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Meco midget


#1

I have a Meco Midget torch that I purchased from Otto Frei. It came
with check valves that I installed between the torch hoses and
regulators. Do I also need flashback arresters between the torch
body and hoses? If so, what is the difference between flashback
arresters and check valves and why do I need both. I know that there
is a similar Orchid discussion going right now, but I lost track of
it and it doesn’t seem to address this specific question. As always,
thanks. Rob


#2

Generally speaking for bench soldering running lower gas pressures
check valves should be all you’d need.

Flashback arrestors are built differently (inside) than check
valves. Each serves a different purpose. Check valves operate by
only allowing gas flow in one direction. from the gas source to the
Torch. Often a spring diaphragm inside the check valve opens when
gas flows the from the source to the Torch. Gas trying to flow
’backwards,’ e. g., back to the source, is blocked by the valve
mechanism. Flashback arresters generally have a gas filtering
element made of sintered metal, layers of mesh or ceramic beads.
These filters easily pass gas but will extinguish a flame. Both
types of arrestors are used (should be used) on higher pressure
Torches for casting and/or traditional Torch welding. ‘Check’ valves
may not act fast enough to prevent a flame from propagating to the
regulator (called a flashback) so the added protection of a
flashback arrestors, one in the fuel line and another on the oxygen
line, is a good policy when higher pressures are run to the Torch.
High pressure (industrial)Torches often have the arrestors attached
at the Torch but that’s unhandy for most jewelry making situations.
Some companies make ‘combined’ arrestor incorporating a check valve
and flashback arrestor in the same unit which is handy. The Meco
Midget is a a well made Torch and paying attention to always -fully-
turning gasses on / off in the correct order is the best safety
First policy.

Richard Paille
Paige Tools


#3

Yes you HAVE to have the arrester installed. Check valves have their
purpose but do not protect you from a explosive situation. spend the
extra money to save your life and property…

Panama Bay Jewelers


#4

I’m curious… has anyone here ever had a torch flashback and start
a fire or have an explosion?

Jo Haemer
timothywgreen.com


#5

No. But then i try to not do things that would. In my other life, we
had an ambulance burst into fire caused by vapors igniting in an
oxygen atmosphere. No deaths but one paramedic critically burned.

John


#6
I'm curious.... has anyone here ever had a torch flashback and
start a fire or have an explosion? 

Well seeing as I use propane only torches, flash back hasn’t been an
issue.

When you add oxygen, then it’s very necessary to have the safeties
as part of the set up.

I have heard of flash back, but don’t know anyone personally that
has experienced it. The stories I usually hear are more about people
not following safety procedures when hooking up gas appliances.

Regards Charles A.


#7

38 years and counting, in myriad of locations and none here.


#8

No because if there had been a flashback I wouldn;t be alive to tell
you so. BOOM I use the protective attachments always they cost very
little compared to eternal rest.

Teri


#9

Jo Asked

I'm curious.... has anyone here ever had a torch flashback and
start a fire or have an explosion? 

Not with a Jeweler’s torch, but I have seen it and treated burned
welders who were using Oxy-acetylene cutting torches that had a
flashback burn through the acetylene hose (and then the oxygen hose)
leaving the hose jetting a flame until the tank was shut off when I
worked health and safety at Montreal Locomotive Works. Rather
nasty… But those torches were working at higher pressures than you
would be seeing on small torch.

Kay

PS yes it would have been great if flashback arrestors would have
been in common use back then, but they were just starting to be used
and could not handle the volume of gas needed to cut 2 and 3 inch
plate…


#10
I'm curious.... has anyone here ever had a torch flashback and
start a fire or have an explosion? 

It happened on Jeweler’s Row in Chicago:

Elaine


#11

I think people get a little out of hand with this stuff. I’ve never
had any problems and have known no one who has and I’ve worked many
jobs involving torches. These baby torches for our trade there is
such a small hose size and orafice size that I don’t think you could
make an explosion happen, besides filling a balloon with oxy-propane
and igniting it with a cigarette on a long stick, which I don’t
condone but would have to watch if it was happening near me. ;).

Turn off your gas first and the flame snuffs out.


#12
These baby torches for our trade there is such a small hose size
and orafice size that I don't think you could make an explosion
happen, besides filling a balloon with oxy-propane and igniting it
with a cigarette on a long stick, which I don't condone but would
have to watch if it was happening near me. ;). 

In the late 70s/early 80s, I worked for a retail store in the
Fairlane Town Center mall in Dearborn Michigan (store is now long
closed). Ours was, I think, one of the first of a trend of stores in
malls, where a certain percentage of merchandise was made in shop,
and of course, the usual range of repairs and custom work, but unlike
most stores, our shop was right out front, with windows to the mall
so passers-by could watch us work (or pretend to). It was a bit like
working in a fish bowl, with resulting temptations. Occasionally,
there’d be boredom, which we young fools would take advantage of.
Baked apples in the burnout oven, or pretending to be taking a phone
call, chatting on the phone while pretending to solder something on a
ring while customers on the other side of the window watched.
Distracted, the ring would start to melt into a puddle with customers
sometimes trying to call our attention to the disaster in front of
them (It would be a scrap ring, of course). Then there were the
quarters soldered to a tack, and hammered into the linoleum tile out
front, so we could watch people try and pick them up. But one such
stupid stunt we only tried once, was just what you describe. We were
running acetylene and oxygen in Little torches, with a Meco Midget
for casting. Set the oxy/acetylene mix to neutral on a little torch,
dip the tip in a glass of water to extinguish the flame without
changing the valves, and fill a small ziplock bag with the mix.
Seal, set it on the floor, and hit it with the relit torch. All in
the name of science and curiosity, of course. The resulting bang was
REALLY loud. Apparently, mall security, located just around the
corner from us, was convinced they’d heard a gunshot. Probably a
bunch of them no doubt; and came racing around the corner to the
store, guns drawn, perhaps expecting a gunfighte!! Needless to say,
we had a bit of seriously white lie to invent real fast. And we
didn’t do that again.

The wonder of all these stunts is that we kept our jobs. Maybe it
was just the times, or maybe, unbeknownst to us, either the boss was
just as much a cutup kid at heart as we were, or we were good enough
goldsmiths when not screwing around, that he forgave us. Memories…

Peter


#13
It happened on Jeweler's Row in Chicago:
http://www.ganoksin.com/gnkurl/ep813y 

It wasn’t a torch flashback, though. A faulty leaking propane tank,
and the leaked propane found a spark somewhere. As I recall, it was
when the shop itself was closed…


#14
It happened on Jeweler's Row in Chicago:
http://www.ganoksin.com/gnkurl/ep813y 

So, does anyone know what it was that caused the propane tank to
explode?

alonzo


#15

This article actually says they don’t know why the explosion occurred.


#16

article says nothing about How the tank exploded, or how the fire
started. if not sure please refrain from posting these articles
under this or any article non connected with the subject at hand.

Hratch
Atelier Hratch Babikian contemporary Jewelery and sculpture


#17
This article actually says they don't know why the explosion
occurred. 

Well, using a 20 lb propane tank indoors was surely part of the
problem.

Elaine


#18
We were running acetylene and oxygen in Little torches, with a Meco
Midget for casting. Set the oxy/acetylene mix to neutral on a
little torch, dip the tip in a glass of water to extinguish the
flame without changing the valves, and fill a small ziplock bag
with the mix. 

I know you can still buy “Super Elastic Bubble Plastic.” Works much
better than a ziplock.

Paf Dvorak


#19

Jo,

I have in the distant past had an acetylene torch pop and back burn
as they call it. The torch body got hot quite quickly but simply
turning off the valves on the torch put out the flame in the torch
body.

The back burn will sometimes make a shrill whistle from the torch
tip. The first sign that all is not right.

I can’t remember what caused the burn back, probably something
stupid on my part no doubt.

I have never heard of one causing an explosion that would blow the
torch body apart but I would imagine it could be possible under the
right conditions.

There are arresters that are available that consists of the
acetylene going through a water chamber to prevent a flame from
reaching the bottle itself.

I am in the habit of turning off the gas first then the oxygen,
sometimes a pop will be heard. It usually gets the cat off of the
couch in a hurry.

Be safe,
Gary D.


#20

This article actually says they don’t know why the explosion
occurred.

Well, using a 20 lb propane tank indoors was surely part of the
problem. 

one of the followup articles mentioned it was a hundred pound or
hundred gallon (forget which) size tank. Definatly large enough to
really go big boooom. And most certainly not something they should
have had in the building…