We have experienced a border failure and are hopeing someone here can shed some light on why. We wrapped a gas station canopy with about 250 (2 rows upper and lower of 15 mm clear red glass. It has been up about 1 year. So far we have had maybe 12 units fail. We used EGL 15cm electrodes, and processed on a Transco Ultra Vac with milliamp meter and Signum temperature guage according to EGL instructions. The problem is that the electrodes are falling off. They are cracking, sometimes at the insulator line,sometimes at the weld. We have used the same bender for the last four years without a problem. Any Ideas? Thank you for your time.
You mentioned that all the failures were a result of the electrode cracking or the weld coming apart. If some failed with no evidence of glass failure please let me know and I will be glad to cover that as well. If they were all caused by the type of glass failure indicated, then it has nothing to do with fill pressure.
The electrode glass cracking around the ceramic collar may be a result of over processing the electrodes (getting them too hot for too long). It may also be a manufacturing quality control issue. Another possibility is, EGL does not use anything to keep the collar from coming in contact with the glass jacket. If there is contact of the collar with the glass during processing it will cause a "hot spot" in the glass and create a stress point in that area. This may cause the glass to crack immediately, or at a later time (months or even years later - called fatigue failure). Another possibility for cracked electrode glass is rough handling, particularly with certain brands of electrodes. With EGL electrodes, because there is no provision to prevent the ceramic collar from "hitting" the glass, rough handling may cause the collar to scratch the glass on the inside. This can have the same effect as scratching the glass on the outside: Once the glass is scratched perpendicular to its length it doesn't take much force to crack it.
Regarding the welds coming apart, this is usually a result of bending technique unless the electrode and tubing glasses are incompatible for some reason. But considering this is clear red border tubing I will assume there are no glass incompatibility issues. After your bender seals the electrode to the end of the tube, is he/she in the habit of rolling the weld on the table in an attempt to "smooth out" the weld? If so, this may be the problem as it induces a great deal of stress in the glass in the heated area. Similar to above, the failure (the weld coming apart) may occur almost immediately, or some time after the tube is in service. There may be other causes too, but again, it is usually a result of bender technique.
Concerning the inaccuracies of the butyl phthalate oil U-gauge manometer that Mike mentioned (if you are using a U-gauge and not a dial gauge), I firmly disagree. If the interior surface of the U-gauge glass is clean and clean butyl phthalate oil is used, after filling a unit the oil will "zero" in several seconds. If it doesn't, the surface tension on the oil is too great, which brings us back to not having clean glass and oil. (Actually, these days most shops use a silicone oil instead of butyl phthalate). Dirty glass/oil is usually the case as neon manifolds are rarely maintained as they should be. With that said, if the manifold is not maintained as it should be you will have even greater problems with accuracy using an analog dial gauge. All things being equal, the U-gauge manometer is by far the most accurate and reliable instrument to measure fill pressures.
If you need further assistance please feel free to contact me directly. My contact info is below and may also be found on our website, which is listed below as well. And if you would like your bender to try a different brand of electrodes I will be glad to send them a generous free sample pack.
Mark Snyder
SVP Neon Equipment
113 Leventis Drive
Suite A
Columbia, SC 29209
803-783-1165
www.svpneon.com
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Hello
Most of the time it is a under pumped unit or the unit is pumped too fast we add 1mm of pressure more than needed, if your neon person/pumper is using a butilfilate gauge the butilfilate in the gauge will not read the right mm of pressure after the third or forth pumped unit the liquid hangs on the side of the tube and starts to give false readings. look at it next time you pump more than five units in a row it will not be zero in. check it befor you start to pump it will be at zero then pump a few and the liquid will be under the line.
good luck
and keep bending
Mike
NSW Systems LLC.