steam boiler -top of cast eaten through

terry_5

why would cast eat through top of boiler? combustion prob?

JackR

two words

Internal Corrosion

Usually caused by excessive amounts of make-up water due leaking vents, piping ect. I'd be willing to bet the boiler in questions has an automatic water feeder. Along that same lines excessive chlorides in the water will do the same thing and accelerate the process.

Is this gas or oil?

ttekushan_3

You are right

but chlorites seem to attack at the water line most often. The graphitic corrosion at the tops is likely both chlorites and excess water as you said but complete clogging of the section tops in question has likely occurred. I see this where the return, water feed, controls and steam outlet are all on the same side of the boiler. Its the lower circulation sections that clog top and bottom starting at the farthest section from these (but not including the end casting).

If the boilers inlet and outlets are oriented one above the other vertically as opposed to diagonally (say, the inlet at the back of the boiler and the steam outlet at the front of the boiler), you're really in trouble. There's no cross flow to help. These boilers should get water treatment as far as I'm concerned. Once the clogging occurs, the water in the sight glass can remain deceptively clear for years, only to suddenly go ugly and unstable once the casting is breached and the offending section begins to get steam cleaned.

This is the point where water hammer begins, boiler water feeder goes crazy, and the plume of steam blows out of the chimney!

The above arrangement is extremely sensitive to poor maintenance. And it doesn't take long for the process to begin.

bob young

Great treatise, Terry. very well written.

terry_5

gas boiler 2 sections at top completely eaton through,put in new boiler yesterday .Found venting problems & existing burners corroded!