We are continuing preservation activities for our GE Frame-9E gas turbines. After installation and commissioning, we started preservation of turbines.

Did anyone have experience in this regard?

we have concern about turning gear operation. Since we are covering Air inlet and Bellmouth of Compressor, so it's not possible to continue with turning gear operation. Do anyone have any idea? One of the suggestion I received is to reduce the rpm of Turning gear for time period (Preservation only).

 

muz_sindhu,

You seem to be saying that you have installed more than one GE-design Frame 9E heavy duty gas turbine and commissioned them, and are now preparing them for some period of planned non-operation. Is that correct? (I don't think too many people would have experience with this, as even a single unit represents a very large monetary investment and idling the unit very soon after commissioning would mean little to no return on the investment. Of course, contracts and situations change all the time, but, this seems unusual.)

GE publishes at least one document regarding storage, sometimes called "lay-up." Have you contacted the packager of the units for help with this?

How fast does the turning gear mechanism turn the rotor? Very low-speed operation of the unit while on turning gear shouldn't result in any appreciable air flow for the axial compressor of a Frame 9E--<i><b>unless</i></b> you are sealing the inlet and exhaust very securely.

If you're securely sealing the inlet and exhaust, and you have a method for slowing the turning gear operation to a very low (single-digit) RPM, you might be okay. (How would you slow the RPM, by the way? Does the turning gear mechanism use a variable speed/frequency drive?)

What kind(s) of fuel(s) is(are) burned/have been burned? If one or more the fuels is liquid, have you purged the lines of the fuel, including filter vessels, etc.? Or will you be able to periodically flush the lines with "fresh" fuel? (I'm really only referring to diesel/HSD (High-Speed Diesel)/distillate fuel; if heavy fuel oil (HFO) was used, you should certainly purge that with lighter grade distillate.)

By the way, how long is the planned period of non-operation expected to last? Will the site be manned, even occasionally? If the period is expected to be more than a few months, I would have concerns about L.O. varnishing causing problems with the hydraulic dump valves (fuel stop and IGV), as well as the servo-valves. When you start the Aux. L.O. Pump for these periodic turning gear cycles, will you also start/run the Aux. Hyd. Pump?

 

Installing a 9E in this era, does that mean it has been bought second hand, quite a few have been sold from a station in the UK.

We have two 9E units in full preservation, but only for an 8 month off peak period each year. the other 4 months we are on standby.

GE do not recommend long term barring at low speeds, or even the standard barring speed. This has been found to cause excessive wear due to blade rattling in the roots.
We did tests with raising the barring speed but that was deemed unsuccessful by GE.

Also if the shafts are left stationary for long periods it has been seen that there will be excessive vibration from bearing 1 until the shaft has conditioned from cold start up.

As we require to stand for long periods even in peak winter times then fire the GT's at a moments notice, we have found that we have to run on turning gear once every day for 1 hour to prevent this.

We also have a preservation schedule where we stroke check the IGV's and gas valves once a month, all cooling systems, and fans.

The comments on varnishing of the control valves is interesting, and something we worry about. I thought this would be less of a risk with the low barring cycle regime. Oil pumps running once a day.

The inlets are not sealed as yours, we have units pumping in dehumidified air in the inlet plenum with the IGV valves held open mechanically.