Odd question - what is the most staining gas/smoke you've worked with?

[some bloke]

TL;DR

I work with a very poor system for detecting leaks, and would like to improve it.

I am trying to work out if there is any guide anywhere to the fineness of smoke particles. Where I work we use incence cones to detect leaks in sheets of material, because it stains it where it leaks through, but most of the time it seems the holes are too small. I have been told we used to use cigarettes in the 80's but had to stop for obvious reasons!

Is there some guide or measurement which will help me to gauge the particle size of smoke? Would oil on the incence be likely to offer an improvement (smoke from a frying pan I imagine has a very fine size).

I am also considering using an indicator (methyl red, as smoke is supposedly PH5.5) to try and reveal invisible stains.

Any advice on this would be greatly appreciated!

 

[some bloke]

[Mentor Note -- Two similar threads merged]

I work with a very poor system for detecting leaks, and I'd like to improve it.

The system is that the known leaking part is put in a rig which pumps smoke through it, from incence cones, and these are supposed to stain the part where the air is getting through, making it easy to locate. Problem is, the smoke doesn't stain most of the time.

We can't use bubbles because we need to dissect it and still see where the stain is. Ths prompts my question - what is the mot staining smoke or gas you've worked with? The thin which wasn't worth cleaning because the walls were brown within minutes? Does such a thing exist?

Currently we burn incence cones, which occasionally work. I know there's got to be a better option out there, so I'm calling on the wealth of experience on here for guidance!

 

[berkeman]

Can you maybe use gas leak detection instead, to get around the particle size issue? Maybe like a Helium gas leak detection system of some sort?

https://showcase.ulvac.co.jp/en/how-to/product-knowledge07/testmethod.html

 

[DaveE]

I would look into fluorescent dyes instead of smoke. Much easier to see with UV illumination. There are lots of google links for "gas leak detection with fluorescent stains".

 

[Tom.G]

Summary:: I work with a very poor system for detecting leaks, and would like to improve it.

Is there some guide or measurement which will help me to gauge the particle size of smoke?

https://www.aafintl.com/-/media/fil...aaf-technote-tobacco-smoke-gpf-8-103b-new.pdf

https://pubmed.ncbi.nlm.nih.gov/2751166

(above found with:
http://www.google.com/search?&q=particle+size+cigarette+smoke)

Cheers,
Tom

 

[some bloke]

Thankyou for the responses!
@berkeman I am not really certain of how the helium detection would work for this. We already have a method for determining where hte leak is coming out of the part, but we need to leave a stained trail behind so that when we dissect the part (and thus can no longer use leaking gas to detect the location) we can see exactly the path the leak took.

@DaveE I looked into the google results for this, without the quotes it was all referring to liquids and not gases, and with the quotes, the only on-sponsored link was to this thread!

@Tom.G We used to use cigarettes a long time ago, that's the sort of info I've already found, but I've now taken what you've shwon me and found further studies on incence particle sizes, and it does seem that cigarettes have smaller particles. That said, I don't know whether the cigarettes actually worked better or if it's the rose-tinted glasses going on!

 

[anorlunda]

We already have a method for determining where hte leak is coming out of the part, but we need to leave a stained trail behind so that when we dissect the part (and thus can no longer use leaking gas to detect the location) we can see exactly the path the leak took.

Won't that depend on the material and the surface of the leaking part as much as it depends on the gas?

Have you considered using electric charge, analogous to what they do with paint spraying and powder coating?

 

[some bloke]

Won't that depend on the material and the surface of the leaking part as much as it depends on the gas?

Have you considered using electric charge, analogous to what they do with paint spraying and powder coating?

I had not. It is true that different materials seem to stain better...

To the google! (Thanks!)

 

[Baluncore]

I am also considering using an indicator (methyl red, as smoke is supposedly PH5.5) to try and reveal invisible stains.

You might consider iodine vapour to lay a track through a fracture or failed seal.
Use stable 127 iodine. I am NOT suggesting radioactive iodine.
Iodine vapour is a universal developer for differential detection of faded or hidden writing.

 

[some bloke]

You might consider iodine vapour to lay a track through a fracture or failed seal.
Use stable 127 iodine. I am NOT suggesting radioactive iodine.
Iodine vapour is a universal developer for differential detection of faded or hidden writing.

I've just done some research on iodine vapour staining in response to this, and I must say it seems a bit beyond my knowledge! Cn you summarise how it works? The sites and documents I've found are full of acronyms without glossaries!

 

[Baluncore]

We already have a method for determining where hte leak is coming out of the part, but we need to leave a stained trail behind so that when we dissect the part (and thus can no longer use leaking gas to detect the location) we can see exactly the path the leak took.

The age old art of Thin-Layer Chromatography, TLC, employs molecular diffusion velocity, often along a strip or sheet of paper, to separate different compounds.
https://en.wikipedia.org/wiki/Thin-layer_chromatography
Iodine is widely used as a universal developer because it forms complexes with many organic compounds. Secret writing on paper was once detected with an iodine stripe test, since it would develop all known invisible inks being used at the time.

You have not identified the materials you are working with. What are the solid materials involved? Is the material black or white? What is the fluid that leaks?

Once you have identified a leak, you can justify investment in a more expensive process as part of the investigation, to highlight the path taken.

For crack detection, a drop of solvent containing a dye is used. That can wick along a leak path, then the solvent evaporates at the surface, to mark the entry and exit. But you are looking for the path so you could use a vapour or liquid, driven by capillary or differential pressure to carry a compound along the path. You could then stain that trail if needed.

Vacuum impregnation is a low cost technology. You might fill the path with a fluid polymer, such as cyanoacrylate super glue, then dissolve the parent material to reveal the tree structure of the leakage path.