softened water for steam boiler

Barbarossa

If the water is softened by a salt brine resin exchange, you can be putting salt into the boiler water not a great idea; RO types work better. Does the level surge in the glass, and what is there blowdown rate as a function of input? With a once through you are running a concentration cycle. They need their boiler water chemistry checked or you could switch to a borosilicate sight glass (red line) which may last longer. I have seen the glass erosion in cases where the alkalinity was too high and conversely with high-purity feeds that will leach anything.

R. B. (Buzz) Estes

Eroding Sight glasses for steam boiler

Most of my of 45 year carreer has been with heat pumps, gas furnaces, etc. and only an occasional boiler, usually hot water. We have serviced several steam boilers and even changed out a couple. Therefore I always feel like my boiler (and especially steam education is sadly lacking)
Customer called on a small steam boiler used to supply a steam room/sauna. This is a once - through system in which no condensate comes back and the water supply is softened.
The complaint was that the relief valve was popping off every week or so but that may be due to the relief valve was 15# but the pressuretrol was set at 9" (plus differential). We have ordered new relief valve and pressurtrol (to be set # 3 + differential ) and that will hopefully solve that problem.
Another problem that bothered me because I had no answer was that the sight glass "erodes" at the bottom end and starts leaking in less than a year. Their maint. cheif tells me he turns the tube over after about six months and puts the "rough lower bottom" end at the top and the smooth upper end at the bottom and then after another six months he replaces the tube. I am unfamiliar with a steam system that attempts to operate at more the 7 psig and wondered if that was part of the tube failure. Another hypotheses was whether the softening of the water had any effect. OR. Whether the once-through system with a so much make-up
water might be causing it.
I will be glad to furnish other info. such as brand, model, btuh, etc. if anyone thinks it might be pertinent, but the question seemed generic.