Overspeed Issues

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Halifax_Stoker
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Overspeed Issues

Postby Halifax_Stoker » Wed Jun 04, 2014 10:49 am

Hello Everyone...

I am having an issue with one of my Generators over speeding on Start up and Load Change. I have 3 x MAK M282 Generators with Woodward UG governors. Doing my monthly Alarm and Shut Down Checks I tried Lowering the over speed Percentage on the SELCO M2500 Digital controller to 101%. I tried this method before and it threw the mechanical governor out of whack. I am not too familiar with working on governors so I assume the Mechanical governor was fighting the Electronic Shutdown to stay alive... Once I tried to restart the engine, after the test and the setting returned to it's original state (Digital), it would over speed. SO I had to locally start it, hold the fuel rack and dial back the SPEED SETTING so the engine was again 900RPM. After I had no issues with this.... Since then I have been testing the over speed by physically moving the fuel rack to Over Speed the Engine and have had no issues. But this time I was asked to try the SELCO M2500 method again. Well I had the same results except now when I use the speed setting to bring the engine to 900 RPM, it still over speed's if I try to put load on it, or shut it down and try to restart.... Any Suggestions?

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Halifax_Stoker
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Re: Overspeed Issues

Postby Halifax_Stoker » Wed Jun 04, 2014 10:58 pm

OK, Just an Update...

Turns out it was the controller. After setting the SELCO M2500 back to %115 Over speed the display and CPU confirmed that the setting was saved and applied, but using a Photo Tach I noticed it was Over speeding way too soon. We then decided to pull the main fuses for the Generator Control Power and physically shut down the controller. Once powered back up the engine is now normal and the controller again acting properly... I have never used SELCO products before but this may be something to keep in mind if anyone else switches to these controllers

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Big Pete
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Re: Overspeed Issues

Postby Big Pete » Thu Jun 05, 2014 9:55 am

I am finding more and more problems with electronics on board. often the answer appears to be to "reboot" the gizmo, by pulling the plug or the power wires out for a few minutes then plugging it back in.
Works for the windscreen wipers on our bridge, their computer regularly gets confused and has to be rebooted.

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

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JollyJack
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Re: Overspeed Issues

Postby JollyJack » Thu Jun 05, 2014 5:00 pm

electronics and ship's machinery don't go together very well, as I have found out since my first "UMS" ship in '73.
Discourage incest, ban country "music".

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D Winsor
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Re: Overspeed Issues

Postby D Winsor » Fri Jun 06, 2014 2:38 pm

Even though there may be an issue with the electronic over speed I wouldn't be too quick to lay all the blame on the over speed
I would also look at the settings and general condition of the UG8 Governor especially if there are load sharing or load response issues.
It is not uncommon to find, where the governor adjustment dials for droop, load limit and compensation can easily be adjusted, one or a number of these settings could be out of adjustment to the point governor response is adversely affected. A poorly responsive governor will cause an engine to over speed at start up or sudden load changes.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

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Halifax_Stoker
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Re: Overspeed Issues

Postby Halifax_Stoker » Sat Jun 07, 2014 9:26 pm

The first thing I thought was the Governor, sort of a mechanical fighting the electronic signal thing. Until I started to dig a little deeper in the history. Seems since they have gone over to these controllers there have been issues with the Pre lube pumps and pre heat working, false alarms while shutting down, and now this over speed. All which were resolved just by pulling the fuses. All three governors are set between 30 and 40 on the droop and fuel rack is restricted to 80% on start up. So for me I am leaning towards improper wiring of the Controller or just a poor quality device. Either way I have been on new builds where the automation has been great. But I personally am not a fan of adding new devices to 35 year old equipment. They said they installed them because people were having trouble paralleling the Generators, but in all honesty I wish load sharing between 3 Generators was the most difficult part of my job... But I am just relieved that although it is not the proper solution, for now I have a solution....
Thanks Guys

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JK
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Re: Overspeed Issues

Postby JK » Sun Jun 08, 2014 2:39 am

It sounds like the installer didn't finish the job. There should be a blocking signal sent to the alarms on shut down and the preheats starting on auto.
Our electrician tells me that if the mechanical droop gets inside of the electronic governor range then this is what can happen as you surmise.
I have done many upgrades to old equipment. It is getting harder because there are so much changes in what the controls touch. You can't do installs like you did even 10 years ago without sitting down and studying how the integration will go.

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D Winsor
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Re: Overspeed Issues

Postby D Winsor » Tue Jun 10, 2014 2:59 am

Sounds like someone tried to save a few pennies by using the original control system wiring for the new electronic controls and now there are grounds, short circuits, cross connections and shielding issues with the wiring. If that is the case a complete control system rewiring is in order.

If the control system operates on 24VDC I would also look at providing a dedicated power supply for each generator because I've seen issues caused when multiple independent control systems are supplied from a common source.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

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JK
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Re: Overspeed Issues

Postby JK » Tue Jun 10, 2014 7:20 am

Good point about the source. I have also experienced engines that are off load "following" the onload engine speed changes because of incorrect control wiring being used and signals being transmitted across the wire runs. This is sure to induce fear when an unloaded generator engine RPM takes off while you are standing beside it :shock:


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