How to clean liquid fuel nozzle lines for 7ea gas turbine.

[flipper26]

We have a duel fuel combined cycle unit here in Florida. How ever we cannot run on #2 diesel because of coking deposits in the fuel lines. I would like to get some input as to go about correcting this problem. Any thoughts?

 

[MikeHalloran]

To prevent coking in the first place, keep the lines cooler, e.g. by putting a radiation shield between the lines and whatever heat source is nearby.

To dissolve coke that's already present without disassembling anything, run a few gallons of Marvel Mystery Oil through the lines, e.g. by adding it to the fuel supply. Directions for dosing are on the bright red can, ~$10/gal at Pep Boys.



Mike Halloran
Pembroke Pines, FL, USA

 

[abeltio]

Dual fuel units are known for having this problem. Is this a DLN unit or Std. Combustor? recommendations differ
The only way to clean the lines is:
Disassembly
Thorough cleaning with steam or another product that will dislodge the coke lumps
Inspection with borescope where possible.
Otherwise, you will push the dirt into the combustion chamber.

The recommendation for GE units is to run the liquid fuel system once a week (TIL 1107) also not running below 50% liquid as this may cause overheating of the main fuel oil pump.

If the liquid fuel is used sparingly (e.g. once a year or so, when there is no gas available) several users have opted to remove the liquid fuel lines from the tee where it connects to the purge air line, cap off the unused tee branch (careful, that is a SAE thread with an o-ring) and leave the purge air line only for normal operation.

The other end of the liquid fuel line also needs a cap (regular threaded connection).

For long periods in stand-by the flow divider will also need to be drained of liquid fuel and filled with an oil recommended by the flow divider manufacturer and changed with the frequency recommended by the flow divider manufacturer (typically once a month).

It is also advisable to drain all the liquid fuel piping and pressurize it with Nitrogen to avoid precipitation in the diesel fuel or rust formation (when empty).

The fuel oil tanks will also need to be drained of the water accumulation at the bottom.

The water injection system also needs to be drained and maintained.

A full system by system review is needed to assess the particular requirements at your site.

Should you need more detailed advise, please let me know.






saludos.
a.

 

[flipper26]

Thanks for the replies. It is a DLN unit, it hasn't run in the thirteen years I have been with the company. Can you give me the recommendations for sparingly used liquid fuel systems.