Sciencemadness Discussion Board

Nightmare called "filling tight tubes"

Endimion17 - 18-2-2012 at 12:49

Please don't laught at the title...
Here's the problem. Let's suppose you want to build a thermometer. How do you stuff the liquid inside, at home, without strong vacuum?

What if the tube one is trying to fill is not a thermometer, but a pressure reading device, curved, or looped, once, twice? It's fairly easy for tubes wider than 2-3 mm (you can agitate them so the liquid falls through), but when it gets tighter, the liquid plugs the air inside. Good luck with agitating that...

I supposed that an industrial process with mercury thermometers would be to seal the end of a tube into a bulb and blow out a little container for the liquid, vacuuming the tube and then filling it by letting the atmosphere push in the liquid... but how to do this at home?
All I can think of are two procedures:

a) help with partial vacuum (syringe) and agitation
b) tiny, flexible, slick tube for introducing it into the tube and pulling it gradually out while filling the apparatus (yeah, fantasy world, I know:()

I'm thinking of making one instrument soon, and knowing just how difficult it is to fill a simple straight barometer tube with a 2 mm bore, the thought of working with looped capillaries makes me sick. :(

Hexavalent - 18-2-2012 at 14:53

I appreciate your desire to make your own items and I hold respect for home-made apparatus, but perhaps some things are just better bought?

-Hexavalent

Endimion17 - 18-2-2012 at 16:01

That's true for very complicated things that require precise ammalgamation of flameworking and graduation, but things I'm planning to make aren't one of those.
One thing I'm planning to make is either commercially available, relatively expensive and shoddy, or extremely expensive, and another thing is just plain expensive.
I've got elementary flameworking and woodworking skills, materials and tools. Haven't got much time, but that's the least important thing here.

And I think that a properly built apparatus is always better than a crappy one from some Chinese manufacturer. Plus, you get to know how something's done and you get the satisfaction.

I'll probably go with the first option, but I'd like to read more opinions on this problem.

bfesser - 18-2-2012 at 16:10

Could you be more specific? What exactly are you trying to construct?

Endimion17 - 18-2-2012 at 16:40

I can't, I'm sorry. It's a project for YouTube. I can only say it involves tubes and flameworking. That's not a problem at all. Only stuffing the liquid inside. I think I'll have to find a refrigerator pump somewhere. That's the best vacuum I can create at home.

bfesser - 18-2-2012 at 17:09

Quote: Originally posted by Endimion17  
b) tiny, flexible, slick tube for introducing it into the tube and pulling it gradually out while filling the apparatus (yeah, fantasy world, I know:()


What is the exact inside diameter of the capillary you're trying to fill, and what's the total length. I have some very thin PTFE and other fluorinated polymer tubing around here somewhere . . . if I can find one to spec. I will mail a length of it to you. I rarely find use for it. In fact, one of the few times I remember using it was to inject silver-laden thermal grease into the bottom of a long thin stainless tube while repairing a digital thermometer for a school--very similar to your intention. I could also source syringes (plastic or glass) and needles to fit tubing, if needed. They would have to be at cost, however.

Panache - 18-2-2012 at 18:01

A disposable pippette can be stretched out ridiculously thinly given careful heat and a few attempts, then the hg can be forced through it after you have stuck it in, obviously it wouldn't have much use under suction. Also try some of that shrink wrap electrical insulation, it comes in thin diameters and is polyolefinnic in nature i believe.

Endimion17 - 19-2-2012 at 07:36

Quote: Originally posted by bfesser  
What is the exact inside diameter of the capillary you're trying to fill, and what's the total length. I have some very thin PTFE and other fluorinated polymer tubing around here somewhere . . . if I can find one to spec. I will mail a length of it to you. I rarely find use for it. In fact, one of the few times I remember using it was to inject silver-laden thermal grease into the bottom of a long thin stainless tube while repairing a digital thermometer for a school--very similar to your intention. I could also source syringes (plastic or glass) and needles to fit tubing, if needed. They would have to be at cost, however.


I'm still not sure because I don't have the tubes with me (there's a handful of tubes with different bores), but I think I've ran out of long enough tubes with 2 mm bores while building a barometer. There might be only 1.5 and less than that in the box, going down to <0.5 mm.
The length of one tube will be around 50 cm, and another one (later project) perhaps 70 cm or a bit longer.

Thank you, I will consider your offer. I'll try with the vacuum first and let you know what came out of it.
Quote: Originally posted by Panache  
A disposable pippette can be stretched out ridiculously thinly given careful heat and a few attempts, then the hg can be forced through it after you have stuck it in, obviously it wouldn't have much use under suction. Also try some of that shrink wrap electrical insulation, it comes in thin diameters and is polyolefinnic in nature i believe.


Thanks, I totally forgot about those pippettes. Yeah, their stretching can be a nuisance, but could come in handy this time.
It might work even better than the shrink wrap, but I'll keep that in mind, too.

Wizzard - 19-2-2012 at 19:49

You should be able to allow the material to condense inside the vessel from a gas. Given enough time, it will work it's way in there eventually!

bquirky - 20-2-2012 at 01:08

id use a syringe to suck through your tube i often have to get UV curable glue up inside some glass capillarity and find this works well.

i often loosely attach the syringe to the capillary by means of a series of small tubes loosely sealed with blue tack or some other soft squishy substance it takes very very little suction to fill up the capilary

Endimion17 - 20-2-2012 at 06:34

Quote: Originally posted by Wizzard  
You should be able to allow the material to condense inside the vessel from a gas. Given enough time, it will work it's way in there eventually!


That would work if the vessel wasn't essentially a flask with a 1 mm wide and 70 cm long curved neck. It's impossible to fill it with any fluid like that, let alone mercury.
OK, it would be possible if I had a leak-tight chamber with a thermostat and few years worth of heating. :D
Quote: Originally posted by bquirky  
id use a syringe to suck through your tube i often have to get UV curable glue up inside some glass capillarity and find this works well.

i often loosely attach the syringe to the capillary by means of a series of small tubes loosely sealed with blue tack or some other soft squishy substance it takes very very little suction to fill up the capilary


The capillary is sealed at one end, so I've got one opened end only. No straw action here...

Wizzard - 20-2-2012 at 08:08

@Endimon- Cool the far end of the tube in ice, and heat the sealed end with the liquid- Even at 70cm, with enough insulation I can't see it taking more than a few days with any STP liquid.

Endimion17 - 20-2-2012 at 08:13

That would be too demanding even for diethyl ether, I'm sure of it.

GreenD - 20-2-2012 at 08:37

I would say what has already been suggested, if the tube is large enough in diameter, use either a long needle or flame-stretch a pippette and (very analytically) load your liquid.

This will need the steadiest of hands to do it without getting air pockets!

White Yeti - 1-4-2012 at 13:27

Do you think you can shove a solid through the capillary, or is it too thin for that as well? If you replaced the air in your capillary with CO2 and then managed to get a moist piece of KOH at the bottom of your capillary, you could get a reaction that would create a partial vacuum:
KOH +CO2---> KHCO3

Then, you can draw whatever liquid you need up the capillary.

I don't think you need to worry about the KOH eating through the glass.

peach - 1-4-2012 at 14:26

Quote:
Good luck with agitating that...


Try an electric toothbrush, or something else that's designed to vibrate. ;)

It may not work but, for some things, it works really well. You may have to play around with the positioning and force to strike the correct note.

Same thing is done with concrete when big foundation slabs are being poured - vibrating probe (petrol powered in this instance) is poked in to shake the air pockets out. Same for investment cast moulds in plaster, but this time using a vibrating table under a bell jar (with a vacuum pulled in it to get even better bubble removal).

Vibrating concrete poker


Vibrating investment casting bench


[Edited on 1-4-2012 by peach]