Auto Start of a DG

What's the facility available in modern diesel generators?I hope somebody would help me.

Lub oil pressure can be low for few minutes. Hence Lub oil pressure interlock can be temporarily bypassed till the DG is manually started.

So the lube oil pump must start prior to engine start, correct?

I would not by-pass the oil pressure interlock switch. Sounds like the generator lube system was designed to pre-lube prior to start.

Can the lube oil pump be converted to 12 volt (or whatever the starting voltage is) to pre-lube prior to start-up?

Can a reservoir tank be mounted in the lube circuit to capture and maintain a quantity of pressurized lube oil which would be released via a solenoid prior to a black start?

Your best bet would be to contact the generator engine manufacturer or a local firm that has experience servicing this particular type of unit.

We can black start EMD diesel engines 2.5MW alternators with this OME setup. The short time before its internal lube pressure is up to spec does not cause any harm. Normally they are up to pressure just while cranking to start.

Use a time relay

• "Use a time relay"

How on Earth is a time relay going to predict the failure of the mains power and start the lubrication pump before the power actually fails.

I've seen DG sets that need to start quickly when there's a power failure that are kept at running temperature and lubricated so they are always ready to go. One possibility is constantly running the lubrication oil pump. However, this would mean constant wear and tear on the pump, drive motor, filters, oil etcetera.

Apart from that converting the motor to run from a battery would be the only other feasible solution I can see.

This doesn't necessarily mean replacing the pump motor as you could try using an appropriately sized inverter that can supply the AC power required to start the lubrication pump motor from a DC battery supply.

What I mean by "time relay" is to suppress the l.o. pressure switch for a few sec, after power back then he can start ext. L.O. pump. How many seconds, you have to ask the generator maker. What happen to internal pump?

Lube oil pumps on Generation set are generally for fast start applications. If you are starting from a black situation (no power at all) your set at that size should handle it until it own pump is turning. This point has been stated before in this thread.

Case in point: Does your car or even the biggest truck engine you can think of have an external lube pump that runs while the engine is not turning?

• "Does your car or even the biggest truck engine you can think of have an external lube pump that runs while the engine is not turning?"

I've seen huge mining trucks that have computer controlled start up and shutdown systems that include starting the lubricating pump/s before starting the main engine.

I was thinking of road going trucks which can have engines as big as the size being asked ask about.

You did sat the biggest truck you could think of, but nevertheless I haven't seen electric oil pumps on any road vehicle.

Having said that and I don't know how true this is, but it's often stated that most of the wear an internal combustion experiences happens during the starting process while the oil pressure is low and the bearings are relatively free of oil because it has drained into the sump while the engine is sitting stationary.

There's been a lot of advertising lately about oils that are supposed to prevent this type of wear by sticking to the bearings rather than draining away like normal oils so at least the oil companies would like us to believe that start up wear is a problem that requires addressing.

If it is true that start up wear is the major source of wear in an engine then some sort of pre start electric oil pump that got the oil pressure up and all the bearings properly lubricated prior to the engine being started would be something worth looking into. Perhaps it's a subject worthy of a thread of its own?

Anyway, the fact that those humongous mining trucks and the diesel generator the original poster is writing about use a pre start electric oil pump that lubricates the bearings prior to the engine being started would seem to suggest that at least in such large an expensive engines start up wear due to lack of lubrication is a problem worth addressing.

In your installation the 500KVA genset would never start up if there is a power failure.Sounds abit unusual for a practical condition.,Anyway the AC operated lub oil pump is installed to minimise the engines wear and tear during your weekly test run which would be more often than actual power failure.The engine would be designed to run as and when necessary with a time lag pressure switch(less than a min) installed where if the desired LOPress is not built up by the internal pump the engine would shut down.Try starting first or maybe there is something else that is preventing it from starting.Safe to bypass if this is the situation.

Normally for power generator the engine will fitted with l.o. gear driven pump, but for others purpose like marine propulsion system l.o. system will use external pump

Hi giri,

Firstly the best thing to begin is to findout if the manufacturing company of your DG still exist, (if trouble shooting manuals is not available in your facility although as you mentioned the system is old) contacting them can give you the best answer. However, based on my actual experience, you can do bypass ensuring that your oil level is alright the engine should run but, stop it after few seconds once you feel that the lubricating oil was already in the system, then you can back in normal auto starting procedure. (never try to run too long in the bypass position, what if there was actual failure on the built in oil pump and the lube oil failed to distribute in moving part etc. you can first time experience a BIG hole besides your engine caused by coming out of piston rods kick off due to unit runs lack of lubes oil!).

In addition you should also mentioned the unit brand and model so our expert member can tell you straight how, where and what the best way to do, maybe one of our member using the same unit brand and model have had been encountered will tell and recommend what should you do.

Kind regards

Roman

Thanks Roman.Its Cummins engine driving the alternator of Kirloskar make.

How to know that the system is having enough lube oil before stopping the engine as you mentioned?.

• "How to know that the system is having enough lube oil before stopping the engine as you mentioned?"

I'm going to assume that the DG set has an oil pressure gauge, in which case you if the oil pressure is within the proper range when the diesel is stopped then you can be reasonably certain that the system has sufficient oil to lubricate the bearings etcetera. However, that doesn't help you one iota (slang for very little to none) when it comes to a black or cold start as the oil will have drained from the system and accumulated in the sump leaving the bearings etcetera relatively unlubricated.

Considering that Cummings have installed an external electrically powered oil pump that has to be running before the diesel can be started is a pretty good indication that starting the diesel without pre-lubrication of the bearings etcetera is going to damage the unit. That leaves you the following options:

• Contact Cummings and see if it is ok to start the system without the lubrication pump running
• If the answer is yes then ask them how to do it.
• If the answer is no then ask them if they have a DC electric motor that can be used instead of the AC motor that drives the lubrication pump. Then replace the AC motor with one of these and then run it from a battery.
• If they don't have a DC pump and you have to run the lubrication pump prior to a black or cold start then install an appropriately sized DC to AC inverter then power the AC pump form a battery via the inverter.

One other thing that might be worth checking is that if the AC lubrication pump motor is what is called a universal motor. Universal motors can be run from both AC or DC supplies which means that if it is a universal motor all you have to do is install an appropriate battery and charger system to run the motor.

You can see from the oil pressure guage, or if your system was equip with safety sensor detecting low oil pressure, then your unit itself will not start if you try to restart in auto start mode, regardless you managed to start and run it in manual after bypassing it. I would hghly suggest if you have no qualified mechanic with good understanding on the unit, better contact Cummins technical team and they will guide you step by step instruction after giving them detailed situation also that make sure that model number, serial number and other important related information all of these must be ready and available. I would also say, " It is more cheapper to hire qualified sevice personnel" and save your engine than to try to save something and you will have engine later looks like in my Avatar... I also have 500 kVA Perkin engine and 2 x 350 kVa Volvo, if I encountered problem and I am doubt on what we are doing with my mechanic it was very cheap to call the Volvo technical team and do trouble shooting by phone and make my unit run into normal back again.

Kind regards

Roman

Whole hearted thanks for everybody for the valuable comments........