bubbles in steam glass

bagcag2

I have a steam boiler about 4 years old.  I maintain the unit annually and blow off the low water cutoff weekly.  Add water to the correct level and start the unit.  Recently, for the first time, bubbles appeared in the sight glass.  I let out a little water and the bubbles dissapear. About every three days or so I notice the bubbles.. I havenot yete been able to dertermine when the bubles start...begining middle or end of heating cycle.  What would cause the bubbles to suddenly appear as they have never been there before.  Yes, I do look at the boiler on an almost daily basis and have never seen them before until recently. 

JStar

RE

The ph level of the boiler water may have become lopsided. Bubbling can be caused by high alkalinity. You can get those ph strips to test on your own before calling for help. Anything over 9 on the ph scale is too high.



Or, the boiler may just be getting a little dirty on the bottom. Have you been flushing the actual boiler, or the return?



Has anything changed recently? Did you get rid of a water softener?

bagcag2

re bubbles in sight glass

I have been blowing off at the low water cutoff.  I have only blown off at thereturn once and that was this last time I did the servicing.  No other changes to the system have been made.

JStar

RE

If possible, I would flush the water from the boiler, and not just the LWCO. Sediment may be building up on the bottom of the boiler, causing pockets of air to form and then fizzle out. You'd also benefit from a good skimming to make sure the water surface is clean as well.

Hap_Hazzard

Gases come out of solution

when water is heated. At the boiling point, their solubility is zero, so you'll always get bubbles forming when you heat water, the question is why you're seeing them in your gauge glass.



Unless you're adding really large amounts of makeup water after you blow down your LWCO, the water in your system should be essentially devoid of dissolved gases, and if you're adding the makeup water while the boiler is heating, it should be evolved and driven out the vents immediately.



Since this just started happening this year, there are only two possible explanations I can think of: either you've changed your procedure for blowing down your LWCO and replacing the water or some change in the configuration of your piping is allowing the water to become aerated during normal cycling. I guess it's also possible that the gauge glass is just dirty and that's somehow causing the bubbles to stick longer than they normally would.



If you can eliminate all of these possibilities then I'm stumped, but maybe some of the more experienced folks here can think of other possible explanations.

bagcag2

re

Thanks for everyones help.  It takes about three days for the bubbles to appear.  I did blow down the boiler thru the return valve.  A lot of nasty water came out. Waitng to nsee what happens.  I tried to skim it.  Nothing came out of the skim valve.  May also be plugged.  Will try cleaning this port later and do a good skimming.  I will be back if I am still baffled.