Diesel Generator low frequency on high load.

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sabih
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Diesel Generator low frequency on high load.

Post by sabih »

Dear sir,
I have diesel generator of 630KW capacity installed onboard. We have recently conducted its 3000hrs routine in which we have carried out following work:
1- Removal and cleaning of all heads.
2- All cylinders and pistons were de-carbonized.
3- Gauging of valve guides.
4- Valve grinding and lapping.
5- Injector testing.
6- Testing of cylinder heads.
7- Overhauling of fuel pumps.
It is pertinent to mention that we did not touch its governor. and alternator side. But upon trial, we are facing a problem that after 350KW load, its frequency starts decreasing. We have then also cleaned its turbocharger and its accessories but the problem persists.

Plz help me with your knowledge that what could be the reason of frequency decrease.

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JK
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Re: Diesel Generator low frequency on high load.

Post by JK »

Have you done any compression readings on the engine. If it worked before the overall, there is something up with the engine. Obviously.
Did you use OEM parts? Bootlegged injectors are the kiss of death

Revolver
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Re: Diesel Generator low frequency on high load.

Post by Revolver »

Steadily decreasing to the under frequency trip, and manually bringing freq up before the trip has it continue to drop steadily, yeah. And gov wasn't touched...
Hrmm.

Like jk said, oem parts? And injector tests were spot on...

All potential air was properly bled from fuel pump over haul?
No stickey parts in the fuel pumps, keep a good eye on the fuel rack. A mix of oil + diesel is usually good to get them loosey goosey, make sure there's no sticking going on.

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The Dieselduck
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Re: Diesel Generator low frequency on high load.

Post by The Dieselduck »

Do you have enough fuel to the machine? check the stack, if not blowing a bit of black under that kind of load, maybe she's starving for fuel. I would check the simple things should be checked first - filters, fuel valves position, fuel pressure, etc.
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Merlyn
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Re: Diesel Generator low frequency on high load.

Post by Merlyn »

Dragging in air thro' a union let go for stripping?
Is it CR or older straight mechanical job?
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sabih
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Re: Diesel Generator low frequency on high load.

Post by sabih »

JK wrote:Have you done any compression readings on the engine. If it worked before the overall, there is something up with the engine. Obviously.
Did you use OEM parts? Bootlegged injectors are the kiss of death
All parts are original as per OEM and technical manual but the the problem persists.

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Merlyn
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Re: Diesel Generator low frequency on high load.

Post by Merlyn »

How goes the genset RPM?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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D Winsor
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Re: Diesel Generator low frequency on high load.

Post by D Winsor »

I understand the governor wasn't touched but was the linkage to the fuel rack disconnected from the governor?
If so you should check to make sure it was placed back in the correct position on the governor spline shaft or linkage connection points. If the linkage is in the wrong position or the wrong length the governor and or fuel rack will reach it's maximum travel or load limit setting before maximum load is reached on the engine causing the engine to slow down at high loads. I've seen this many times on overhauled engines with mechanical actuators and governors such as the Woodward UG8 or similar type Governors
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

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Merlyn
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Re: Diesel Generator low frequency on high load.

Post by Merlyn »

Wonder how the new fangled Rolls Royce Remote control boys would handle this from their control room thousands of miles away?
You know, the people that are going to make us all redundant ?
It's bad enough trying to sort a remote problem out without even being on the scene.
How are they going to whip the linkages off and physically bar it up against the stop remotely?
How are they going to adjust the max rpm stop?
But is it common rail or straight mechanical?
What engine can it be and what model?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Merlyn
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Re: Diesel Generator low frequency on high load.

Post by Merlyn »

Genset seized up then?
Or is it a " so that's all it was then jobby ? "
Shhhhhhhh.
Must have been trapped air on that bend I told you about said the voice.
H.E. Jobby?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Merlyn
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Re: Diesel Generator low frequency on high load.

Post by Merlyn »

Ah well, looks like the genset has gone the same way as pushrods Pete ( Frank Perkins article re the bent pushrods since turbo change? )
Now we will never know the outcome.
I reckon a Shhhhh jobby.
Don't say anything but ...........
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

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Re: Diesel Generator low frequency on high load.

Post by Adiamanzph »

sabih wrote:
Thu Jun 16, 2016 11:23 pm
Dear sir,
I have diesel generator of 630KW capacity installed onboard. We have recently conducted its 3000hrs routine in which we have carried out following work:
1- Removal and cleaning of all heads.
2- All cylinders and pistons were de-carbonized.
3- Gauging of valve guides.
4- Valve grinding and lapping.
5- Injector testing.
6- Testing of cylinder heads.
7- Overhauling of fuel pumps.
It is pertinent to mention that we did not touch its governor. and alternator side. But upon trial, we are facing a problem that after 350KW load, its frequency starts decreasing. We have then also cleaned its turbocharger and its accessories but the problem persists.

Plz help me with your knowledge that what could be the reason of frequency decrease.

Hello everyone we are now experiencing almost the same problem as above subject here onboard..

Had anyone got the solution or had a trouble shooting update on this?..

Appreciate for the help in advance..

Stay safe!!

Vegman
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Re: Diesel Generator low frequency on high load.

Post by Vegman »

Hey Sabih,
Well there a a number of things it could be - insufficient fuel or insufficient air or perhaps injection timing is out.
350 kw is just over half the rated power, so you have some major issue there.
Could possibly be something to do with the fuel pumps you overhauled- did you spill time them when you put them back?

But there are so many things we need to know before we can help you

Can you advise what is the make /model of the engine ?
what fuel is it running on MDO?/ HFO?, blend? ( do we even have HFO any more with new regs?)
what type of fuel pumps- bosch/ lorange/common rail?

Can you post up an image of the running log at the load where the problem starts to occur so we can look at all a parameters,

Do you have your original books/manuals from the shipyard on board that show the test bed or sea trials performance figures, that is a good place to start.
Then you can see in the past , when the engine was new , what all the parameters were at the load you are trying to achieve now.
or failing that just go back to some old log sheets form a year ago when the engine was ( presumably) running OK.

For example if rpm is okay at 300kw check what all the below original parameters were at 300 kw on the test bed- that may give you an idea of whats going on.

Just off the top of my head some things to check are
Governor indicator position , is it at maximum, when Rpm starts to drop , can you put a spanner on fuel rack linkage arm and move it (carefully!)just a little bit more, or is it at full travel or stuck somehow?
fuel pressure in out of fuel filter?
Fuel temperature? Viscosity if HFO or blend?
Charge air pressure before/after charge air cooler?
TC rpm and exh temp out
charge air temperature OK?
exhaust temps- are they balanced on all cylinders?
fuel rack position- are they balanced on all cylinders?

Do you have one of those electronic engine monitoring setups - if so put it one and check your "cards". If not you must have the old school Pax max indicator so take some Pmax and Pcomp readings and compare to test bed readings.

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Re: Diesel Generator low frequency on high load.

Post by Jameseze24 »

Probably you might have gotten a solution to the problem... But in case not, I suggest you to re-check your injectors.. non original fuel valves might malfunction when give more load. To understand the situation, monitor the exhaust outlet while increasing the load, it might give black smoke before dropping. Secondly, depending on the listed overhauled parts, it's important to check fuel system or try another governor if all of the above fails.
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