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Re: filling pressure
Posted By: George Vidas In Response To: filling pressure (Bill's neon)
Date: Saturday, 27 April 2013, at 12:25 a.m.
> I'm looking for current charts for different
> recommended filling pressures for each
> diameter of glass for the following gases> 80%argon and 20%neon with mercury
> and also for 100%neon
> Thanks!
I've been using this chart (see link below), originally made by John Anderson, posted a year+ ago to the neon mailing list. I took the liberty of adding the Torr conversion, since he was kind enough to pass around an editable PDF.
The decimal places on the Torr numbers are kind of like the way we all know the body temperature as "97.1" degrees Celsius: it's a falsely precise number due to the conversion. The fill pressures given in mbar were probably rounded, the ones in Torr weren't.
His original email, describing the chart:
I've posted this before a couple of years ago. I've corrected the error that was on the 9mm tube size. This chart is based on the European sign association's research (which I think is the same both Marcus and Dave are referring to). I derived this chart from some that data Marcus sent me a copy of 10 years ago. There data was in centimeters, so I've translated to something I think is a little easier to use for a US based shop.
Under each diameter tube, you will see 4 bars. Each bar approximates a 1ft, 2ft, 3ft, or >4ft tube. Just pick the value that most closely approximates your unit length. If you've been using one of the old US charts some of the transformer mfgs made years ago, you'll probably be surprised at how MUCH overfilling you need to do as a unit gets shorter. Also, it neon and argon/Hg have different ideal filling pressures.
Give this chart a try if you're looking for something a little better. I've used it for a decade now and it really becomes pretty easy to use with practice. I've also had a lot of chance to see the long-term operation of many hundreds of short tubes filled with these levels, and I've been very pleased.
One caution!!! Units are in Millibar, NOT torr. If your filling gauge is in torr (or millimeters Hg), you need to multiply each of these numbers by 0.75 to convert. If someone wants to do the math on this, I'd be happy to make an additional chart in the torr scale. If you are using a u-gauge, you can of course create your own scale in mbar. In this case, multiply torr by 1 torr = 1.3332 to convert to mbar. I used mbar because that's the scale my Edward's gauge was in.
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