steam boiler making strange sounds?

Joseph_4

Was at a job today where I had to empty a steam boiler of all water. When I was finished, I filled boiler to half way mark on gauge glass. Turned boiler on. About 2 hours later customer calls me frantically that all water is out of gauge glass and so he added more water could I please come over. I explained to him that water is out to do its job and will return as condensate. he brings me over to boiler and we hear boiler making a "glug, glug, glug sound" The sound you hear when a bottle is turned over and water is emptying from it. The sound went on for a good 10 minutes and then finally stopped. He said in 30 years he never heard such a sound. 2 things bother me. 1- I filled it to halfway on gauge glass and he also added water 2 hours later. when I was watching boiler with him, the gauge glass didn't get any higher. where did the extra water go (we checked for leaks in basement and didn't find any water on floor.) 2- that sound really did sound like water was emptying from boiler. What is it.  (could it be the sound of the condensate returning to boiler? The gauge glass got no higher during the 10 minutes we watched it) 

crash2009

The waters job is to stay in the boiler.

It sounds like your boiler is pumping the water out of itself.  I have heard that sound and seen that condition before.  In my case, it was a completely blocked return.  I have valves on the system risers and the Hartford.  I forgot to open the Hartford valve and caused the blockage myself.  When I opened the Hartford valve all the water came back including all the water that the automatic feeder put in. 

Likely what has happened in your case is that when you drained the boiler the return (s) got plugged.  MAKE SURE THE BOILER IS COLD WHEN YOU TRY TO CLEAR THE BLOCKAGE.