Help me Understand this Paragraph from Dan's Lost Art of Steam

Fred Harwood_2

If you remove the glass tube and open the upper valve, you probably will get a lot of steam rushing out. That will tend to carry over water, and confuse your testing.

The point, as I understand it, of using the "petcock" on the bottom fitting also is to limit the velocity of the steam leaving the boiler at the upper fitting, where boiling splash is normally large. You want to know if foamy crud is present near that upper fitting. If it is, it has to come out for proper performance.

sreja

Help me Understand this Paragraph from Dan's Lost Art of Steam

On p.276 of my edition of Dan's (WONDERFUL) book "The Lost Art of Steam Heating" he describes a method for checking for dirty water that he learned from Fremont Lobbestael.

Basically he says to close the bottom valve on the gauge glass , which isolates the bottom of the glass from the boiler. Then he says to "open the *pet cock* at the bottom of the glass, but be careful! If the boiler water is clean, you'll flash down steam through the top of the gauge glass.. But if the water is dirty, you'll prime water right over the top of the glass when you open the pet cock. You won't get much steam. Just water. Then you know you have to clean the system."

OK, so i think i understand most of this but..

Is the "pet cock" the handle valve thing that i use to blow down the low water cutoff thing? Picture here:
http://mouser.dcmembers.com/boiler/thumbs/Picture%20012.jpg

?

Unknown

No,

The petcock in this case, if there is one, is a tiny valve located on the bottom of the sight glass itself.

sreja

so does that mean (if you look at picture) that i don't have a petcock, and therefore cannot perform this test?

Paul Fredricks_9

On the bottom of the bottom sight glass valve should be a little fitting. I think it's a 7/16" hex, might be 1/2". If you turn this it open up and let the water out of the sight glass. Though it just looks like a nut, it's actually a valve, or petcock.

If it's not there, look on the top. I've seen the gauge glass assemblies in stalled upside down many times.

Unknown

Makes it,,,

hard to drain the water like that. Stupid gravity and all.

Unknown

Picture...

here's the best I can find. Go to this link, the little device on the bottom with the yellow handle is a petcock. It's really just a little valve.

http://www.johnernst.com/level_gauges_index.html

sreja

Sorry i posted a link to a thumbnail image, the full image on our boiler is here:

http://mouser.dcmembers.com/boiler/Picture%20012.jpg

From that you can see that we dont have a petcock directly on the glass tube -- but rather it goes to a larger blowdown thing which serves the same "basic" purpose.

But the question is, although it seems to serve the same basic function as a petcock, is that tricky test procedure still valid.. ?

Paul Fredricks_9

No, the blowdown is a different deal.

In you picture, the petcock would be behind the bottom black valve on the sight glass assembly. It is part of the brass piece that the sight glass fits into and it sticks straight off the bottom. From the angle of the picture we can't see it.

sreja

Thanks guys, i will look for it and post again if i don't understand what i see -- maybe there is a threading for a petcock but none actually installed.

nicholas bonham-carter

dan's siteglass test

i also have a non-turning siteglass drain so i wonder if the test could be performed by removing the glass tube and then opening the top valve [which does work].
naturally one would have to be careful-maybe wear a chainsaw helmet, or bruins goalie mask!--nbc

nicholas bonham-carter

THE SIGHTGLASS TEST--FAIL!

i took a 7/16" wrench, and unscrewed the bottom drain of the sightglass [after closing both valves].
then i opened the upper valve with a container ready to catch any drips.out came brown water and steam, so i will have to do some more skimming.i will wait a week or 2 as i am getting ready to have my reservoir tank installed and we may be introducing a small length of new pipe into the system with some unavoidable cutting oils, etc.--nbc