Hi everyone,

I'm not new to this site as I would often browse the threads on gas turbines. I was really worried when one of the best authors markvguy left this portal for some specific reasons, he was a encyclopedia for GE units. Ok but we all have CSA now.

Regarding 9fa units on line water wash, what actually are the basics during on line water wash like load, ttrf, water flow, etc.? In our plant we keep the machine @200mw for 5 minutes during online water wash with 2.65 tonnes/hr water flow, which was set during initial commissioning works by GE. But during summer days we find it difficult to negotiate with dispatch for this load of 200mw as we have 5 machines and the demand is high.

 

Hi,
We also have a 9fa, when we go for an on line wash we need only two permissives to initiate the wash.
One this that the IBH (G1:CSBHX) is closed and the other is that the inlet air temp (G1:CTIM) is @ or > 10c (50f).

Our IBH opens when the GT load goes below 180mw. We have carried out the on line wash @ 185mw and upwards.

Hope this helps

 

GE has several technical publications which describe water washing and the constraints involved. There are many, including type of compressor, type of inlet guide vanes, ambient temperature, type of detergent, type of combustion system, etc. Best to consult the publications, then to ask the packager for any other guidelines or clarification.

Be sure to inform anyone you ask about frequency excursions the units might experience during periods of high system demand; compressor speed and airflow in most of the technical publications presume rated speed operation. If the units have frequent extended periods of below-rated frequency operation when you would be wanting to execute on-line water washes this is an important consideration, at any load.

 

Not all 9FAs are the same, and there are 9Fs, 9FAs, 9FA+, 9FA+e units. (Isn't this fun?) Though, in the same way that people who have GE-design heavy duty gas turbines always say they have GE machines, most F-class users these days always say they have FA+e unit when they aren't sure if they do or they don't; it just sounds more impressive.

One of the considerations is the type of combustion system; F-class units can have DLN 2.0, DLN2.0+, DLN 2.6, and DLN 2.6+. When describing how you operate your unit, please provide a few more details, such as type of combustion system, type of IGVs and compressor (cambered, uncambered, Snowflake, etc.). It can be very dangerous to operate your unit the way someone else operates theirs unless you know your unit is exactly like theirs.

What is the IGV angle when you perform on-line water washes, a_w_p_d and skumar?

And a_w_p_d brings up another question, skumar: What is the IBH control valve position when you are performing you on-line water washes?

It's also important to make sure than any moisture which condenses in the low point of the IBH piping during and after an on-line water wash gets drained before the IBH system is put in service again. A slug of water moving through the IBH piping can ruin your day!

 

Hi, CSA/skumar.

We have a 9FA DLN 2.0+. I have looked back thorough the history over the past -100 days at the IGV angle. The results show that during the online wash we had a min IGV angle of 61dgree @ 186mw and a max 86 degree @ 232mw.

I don’t consider myself an expert on gas turbines neither do consider myself a novice, but as you say there are a number for factors to be considered when doing the wash, and yet the logic at my plant is only asking for two permissives, IBH & ambient temp. So am I correct in my thinking that IGV angle is taken in to consideration in relation to IBH as the IBH opens in relation to IGV angle, air temp and humidity.

As I mentioned in my previous reply that the IBH has to be closed for the wash, so if the IBH was open we could not perform a wash as the IGV angle would be @ say’ below 65degrees and the load around 165 mw, depending on air temps/humidity.

As for the inlet air temp this has to be above 10c/50f to prevent icing on the IGV’s and freezing of the wash water due to the fact that the IBH is closed.

a_w_p_d

 

a_w_p_d,

It's pretty clear that you're no novice and know your machine and it's control schemes.

It's been said before on control.com: F-class units are "fragile" machines. They are being operated very close to their mechanical limits and can't take much if any "abuse". All of this is evident in many of the things that GE is now doing with the application code of these units (preventing anyone from making any modifications) and in the power enhancement options they are offering for these units (fractions of a percent).

I've always been conservative, and will always be so. One can really learn a lot about machines and equipment by observing how the OEM deals with the machines. All I'm trying to say is, all F-class Frame 9s are not created equal, and shouldn't be operated equal, either.

F-class units are engineering marvels; there's nothing like them. They are among the most efficient and powerful machines ever created. They are just not all equal and can't all be operated identically. Unfortunately, we can't know all the differences, and in some cases, GE doesn't even know them.

I've been wrong before, and I'll be wrong many times in the future. But, I am conservative and try to pay attention to the "little things".

I believe the IBH Control Valve should be closed to prevent a slug of water from getting to the IBH manifold and that the compressor inlet temperature is very important, also.

If GE commissioned skumar's unit and that's they way they told the plant personnel to operate the machine, they should go back to GE and ask if they can perform on-line water washes at a higher load than originally indicated.

 

sorry for the delay, the type of compressor requested by CSA delayed me but unfortunately I could not get the information.

Here are the other informations- the unit is ms9001fa with dln2 combustor,generator driven.

During online water wash the parameters are - dwatt-200mw,igv@72'(max-88'), Inlet bleed heat @ closed condition, water wash flow-2.70t/hr for 5 minutes (this timing was set for RO blade construction as i heard it to be a non p-cut blade).

The permissive is only compressor inlet temperature (L3WCTIM) to be greater than 10'c calculated with IBH in closed condition.
How this water flow is calculated? does this vary with load?

From other documents on online water wash I collected some information that the IGV and first 6 to 7 stages of the compressor are the maximum fouled parts, so this water flow is set to clean these blades and before it reaches the last stage the water is evaporated.Is this true?I request the forum give me the basic details of the happenings in the compressor or the whole machine during online water wash.

 

Check with your OEM, or you own the consequences. Most things (but not everything) are done for at least one reason or another.

An ounce of prevention is worth a pound of cure.