Exercising an Emergnecy Generator

Status
Not open for further replies.
Joined
Nov 8, 2003
Messages
3,909
Location
Cape Cod, MA
OK, this may not be strictly a lubrication question, but here goes:

The company I work for has recently decided that it wants us to exercise all the emergency generators for 1 hour per week, instead of the ½ hour we've been doing for years. Just about every diesel mechanic I've ever talked to, including some that work on big ships, and many that work on trucks and smaller marine engines and gensets, all say that running a diesel without a load for that period of time is not good for it on a regular basis (for technical reasons we can't run them under load unless there's an actual power failure).

Are there any old hands out there who can confirm this for me? I don't want to start a ruckus if I'm not on firm ground.
 
Being realistic, a power generator is very rarely used. Even running it under "abusive" conditions is less use than the typical engine placed elsewhere. My experience comes from designing waste water pump stations with backup power systems. Typically we avoided diesel due to the fuel life problems and used natural gas if at all possible.
 
How big is the thing? Could you wire in something to be a load? Even an air compressor feeding into the plant air?
 
Diesels are very fuel efficient and, without a load, do not warm up to proper operating temperature. As a result, I believe that either you should have an electrical load on the generator, or, keep the exercise period as short as practical to avoid the engine running cold for extended periods.
 
As I said above, we CAN'T put a load on it...there's an automatic transfer switch that switches the entire building in or out, and this causes significant disruptions to a lot of the high-speed data equipment, which causes disruptions to our customers.

k1xv, I agree that the exercise period should be just long enough to circulate the oil and burn off any condensation...we have a variety of motors in this service, and most seem to get as warm as they're going to after about 20 minutes of no-load running, so I believe the original ½-hour time is ideal, I just wanted to hear from others whether I was way off base...
 
What no UPS's???? I work for a utility down here in Florida. We have radio tower sites with 150-190KW Cat Diesel gensets. All sites are 100% UPS powered and backed up by the gensets. They are exercised for 1 hour per week at full load. By full load, I mean they run the UPS systems in each building, which power ALL of the electronics and the air conditioning units for that building. Gensets are load tested at full rated output every 2 years.
 
I know your quandry well.

At the power stations, we've got 3 2MW emergency generator sets. They get run for 1 hour per month with no load, just to prove that they are still there. (Our marketting people require the proof for code complience, and our financial people won't let us load them, becasue it will use too much fuel).

I'm trying to get them run on biodiesel so that there is a financial incentive (Renewable Energy Certificates) to get them up and loaded for 10 hours per week.

There used to be 10 off 25MW oil fired G.E. gas turbine gensets for state emergency use. They too were started for an hour unloaded per month. 5 years later, they were in very very poor condition.
 
do you have a local generator mechanic? we have a local place that will rent out their load bank. they recommend loading it at least once a year. i believe they call it "stacking" when the engine/exhaust gets loaded up with too much soot from no load.
what is the OEMs recomendation on how much to exercize the machine?
 
if your company is serious about emergency electrical backup they should have a large UPS system and if they are serious about the generators being in top notch shape they should purchase a load bank to exercize and test them properly.
how do you know they currently even work? they start up but you never load them. how do you test the generator side? the load bank probably costs less than a failed generator backup system.
 
Slick, we do have a UPS that protects the more critical systems, but a whole-building UPS is not only very expensive, it has maintenance issues of its own, especially with the large number of batteries involved...also, the genset IS load-bank tested once a year to full rated output for 2 hrs...

I didn't want this thread to turn into a discussion of the right or wrong way to power a building; I'm stuck dealing with the way it is...I just wanted to know whether running a 250 kW Cummins/Onan genset for 1 hr every week w/no load was better or worse for it than running it for a ½ hour...
 
The answer is oil analysis. I have dozens of hotels and pumping stations with the same problem, and most of them had cycles too short to proberly burn off contaminants. We watched the iron and copper on the analisis reports and have them on intervals for their climate, engine, and fuel (some are natural gas or propane, but most are diesel).
 
Status
Not open for further replies.
Back
Top