I have searched repeatedly on the Orchid forums for reference to this
problem. No where did I see any reference to the safety of fans in
relation to the exhausting of gases (propane in my case) from the
soldering area.
Grainger Supply would not sell me a shaded pole vent fan (squirrel
cage) because I told them I would be exhausting small amounts of
propane when bleeding my hoses. The sparks from the electric motor
could cause problems (I guess he means they could ignite).
On this forum I have seen references to in line fans, muffin fans,
bathroom fans, Attic fans, stove venting fans and Jenn-Air fans. As I
understand in all of these, the motor is in contact with the exhaust
fumes. Is this is a serious problem?
The only fans I can find for exhausting flammable gases are very
expensive and much more fan than I need. At another studio which I
shared, I used a squirrel cage type fan mounted right next to my
soldering area for 10 years with no problems.
This fan is for a small studio in my basement. I will be storing the
Propane outside and copper plumbing it in with a turn off. Natural
gas is not possible in my situation. My furnace guy will set this up
for me, but he doesn’t know what type of fan to use for exhausting
gases and fumes.
I was taught to use turn off the bottle valve and light the torch to
bleed the lines. Then you are not directly venting the flammable
gasses.
You should be able to use a standard exhaust fan. Even venting
un-burnt propane with a proper vent fan running it should be hard to
get the propane above 2% concentration required for ignition.
Nobody will sell you an open frame/open, motor to insert in the fume
stream of explosive gases. When told that what you are going to use
it for. The salesman not knowing exactly what you are talking about
using it for. This is due to our litigious world. You may not think
of suing but your remaining family might. The air/fuel mixture has
to be the right mixture only once for a nice boom. As per the cable
news this morning with a gas explosion at a house in Ill. Using a
squirrel cage fan with the motor outside the exhaust stream would
solve your problem. I have a small spray booth in the basement I
used an old dyer motor/fan unit that was hooked to the dryer vent
that dumped outside.
Here are two sites that will give you some info on vent ducting and
fume removal equipment. Spend some time looking and reading the
catalog section. and will be able to educate yourself enough to make
a choice. As you are not doing large volumes of fume generation (ie
production work) a fan unit that has a couple of cubic feet per
minute air flow would work. air flow is measured in cubic feet per
minute. Kimberley Adams has a section in her book on setting up a
vent system for lampworking beads. The complete book of glass
beadmaking from Lark books http://www.teksupply.com TekSupply Has
exhaust fans of all descriptions. http://www.AllElectronics.com Has
surplus type fans and other equipment
The above info is for educational purposes, no warranties expressed
or implied Also all the legal mumbo jumbo about the the web sites
above. Just a long term satisfied customer.
The essential, rhetorical question to answer your question (try
writing THAT again!) is: Why would you be exhausting flammable gases?
Are you going to have leaky tanks? Are you going to leave your
torches open all the time? This is what got the Grainger guy. You see,
you are not exhasting flammable gases per se, you are exhausting
fumes. When you say what you said, you meant (unknowingly) that you
were going to exhaust a room full of gas, as in an industrial gas
plant, and you need a TEFC motor for that. What you are really doing,
though, is ventilating a room, which you can do with about any fan
you like. Since there is gas present (like in your kitchen), it would
be smart to have some “natural” ventilation, too, like for at night or
when you are away, so gas can’t build up in the room. What they call
“vents” - there are many kinds - can do that, so you always have a
crossdraft even when the room is closed up. The point to understand,
and about the Grainger guy: The level of gas at which point you can
light a match in the center of the room, and it will explode, is so
high that you will likely be suffocated before that time. It takes
like a 50/50 mix of gas and air for that to happen. I’m not saying to
take it casually, but don’t be all paranoid about a little seepage,
either - careful and safe, yes - paranoid, no.
The flammable limits of propane in air are 2.4 - 9.5%, not quite the
50/50 mix mentioned below, but John’s point is still valid. Unless
you have a leak, or are leaving your torch valve open for quite long
periods of time, it is very unlikely that you will reach the
flammable limits in the ambient air. There are a couple of important
things to consider, though.
The exhaust system you’re talking about will remove air from the
room. It will be important to make sure that sufficient replacement
air comes into the work area, otherwise any exhaust will be
inefficient. An open window opposite the exhaust will often suffice.
McMaster Carr (http://www.mcmaster.com - search for part number
5159T41 ), sells a variety of hazardous location fans. Their
DC-powered fans are reasonably economical. Since they are 12 VDC, you
would also need an AC-DC converter and associated wiring. Still
cheaper than the available AC fans, I think.
One last thing that may be important to keep in mind. Propane is
heavier than air. Obviously, this means it will sink to the floor
where it will accumulate. Your exhaust system should have sufficient
airflow at the source of the propane emission to capture the gas and
vent it outside. If it doesn’t, then the gas may accumulate low in
the room where most vents won’t get at it. Now, my opinion (standard
disclaimers apply), is that you still won’t build up enough gas to
cause any problem during any reasonable usage. However, I thought
that this point was important to consider, especially since the
workroom is in your basement.
on page 188 in the hard copy catalog of “usplastic.com” there are
new zip-lock plastice bags with anti-tarnish material insides. i’m
ordering some of the four sizes they have.
I was taught to use turn off the bottle valve and light the torch
to bleed the lines. Then you are not directly venting the flammable
gasses.
This is not the best practice as you can cause a flashback when
doing this which can in extreme cases damage your hoses and or torch.
You should just bleed down each line separately with only the valve
for that line open.
Jim
James Binnion @James_Binnion
James Binnion Metal Arts
Hi Michael, a good point about the propane being heavy and sinking
to the lowest level, Years ago in my local marina a guy had a leaking
propane valve and after some weeks it collected in the bilge, on
going aboard he went to light the lamp and blew himself up, the
police said he was lucky to still be alive.
It is most unlikely that simply venting off propane hoses will
produce a sufficiently concentrated mix with the workshop air to be
explosive. However, if you are intending to vent off the propane
into a very confined area close to the fan you would be fine using
any kind of fan which doesn’t use a ‘brush-type motor’ but uses an
induction motor. This is the majority of small fans such as bathroom
vent fans. One source you might like to try is computer fans which
have brushes to produce sparks and so are completely safe for this
application. They do, however, run off 12 volts which, while being a
plus point in that the low voltage is much safer than mains, does
mean that they will have to be run off some form of
transformer/rectifier. However, the current they take is minimal and
a normal type of ‘wall wart’ plug mounted power supply will give
ample current. You can stack several fans in line if you want more
air throughput. One thing you may wish to consider if you are
seriously concerned about the risk of explosion is the switch which
operates the fan - this could produce a spark and so you should use
a ‘fire rated’ switch - over here in the UK it is referred to as an
’IP66’ type. Similarly, you should consider any other equipment
which could be in the immediate vicinity - power tools, heaters,
mobile phone (the vibrator uses an ordinary brush-type motor). For
all normal purposes it is not necessary to go to these lengths as the
amount of gas involved is too small - just vent it off slowly and
stop worrying…