Hi I am working in a power plant using GE gas turbine (frame 6B with Mark-V operating system). During off-line water wash of the compressor we always use the portable water. Now our plant is going for combined cycle operation. So we have a WTU that makes DI water. Is this DI water is good for compressor wash? Our STG is S/D condition for many days. But due to keep the WTU in operation, we have to produce some DI water and drain it everyday. So we want to use this water for compressor washing. Is this ok or not?

 

If you have a heavy-duty gas turbine packaged and provided by GE and supplied with off-line water washing, your instruction manual will include a publication which lists the water quality required for water washing, as well as the required detergent characteristics. This should all be available in the Off-Line Water Washing tab of Vol. I of the GE Instruction books.

If you don't have this publication, you can contact your GE Energy Services representative and he/she should be able to provide an electronic copy of the document very quickly.

markvguy

 

Hi,

In reference to your query, please note that demineralised water is almost always specified by the OEMS. This helps avoid contamination by trace elements such as NA and K. if you need more information on online and offline compressor washing please write to me on altaf. kadri @ woodgroup. com

 

I have some inquiries.

I work in a technology center. We are working in an offline washing system for axial compressor (Ruston TB 5000 Turbine). We have designed a mobile equipment to supply DI water and Biodegradable detergent. We defined some points to drain in the turbine and designed the tubing and flexible hoses arrangement to connect them in a common header. I would like to know if you have any experience in complete washing system and if you could give me any important advice.

Thanks.
martm03 @ yahoo. com

 

About the question raised by the originator, it is always advisable to use demineralised water to do the compressor washing (offline and online) to ensure the thorough cleaning and life span of the compressor blades. During offline wash also, detergent such as ardox are used in certain volume to be mixed with the DI water before injection to the blades. However please note that should the water based detergent such as ardox is used, ensure that the soaking time is not to long and there is enough rinsing to prevent detergent clogging to the blades and thus decreasing the load after the wash.

 

I wish to get some suggestions and advices regarding the offline washing. Is it advisable to to utilize the inspection holes available on GTs to shoot in water jet (maybe with hot water) for some extra cleaning. Has anybody tried this method and is there any possible problems that could arise from doing this?

Another question is during the online washing, the recommended washing water temperature is about 16-20C but will it be better if the wash water temperature is set to 80-90C? For info I'm operating GE Frame 9E GTs. Thx for any input.

 

Where did you get the 16-20 degree number? We perform washes frequently here and always use hot (66-93 degrees C) water. The GE procedure states that hot water (66-93 degrees C) may clean deposits better than cooler water when used without a detergent. According to the procedure, you need wheelspace temperatures below 66 degrees. You also need to ensure that the wheelspace temperatures are within 49 degrees of the water temperature to prevent thermal shock.

 

well actually the washing skid has 2 water temperature selector namely cold and hot. from the MS9000 Service Manual: Turbine Accessories and Generator V1B, i found that the temperature setting for cold is about 16-20C and 80C for hot. it also stated that for online washing, the selector should b set to cold and reduced load. However, at the moment, we set the selector to hot even for online washing as well as we believe that it would yield better cleaning. about the wheel space temp, the temp difference between the water and wheel space should be less 49C.

 

Those holes on compressor are meant for inspection only, hence leave them alone. What if some foreign particle is present in the water hose? If this enters the GT compressor, you'll have to dismantle your compressor after your next start-up!

For GE GTs Onlinewash is done at baseload, you should not play with your inlet temp. by spraying hot water. Hence Online wash is best done with the wash water at ambient temp.

My performance Tests on GE-9E machines reveal following waterwash frequency as optimum.

Online water wash - Twice a week (say Monday & then Thursday)

Offline waterwash - Once in 4 months. (Thrice a year)

 

Dear JRao,

You mentioned, 3 times a year is good interval for offline water wash. Also can you please suggest how many gallons of detergent must be used in every offline wash.

Another question, If I would perform wash for every 6 month, what is the detergent amount to be used.
Gas turbine: GE 9FA

Regards...

 

Mxromen,

You are a bit off the mark in your interpretation of water washing principles. It is really all performance based, what improvement you get will dictate how regularly you wash and how much cleaning agent you use is really dictated by monitoring your drains to see when they are running clean. GEK103623A - Gas turbine Compressor washing will tell you most things that you need to know (for DLN machines). At a glance the rate for a 9FA is 117 Gal/min @ 85psig @ 150-180 Deg. F. If you don't have this document, drop me your Email and I can send.

 

Dear Gents,

we are operating GE 7FA DLN 2.6 Gas Turbines in Cogeneration mode, Earlier we used to do offline water wash every 4 months, and after each offline water wash we almost recover 6 to 8 MW after offline water wash.

Now a days, our management decided to stop offline water wash as we are meeting the contracted power and steam values which are committed to our customer. recently we did offline water wash at one of the unit after 8 months!! and what we found that the M/C only recovered 3 MW !! it is not as per our previous experience (6 to 8 MW).

My question is

1. Is the change is irreversible?

please give your expert comments

Thanks for your support and guidance

Regards
KKK

 

Dear Gent,

Off-line water washing is just like putting your clothes in an "automatic" washing machine. Sometimes the clothes have more dirt than others or the dirt/stains are of a different nature than usual. Sometimes a little extra detergent, applied directly to stains, is appropriate. Sometimes, even further "pre-treating" is required. Sometimes, one washes an article of clothing a second time to get rid of the skid marks if the first washing didn't. But using too much detergent can lead to disastrous results (excessive sudsing), and even poor rinsing since the amount of rinse water may not be sufficient to remove all of the detergent from the clothes. And we all know there is no detergent sensor on the automatic washing machine effluent.

Just as there is no detergent sensor on the gas turbine drains to detect clear rinse water....

There are for too many intangibles to be able to make any comment on whether or not the loss of generation is irreversible. We don't know how the machine has been operated (Base Load; load following/cycling; ambient conditions; time since last inspection outage; etc.).

We don't know how well the water wash was was conducted. Did someone inspect the IGVs and first stages of axial compressor after the rinse to see if the compressor was acceptably clean? If the type of dirt and ambient contaminants lead to an oily coating of the IGVs and compressor stages (rotating and stationary blading) then sometimes it's necessary to manually clean the first stages of the compressor and IGVs and/or to perform more than one off-line water wash.

Using excessive detergent only leads to excruciatingly long rinses, which leads to Operations Supervisors getting very anxious and Bean Counters getting even more anxious and an untimely and early end to rinsing which may leave detergent still in the compressor, which can also lead to further performance degradation.

Water washing is not as simple as most people believe. It is not just a "button" to push (even with manual valving operations). It involves visual inspections to determine how dirty the compressor inlet is prior to the wash to determine after a wash if the compressor inlet is any cleaner or needs further cleaning.

Careful and proper monitoring of the "false start drains" to observe clear water flowing out of them during rinsing is also critical to a proper wash.

Most sites just think they have to operate some valves, put some detergent in the detergent tank (oh--and if eight liters is recommended, we'll just use twelve because that should result in a much cleaner compressor--which is just bad thinking because the detergent manufacturer is already telling you to use the "maximum" amount of detergent anyway so you will buy even more detergent), push the START button, select Off-Line Water Wash ON, do a twenty-minute soak, do a half-hour rinse, and return the valves to their running position and re-start the turbine. WRONG!!!

It's much more involved than that. And the amount of detergent should always be determined by the initial inspection of the inlet before the wash is started. And, the manufacturer's recommended amount of detergent should always be halved at least until site has some experience with washing and rinsing.

And, sometimes, it's necessary to manually clean the IGVs and first stages of the compressor, and sometimes it's necessary to perform multiple washes to achieve the desired cleanliness.

So, you may only get your lost 3 MW back after the next maintenance outage when hot gas path components are replaced. Or, you may try another off-line water wash, but it doesn't sound like "management" wants to spend the time necessary to do this. And they have to live with the results--even if they try to blame it on the controls technicians!!!!!!

Water washing is something that varies from site to site, and is something that is not static--it varies depending on operating conditions and ambient conditions and experience. It's not just a "button" and a completely automatic process. Just like washing clothes is not always a completely automatic process.

 

kindly send me the Manual GEK103623A to [email protected]

 

CSA,

Very nice explanation of the variables of successful (and not) off-line water washes. I would add that a "general" indication of a "proper" rinse is to use a hand held conductivity meter, and measure the rinse water at both the compressor, and false-start drain valves. You can get to <10 µs in a reasonable amount of time, which should be the limit of rinse water conductivity. If rinsing for another 5 minutes or so brings it down a few more µm's, great, but to spend a great deal more time, as you say, starts to worry Ops Managers who have to answer for the auxiliary load or diesel fuel (used in older GT starting devices) used for this extra time. This of course is in addition to ensuring you're not overflowing the floor drains with suds.

 

What are the recommended detergents for compressor washing of GE frame 9E gas turbine?