Re: Scale Build-up in Steam Turbines

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Posted by Carl Jones on February 12, 2000 at 10:05:49:

In Reply to: Scale Build-up in Steam Turbines posted by Letitia Langens on February 09, 2000 at 22:15:20:

: Hi! My name is Letitia Langens and I am a third year mechanical engineering co-op student. I am currently work on methods for cleaning scale build-up from the inside of a steam turbine combined reheat valve (CRV). I have been told that the scale forms due to contaminants in the steam and that oxygen dosing can help to remove the contaminants. Are there any other methods known that will effectively remove contaminants and prevent scale build-up?

First of all, not real life in some cases, scale should not be forming in your turbine. The process of removal takes on many facets. First you need to know exactly what is building up and the rates. If the steam is contaminated with boiler salts and corrosive constiuents there are primary safeguards to prevent formation. You do not say if the steam is superheated, what pressures are involved at the inlet and controlled reheat. With proper mositure removal from the saturated to superheated regiems in the boiler a moisture content most probably should not be seen at the reheat valve. Go to square one and determine the amount of and types of foulants coming from the boiler itself. Then detemine based on chemical analysis of the deposits what is needed. You can't just throw stuff into the turbine without knowing exactly what your dealing with. If you are not equipped with on-line and grab sampling equipment you would be advised to investigate the purchase and installation of the same. Your feedwater treatment provider should be able, if you have no inhouse lab, to provide a complete spectograpic analysis of the deposits and recommend additional steps based on the analysis. You may have a serious enough problem that the only efficient and complete method of removal would be popping the casing half and removing the rotor for blast cleaning. If deposits are making their way into the fir trees then you may have developed some corrosion in those areas which can lead to a major failure if not properly removed. If you would like, give me more details via my e-mail and I may be able to provide somne additional information rather than being generic.

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