Boiler Boilout Procedure

Figure 1: Water Capacity (normal and flooded) of several Cleaver-Brooks Boilers

​

     Most boiler manufacturers and high-pressure boilers will include their recommended boilout procedure which is important to note as there may be subtle differences. Also included in most operation manuals will be internal water volumes important for calculating the correct amount of boilout chemicals (Figure 1).

 

 

Typical Boilout Procedure

 

     1.) Prior to commencing, clear the boiler for firing by taking all safety and standard precautions. This would include isolating the boiler so that it is valved off properly and has been hydrostatically verified.

​

     2.) Flush and rinse the waterside thoroughly with water to initially remove as much debris and oil as possible. Although the boiler will not reach the max firing rate during the procedure, this will aid in avoiding any material getting baked onto internal metallurgy.

​

     3.) Using the manufacturer’s recommendations, compute the quantity of alkaline cleaner necessary to perform the task. This can be accomplished by obtaining the volume of water (flooded) within the boiler and calculating the required ppm of cleaner. Sometimes chemical quantities can be estimated based on boiler HP if internal volumes can’t be obtained. Another ‘Rule of Thumb’ used in boilout procedures is that 1 HP is construed as being equal to 10 ft2 of heat exchange surface.

​

     4.) An overflow pipe should be attached to one of the boiler openings and routed to a safe discharge point. Remove relief and steam safety valves before the boilout chemical addition to avoid contamination.

​

     5.) Introduce the recommended dose of alkaline cleaner into the boiler while the boiler is being filled. Of course, wear the recommended PPE as mixing caustic solution with water is an exothermic reaction. Ideally, cleaner is added in a way to promote it being mixed and dissolved.

​

     6.) Close the boiler, fire lightly to raise the pressure no less than 10-15 PSIG, and boil out for at least 12 hours. Slightly increase the pressure if good circulation cannot be obtained. The boiler should be fired intermittently to hold the solution just at the boiling point. While boiling out, open each blowdown connection for a short duration hourly to help remove debris and oil. Typically hydrate alkalinity should be maintained above 150 ppm.

​

     7.) When the overflow water appears clear, the burner can be stopped, and the boiler can be drained when sufficiently cooled (internal water should be cooled to around 140°F). The manhole and handholes can then be removed for internal inspection. It is recommended to wash the interior until there is no evidence of debris, oil, and impurities.

​

     8.) If at this point the internal surfaces do not appear to be clean, the boilout procedure can be repeated.

​

     The boilout procedure is a necessity when it comes to new boilers and ensuring the longevity of their use. As previously mentioned, the boilout process not only improves thermal efficiency but increases the boiler’s reliability. This process can be quite rewarding as visual improvements can be made quite rapidly. Regardless, make sure to adhere to operational manuals and a professional water treater!