pH varies in the Condensate System
1. Condensate pH is not always the same at different points of testing in the return system.
pH varies in the condensate system by as much as 1 to 2 pH points at different testing points in the system. This is true because the steam travels to different areas through longer or shorter lengths of pipe, sometimes accumulating at deadheads along the way. And carbon dioxide accumulates in the deadhead legs, also lowering the pH. Also, heat exchangers for heating domestic hot water frequently have uncharacteristically low pH.
Therefore, corrosion may be occurring, but not be identified, in some areas of the return system. The operator needs to test at more than one test point.
2. Different types of steam line treatments have different distribution ratios.
Amine products used for steam line treatment have different distribution ratios. The distribution ratio is the ratio of the amount of amine in the vapor phase (steam) over the amount of amine in the condensate. So a larger number means that more amine is carried farther into the steam system. Consequently, the amine will be present longer in the steam than in the condensate water. So after its travel through the system more amine is present at the end of long steam lines.
RTA frequently uses cyclohexylamine in larger steam systems. DEEA distribution ratio is a small amount lower and is also used in these types of systems. Morpholine, to the contrary, has a lower distribution ratio. It leaves the steam more quickly as it dissolves in the condensate quickly, but doesn’t travel as far in the vapor phase. Therefore, it is more effective nearer to the boiler. So pH varies in the condensate system because of the system itself, but also because of the choice of amines present in the steam line treatment.
3. RTA formulates different balances of amine concentrations in any given specific steam line treatment
To address the problem when pH varies in the condensate system, RTA offers different composition of amine products. For long steam lines, such as in large plants, such as for plant heating, RTA uses cyclohexylamine or DEEA. For smaller plants and for higher pressure process type boilers, RTA normally uses morpholine as an ingredient, along with cyclohexylamine and/or DEEA. Morpholine does not theoretically leave the boiler and go into the steam in a low pressure system since the boiling point is higher than that of a low pressure boiler of 15 lb. Other amines with differing steam to condensate ratios may occasionally be used by RTA. See Custom Chemicals.