boiler tube failures

Paul Bock

refigerant leak? if the tube bundle has a leak into the steam side it wont show up as water in the compressor, but when that refrigerant gets back to the boiler its going to boil off really fast and could be causing your problem. I just had a hot/chilled water system this spring where the refrig. leaked into the boiler, and stayed in soloution, soon as i started to drain the boiler the high ref. alarms started going off.

Paul

steven grant

boiler tube failures

We have two Kewanee steam scotch marine low pressure boilers 500 hp, and need about one tube replacement a month. The tubes that fail are in the first arc around the Morison tube.The failure appears to be cavitation pitting on the waterside close to the front tube sheet. Tubes beyond this first arc do not fail. There is a gas burner with some refractory around the flame. Boiler water conditions are good, no scaling, little makeup. The boiler remains on the line for a month at a time with the burner modulating and most periods at constant load. The building is an apartment building using steam for heating and an absorbtion refrigeration unit.

Any ideas as to the reason for the tube failures and a cure?

Gary Fereday

Only brainstorming here~~~~~~~~~~~~

Could the inlet becausing a lot of turbulance, un reamed pipe, or closely spaced 90* ells just outside of the boiler. Of course high velocity of water would be a concern. If it is on the steam side could it be that there is a lot of air getting in to the system causing carbolic acid to form at that point? If water velocity, measure the pump delta pressure and determine how close it is to the requierments of the system. like I said just Brainstorming~~~~ bigugh

newlove

boiler tube fail

first thought would be design problem, ie, load greater than designed capacity. most problem in summer or winter?is flowmeter correct? history of boiler maintain? same condition on both boilers? age of boilers.my breath smells like dyecheck. cure could be political! lol

Gary Fereday

Now I know

The smell of brainstorming! Dye Check! ok! bigugh

canuckDale

I bet...

The tubes always crack on the main fire-tube side? Side closest to the burner???

If so, that's because it's over fired, by design or otherwise. The fire tube may have great expansion. Delta T that puppy much? I have Napanees that did that. There was so much heat by the burner, and other end, that the tube sheet would flex lontitudally. The outside tubes didn't leak. The expansion wasn't as great there.

And when you continually re-tube, the holes in the tube sheet get bigger and out of round. So those tube guys drive the expanders in way too hard to seal the new tubes. A few years of that and you have out of round holes. Then, because the axial dimensions are not equal, those tube guys drive the expanders in even farther. So much stress is induced into the tube, that your water treatment program can be FAB!!, but, as high pressure goes to low - corossion ALWAYS goes to the high stress point. You get stress corossion cracking.

The fix for me was to de-rate the firing, keep a constant water temp, hire a machine shop to round the tube sheet holes and use ferrules to make up the the huge tolerances. Those ferrules also displaced the stress along a larger area on the tubes as opposed to the point loading that they were previously subjected to.