What are the requirements for boiler water quality for 0Cr18Ni9 heat exchange tubes?

Attachment: Standard of the People’s Republic of China **GB 1576-2001 – Water quality for industrial boilers. Quality standards: For feed water in steam boilers and boilers capable of producing both steam and water, external chemical water treatment is generally required, and the water quality must comply with the specifications in Table 1. Table 1: Parameters for water supply boilers – Rated steam pressure, MPa: ≤1.0, >1.0; ≤1.6, >1.6; ≤2.5. Suspended solids, mg/L: ≤5, ≤5, ≤5; — — —. Total hardness, mmol/L: ≤0.03, ≤0.03, ≤0.03; — — —. Total alkalinity, mmol/L: No superheater – — —; 6–26, 6–24, 6–16. With superheater – — —; ≤14, ≤12. pH (25°C): ≥7, ≥7, ≥7; 10–12, 10–12, 10–12. Dissolved oxygen, mg/L: ≤0.1, ≤0.1, ≤0.05; — — —. Dissolved solids, mg/L: No superheater – — —; <4,000, <3,500, <3,000. With superheater – — —; <3,000, <2,500. SO32-, mg/L: — — —; 10–30, 10–30. PO43-, mg/L: — — —; 10–30, 10–30. Relative alkalinity (free NaOH equivalent of dissolved solids): — — —; <0.2, <0.2. Oil content, mg/L: ≤2, ≤2, ≤2; — — —. Iron content, mg/L: ≤0.3, ≤0.3, ≤0.3; — — —. 1) The basic unit for hardness in mmol/L is с(1/2Ca2+, 1/2Mg2+); the same applies hereinafter. 2) The basic units for alkalinity in mmol/L are с(OH-), 1/2CO32-, and HCO3-, the same applies hereafter. For boilers that have low requirements regarding steam quality and do not come equipped with superheaters, the upper limit for the alkalinity value can be appropriately increased, provided that the operating unit obtains approval from the local boiler and pressure vessel safety supervision authority. 3) Deoxidization is required when the rated evaporation capacity of the boiler is 6 t/h or more. For boilers with a rated evaporation capacity of less than 6 t/h, deoxidization measures should be applied to the feedwater in case of localized corrosion; the oxygen content in the feedwater supplied to turbines should be less than or equal to 0.05 mg/L. 4) If it is difficult to determine the dissolved solids, conductivity or chloride (Cl-) levels can be used as indirect indicators; however, the ratio between dissolved solids and conductivity, or between dissolved solids and chloride (Cl-), must be determined through experimentation. This ratio should also be rechecked and adjusted regularly. 5) The relative alkalinity of fully welded structure boilers can be left uncontrolled. 6) Only for fuel and gas boilers.

It is mainly to control its chloride ion content.

We have a heat exchanger whose heat exchange tubes are made of 0Cr18Ni9; boiler water flows through the shell side. What are the requirements regarding the quality of the boiler water used in operation?

Control the chloride ion content to prevent intergranular corrosion

Control the Cl- content to reduce its corrosion rate

The main requirement is that the chloride ions in water must not exceed 25 mpp; there are no other requirements