STEAM BOILERS 



133 



Prevention of Incrustation and Corrosion. Incrustation 

 can best be prevented by purifying the feedwater prior to its 

 entering the boiler, and can be fairly satisfactorily prevented 

 by a chemical treatment of the water in case there is no puri- 

 fication of the water prior to its entering the boiler. When 



SCALE-FORMING SUBSTANCES AND THEIR 

 REMEDIES 



the water contains large quantities of substances that float 

 on the surface, mechanical means may be resorted to, using 

 the surface blow-off at frequent intervals or some equivalent 

 skimming device. Corrosion is prevented by neutralizing 

 the corrosive acids by an alkali; corrosion due to a perfectly 



