When are flashback arrestors needed?
 

I have been using a torch since 2005 but am suddenly a bit confused about when flashback arrestors and check valves are needed. I have never used either of these things on my current setup which is a Mini CC with a 10 lpm concentrator and a propane tank with regulator. I’m getting ready to buy a new torch and want to make sure that I do things right. After doing some research, this is what I’m lead to believe:

Pre-mix torches MUST have flashback arrestors installed.

Surface mix torches don’t need flashback arrestors, but it is a good idea to have one installed on the fuel hose.

A flashback arrestor should not be used on an oxygen concentrator hose. Is this true even with a pre-mix torch?

Never even heard of a check valve until today. Are these necessary?

Can somebody clear things up for me please?

I have a German burner (not a Herbert Arnold) that uses propane, oxygen, and air. The manufacturer recommends a check valve in the air line to prevent oxygen from backing up into the air supply line.

I would say that flashback arrestors are usually paired with check valves. Flashback occurs when the oxygen flows into the fuel line (and less frequently, when the fuel flows into the oxygen line, since oxygen pressures are generally higher than fuel pressures ... until the tank runs out). Check valves prevent the reverse flow of gas and flashback arrestors dissipate the heat of the flame flowing through them, so by that description, they both have a function in preventing a flashback from reaching the cylinders.

I would guess that a check valve would not be favored with an oxygen concentrator since it is an additional pressure drop.

Careful with the terminology and how its used... A "flashback arrestor" is by nature a check valve.... And it does not stop the transfer of heat, it stops the reverse flow of gasses so they do not intermix and explode as a fame front travels back down hose (or torch body) ....

A "fire check" is constructed as a screen of porous materials that is dense enough the fuel gas (natural gas or propane) can flow through it at molecular level but a flame front can not pass through it.... And constructed differently then a check valve... And is generally used with natural gas supplies at levels local utility company supplies it at (pressure to low for gas pressure to open a "check valve" flashback arrestor)...

Dale

Thank you both for your input!