We have seen severe scaling during recent borescope inspections. We plan to cut a tube coupon for further evaluation. Blowdowns has increased from weekly to every other day and contamination is still evident.

Any suggestions to the water chemistry to reduce boiler tube scaling?

It will depend on the results of the tests as to what the scale is and the chemicals you treat with. Do you treat with phosphates? If so, you may consider that you are blowing down all of the phosphates that would precipitate the water impurities leaving only the tube walls for the impurities to collect on. To know this, you would need to be wet testing the drum water consistently. We need to know more...

What chemicals do you use?
What is the normal working pressure of the boiler?
What is the feedwater quality?
Is the feedwater properly deaerated?
What contamination are you talking about?