Resettable Flashback Arrestors

[mightymig]

Hello all,

Just a quick question more as I'm about to pull the trigger on getting an oxy tank to go with my propane tank, and will then require gauges, flashback arrestors and check valves etc.

Does anybody use the resettable flashback arrestors or am I being OCD wanting to be able to check their function before using the setup?

It will sit in my garage for a while and just gives peace of mind that things still work when I go to use them with months in between.

The ones I posted below look good, but maybe too good to be true as they're *relatively* cheap to compared to others.

WDYT? What's the general consensus on flashbacks?

Cheers

 

[Erie Fred]

I use these at the regulator:

308800 Cigweld Comet F1 Super Flashback Arrestor Regulator Mount – Fuel – Collins Tools & Welding

collinstools.com.au

 

[Memmeddu]

Useless in my opinion especially with propane.
You're not getting flashbacks easily and we have regular arrestors at work none fail.
And if an arrestor comes to a point where it shuts close you're probably at the hospital already and no OXY fuel set up survived

 

[Jelly_Sheffield]

There's probably no safety advantage to a resettable type.

There's an arguable safety advantage to saving money by buying non-resettable, and thus being willing to replace them regularly.


Firstly, it's worth noting that the actual flashback arrestor element is passive in both, usually a sintered plug or labyrinthine path that allows gas to flow freely, but has enough surface area and thermal mass to cool burning gasses down extinguishing a flame front.


Secondly, both resettable and non-resettable types have the same basic failure mode:

Some dirt or corrosion gets into the body and blocks the path of either:
- the spring loaded plug that seals it when the thermal trigger is activated, or
- the check valve that prevents back-flow.

In both types, because they're not user serviceable, your only guard against that failure is to:
• scrupulously avoid contamination,
• use them only in the climatic conditions stated in the manufacturers instructions, and
• replace them as per their stated service life.

Because you can't see inside the resettable arrestor, you can't actually confirm that either of the shut-off valves is actually seating like it should, only that the mechanism that releases it to close under spring pressure is triggering.


Unfortunately it's those mechanical parts that can fail which are important with propane, as it doesn't explosively decompose in the absence of oxygen like acetylene can, so either uncontrolled release (from thermal cut-off failure) or oxygen entering the cylinder (from check valve failure) are the primary dangerous conditions in the event of an accident.

 

[Memmeddu]

There's probably no safety advantage to a resettable type.

There's an arguable safety advantage to saving money by buying non-resettable, and thus being willing to replace them regularly.


Firstly, it's worth noting that the actual flashback arrestor element is passive in both, usually a sintered plug or labyrinthine path that allows gas to flow freely, but has enough surface area and thermal mass to cool burning gasses down extinguishing a flame front.


Secondly, both resettable and non-resettable types have the same basic failure mode:

Some dirt or corrosion gets into the body and blocks the path of either:
- the spring loaded plug that seals it when the thermal trigger is activated, or
- the check valve that prevents back-flow.

In both types, because they're not user serviceable, your only guard against that failure is to:
• scrupulously avoid contamination,
• use them only in the climatic conditions stated in the manufacturers instructions, and
• replace them as per their stated service life.

Because you can't see inside the resettable arrestor, you can't actually confirm that either of the shut-off valves is actually seating like it should, only that the mechanism that releases it to close under spring pressure is triggering.


Unfortunately it's those mechanical parts that can fail which are important with propane, as it doesn't explosively decompose in the absence of oxygen like acetylene can, so either uncontrolled release (from thermal cut-off failure) or oxygen entering the cylinder (from check valve failure) are the primary dangerous conditions in the event of an accident.

And those are nowadays even less probable to happen because modern regulators from reputable manufacturer comes with built in safety devices.
Oxygen regulators have a sintered filter.
And on any type of regulator and European built cylinder have a shut off valve that closes if the bottle drops snapping the regulator (safety on the regulator high pressure tube) or cylinder valve itself but that's only on modern cylinders.
Said that the diaphragm and physics avoid the backflow as low pressure can't win high pressure and that's also why you cannot completely drain cylinders.
Said that agreeing with what you said Wich essentially translates as "you can't trust safety devices anyways".
We still have the torch itself as almost of them works due to Venturi effect, mixing chambers themselves avoid backflow.
But tragedies happens too....
Let's say an obstruction that causes to build up enough pressure in the mixing chamber here we have a favourable condition to backflow.
But I'm still convinced that any reputable manufacturer flashback arrestor will do the job but the torch at this point is destroyed (remember that we are talking about the resettable function)
Because if you reach an high enough temperature to trigger the safety hose don't even exist anymore most likely.
Operator is seriously injured and torch has already turned itself into a thermal lance and burnt to metal vapours.
Hoses will probably melt detaching from the connectors too .
We have to be realistic here and aware about what can actually happen.
Pops and hissing sounds mean you to shut off everything and check.
Ignorance kills if you neglect those signal no safety device will help you.

 

[brightspark]

I use these at the regulator:

308800 Cigweld Comet F1 Super Flashback Arrestor Regulator Mount – Fuel – Collins Tools & Welding

collinstools.com.au

i have the same type on mine but a diffrent make , its easy to test them pressurize the pipes and then shut off the bottles . slacken the regulator off and the arestor will trip due to the back pressure tighten em back up reset them check for leaks and away you go . they have tripped twice in use over 50 years ,

 

[mightymig]

There's probably no safety advantage to a resettable type.

There's an arguable safety advantage to saving money by buying non-resettable, and thus being willing to replace them regularly.


Firstly, it's worth noting that the actual flashback arrestor element is passive in both, usually a sintered plug or labyrinthine path that allows gas to flow freely, but has enough surface area and thermal mass to cool burning gasses down extinguishing a flame front.


Secondly, both resettable and non-resettable types have the same basic failure mode:

Some dirt or corrosion gets into the body and blocks the path of either:
- the spring loaded plug that seals it when the thermal trigger is activated, or
- the check valve that prevents back-flow.

In both types, because they're not user serviceable, your only guard against that failure is to:
• scrupulously avoid contamination,
• use them only in the climatic conditions stated in the manufacturers instructions, and
• replace them as per their stated service life.

Because you can't see inside the resettable arrestor, you can't actually confirm that either of the shut-off valves is actually seating like it should, only that the mechanism that releases it to close under spring pressure is triggering.


Unfortunately it's those mechanical parts that can fail which are important with propane, as it doesn't explosively decompose in the absence of oxygen like acetylene can, so either uncontrolled release (from thermal cut-off failure) or oxygen entering the cylinder (from check valve failure) are the primary dangerous conditions in the event of an accident.

Keep clean and replace them on schedule it is. Cheers.