Sight Glass Surge, Old American Standard Boiler?

Casinojunkie

I have a sight glass that is surging about 3/4" when boiler is fired and making steam. When shut down sight glass level is about level 1/2 full. This is an old American Standard Boiler.
I have skimmed the boiler at the start of the heating season for about 4 hours, after that water was running clear.
The sight glass is rusty on the bottom and a little misty on top (not dripping wet).
What needs to be done to correct the surging or is this normal?

Steamhead (in transit)

3/4-inch isn't too bad

but if you're so inclined, flush it with a hose from top to bottom (do NOT do this to a hot boiler!). Bet there's some sludge in the bottom, and removing it should steady the waterline even more.

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William Faust

flushing boiler with a hose

Steamhead - When you have done this, did you use a regular garden hose through the skim tap? Better to use water from a hot water heater?

Steamhead (in transit)

That's how we usually do it

cold water will congeal some of the grease so warmer water will work better. You MUST start with a cooled-down boiler- even with warm hose water, a hot boiler will probably crack from thermal shock.

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Casinojunkie

The way I did it was!!!
There is a drain faucet connected to the low water cut off.
I conected a short piece of garden hose to this and drained the boiler from here till no more water would run out. I left this drain faucet open, then started to add water from the hot water heater which enters the boiler close to the bottom very slowly till water dribbled out of the hose. (water was real dirty)
I did not get a full force of water from the hose. Continued this for about 4 hours and water ran clear.
Shut drain and remover hose, filled boiler till 1/2 on sight glass. Nothing further.