# Float in the sight glass



## Chris Scott (Jan 2, 2008)

Why not put a (red) float in the sight glass to make the level easier to see? 

I'm sure a small enough plastic bead could be found light enough to do the job. Maybe I'm too optimistic, I think a little inventiveness would solve the opinion it will get stuck at the bottom or top.


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## aceinspp (Jan 2, 2008)

Use a small piece of brass rod and it helps eliminate the bubbles and makes it easier to see the water level. Later RJD


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## Semper Vaporo (Jan 2, 2008)

An interesting idea. Just cogitating here...

It would have to be a material that does not melt at the temperatures of boiling water at elevated pressures (a maximum of around 338 degrees if we set an arbitrary limit of 100 PSI and of course if there were a low or no water situation the temperature at the sightglass might exceed that by a wide margin).


It would have to be something that repels water so that it does not adhere to the sides of the sight glass.

Light enough to float in water, but heavy enough to not float in the steam above it (not a big problem, but something to consider).

It would have to be small enough to move easily in the narrow glass tube of the sight glass, yet be large enough to be trapped by something at the top and bottom so it does not come out in an over full or low water situation.

Whatever blocks it from coming out would have to be porous enough that if the indicator ball (whatever) hits it, water and steam could still pass unheeded and not get stuck against these "stops" by pressure from above or below or the sticky property of water.

I am certain a material could be found that meets the criteria, but I am concerned about the possibility of blocking the sight glass and causing unreliable readings (the things are so small already that they are fairly unreliable anyway!).

We do (or are supposed to) use distilled water (which should have zero mineral content) and we should be careful to not let steam oil get drawn back into the boiler through the throttle during cool down, and I think I am diligent about that and I use only distilled water, but I still find that my sight glass is slightly frosted due to contaminates in the boiler and that sort of thing could clog any small opening in the top or bottom of any device used to prevent the indicator ball from coming out and that would render the sight glass as useless.


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## Charles (Jan 2, 2008)

"Why not put a (red) float in the sight glass to make the level easier to see? "

Things that work:

Painted line on sight glass
Painted angle stripe background
Light bulb
Location
Size of pipes
Blow down

Would be interesting to see what material would withstand the temperature & changes, not deteriorate and would float with the change of water level: maybe a miniature waffle ball design that would not float to the top and seal off incoming water as the engine primed. The other factor is top float position relative to crown sheet given the ball would replace a volume of space (if solid).


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## Pete Thornton (Jan 2, 2008)

Posted By Chris Scott on 19 Feb 2013 11:10 AM 
Why not put a (red) float in the sight glass to make the level easier to see? 

I'm sure a small enough plastic bead could be found light enough to do the job. Maybe I'm too optimistic, I think a little inventiveness would solve the opinion it will get stuck at the bottom or top. 


I think an electronic device could do a much more accurate job? Even the red/green LED systems currently available are better than any of my sight glasses. Apart from anything else, they are difficult to see when the loco is moving!


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## Charles (Jan 2, 2008)

Pete

I did not know that Bill Ford was still offering units.


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## David Leech (Dec 9, 2008)

Charles, 
I know that Peter Spoerer in the UK makes them, called LocoSaver. 
It's been in the G1MRA Newsletter and Journal. 
He even has one with a probe for the boiler, plus one for the tender. 
How many times has our tender run dry and we don't notice???? 
All the best, 
David Leech, Delta, Canada


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## David Leech (Dec 9, 2008)

Back to the original question. 
Since some locos seem to have problems with the water gauge being accurate, or getting bubbles in them, then adding a float is not going to help. 
BUT, if you are going to use one, then I would perhaps suggest a small hollow 'donut' with straight sides made out of brass or copper. 
Would that work? 
Chris, just try something, and tell us how it works!!! (or not) 
All the best, 
David Leech, Delta, Canada


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## Phippsburg Eric (Jan 10, 2008)

As we know, steam engines have been around for 150+ years and so there is plenty of experience with water glasses. I have never seen a float in the glass...perhaps there is a reason? it does seem an obvious addition. I suspect that the float would get stuck and not read true. 

I have seen solid sinking "floats?" in glass tubes which were used to measure flow rate. the glass is tapered (narrower at the bottom wider at the top) and the flow raises the "float" proportional to the flow rate.


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## SteveC (Jan 2, 2008)

Posted By Phippsburg Eric on 19 Feb 2013 01:36 PM 
As we know, steam engines have been around for 150+ years and so there is plenty of experience with water glasses. I have never seen a float in the glass...perhaps there is a reason? {snip...}[/i] Eric

Funny that you mentioned that, just last week I ran across the following.









Reliance Safety Water Column c. 1897 (PDF 295KB)[/b]


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## Semper Vaporo (Jan 2, 2008)

There are two usual problems with a sight glass and we seem to be confusing them here. One is the difficulty of seeing the level in the glass and the other is inaccuracy due to bubbles, blockages and capillary action of water on glass (water wets glass). A "float" would possibly improve the ability to see the level, but would not improve the accuracy if there are bubbles, blockages or water climbing the glass due to capillary action. I fear that a "float" might make blockages more common and defeat the purpose of making it easier to read.

Flow rate meters (sinking floats in tapered glass tubes) have nothing to do with the boiler sight glass. In a flow rate meter the "sinking float" is not a "float" at all, it is heavier than the liquid and sinks by gravity, but the flow of the liquid displaces it up the tapered tube until the area between the tube sides and the ball is enough to allow the liquid to flow. The higher the ball, the more flow there is.

The sight glass is not supposed to have water flow "through it", but rather to have liquid flow IN through the bottom and steam flow IN through the top to show the level of liquid in the boiler (water seeks its own level). Water comes in through the bottom and stops when the level in the glass is the same as the level in the boiler.

Sometimes a valve is inserted in the bottom of the glass to allow the user to open it and the pressure of the steam and water will blow water out the vent. There will be more steam because water is thicker and flows slower than steam. This empties the glass completely and when the valve is closed, the water will (or should) return to the same level as the water in the boiler. Troublesome bubbles can be removed this way.

In the real world of boilers, there are 4 valves. One in the top to cut the glass off from the steam space of the boiler and one in the bottom to cut the glass off from the water space of the boiler. Close both of these and you can remove the glass without scalding yourself. There is another one in the top of the glass that vents to the outside and one in the bottom that vents to the outside. 

The boiler engineer can clear the glass in multiple ways and verify the proper operation of the glass and that there are no blockages. Close the bottom boiler valve and open the bottom vent valve to have steam exit the boiler from the steam space, through the glass. And then close the bottom vent, open the bottom boiler valve and the level in the glass should return to normal. 

Then close the upper boiler valve and open the upper vent to have water vent from the boiler up from the bottom, through the glass and out the top. Then close the upper vent and open the upper boiler valve and the level of the sight glass should return to normal. 

These two procedures prove that there are no blockages in either the upper or lower connections from the boiler to the sight glass. The boiler engineer has to double check that both of the vent valves are closed and that both the upper and lower boiler valves are open at all other times. On some boilers, these upper and lower boiler valves are padlocked in the open position so that someone cannot accidentally (or on purpose) cause the sight glass to be disconnected from the boiler during normal operation.

The idea of adding a float to the glass is only to improve the ability of us bifocaled folk to see the level and maybe all the others to see it from a greater distance.


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## Gary Armitstead (Jan 2, 2008)

On my 1.5" ten-wheeler, I use a "Red Line" sight glass. That's the brand name of the glass. Maybe they are available in your smaller size.


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## Pete Thornton (Jan 2, 2008)

In the real world of boilers, there are 4 valves. 
I recall from my B&O RR Museum days that many of the locos had a sight glass AND a set of valves (faucets) adjacent to them. Like this loco whose image I found.

The idea was to open each one and find out whether steam came out or water! I don't know if it was back-up for the sight glass or what.


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## Semper Vaporo (Jan 2, 2008)

Posted By Pete Thornton on 19 Feb 2013 04:46 PM 
In the real world of boilers, there are 4 valves. 
I recall from my B&O RR Museum days that many of the locos had a sight glass AND a set of valves (faucets) adjacent to them. Like this loco whose image I found.

The idea was to open each one and find out whether steam came out or water! I don't know if it was back-up for the sight glass or what.












Yes, they are backup for the sightglass.. some say it is the other way around... the sight glass is the back up for the supposedly "better reading" one gets from the "try-cocks". In your photo they are the three faucet knobs in a diagonal row on the right of the boiler backhead.

Some people will call them "Tri-cocks" since there are usually 3 of them, but the proper term is "Try-cocks" as they are used to "try" the level of the water in the boiler.

The "Try-cocks" were often incorporated into a water column that was then fitted with a seperate sight glass. The water column supposedly took the brunt of sloshing of water and smoothed the level in the sight glass itself. Many times the Try-cocks were totaly seperate from the sight-glass (as it shows in the photo).

They are mounted such that each is at a different level on the boiler. One is at the upper permitted water level, and one as at the lower limit and one inbetween just as a check on the other two.

The idea is that if you open the top one, you should get just steam. Open the bottom one and you should get just water. The middle one could be either. The problems with the tri-cocks is that the bottom one might show mostly steam because the water exiting the pressurized boiler will instantly flash to steam and the inexperienced engineer/fireman might not be able to tell the difference. They also needed to vent directly into the cab(usually aimed at a funnel that drains out below the floor of the cab) and that just raised the temperature and humidity in the cab to make the work environment more miserable.

For years, the FRA required both a sight glass and try-cocks on an engine as checks against each other, but I vaguely remember that now they require two sight glasses and the try-cocks are no longer required (but not banned!). (There is also now a requirement for a water level glass to be on the tender that can be checked by anyone in the cab to know if there is water available to replenish the boiler.... it used to be that someone had to climb up on the tender and open the hatch to look in, or drop a stick to measure the depth of the water in the tender... a dangerous thing to be doing on a moving engine!)


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## johnsteam (Feb 16, 2008)

Would a small bead, say like from a craft store, with a brass wire through it with a bend in the wire above and below the bead, to keep it from disappearing out of the the glass. Maybe it won't handle the heat. Just a thought. John


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## Semper Vaporo (Jan 2, 2008)

Will the bead float? And not get hung up on the wire?


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## zephyra (Jan 2, 2008)

Posted By Chris Scott on 19 Feb 2013 11:10 AM 
Why not put a (red) float in the sight glass to make the level easier to see? 

I'm sure a small enough plastic bead could be found light enough to do the job. Maybe I'm too optimistic, I think a little inventiveness would solve the opinion it will get stuck at the bottom or top. 


I have a stationary mill engine from vision engineering that does exactly this and it works pretty well. Sometimes gets stuck but a quick tap usually brings it to the surface. I have no idea what the float is made from..... 
Robert


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## Greg Elmassian (Jan 3, 2008)

I think a float might work in 1:1, but in 1:20.3, the meniscus of the water is so "strong" since the diameter of the glass is small. I believe that it's too strong force a to overcome with the small float you would need and the gravitational attraction on such a small float. 

A larger float, like a longer thin hollow tube might work, more "force" to overcome this, but heck, it's so small to begin with. As previously mentioned, any contaminants would just cause more issues. 

Greg


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## Chris Scott (Jan 2, 2008)

The principle is cohesion and adhesion of the water and glass molecules. The glass adhesion is stronger than the water's surface cohesion. 












Reading the true water level pretty impossible.









Adding a float, below a ball, "The positive buoyancy seen in the drawing [A] results in, as previously described, an upward net force on the particle out of the liquid."

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Kozo created the water galss design below. The meniscus forms in the rear column while the glass water level is flat. If someone has Kozo's book could you add his description.










Below is David Bailey's water glass blow down valve installed on an Accucraft site glass.


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## Chris Scott (Jan 2, 2008)

Posted By Greg Elmassian on 19 Feb 2013 07:28 PM 
I think a float might work in 1:1, but in 1:20.3, the meniscus of the water is so "strong" since the diameter of the glass is small. I believe that it's too strong force a to overcome with the small float you would need and the gravitational attraction on such a small float. 

A larger float, like a longer thin hollow tube might work, more "force" to overcome this, but heck, it's so small to begin with. As previously mentioned, any contaminants would just cause more issues. 

Greg 


Greg:
The float would need to be small enough to move freely atop the water. I'm not sure why the float need overcome the strong meniscus since we want the float to float. If the float did overcome the meniscus entirely (the surface tension) it would sink not float. As I gather from looking into using a float the picture above of the ball floating shows altering the cohesion/adhesion pushing the ball up supporting the ball. As mentioned in one piece I read replying to a reference to a float and to gravity , ".. unless you're talking about the moon's effects on tides" it doesn't really materially apply to this.









I think in this micro-to-nano world a small enough and appropriate float of the right characteristics can be found. As far as the glass tube diameter the Accucraft fitting fits ~4mm OD qnd too small an ID. But a 5mm thin wall glass would seem a good first to try. But the Accucraft glass collar nut would have to be drilled out a little. 

This all may be academic but it makes for a good thought experiment. 


Sidebar;
To improve the water flow in the site glass fittings I cross drill a second couple of holes in the banjo bolt in the top fitting. The factory holes are 3mm, I drilled the second holes 2mm dia. perpendicular to the factory holes and about 3mm lower to maintain the strength of the bolt. Be careful when tightening the banjo bolt that you don't break it. The bolt will seal fine. Use a fresh washer, if it's paper soak it in oil.


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## Semper Vaporo (Jan 2, 2008)

Posted By Chris Scott on 22 Feb 2013 04:00 PM 

The principle is cohesion and adhesion of the water and glass molecules. The glass adhesion is stronger than the water's surface cohesion. 












Reading the true water level pretty impossible.









Adding a float, below a ball, "The positive buoyancy seen in the drawing [A] results in, as previously described, an upward net force on the particle out of the liquid."

*







*


Kozo created the water glass design below. The meniscus forms in the rear column while the glass water level is flat. If someone has Kozo's book could you add his description.











(SNIP) 










I have to admit that I am confused by some of what you have said. I agree that Adhesion is greater than Cohesion. Water "Wets" glass and will climb up (adhere) the glass against gravity holding it down (toward the center of the earth) by the cohesion of the water to itself. 

But gravity also would affect a float in the same way. Whether the "float" floats or sinks depends on the relative mass of the water and the float. But it it weren't for gravity affecting them both, they would just wander around in the 3-space of the sight glass and give no indication of the level of the water whatsoever. (Besides, if it sinks, it ain't a "FLOAT!"!)

Considering that it is a given that we want a "Float" that will be lighter than water and as such will actually do its namesake; If water also "wets" the float material then it will float lower in the water due to the weight of the water that has climbed up onto it. If water does not "wet" it, then it may set higher in the water. But no matter, it would make it easier to tell the level of the water.

You will still have the difficulty of reading the precise water level in the glass. But I contend we don't really need to know the "PRECISE" level... all we are looking for is whether the boiler is full and does not need to have water added or if it is indicating that the water level is getting low and we need to add water. It is not really a digital; "Don't add"/"Add" but an analog reading of "I am close to having too much"/"Things are copacetic"/"Better think about adding"/"Good Grief, turn on the pumps!" and "JUMP!".

The real difficulty is seeing that relatively invisible line between the water and the steam above it. Water is clear and so it steam, so it is only that narrow line between that must be detected. 

A narrow red stripe painted on the back of the glass is magnified by the liquid water and at the proper viewing angle will make the water appear as a broad red stripe and the steam above it will be a narrow stripe. 

Diagonal stripes on a card behind the glass shows the level because the angle of the stripes is reversed by the lens effect of the water and not reversed by the steam, so the viewer sees the chevron shape where the stripes abruptly change the angle of slope. There is no paralax error here because you are seeing the lines at the eye's side of the water.

A float would accomplish the same thing as being more visible than the narrow demarcation between the liquid (water) and the gas (steam).

The main thing that confuses me is the claim that the water column behind the glass would eliminate the meniscus of water in the glass. I don't believe that at all. Water wets glass no matter where it is in a complex of plumbing. The "Water column" is used on full sized boiler as a way to reduce sloshing in the water glass by presenting a more complex route for the water to travel which slows it down, but does nothing to affect the law of physics that "water seeks its own level".


One more comment. The small diameter water glass of our miniature boilers causes problems in that bubbles can form in the column of water and the adhesion of water to the glass will cause a slug of water to be above the true level of water in the boiler (a case where water is being displaced from seeking its own level by the meniscus of the water above and below the bubble). When the glass is of a larger diameter the cohesion and adhesion forces work such that a bubble will immediately work to the top and flow out of the sight glass. Inserting a brass wire in the tube tends to help break the cohesive nature (surface tension) and let bubbles flow past and up the wire and lets the water in the sight glass equal the level in the boiler.


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## zephyra (Jan 2, 2008)

Chris, photo of mill engine as promised - it is empty so the little red ball doesn't show in the sight glass but it is there (I promise).










Robert


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## Greg Elmassian (Jan 3, 2008)

Chris: 

" If the float did overcome the meniscus entirely (the surface tension) it would sink not float." 

If the float is lighter than water (which is stated) then it cannot sink. I'm just trying to overcome the extra effect of the meniscus... since it causes undue offset and "friction" in such a small area and if you are using little clearance between the float and chamber. 


Greg


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