There is a little more to this than has been posted so far.
SuperFlash does not sell a flashback arrestor that works with low
pressure natural gas at this time. After reading Todd’s post I called
SuperFlash and asked their Sales Manager for the specific DGN model
(there are several in the series) that works with low pressure
natural gas and he said there isn’t one. They do have a flashback
arrestor that has A fittings that starts to crack at.85 psi but, as
with most other UL Listed flashback arrestors gas pressure needs to
be between 1-3 psi (it varies by manufacturer) to get a steady gas
flow to the torch. Whether they make one in the future or not remains
to be seen but there isn’t such a device at the moment.
The only device that reliably protects the gas meter in the event of
a flashback is a listed combination flashback arrestor check valve.
“Listed” as defined by the National Fire Protection Association
(NFPA) means tested and approved by a recognized organization such as
UL, CSA, etc.
I know this because a couple years ago the NYC gas utility hired an
Aurora, IL company that specializes in product failure analysis
Engineering Systems, Inc. http://www.esi-website.com/ to test check
valve and flashback arrestor devices to determine which ones were
effective in preventing torch flashbacks from blowing up gas meters.
In NYC several jewelers had exploded their gas meters and the problem
continues…the most recent being on 35th Street a couple months ago
(as well as a jeweler in NJ who blew up his meter in February).
ESI determined that only UL listed flashback arrestors worked all
the time and in each case the minimum cracking pressure was at least
1 psi, sometimes more. There are devices advertised as working with
low pressure natural gas but most often these are check valves or are
not UL listed.
Check valves are designed to keep high-pressure oxygen from flowing
into the natural gas pipe but they are not designed to handle the
5,000F flame of a flashback. When a flashback reaches a check valve
it most often melts and the flashback continues to the gas meter.
In NYC the Fire Code was changed to require listed combination
flashback arrestor checkvalves on torches connected to the gas pipe
but in every case they were found to block gas flow across the
variety of flashback arrestors that jewelers purchased. Interestingly
some claimed to have found flashback arrestor check valves that
worked with low pressure gas but upon investigation it was found that
they had bought the UL listed device then drilled it out, defeating
the protection capability, but to the Fire Inspector it looked OK.
You had to actually disconnect it to know it had been drilled.
So right now if you want to put a UL listed flashback arrestor on
your torch you need at least 1 psi to get good performance, perhaps
more pressure depending on the whose device you buy. In areas where
the gas infrastructure is older you may get only 1/4 psi (also
referred to as 7 inches water column) while in areas with newer gas
pipelines you may get as much as 2 psi. The only way to know for sure
is to install the flashback arrestor and see if your torch lights.
If you have low gas pressure then a G-TEC Torch Booster will supply
the pressure you need to make the flashback arrestor work
properly…we have many individual jewelers using our boosters as
well as schools such as Metalwerx, North Bennet Street School, George
Brown College in Toronto (135 benches) and we will be installing a
system for Fashion Institute of Technology (62 benches) in NY this
You can find out more about Torch Boosters here www.safe-t-gas.com
click on NYC Jewelers if you are in New York, everyone else should
click on Jewelry Manufacturing. Call or write if you have questions.