. State of the art highspeed diesel engines (like car engines and some smaller gensets) should not be warmed up in idle according to their manuals. But not under full load either.

Stby Gensets or Gensets as part of a generator array which start more or less automatically and being required by class to be under full load in very short time are normally preheated. In some cases, when an emergency genset has to be under full load in a fraction of a second, an electric motor is driving the alternator permanently through a big flywheel. In case of power loss, the momentum of the flywheel is starting the preheated diesel engine and the electrical network never notices any loss of power (hospitals, large computer server buildings and some special ships and offshore platforms). In smaller applications a battery/inverter setup will cover that gap. This should work on most smaller yachts either.

The high quality and reliable power supply is what makes a hybrid or diesel-electric battery buffered DC propulsion so interesting both for bigger yachts and several commercial type of ships.

It sounds like you are conflating a couple of different systems. A flywheel system does not use a motor and flywheel to turn the alternator. If it did it would also turn the diesel attached to it and that would create some very interesting issues and a mechanical arrangement that would make Rube Goldberg smile.

The flywheel system exists but it is a small device that can produce a only few seconds of low power DC to feed a UPS inverter until the standby generator comes online. It is normally used in computer data centers and other ultra-critical systems.

http://www.datacenterdynamics.com/c...-battery-in-the-data-center/71642.fullarticle

That is exactly what I did try to explain in my humble english Marmot. You are 100 % correct.




fig.5 would be the diesel engine
fig.7 clutch and hydraulic coupling
fig.9 the flywheel
fig.11 the alternator
fig 13 the electric motor

Plus some other electrical gimmicks to keep the components from fighting each other .

The flywheel is spinning all the time and is only used to start the diesel engine and drive the alternator til the engine is running. when the Net is working again, the electric motor cuts in again and the diesel is disconnected and stopped. We have two of those in our office building. Pretty heavy stuff. The Net does not recognize any power cut at all. But this is old but reliable technology. The future belongs to battery/ static inverter buffers.

It is not that bad Zud. Preheating a generator and/or a propulsion engine is no mystery even on a smaller yacht.

On my 50 ft inland waterway displacement boat, the watercircuits of the propulsion engines (2 x Volvo Penta D4-180), the Fischer Panda 15 KW Generator and the Webasto Heating system are interconnected. Means: Both main engines, when running, heat the calorifier, preheat the Generator and the complete boat. The same can be done with only the Generator running and both engines and the generator can preheated by the boat heating system which also feeds the calorifier and the chiller AC system in reverse mode. And everthing of course with the 2 KW, 230 Volt AC electric heating element in the calorifier. Quite simple system where some components can be isolated by valves. Still a waste, because I do not use the boat enough. But it would be a great live aboard for a couple plus one kid, both in cold and warmer regions.

Many moons ago I remember reading about a production facility that had a large diesel engine as its UPS. The engine was pre lubed and pre heated, there was an electric motor that drove the alternator around and it also drove a pump that kept a hydraulic accumulator charged, a power interruption would cause the clutch between the alternator and engine to close and this would start the engine which could accept full load almost instantly.

If I recall correctly it was a razor blade factory

There it is, the No Break Emergency Generator. Pretty heavy stuff. Our ones are definately a little bit smaller.



That must a little earthquake when the flywheel starts this MTU 20 V 4000 diesel engine.

The flywheel contains enough energy to bridge the time to both make a decision and for a "normal" (read FAST) start of the diesel. Yes, there will be a bit of power loss as the stored kinetic energy gets depleted but still with in tolerances.
After a bit the engine reaches operation speed, oil pressure, etc. and the clutch engages, normal generator usage from there on. (Spinning the wheel back up, it is between engine and motor/generator)
If the engine does NOT start for whatever reason the clutch still engages and starts the motor the hard way. It's a diesel, chances are that will start. If it does not start there is no fuel or something breaks spectacularly.

Just like online UPS flywheel systems also smooth out small problems on the supply side.
The nice part about them is that they are mechanical, there is not much to go wrong and more importantly no need for heaps of batteries which need regular replacement. The bad part is that they are mechanical, rotating 24/7. So not exactly maintenance free either.

As far as I know, this is a forum about Big Boats and Superyachts and a member asked a question about Big Generators, therefore the thread drifted slightly. That happens here all the time. Do not worry, you do not have to pay for it, additional knowledge is free on YF .

Obviously if you think this is a forum just about big boats and superyachts, you haven't been following many threads. Today's threads moderately sized engines, 43'-70', 65 Donzi, Post, rough water in med, 54' Grebe, 46' Viking, Carver 3607, 28' Trojan, Sunseekers (92', 115', 130'), Mondo 177', A 328', Mondo 130', Cheoy Lee 84', Post, Post, Post, 72' Aldir, 39' Carver, and a Duffy. We would seem to be a broad based forum that welcomes large and small boat owners and don't look down on any size boat or it's owner. So you wanted to share your vast knowledge of superyacht generators and that is fine, but this thread had nothing to do with Superyachts and 80% of the threads with new posts today were not about Big Boats or Superyachts. And I might add that a large percentage of the paid advertisements are not for superyachts either.