making laminated glass tubes

Actually I first thought of filling the gap with a viscous liquid like glycerol or silicone oil.

A test explosion of a 1 cm OD pressure tube shattered a 60mm OD borosilicate glass tube with 7mm wall to rather large pieces. I think, if the outer tube were not struck by the glass fragments of the pressure tube, the protective glass tube will withstand the shock wave. The pressure in the pressure tube (10mm OD, 5.5mm ID) may exceed 200bar. It was up to 240 bar without breaking.

With a laminated glass tube, is there a possibility that the glass will crack from thermal expansion of the resin layer? The resin also should not separate from the glass as this would create additional optical surfaces which decrease optical transparency.

Bernhard

Really, in glass? What is the application?

"Double bagging" seems a fool's errand. Things just cascade until the energy is absorbed. You must disperse the energy, such as through a stainless mesh.

I'm a pretty adventurous soul, but I wouldn't keep those tubes anywhere near me....

In the British Science Museum located in London, there is an exhibit using liquid carbon dioxide in a glass tube. It is used to demonstrate what happens when the triple point temperature is exceeded. As the tube is heated, the interface between liquid and gas becomes invisible.

AFAIK that may have been around for over a hundred years. Why not find out what they do and how they protect the public?

Bill

1. Substitute another liquid and tell the customers it's CO2. It can even be a fluorocarbon that will demonstrate the triple point, but at a lower pressure.
2. Use concentric PC tubes and test, test, test. (But visibility will be reduced.)
3. Embed in solid transparent polymer and provide a pressure relief at one end.
4. Use pressure rated steam boiler sight tubes and pass on the liability to the manufacturer.
5. Buy lots of liability insurance.

DB

To demonstrate the critical point. There's an image of one on

.> "Double bagging" seems a fool's errand. Things just cascade until the > energy is absorbed. The technology is applied in e.g. car windows.

I believe, a glass tube can take the pressure of the CO2 shock wave. Only the splinters that hit the tube make it break, and the pressure then drives the splinters away. But liquid or resin layer between 2 concentric glass tubes will prevent splinters hitting the outer glass tube and disperse the impact pressure evenly.

Maybe it doesn't actually matter much, what middle layer I use. But if the device breaks from external force a simple (viscous) liquid filler would not hold the pieces together and then it might be dangerous if the pressure tube exploded.

The protective tube shall be completely clear to allow good vision of the critical point events.

Bernhard

Thought of that. C2F6 has a slightly to low Tc. CFCl3 is unavailable because it's destroys the ozone layer. And both are much more expensive than CO2 and prossibly more difficult to handle.

One PC tube would suffice, but it might fail if it degrades by age or UV.

Good idea, I thought at first. But that would make heating/cooling the pressure tube difficult.

Hmm, if they are suitable and available at reasonable cost, that might be it. I've seen laminated glass tubes as structural elements for buildings, but they'd charge me around 100 EUR for 25cm pieces.

I want to earn money, not pay. And the insurance probably would try not to pay if they could blame me. Also I want to avoid accidents.

Thanks, Bernhard

s/to/too. s/CFCl3/CClF3

Sounds like you need to do some experiments. The pressure above liquid CO2 at room temp is about 850 psi, so if you had a tank of air or nitrogen at 2000 psi, you can pressurize the tubes until they explode, or don't.

If they can take 2000 psi, good, but then you'll have to test for shock resistance, if only to cause the glass to fracture. This will test the ability of the PC shell to hold in the explosion.

Finally, you have to get some information from the PC maker on long term performance of their products. Atlas Material Testing Co, of Chicago, IL, may be able to point you in the right direction. That's what they do for a living.

Dangerous Bill

When I was an Assistant Professor of Natural Science in the College of the University of Chicago I was one of the lecturers in its physics course in 1959. We had an apparatus for displaying the critical properties of liquid CO2 to the students. It was the liquid in a glass tube that in turn was mounted in wooden box (thick side walls) with glass windows front and back. Underneath was both a heater and an air cooling device. We shone a projector light on the tube and the image was projected on a screen in the corner of the large lecture hall. If it were to explode the glass fragments would not blow out toward the students. The wooden walls were very thick. The apparatus had lasted for decades and to my knowledge never caused a problem. But it showed beautifully the disappearance and reappearance of the meniscus. Impressive display! And safe. FK

Presumably safe. We're talking in excess of 850 psi here. The designers of the device may have tested it, or maybe not, or calculated the strength of the enclosure, or not. Possibly it's only decades of good luck.

Who can predict what will happen in the long term?

Years ago, there was an incident at a lab where I worked. Plutonium

239 had been sealed in glass vials, apparently for safety reasons. A couple of decades later, the vials were retrieved from storage, and the first one touched exploded in the face of the man handling it. Alpha radiation had generated an unknown pressure of helium within the vial to a point apparently just short of the breaking strength of the glass. The area had to be enclosed and monitored before the rest of the vials could be moved and 'disarmed'.

DB