Plumbing in water gauge questions

[zimirken]

Yeah. I ran some numbers and aiming for 30-40lbs/hr means I'll be feeding it 4 or so gallons an hour. If I only want to have to feed it every 10 or 15 minutes, that means I'll want a capacity of at least 3 gallons if my tank has a 50% or so usable water level range. That leaves 25% room for steam separation, and 25% minimum water level. I'm planning on a steel tank oriented vertically, perhaps 8 or 10 inches in diameter, so that should be pretty reasonable.

[zimirken]

I've got a preliminary gauge put together. I think I'm going to remake the plates that hold the rods, as the rods are way too close to the fittings. I just made adapters to hold the glass with o-rings that screw into 1/4npt, with some off the shelf needle valves. I can't recommend enough using a CNC to thread mill large diameter threads. Perfect threads with little to no effort even in tool steel.

The glass is 8mm x 12mm borosilicate, and cutting it was a bit of a nightmare. Several techniques just didn't seem to work because it was so thick and resistant to heat shock. Luckily I bought a pack of five tubes, so I have plenty to practice with. On the plus side the glass thickness makes it feel extremely sturdy.

[Bill Shields]

Cut it off, chuck in a drill press and spin slowly on a piece of sandpaper to square up

[Gra2472]

Cut it off, chuck in a drill press and spin slowly on a piece of sandpaper to square up

Hey that’s a great idea Bill. Now I know how to save a piece of gauge glass that I have that has a nick in the end of it.

[Bill Shields]

i always cut my glass longer than needed.

it is remarkable how quickly you can 'sand off' 1/8" of glass tube using this method

[zimirken]

I used a torch on a low flame to smooth the sharp edges. I tried looping wire around the tube and running current to make it glow, but that did nothing. None of those heat based tricks worked either, like scoring, heating, and quenching. It must be real borosilicate, because I only get heat cracks if I hit it with a high torch while it's room temperature. I finally used a dremel with a cutting wheel to make a big notch around the glass and broke it with a pliers. That only kind of worked. I had to do it a few times to get an even enough edge. I've got one of those cheap harbor freight "metal cutting" miter saws, that doesn't really have the horsepower to cut metal. I might try to use that to just cut the glass. On the flip side I won't have to worry about it shattering from pressure or temperature.

[Bill Shields]

sandpaper to the rescue....

be careful about brass fittings sitting long-term unattended in a boiler..

before too long (more than a few years)...they zinc out and become brittle / porous and fall apart.

as a general rule...brass is a no-no on / in a boiler...

Then there is the problem of galvanic corrosion which I might think you should consider

[Greg_Lewis]

What if you chucked the glass carefully in the lathe, turned it in the slowest back gear and then put a Dremel in the toolpost and carefully and slowly cut through with the cutoff wheel?

[NP317]

I have cut many a borosilicate tube by scoring around the tube with a triangular diamond file and then snapping the tube by hand. With gloves on.
Two pieces of masking tape with a thin space between them guides the file.
Then the ends can be squared as needed with a green wheel on my grinder.
RussN

[rmac]

What if you chucked the glass carefully in the lathe, turned it in the slowest back gear and then put a Dremel in the toolpost and carefully and slowly cut through with the cutoff wheel?

There are YouTube videos that show that exact method.

From what I've read and from very limited experience, here are a few things to watch out for:

1. A diamond wheel (or file as RussN suggests) works best.
2. It helps to lubricate the cut with water to keep the heat from building up. Borosilicate glass (Pyrex) probably doesn't care about the heat, but the cutoff wheel might.
3. Go slow.

-- Russell Mac

[zimirken]

Yeah, this particular glass must have too high of a wall thickness to diameter ratio, so scoring and breaking really wasn't working. I wrapped it in a paper towel and put it in the lathe to score with a file.

I've got a piece with a good enough length and edge consistency, but I could use about another half inch to inch of length, so I might try the lathe dremel trick.

I know that it's possible to leech the surface zinc off of brass, but brass fittings on boilers are everywhere. I'd guess it's really only an issue on say, 24/7 operating boilers, and only under the water line.