"Ray" wrote in message
news:A19gj.800$xA6.394@trndny09...
I think that by "flushing" I mean the same thing as you mean in "blowdown."

Daily? No one ever suggested that often before. The guy who installed it
suggested weekly.

I've never been clear what the "blowdown" does anyway.

-- Ray

OK we are probably talking about the same thing. The frequency depends on
the quality of the water and how much loss you have.

In a perfect system, you'd fill the boiler to the recommended level and
you'd never had a loss and you'd never add water, and you'd never have to
blowdown the system.

reality is, you do have some losses of water or vapor through leaks and
vents so water is added as needed, usually through an automatic valve. As
you add water, you also add dissolved solids that are in the water. When
you make steam, the water is turned into vapor and the solids drop out.
Over time, the solids accumulate and can form a mud on the bottom of the
boiler. This coating inhibits heat transfer, plugs up tubes and other
potential problems depending on the boiler type. So, to get rid of them,
you blowdown (or as you say, flush) out the bottom of the boiler. Some have
a mud drum for that reason. You do this while the boiler is hot, under
pressure, but you don't take the water level down out of the sight glass.

Again, using industrial boilers as an example, the water is checked daily.
We have a meter to tell us what the TDS (total dissolved solids) is and we
do the blowdown accordingly. In our case, this is a process boiler and we
use up to 10,000 gallons of water a day for steam so a lot of stuff can be
left behind. We also add chemicals as I noted before to assist in keeping
the insides clean, keeping the solids dispersed, and driving off oxygen.