cnidocyte
Hazard to Others
Posts: 214
Registered: 7-7-2010
Member Is Offline
Mood: No Mood
|
|
Height for a general purpose fume cupboard
I'm setting up a tiny lab in my shed but the shed also happens to be tiny (if I recall correctly its 1.9m in height, 80cm in width and about 3m in
length) so all the lab is going to consist of is a fume cupboard and a few shelves. I built the frame but I realize now that the fume cupboard is only
70cm in height, 70cm in width and about 60cm in depth. Did I skimp on the height of the fume cupboard a bit too much? There is at least a meter of
space underneath it which I was going to use for shelves but I'd be better off expanding the fume cupboard wouldn't I? Considering I have about 1m of
space leftover what height would you recommend I make it in order to use it as a general purpose chemistry workspace?
BTW I'll borrow a camera tomorrow and post pics.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
My hood internal working height is right at 100cm. This has been adequate for my needs, so far, after 5 years of use, but I wouldn't want it any
shorter. And I generally use 19/22 tapered glassware which is smaller than the more standard 24/40 tapered glassware.
|
|
|
cnidocyte
Hazard to Others
Posts: 214
Registered: 7-7-2010
Member Is Offline
Mood: No Mood
|
|
Thanks. I'm gonna expand it to 1m, that will still leave a bit of shelf space underneath. BTW what are the other dimensions of your hood?
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
depth = 55cm; width = 122cm
(122cm (4 ft) is a standard sliding window width in the US. This window (double pane, tempered glass) can very advantageously be fit up to that
width.)
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
I have found the length of condensers to be the limiting factor for determining the minimum hood clearances. A smaller hood is much easier to use if
your condensers are 100 or 200 mm instead of the more common 300 mm. This somewhat limits the scale of reactions, but a 24/40 Friedrichs condenser
will fit into a small hood and still allow larger scale reactions, say up to a 1 liter flask.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
A lot of kitchen units and surfaces are made to a standard height of 900mm, which is around comfortable work height. I'm not that tall and 700 would
get under my tits.
If you're having trouble with condensers, consider getting something like this and have the condenser point vertically down.
I would also recommend you invest in some gas wash heads if you'll be working with things that require a fume hood. You should aim to chemically
neutralize fumes as they leave the glass and only rely on the hood for accidents or handling; e.g. HCl(g), scrub it through a strong base solution to
immediately salt it out.
I had a 600mm B24 condenser at one point, but virtually all of what went through it condensed in the first few inches. Should space be an issue, got a
more expensive condenser, like a coil, double coil, jacketed coil etc. I found one of those car coolers being thrown out. And a garden pump in a
similar state. Both were absolutely fine. I run my condenser from that. I don't switch the cooler on, I just make use of it's insulation.
I fill a bunch of squash / fizzy drinks bottles with water and freeze them, then chuck them into the car cooler to get ice cold water through the
condenser. Works a charm, 90% of the vapor is liquid as soon as it hits the coil of my much shorter 300mm.
If you're doing liters and liters a day through B24+, you could grab an old freezer from the dump, stick a bin in it, fill it with anti-freeze and
cool packs, drill two holes in the top and do the same - heavy duty style.
[Edited on 8-7-2010 by peach]
|
|
|
quicksilver
International Hazard
Posts: 1820
Registered: 7-9-2005
Location: Inches from the keyboard....
Member Is Offline
Mood: ~-=SWINGS=-~
|
|
What may be important to your efforts is the "wrap height" of the surrounding portion of the fume hood. Most of the time fumes do not "settle" and
move from the originating container up & out via any gentle fan providing a vortex to pull the fumes into a chute or "chimney".
However, some poisonous materiel is rather heavy and will settle (classically observed in the mixture of things from fulmination or thick brown NOx).
Therefore the area that you place your hands should be minimized and perhaps the interior should be raised to place the standing vessels upward into
the hood.
EDIT:
The Gas-wash head are quite lovely; had I known about them I would have bought several as I stuck with 24/40 in the overwhelming majority of my glass
items. I believe they are a great idea.
[Edited on 8-7-2010 by quicksilver]
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by quicksilver  |
EDIT:
The Gas-wash head are quite lovely; had I known about them I would have bought several as I stuck with 24/40 in the overwhelming majority of my glass
items. I believe they are a great idea.
[Edited on 8-7-2010 by quicksilver] |
I can't even remember why I got mine, but boy o' boy am I glad I did. They can turn something horribly dangerous into something harmless or tasty,
with next to no effort. And they can be used for so many other things, like gassing a substrate or venting an inert atmosphere through some drying
agent. They fit in a draw and they cost next to nothing compared to a fume hood, yet out perform them in my opinion.
Two things I don't like about standard heads.
1.) They need frits on them. The normal bubble kind are quite shit; usable, but not good enough IMO.
2.) I don't like having a set length on the downtube, as it often won't submerge or won't fit in some bits of glass. I'd prefer it if the glass was
replaced with a barb, so I could attack some custom length tygon etc to it and dangle the frit at whatever height I liked.
3.) I said two, but here's a third. I have quickfit branded heads, I think they're the older kind, and the connection points are long, slender, angled
tubes. They're too easy to snap and actually seem to encourage back siphoning and other annoying tricks. Get ones with short push ons. They should be
barbed really, but the smooth kind work if the tubing is grippy / elastic. They are quite closely related to handling dangerous gases however, so
barbs would be nice. Also, use clear tubing, and some of those little hose clips if you can.
4.) Adding yet more, it might be worth adding a little active carbon to a wash mix to improve gas absorption. I haven't tried this yet, but it seems
like it'd help a lot, by providing trillions of pores to hold the bubbles in the solution.
Wash heads, ROCK.
[Edited on 8-7-2010 by peach]
|
|
|
quicksilver
International Hazard
Posts: 1820
Registered: 7-9-2005
Location: Inches from the keyboard....
Member Is Offline
Mood: ~-=SWINGS=-~
|
|
Ideally, a PORTABLE fume hood concept would be the outstanding. I've thought about that at one time and came up with a variety of ideas. Primarily
because I pack my toys up and away after I'm done, generally.
No, I don't like having a set length on down-tube construction either but I take advantage of things like that to make sure that bastard doesn't
stick.  GREASE THAT BAD BOY!
I have actually tried to repair broken glass & that is one pain in the butt agenda.
I've tried to replace all my tubing with either glass or Teflon (where possible). The clear stuff gets nasty too fast for my taste as I pack the gear
up and don't use it for a long period. I don't like to "mother-Hen" my equipment; I really put from my mind when not playing around.
edit:
How much do those gas wash heads cost (generally)?
[Edited on 8-7-2010 by quicksilver]
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
Not sure, mine were about £15 I think, but they were Quickfits on special offer. They're also not very good. I think they're an old version. I'm
sending them off to have them modified. I want the inlet / outlet shortening to a stub that won't snap off, I want them straight and I want frits on
the down tubes; an open ended tube is far from great. I've had fritted heads before, they work a lot better.
I think they are fairly expensive new if you buy them from a normal supplier. But having at least one to hand can be so helpful.
One will be good for reactions where it's a liquid / liquid or liquid / solid that exhausts something nasty. If you're dealing with a gas / liquid
reaction that vents nasty things, you want two (one for the reaction and one for the scrubber).
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
