Hiraoka Style Sight Glass

[Wrecks]

I'm putting the boiler fittings on my Climax locomotive. When I pressurized the boiler with air to test the fittings for leaks, the water level gauge sight glass leaked. When I tightened the gland nuts, the glass broke. Same thing again after replacing the glass. I think the glass receiver clearance was too small, so I opened it up a little. Now it works fine and the sight glass doesn't leak.

This got me thinking though. That glass is really fragile. What if the sight glass breaks when the boiler is steamed up? I'm imagining a jet of water and steam in the face of the operator. That makes me want to figure out how to add ball check valves to the gauge. Can someone talk me down from this? This design without ball checks is used on all the Kozo locomotives, so it must be ok, but I have this image...

[crueby]

You want free flow of water/steam both ways through the sight glass or it wont work properly. Often there is even a blowdown valve at the bottom to clear sediment and air bubbles, that needs free flowing too. If there are check valves either end, the glass water level wont move as the water level changes.

[uuu]

There are commercial items available, so you can look at the pictures and try and get an idea.  https://maccmodels.co.uk/shop/live-steam-fittings/3-cock-water-gauges/1-4-x-40-3-cock-water-gauge-left-hand-2/

These ones use a PTFE seal on the shut-off cocks.  The same maker does them with linked levers, so you can shut off both ends at the same time.

They do stick out a bit more than the plain gauges, so potentially it makes them more vulnerable.

You could consider a guard glass instead, to both protect the gauge, and deflect the water-steam in the case of breakage.

Clearly with or without the shut-off cocks, you need a quick way of dousing or dropping the fire.  Gauges have been broken at our club and it's not as much of a drama as you might imagine.

Wilf

[Wrecks]

You want free flow of water/steam both ways through the sight glass or it wont work properly. Often there is even a blowdown valve at the bottom to clear sediment and air bubbles, that needs free flowing too. If there are check valves either end, the glass water level wont move as the water level changes.

I was thinking of a loose ball in an oversize tube. When there is minimal pressure drop through the tube, as in normal operation, ball would roll freely. If the glass breaks, the ball would be blown to the end of the tube and seal it.  This wouldn't work if there were a blowdown valve, but Kozo didn't provide that on many of his designs.

[Wrecks]

There are commercial items available, so you can look at the pictures and try and get an idea.  https://maccmodels.co.uk/shop/live-steam-fittings/3-cock-water-gauges/1-4-x-40-3-cock-water-gauge-left-hand-2/

These ones use a PTFE seal on the shut-off cocks.  The same maker does them with linked levers, so you can shut off both ends at the same time.

They do stick out a bit more than the plain gauges, so potentially it makes them more vulnerable.

You could consider a guard glass instead, to both protect the gauge, and deflect the water-steam in the case of breakage.

Clearly with or without the shut-off cocks, you need a quick way of dousing or dropping the fire.  Gauges have been broken at our club and it's not as much of a drama as you might imagine.

Wilf

I like the guard idea. I might do that. And the not much drama thing is what I was hoping to hear, so I might just leave it alone. Gonna have to think about it, I guess.

[steamer]

There are commercial items available, so you can look at the pictures and try and get an idea.  https://maccmodels.co.uk/shop/live-steam-fittings/3-cock-water-gauges/1-4-x-40-3-cock-water-gauge-left-hand-2/

These ones use a PTFE seal on the shut-off cocks.  The same maker does them with linked levers, so you can shut off both ends at the same time.

They do stick out a bit more than the plain gauges, so potentially it makes them more vulnerable.

You could consider a guard glass instead, to both protect the gauge, and deflect the water-steam in the case of breakage.

Clearly with or without the shut-off cocks, you need a quick way of dousing or dropping the fire.  Gauges have been broken at our club and it's not as much of a drama as you might imagine.

Wilf

I like the guard idea. I might do that. And the not much drama thing is what I was hoping to hear, so I might just leave it alone. Gonna have to think about it, I guess.

While full scale stop valves are great,  getting them to work reliably in scale is a problem.   You are much better off with a guard glass and a manual stop valve top and bottom.   Small ball checks can get gummed/plugged up and not work correctly in scale.    Kozo actually did an article on this and how to handle a broken glass in use,  poke around in his book and I'm sure you will find the article.

Dave