Confusion about boiler water pH and alkalinity control

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I visited a power plant today. The 3.8MPa medium-pressure drum boiler uses desalted water as feed water. After adding ammonia to adjust the pH value of the feed water, there are basically no requirements for the phenolphthalein alkalinity of the boiler water (the total alkalinity is less than 0.1mmol/L. The phenolphthalein alkalinity has not been analyzed, and it is estimated to be basically zero? ), the conductivity of the furnace water is 30us/cm, and the measured pH of the furnace water is about 10 points. The introduction said that the boiler water index has always been very good, and the steam index has also been very good. The steam silica is less than 1.0ug/kg, and the sodium ions basically do not need to be analyzed and have been very stable. What is confusing is that many people used to say that the phenolphthalein alkalinity of boiler water should be controlled, otherwise the PH of boiler water will be less than 8.4. However, judging from the experience of this factory, there is no need to add sodium hydroxide to adjust the pH of the boiler water (no addition of hydrazine, etc., at most trisodium phosphate has a little impact). Why can the plant's boiler water pH meet the requirements? Boiler water conductivity as medium pressure boiler * * There is no requirement in the standard. I checked the standard and found that the conductivity of boiler water in high-pressure boilers is required to be less than 130us/cm. The factory monitors conductivity as an important indicator. Is it necessary?