Blue Smoke upon Generator block load start

[CanuckEngineer]

Hello everyone,

I recently commissioned a Kohler 500kW diesel generator set.

During the start-up the generator was block loaded with about 100kW and I notied some blue smoke in the exhaust.

Although it was faint, it was there for about 1-2 minutes and then dispersed.

Is this normal? I know blue smoke is obviously burnt oil, however how much should be apparent upon start-up, if any?

What are some possible causes:

1. Loose piston rings?
2. Valve timing?

Thanks for your help.

Regards,

RK.

 

[rbulsara]

Don't know about fuel or mechanical but 100 kW block load on a 500 kW unit? This 20% "block" load should have no discernible effect like you describe.

I have seen some puff of smoke and change engine noise, when applying 100% block loads. Even that should not last more than a few seconds (4-6).

More importantly what happens to voltage and frequency. How fast do the recover? That is the real test. But you may have more basic fuel burning issue.

Rafiq Bulsara

http://www.srengineersct.com

 

[rbulsara]

If not already, you will be much better off applying voltage to the load (closing gen breaker or transfer switch) only after the gen has reached 95% of voltage and frequency. Somewhere in that region.

Rafiq Bulsara

http://www.srengineersct.com

 

[CanuckEngineer]

Hi Rafiq,

No the genset came up to speed and voltage within its operating limits and assumed the load with no problems except for the fact that there was a hint of blue in the exhuast for about 1-2 minutes under 100kW load.

 

[catserveng]

Was this a brand new engine or a used engine being relocated?

A new engine may have oil collected from assembly in some areas that started to burn off as engine warmed. A used engine may have had oil and fuel from previous low load running collected in the manifolds.

To fully investigate, I think you need to run the engine at or near full load for enough time to get it up to temp and stable, then run long enough to burn out any posible storage lube or coatings, let the smoke stop coming off the manifolds, turbos and other hot areas, then shut it down, let it sit overnight and try starting again. See if the startup blue smoke returns.

Mike L.

 

[rbulsara]

How often is this engine loaded more than 50%? To catserveng's point, determine if it is "wet stacking" or slobbering. For any load test at least 30-35% load should be applied, preferably 50% and occasionally near full load for 30 mins or more.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

I have had this a couple of times when starting new sets. Im my case, the rings were not 100% seated and a little oil was passing the rings at light load. It got worse and I eventually had to load bank the sets for several days. This set the rings and there was no further trouble at light loading.
The worst case was an unattended set with auto start and a light load. This set pumped enough oil past the rings that it eventually shut down on low oil pressure. The set had a further series of misfortunes and misadventures and was eventually rebuilt with only a few hundred hours. Then about 10 years ago it went into storage. About six months ago, it was dusted off and put back into service. It was working well when I left the site.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[nawao]

Blue smoke could be also unburned fuel. Possibly wrong injection pump timing. Try to lightly advance the timing.

 

[waross]

Unburned fuel is generally white.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[CanuckEngineer]

Thank you all for your suggetions.

Going off topic however still with the same general Generator applications.

I understand that a Generator is rated for step load and block load applications, in this case 500kW.

My question is in most instances these types of generators are used for emergency power applications, e.g where the local utility has blacked out and a call is made for the gens to start-up.

In these situations, the generator is ramped up to speed and voltage prior to a downstream ATS transferring to the generator source.

My question, in an application where the generator is shut down for any reason while applying load.

The load is essentially there waiting for a source.

So if the generator is restarted, the downstream ATS is already transferred to the generator source, will the generator still come up to speed and voltage as spec'd with the block load already on its bus?

Thanks,

RK.

 

[davidbeach]

If the generator shuts down, you need to get it disconnected from the load. The ATS should go to a non-connected state if the utility isn't available. Lots of loads wouldn't do well being brought up with the generator as it comes up to speed and voltage. (Other loads would like it just fine.)