StandbyGas Generator Testing

[richanton]

I know that for diesel engine generators we like to use load banks so that monthly testing of the generator can be done under load due to gumming(coking) up of the engine issues, but is the same scenario true for natural gas generators, or not.

 

[davidbeach]

The engine block needs to come up to operating temperature, it won't do that without load. Transferring load to the generator would let you gain something from it besides heat.

 

[catserveng]

Gas engines have more problems with running at light loads, when manifold pressures are below 15 psia oil gets pulled down around the valve guides, and can foul spark plugs and combustion chambers. If gets bad enough causes misfire and rough running, and usually can't be corrected by just "burning out" or runnng at a higher load to clean it out like a diesel engine.

Would recommend that if you have a requirement to do regular testing without building load, a test load source becomes pretty important, or the simple act of doing regular "reliablity tests" actually degrade the engines ability to perform properly.

 

[davidbeach]

or the simple act of doing regular "reliablity tests" actually degrade the engines ability to perform properly

The best way to ensure that your engine-generator set (whatever fuel) won't start and carry load reliably is to start it once a month (or worse once a week) and run it for a few minutes with no load.

The best exercise you can provide for your generator is to be able to parallel it with the utility (special requirements must be met) and run it up to full output for an hour or so per month.

 

[itsmoked]

David; I wonder if you give the utility the power and can base tests on their desired timetable if they would more readily approve it? Seems less expensive than buying and locating your own load bank.

Yes I recognize the technical safety hurtles - they may cost more than a load bank.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[davidbeach]

Generation on the customer side of the meter wouldn't be "giving the utility the power" it would be offsetting load, and possibly demand, on the customer side. Peak shaving can be a good investment, though in that case you might be running the generator every day.

 

[catserveng]

Gas engine standby units are becoming more popular in Southern California due to emissions issues.

Last year we had over a dozen units that had been run no load for 10 minutes once a month that during their annual load test would not carry load due to fouled plugs and loaded cylinders.

Was surprising to many people including us, but we have found this is case with many of our competitors as well, especially the smaller auto derived units. With older design units this was not as much of an probleme, but with people wanting more out of smaller packages, this seems to be an increasing issue.

We have also found many utilites not willing to allow interconnect for smaller units without significant investment into controls and protection, that usually for exceed cost of a duct mounted load bank or smaller external unit. Also find the air districts will not be very receptive to it as well, and if they find you can go parallel to grid, want to rewrite your air permit.

The funny flip side of that is now there are a couple of companies working for SDG&E and SCE actually looking for units to parallel if they can get the required air permits and can install the equipment.

Used to be California was the only place folks had to contend with air pollution issues, but now it seems to be expanding across the US at a pretty good rate, at least based on the inquiries we get.

 

[itsmoked]

catserveng; I bet those gas engines that are brand new and the rings aren't well sealing yet really do suffer in those light short runs..

BTW we are talking Natural Gas, correct?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[catserveng]

Keith,

You hit it right, the newer engines, all turbocharged, all had acceptance tests of less than 1 hour, both NG and propane. Of the 12, seven wore our colors, and 5 were competitors units we have under contract.

The combination of cost concerns and air permit restrictions makes keeping things running as they should a real challenge some days.

 

[richanton]

Thanks for all the input. Looks like bottom line is I should try to get a load bank. Right now they are testing weekly under no load. So seems like that is probably doing more harm than good.