Steam Turbine Deposits

[serendepidy]

Hi All,
Have a 160 MW steam turbine that has been exposed to steam contaminated with seawater. Am interested in advice for how to sample and analyse salt deposits on the turbine and the typical limits for salt levels on turbines to determine whether cleaning is necessary. Any help would be appreciated.
Thanks

 

[rustbuster]

Swab the blades with distilled water and do a chloride ion test. What is the blade maaterial?

 

[serendepidy]

We have done that previously, swabbed the sample and tested for chloride using murcuric thoicyanate and ferric ion. However, I am looking for a repeatable test method that can is commonly accepted as being the industry standard. I need this so that the sampling method and analysis is not contested. I have looked at ASME D3483-05 and D887-08 however they do lack detail. If there are other procedures Id be interested in hearing about them. Blade material varies, but it is nothing unusual and is sensitive to corrosion fatigue and stress corrosion cracking.

 

[rmw]

Steam contaminated with seawater..... There must be a story here.

rmw

 

[serendepidy]

There is a very interesting story, probably the subject of a journal article when I get time to write it up.

However, I dont think I would be doing my stakeholders any favours by elaborating in a public forum, sorry.

 

[rmw]

sdpy,

You have asked for standard tests that test for a very non-standard occurance. I don't think you will find any in the power industry world.

However, since marine operators of steam generation equipment have to deal with the potential presence of salt water carry-over into the fresh water, there may be something in the marine, naval, or nuclear navy technical sub culture.

Are we talking just some minor salinity getting past a desalinator into the fresh water supply, or are we talking pumping pure seawater into the boiler in the place of BFW (in any significant amounts)?

If the latter, first you probably have to find out if there is any carryover at all, and if so how far the salt progressed. So if you weren't already having problems with turbine deposits - which would indicate to me that you didn't have a carryover problem - you might be OK.

If, on the other hand, you were already having problems with turbine deposits, you probably need to get a sample of the deposits to a lab soon to see if they contain salt.

At 160 MW, you surely have superheaters and possibly reheaters and some of that tubing might be SS or other alloy grades highly susceptible to SCC. You need to check there too.

What are your BFW heater's and/or condenser tubed with? If SS, then you may have a problem lurking there too.

You also may and most probably have pumps, valves and other equipment that have SS components (seals, shaft sleeves, plugs, trim, etc.) in them that would be impacted by the presence NaCl.

There may be more, but I think I've mentioned enough stuff to check to last until coffee break.

rmw

 

[Topp]

Hallo,
We are a german company and are specialized in chemical turbine cleaning without opening as well as Analysis.

We cleaned more than 100 turbines very succesfull and it is very importand to clean the machine very quick because of pitting corrosion by chloride ions.

The analysis we carry out by ICP or if concentrations are very low by ion chromatography

If you need any help, please contact me.

Best regards Christoph Topp
c.topp@inwatec.com