Nitrogen filled verses non-nitrogen binos
Posted 31 January 2013 - 11:28 AM
Posted 31 January 2013 - 12:04 PM
Argon is an inert gas heavier than Nitrogen (and therefore air). The rationale (I think) is that if you fill them with Argon, air cannot penetrate the binoculars (because Argon is heavier), any water and oxygen is dislodged out and no corrosion or fogging can take place. It works, but only if the seals are good. So we are back to the same story as nitrogen.
Short story. When employed as a laboratory chemist for Airco (later BOC) Specialty Gases, we were terribly concerned with obtaining the driest gas possible as a "zero" gas for our moisture analyzer. In an effort to clean up even our own, extremely dry nitrogen zero gas, which evolved from a liquid nitrogen receiver on-site, we inserted a commercially available gas drier upstream of the analyzer, which was marketed for use in removing moisture from gas chromatography supply gases in laboratories.
After a reasonable length of time, to permit the lines to purge and the moisture analyzer to settle down (about 2 days of purging), we noticed that the moisture content of the "zero" gas had actually risen considerably! We concluded that the gas drier, which contained Drierite pellets and was constructed of polycarbonate, with some type of rubber o-rings sealing threaded metal end caps, was actually contributing more moisture to the system than the gas had "undried"!
We concluded that moisture was entering through either or both of the polycarbonate cylinder walls or the rubber o-rings (which even at that time were some more exotic polymer, not just plain rubber).
Remember, this was a system which was being continually purged with extremely dry nitrogen, not a static system like that which would exist in a tire, or a bino, so moisture couldn't continue to accumulate.
In my experience, the ONLY seals which can absolutely prevent the permeation of moisture (or really any unwanted contaminant gas present outside the system) is a metal-to-metal seal...and even that has to be quite robustly compressed or even soldered/welded to do the trick. That may be how waterproof binoculars are constructed, with a metal band around the lenses which is silver soldered to the races holding them into the barrels. How they seal the glass to the metal bands is beyond me.
Posted 31 January 2013 - 12:24 PM
It is way heavier than air, and a much better electrical insulator too. I recently filled a fish tank with it and operated a problematic high voltage device on the bottom--cured the sparking! I also floated aluminum foil boats and such on the invisible surface--just nutty. But it's a greenhouse gas, and wouldn't get along well with "eco" glass.
Posted 31 January 2013 - 01:38 PM
This one started out ill-informed and has passed through silly, rediculous and inane. But now, it has emerged into the informative and potentially useful.
Posted 31 January 2013 - 03:18 PM
That's not true. The driving force for oxygen and water vapour to enter the binoculars is the difference in partial pressure of those two gases inside and outside. That difference is identical regardless of which other gas is inside the binocular.
Argon is an inert gas heavier than Nitrogen (and therefore air). The rationale (I think) is that if you fill them with Argon, air cannot penetrate the binoculars (because Argon is heavier), any water and oxygen is dislodged out and no corrosion or fogging can take place.
The only thing the argon does is to make a statement that this company has given some thought to sealing the binoculars and that if they're a reputable company you're lead to believe they've invested in better seals. There is no technical advantage to argon.
Posted 31 January 2013 - 03:59 PM
I thought it was just a thread about relatively safe poetry!
I've used bottled nitrogen regularly over the past 30 years or so for purging through industrial natural gas pipe installations to render the pipework safe for welding work and after decommissioning large installations such as in factories and warehouses when the premises are to become vacant for indefinite periods.
The first and last things that must be done before and after carrying out these types of works is to test the installations for gas tightness to prove no leakage.
For the sake of this post, to simplify the procedure to ignore situations where sections of pipework may pass,for example,both underground and outside,exposed to sunlight,when variations in temperature need to be taken into account, there are strict industry standard procedures and formulae for calculating duration of the tests, an important factor which varies proportionately to the volume of pipework involved, and the systems are left pressurised with nitrogen at whatever the test pressure happened to have been.
On several occasions I have returned to such a site after a number of months or even years, to recommission for incoming new tenants, eventually replacing the nitrogen with 100% natural gas, to find the pressure in the system the same as it was when left, indicating no discernible leakage whatsoever.
In cases of all-welded joints,this is a good example of "metal to metal seals" holding good,although in the case of screwed/threaded joints, not a single one would ever hold tight under such testing if it wasn't for the presence of gas jointing compound.
I can also think of many examples where plastic joints and fittings have held tight for many years under much higher mains water pressure.
I'm not sure what it is about WELL MADE binoculars that makes us users so paranoid about moisture ingress.
Posted 31 January 2013 - 04:01 PM
You are correct, that diffusion will continue until the inside and outside partial pressures are equal. But, in principle at least, I think there would be a difference for different gases: the diffusion will proceed more slowly, the more massive and bigger the molecule. At a given temperature, velocity varies as the inverse of the square root of the mass, so even SF6 would still be going about half as fast as N2, hardly a big effect. For Ar vs N2, the velocity difference is only 20%. The quality of the sealing would probably play a much bigger role in the duration of gas containment, than the mass of the molecules.
Pardon my, uh, hot air.
I think it's just that there's no common test to verify that a binocular actually has N2 in it that causes such merriment and discussion. But after reading Bill's real world accounts of the performance of good marine binoculars in bad conditions, my mind has been set much more at ease about this. How was I supposed to know, unless somebody told me? BillC does it a again.
Posted 31 January 2013 - 04:46 PM
PS ALSO, please remember there are many instruments out there touted as "good marine binoculars," when, in fact, it's all a sham, like all those plastic-based ZOOM binoculars that are sold as "Military."
"Buyer Beware" does not BEGIN to cover the need. How is a person to know? Find a friend who does, and is willing to put his reputation behind his words. That's where the rubber meets the road.
Posted 31 January 2013 - 04:49 PM
I believe that the reason for nitrogen has everything to do with taking advantage of differential gas densities to completely purge the desiccators that are used during manufacturing. N2 has a higher density than H2O vapor. So when they purge the desiccators, they introduce pressurized, dry nitrogen (very cheap and easy to produce) at the bottom and force gas out the top, where any lingering H2O vapor would be hanging out. This has everything to do with keeping the manufacturing environment dry and nothing about the end-product having nitrogen-filled tubes. They could use any gas that is heavier than H2O vapor, but N2 is the most abundant and therefore cheapest.
A similar technique is used when running reactions that involve pyrophoric chemicals (chemicals that spontaneously combust when the contact water). You flow the inert gas in from the bottom, to get maximum evacuation of the water vapor from the reaction vessel. Trust me, it's important. I have scars to prove it. Thankfully, they are only mental scars - I was wearing gloves and a lab coat.
Edit: I appear to have the direction wrong. These devices are more complex than our little chemistry setup was. http://www.terrauniv...e-desiccator...
Posted 31 January 2013 - 05:37 PM
The debate surrounded the question" What is the optimum PRESSURE at which nitrogen ought to be introduced to purge out a large installation containing natural gas in order to ensure or maximise as far as practically possible the COMPLETE displacement of the combustible gas".
The two main opposing schools of thoughts were thus:
1. It is possible,if TOO HIGH a pressure/velocity is applied, for the nitrogen to "force" the natural gas to the outer perimeters of the inside of the pipe, making it possible to leave significant traces of the potentially combustible gas remaining in spite of methane sensing instruments ( called Gascoseekers) placed at the outlets reading less than 1% GAS ( or 20% Lower Explosive Limit - limits being between 5% and 15% in AIR ).
2. The HIGHER the purging pressure/ nitrogen velocity, the more thorough the purging operation will be.
The latter was proven to be correct.
Posted 31 January 2013 - 05:46 PM
Very interesting to read your comments on purging pipe. I imagine those considerations are big-time important before you contemplate putting an acetylene torch to a pipe that had pressurized, flammable substances flowing through it!
Posted 31 January 2013 - 07:01 PM
As you implied,it's ONE thing sitting around well crafted tables in plush surroundings,wearing expensive suits,drinking fine coffee from the best china cups,TALKING about a potential problem,but it can be somewhat different out on the front line,freezing private parts off or sweating like a pig,heart beating like a drum,whilst actually putting the theories into practice,knowing that any mistake can literally spell the end of existence for more than just yourself.
Of course,repairing binoculars is not quite such a potential "life and death" profession,but again,there are far fewer people who actually carry out the work professionally than there are who seem to enjoy speculating about it!
Posted 31 January 2013 - 07:13 PM
Posted 01 February 2013 - 09:25 AM
- Bicycle inner tubes are an example of the diffusion of air through butyl rubber. A standard 700C-23 tire pumped to 120psi will lose enough pressure that it will need to be pumped up within a week or so. Bicycle tires are operating at high pressures, with large surface areas, are quite thin and the enclosed volume is relatively small.
- Binoculars are quite a different situation. There is very little pressure differential driving the diffusion, there may be none. I suspect Jarrod is correct, the reason for the purging is to dry the internals of the binoculars, the purpose of the O-Rings is the prevent moisture from entering the binoculars.
In my line of work, when I want something to be really dry, I hook it up to a vacuum pump and pull it down to micron levels...
Posted 01 February 2013 - 01:33 PM