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Re: filling pressure
Posted By: SVP Neon Equipment In Response To: Re: filling pressure (George Vidas)
Date: Sunday, 28 April 2013, at 1:19 p.m.
> 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 originally made by John Anderson, posted a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.I'm usually the one to split hairs, but on this one I'm not.
Over the years there have been several similar charts all claiming to be "ideal" for various reasons, and all seem to have different recommended filling pressures. Well, they can't all be ideal and it appears this one is also based on calculations and equations rather than real-world results. Yes, I know that John claims he has been using this chart for years with good results. But what was he comparing his results to? But I digress.
I have been using an old Acme Transformer Company filling chart since I started in business more than 35 years ago without issue. I have made countless units of all varieties, sizes and colors, and I know hundreds of other shops who have done the same with near identical charts from different transformer mfgs., all with excellent results. John pointed out this stereotype stating "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". My questions are: According to who, and to accomplish what?
On units less than 4-5 ft. I have always used the old rule of thumb for short tubes under 4 ft. to add one mm more pressure for every foot under 4 ft. for a given diameter, not some filling pressure up in the stratosphere somewhere that will actually diminish light output. And I have always used the same pressure for both neon and Hg units of the same diameter with out issue.
One example is a window sign I made one time that included a 10mm red unit with 1.5 ft. of glass. I used 12mm short electrodes and, as an experiment, put 1 mm *less* gas pressure in it than the chart called for. The Acme chart called for 13mm pressure. Had I gone by the old rule of thumb, I would have put in 16mm. But instead I put in 12mm. The tube lasted 7 years. Had I put in the 16mm pressure it would probably have lasted at least 15 years. But I will admit, if I had put in the 24mm pressure that this chart recommends it would have lasted even longer, although it would have been dimmer than the other tubes and would have looked out of place.
Some of the other things that caught my eye in John's comments are:
>"Also, it neon and argon/Hg have different ideal filling pressures."
I cannot think of one thing in our industry that is "ideal". This is no exception. Once the unit (neon or argon - take your pick) has been in service for a few years, the fill pressure is no longer "ideal".
>"Give this chart a try if you're looking for something a little better."
How much better? Units filled to the "ideal" pressures stated on this chart *might* be marginally more efficient (which is debatable), and they *might" last a little longer. But this brings me back to my opening comment about splitting hairs.
I just wanted to make some quick comments on the subject. Each of you will have to decide which chart is best for you. While deciding, keep this in mind: Somewhere down the road if another shop, who happens to use a "standard" filling chart like 99% of neon shops do in the U.S., repairs one of your "ideal" units, they will not put the same pressure in it as you did, because it is not the accepted norm in the U.S.
Well, I've got a lot of dismantling and packing left to do, so I'd better get to it.
Mark
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