thePetroStreet

To whom it may concern,

Can i have material on CarboBlasting of Axial Compressor of Gas Turbines. How much this technique is effective. What are other ways of washing / cleaning of blades of Axial Compressor. I heard about washing of axial compressor by specially designed nozzles with water. Can you guide me on it and please tell me the effectiveness of different techniques.

Looking forward for your reply.

Regards,
Usman Mahmood Khan
Engro Fertilizers Limited.

usman, let me start from the basics and major difference between washing and carboblasting.
Gas turbine have inlet air filtration systems to reduce or eliminate contaminants that can damage the axial compressor or affect its performance. Regardless of filter efficiency, axial compressor fouling is unavoidable and depends on environmental conditions. Excessive fouling of compressor blades results in lower compressor efficiency and consequently a loss of gas turbine performance.
GT washing is recommended by OEM to be scheduled properly to maintain better performance of gas turbine. It includes both online and offline washing using treated water, detergents or any suitable cleaning chemical as per OEM. These atomized water droplets will try to remove fouling by impingement on blades and high speed.
But in certain cases, turbine wheels and buckets also get fouled and axial compressor fouling is more resistive to water jet cleaning, resulting in increase in heat rate of machine. That also corresponds to increase and imbalance in wheel space and GT exhaust temperatures. Then their come requirement of harder material impingement than water droplets. This also help in improving turbine wheels efficiency. But use of carboblasting has not been an efficient way of cleaning incase the compressor is fouled with oily contaminants. In addition, a lot of problems have been reported as a result of the application of the carbolasting technique such as clogging of instrumentation lines and risk of blocking the turbine blade cooling holes.

Hopefully this will answer your query,

Download this info from GE official website; its all about GT soft washing, only.
http://www.gepower.com/businesses/ge_oi ... ashing.pdf

Good dude ...... he is absolutely right.....

Thanks for the handy information.
There is another issue i am looking into nowadays, can someone help,
"what will be the impact of exhaust gases on metallurgy of HRSG installed downstream of a gas turbine in case we are doing online washing"

HRSG Vendors are unhappy with high moisture contents, as they may lead to corrosion of tubes/fins. They always recommend off-line washing in normal cases (also to avoid thermal stresses) and on-line washing with exhaust venting to atmosphere. But this is not considered to be a feasible option with high load operations. So we do water washing with some precautions. Water quality has a critical impact on both gas turbine and HRSG tubes. Other controlled parameters are the Quantity of water and its Temperature. Special caution should be taken to avoid reaching dew point at HRSG exhaust. Proper BFW flow management should be done to maintain high temperature in all coils, to avoid condensation during this operation.
I hope this clarifies the effect of on-line GT washing on metallurgy of HRSG tubes.