We have 1990 vintage GE frame 6's, dual fuel, although since they were installed, no gas fuel supply was piped in to them. Normal fuel is #2 fuel oil.

The present thought is to remove the flexible gas fuel lines, and install blanks at the gas fuel manifold flanges and the gas connection at the duel fuel burners.

The intent is to give more working room in the turbine compartment, since there are no plans to run a gas fuel line to the site in the foreseeable future.

Before the storm troopers get turned loose on this project, my question is:

Although we do not use gas fuel, there is gas fuel purge air going through the manifold, piping and to the combustion cans.

By blanking off this air, will we see continuous black smoke spewing at out next run?

Besides serving as a manifold purge.... is it serving as a "secondary air" or some other important function?

(better to ask the silly question now.... instead of having to undo a "leap before you look thing!)

Thanks!
RTK

 

The purpose of the gas fuel purge is to prevent backflow of hot combustion gases into the gas fuel passages of the fuel nozzles and from circulating around the unit through the gas fuel manifold. There was catastrophic failures of fuel nozzle tips caused by the heat associated with this backflow, and some gas fuel manifolds (the one around the compressor) were observed to be glowing red when this happened.

So, it was decided to use a portion of the atomzizing air compressor discharge to purge the gas fuel system when running on distillate fuel. I don't believe it really aided the atomization or combustion of the liquid fuel at all.

There will be a slight increase in atomizing air flow to the fuel nozzles (because of the "loss" of the path through the gas fuel manifold) and that would likely not cause a problem with smoking, in fact, it would probably reduce the smoking if anything because it might actually aid in the atomization of liquid fuel. The test would be to insert blinds (temporarily) in one of the gas fuel flex hose flanges and then run the unit up to Base Load while observing the exhaust (stack) and monitoring the spreads. If there was no increase in exhaust smoke or exhaust temperature spread (it was found that when the gas fuel nozzles were purged on units which didn't originally have it that the spreads decreased slightly) then it would probably be okay to remove the flex hoses and gas fuel manifold from the turbine compartment, and blank the gas fuel flanges at the nozzles and blank the feed line which connected to the bottom of the gas fuel manifold.

 

Thank you CSA!!
RTK