Making bursting discs 3

[mingki]

Hi, I will make round plates which bursts when it reaches to a certain pressure(13kgf/cm2) and I am thinking the required processes at the moment.
Here is what I think.
There are two round(100mm diameter, 0.5mm thickness) plate(Stainless 316L) and I will make 50mm diameter dome(dome height: 10mm) in the center of those round plates.
The difference of those two plates is that the dome of one plate shall be formed by pressured air(10kgf/cm2 at 22?) and the dome of the other plate shall be formed by pressurized hydraulic oil(10kgf/cm2 at 50?). Which way will be more stable and the better way to form the dome of those plates?

 

[KENAT]

I'd be tempted to use hydraulic, if for no other reason than safety.

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[rogerbours]

Please note that such critical safety devices are covered by legislation and design codes; specialized manufacturers are to be consulted for such parts instead of experimenting. peoples safety and equipment integrity depend on these items whereas many individual operating parameters may influence the correct functioning.

 

[rb1957]

the oil would be much more effective in forming the part ... any liquid would be less compressible than air.

how will this dome limit the working pressure ?

a more tpical way would be introducing a stress concentration, like a sharp notch.

 

[jpankask]

There are manufacturer's who specialize in making rupture disks. You should obtain these materials from one of them rather than try to make it yourself. Much safer, more effective and probably quicker.

 

[rb1957]

for those who don't know (included me till a few moments ago), 1 kgf/cm2 is just about 1 atm ... yeah it's probably exactly 100/101.325 atm. so over the area in question we're applying just about 1 ton, which equals <10ksi shear stress around the perimeter.

structural fuzes are tricky things to build ... typically build a sharp notch so the panel will fail when you want it to, But you need to check that it won't fail in-service particularly if there're repeated loadings ...

 

[rb1957]

i guess i'd suggest a notch (something like 1/2 the thickness)along a diameter, maybe only over the middle 1/2, on the tension side of the membrane, maybe a pair of notches crossing to make a nice looking cross ??

 

[KENAT]

What's the application?

First thing I thought of was high speed wind tunnels, where they basically scribe an X or similar in the plate as I recall.

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[SnTMan]

I don't have any first hand with this, but..

From interivewing with a couple of rupture disc companies in the past I know that there is a fair amount of art involved, including the "proving" of a disc or panel by test, before making a run of them.

I doubt a novice would get very close the first few times.


Regards,

Mike

 

[btrueblood]

Most industrial burst disc houses won't even look at making discs below a certain size/pressure limit. There is just too much irrepeatability in very thin sheets of material, and difficulty in creating the scribe lines to consistent depths.

There are (probably patented) burst disc designs that use a mechanical (think diaprhagm and pop-thru belleville spring) trigger element to provide a "snap" action at a specified pressure, said snap action driving a punch thru the disk to give a positive burst at a very narrow range of very low pressures. Used for vacuum conveying systems that unload railroad grain or powder-carrying hopper cars.

 

[SnTMan]

The thing is, they have to not fail without fail, until they need to fail, again, without fail.

Regards,

Mike

 

[Compositepro]

Low pressure rupture discs are often made from heavy gauge sheet that has been dished and the sheared through most of the way around except for periodic tabs holding it in place. The tabs break under pressure. A thin foil disc acts as the sealing membrane and is supported by the main disc. These also have to be protected from vacuum which would reverse the dish in the disc.

 

[ginsoakedboy]

mingki,

Get in touch with the people at Fike. You may find this link useful:

http://www.fike.com/products/rupturediscs.asp

 

[unclesyd]

Depending on your application you may want an explosion vent panel or disk. If the application requires an RD you should look at a reverse buckling disk or vent. It the process requires a precise high speed rupture you should look at a reverse buckling with knife edges.
If your process will allow it an explosion vent will be cheaper than a RD of any type.

The link to Fike is good place to start. You might checkout BS&B

http://www.bsbsystems.com/explosion_vents/vent-saf_explosion_vents-77-1015.html