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Comment by Roark66 | Hacker News Reader

It is a very interesting thread, but reading 100+ pages of a forum thread to find the details of the project is _hard_.

I would definitely like to read a detailed description of his pump unit.

I've read it before and it's got some cracking info in there. One of my favourite bits was him using propane as a purge gas to get better quality brazed joints, though interestingly he baulks at the idea of using propane as a refrigerant gas!

Sounds dangerous.

It's a standard refrigerant gas for some settings:

https://www.agas.com/uk/products-and-services/refrigerants/r...

No the brazing sounds dangerous. How does it not ignite?? Brazing is done with high heat open flame. Unless it's just for back purging? But that sounds even more dangerous - intentionally building up a propane resivoir behind the braze.

Probably because you need sufficient oxygen for combustion. The propane would only ignite where it comes out and mixes. Once the flame travels into the purged pipe it will probably die out for lack of oxygen.

Ticklish though I'm sure to do it properly and safely.

It would only ignite where you already want a flame so who cares?

Where is the propane going when used as a purge? If it stays in the pipe, you may create an explosive mixture. If it doesn't stay in the pipe, you might create a fireball in your face.

The propose of a purge is to ensure there is nothing other than the purge gas, so there won't be an explosive mixture

Propane is not an explosive. Environmental concerns aside, millions of people burn propane each day all over the world relatively safely, explosion isn't really the leading concern.

You may be thinking of acetylene. But that isn't really that dangerous in modern usage either.

Propane air mixtures can be explosive in the right measure. Less energetic than acetylene of course.

It doesn't have to explode to burn you though. Where is the purge gas escaping when used this way?

Virtually anything is explosive when combined with air or oxygen in the correct quantity. Non-dairy creamer is an explosive under that definition.

I have no idea what you mean by "purge gas".

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