What issue arises with phosphate hideout at boiler pressures above 17,200 kPa?

Phosphate hideout refers to the phenomenon where phosphates, used for controlling hardness and preventing scale formation in boiler water, can become less effective due to changing conditions in the boiler. When boiler pressures exceed 17,200 kPa, the solubility of phosphates can decrease significantly, causing them to precipitate out of the solution. This precipitation means that the phosphates do not remain dissolved in the water as intended and can instead form solid deposits that settle on the boiler surfaces, effectively capturing and absorbing onto the boiler layer.

This issue can create various problems within the boiler system. For instance, the precipitated phosphates can lead to localized overheating because they act as an insulating layer, preventing efficient heat transfer. Moreover, the accumulation of these deposits can obstruct water flow, reduce the overall efficiency of the boiler, and potentially cause damage over time.

In summary, the correct identification of phosphate precipitating and being absorbed on the boiler layer under high-pressure conditions is crucial for maintaining effective boiler operation and ensuring that scaling and related issues do not compromise the system's performance.