American Boiler Manufacturers Association

Boiler-Water Eimits and Steam Purity Recommendationsfor Watertube Boilers, American Boiler Manufacturers Association, Arlington, Va., 1981. 

The American Boiler Manufacturers Association (ABMA) has established limits for boiler water composition. The limits are set to help assure good quality steam (for example, limiting silica in the steam to 0.02-0.03 ppm). Blowdown is normally based on the most stringent of these limits shown in Table 1. 

Figure 1 from GPSA shows how the silica content of The American Boiler Manufacturers Association... 

ABMA ACH AGR AMP AMP American Boiler Manufacturers Association aluminum chlorhydrate advanced gas-cooled reactor aminotri-(methylenephosphonic acid) 2-amino-2-methyl-l-propanol, AKA isobutanolamine... 

The American Boiler Manufacturers Association (ABMA) has established limits for boiler water composition. The limits are set to help assure good quality steam... 

Hot Lime Zeolite-Split Stream Softening. Many raw waters softened by the first two processes would contain more sodium bicarbonate than is acceptable for boder feedwater purposes. Sodium bicarbonate will decompose in (lie boiler water to give caustic soda. Caustic soda in high concentrations is corrosive and promotes foaming. The American Boiler Manufacturers Association has adopted the standard that the alkalinity content should not exceed 20% of the total solids of the boiler water. Split stream softening provides a means for reducing the alkalinity content. 

The American Boiler Manufacturers Association shoots for less than 0.02-0.03 ppm silica in steam by limiting silica in the boiler water. See the section entitled Blowdown Control. 

Roller Water The steam purity limits define boiler-water limits because the steam cannot be purified once it leaves the boiler. For a once-through boiler, the boiler water must have the same specifications as the steam. A recirculating boiler is a still, and there can be considerable purification of the steam as it boils and is separated from the water in the steam dmm. The process of separation is not perfect, however, and some water is entrained in the steam. This water, called mechanical carryover, contains impurities in the same proportions as the boiler water, and its contribution to steam impurity is in those proportions. Typical mechanical carryover is less than 0.25% and often less than 0.1%, but operating conditions in the boiler can affect the mechanical carryover. In addition to mechanical carryover, chemicals can be carried into the steam because of solubility. This is called vaporous carryover. Total carryover is the sum of mechanical and vaporous carryover. The boiler-water specification must be such that the total carryover conforms to the steam purity requirements. For salts, such as sodium phosphate and sodium chloride, vaporous carryover is not a significant problem below approximately 15 MPa (2175 psia). As boiler pressures approach the critical point, vaporous carryover increases rapidly. Above 15 MPa (150 bar), boiler solids concentrations must be carefully controlled to minimize vaporous carryover. Most boilers operating over 18 MPa (180 bar) use all volatile treatment to prevent deposition of salts in turbines. Boiler-water limits for utility boiler are Us ted in Table 2. Recommendations from American Boiler Manufacturers Association (ABMA) for boiler-water limits for drum-type boilers and associated steam purity for watertube boilers are listed in Table 3. 

The American Boiler Manufacturers Association has established standards for boiler water balances in its standard steam purity guarantees. These are identified as ABMA Limits and are listed in Table 7.2. 

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