Steam Boiler Boil-outs / Passivation 1

[RickFox]

Hey Guys,

I am on a team looking at the commissioning programme for 2 No. 21 Tonne Steam Boilers. The Manufacturers are stating that a pre-clean is not required, however, I have spoken to a number of water treatment companies about this. I have not received a definitive answer.

The manufacturing process of the boilers is clearly a dirty process, and there is a large risk that the boilers will be contaminated with millscale,oils, or slag from the manufacture of the boiler. In order to carry out a thorough passivation, the boiler should be chemically clean. If these products are not removed, corrosion will occur.

Are you aware if there any recommendations or guidance documents relating to boiler boil-outs.

Cheers
Richard

 

[pvraviram]

Ideally an alkali-boil out is carried out not only for the boiler, but the pre-boiler system [the feed water system] to ensure cleanliness. Now-a-days some proprietary chemicals are also available for this purpose.
However, some manufacturers insist on not carrying out a boil-out, and go for a straight acid clean[strong acid like H2SO4], followed by passivation [weak acid like Citric acid].
Most of the national standards give the procedure as to how to go about the process, also you will be able to find these in books like "Modern Power Plant Engineering" by British Electricity International etc.

 

[luissabate]

An acid cleaning may not be necesary if there is not any rust to cleanse. (Always use an inhibited acid chemical).
The pasivation could be performed with an alkaly-phosphate-polimer product, heating for a period of time, then rinsing and starting a chemical program for boiler water treatment.

Regards,
LS

 

[Parthiban]

Alkali boil out is quite adequate for pressures upto 45 kg/cm2g where the circulation is high in normal operation. Beyond this pressure acid cleaning & passivation will be necessary. I can send the standard procedure for alkali boil out, which I use to your e mail address. My e mail address is parthi1@vsnl.com.