Panache
International Hazard
Posts: 1290
Registered: 18-10-2007
Member Is Offline
Mood: Instead of being my deliverance, she had a resemblance to a Kat named Frankenstein
|
|
mechanical vacuum cutoff device
i use a large propane tank (1000mm x 300mm) as a vacuum reservoir for an aspirator system that is turned on/off from two locations via a standard 240v
solenoid valve.
I would like to supplement this system with a device that switches the solenoid on or off depending upon the vacuum in the tank without having to use
an electronic device as i find them quite unreliable for course vacuum work, as they get contaminated quickly. It should also be noted that i rely on
the reservoir as my safety bottle.
I have a float switch that i used to use on my large stil that reliably turns off the power when a certain height is reached, it is a commercial float
switch mechanism.
Does anyone have any ideas as to how could i use this existing mechanism to render a course but reliable vacuum cutoff/cuton?
if photos would help of the whole shebang as it currently exists i will gladly whack some up.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
Here's something that would likely work, but it's probably more than you want to spend. Maybe it will give you some ideas.
http://www.dwyer-inst.com/Products/Product.cfm?Group_ID=268&...
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Panache  | | Does anyone have any ideas as to how could i use this existing mechanism to render a course but reliable vacuum cutoff/cuton? |
One of the earliest electric manostats, possibly the first, uses a mercury barometer, one electrode in the reservoir, and one at a
target pressure height.
|
|
|
densest
Hazard to Others
Posts: 359
Registered: 1-10-2005
Location: in the lehr
Member Is Offline
Mood: slowly warming to strain point
|
|
There are ways to protect a vacuum switch from contamination: absorbent traps, liquid U-tubes, diaphragms, filters, pinhole blocks, etc. Just putting
5 or 10 feet of capillary tubing between the tank and the switch might solve your problem. It would help if you knew what the contaminants were?
Gummy, corrosive, solvents, ??? Many of the switches use buna-N rubber diaphragms or O-rings so blocking substances that degrade rubber would probably
fix your problem. If it's something gummy then an inline trap filled with glass wool or equivalent would work. If it's vapor,, an absorbent trap and a
long line could help. It all depends on what the exact problem(s) are.
|
|
|
Panache
International Hazard
Posts: 1290
Registered: 18-10-2007
Member Is Offline
Mood: Instead of being my deliverance, she had a resemblance to a Kat named Frankenstein
|
|
| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by Panache | | Does anyone have any ideas as to how could i use this existing mechanism to render a course but reliable vacuum cutoff/cuton? |
One of the earliest electric manostats, possibly the first, uses a mercury barometer, one electrode in the reservoir, and one at a
target pressure height. |
ah like this piece i have been saving for reference! this one is for temperature but the same deal applies i guess, i'll try that first, because its
ridiculously simple.
|
|
|
aonomus
Hazard to Others
Posts: 361
Registered: 18-10-2009
Location: Toronto, Canada
Member Is Offline
Mood: Refluxing
|
|
As terrible as this sounds, could you not open up a vacuum gauge, and add in a small microswitch to trip at a certain vacuum level?
|
|
|
Intergalactic_Captain
Hazard to Others
Posts: 228
Registered: 4-9-2004
Location: somewhere where i don\'t know where i am
Member Is Offline
Mood: frabjous
|
|
From what I gather, you want to control your current solenoid shutoffs electronicly via an electonic sensor? Sorry for the rambling explanation to
come, but I'm sure some members here are NOT renters and may appreciate it...
About 18 months ago, my water heater (gas) died and I had to figure out what was up. The last plumber that was called (while I was away, or I'd have
done the job myself) ended up charging us for $600 for what equated to babysitting a space-heater for 4 hours and replacing $12 worth of parts (and
"upgrading" a custom-made, milled, aluminum filter bracket with a piece of sheatmetal shit) - So, I said fuck it and decided to fix it myself.
Checked the valves and relays, everything in the controller circuitry, the powervent blower, all the tubing, and everything checked out fine....After
a day or two of head-scratching, I realized I missed only one thing - The pressure switch. You see, after pondering the schematics, I saw that when
the temp sensor kicked "on," the powervent turned on, which (should have) tripped the pressure switch, which then tripped a relay which opened the
main burner valve - Everything else was fine, so the weak link had to be the pressure switch... I pulled the tubing between the blower and the
switch, blowed into it, nothing... In a flash of insight, I sucked on it, and the main blower kicked on - Pulled the switch, disassembled it, and
weakened the spring (heated it with a lighter to kill the temper in the middle third of it)...Been working fine since then....
...So, that said, I'd look into something along the lines of a water-heater pressure switch. They are made in both positive and negative pressure
varieties, and can be modified incredibly easily by selectively weakening or replacing the spring. In this way, you'll have a robust, easy to install
switch (you'll still need a relay to your solenoid) that can be found relatively cheap on the second-hand market. It's electromechanical, but none of
the electrical circuitry will be "naked" in your setup - Just make sure the diaphragm material is compatible with your needs, though it shouldn't be
hard to diy one after you take a look at how they work...
If you see me running, try to keep up.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
Here yar go, found this one years ago, enjoy me hearty.... ARRRRr.... can I get an arrrr on that arrr?
{edit}Incidentally, connecting a vacuum gauge to a 60ml syringe, I have managed to pull a100mBar and below vacuum with one pull of the plunger. And
produce over 100psi of positive pressure in the reverse direction. Actually, I managed 150psi, before the hose connecting the two looked like a
balloon.
[Edited on 6-10-2010 by peach]
|
|
|
Texium
|
Thread Moved
19-11-2023 at 16:06 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
