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Re: Bombarding question

Posted By: SVP Neon Equipment
Date: Thursday, 19 November 2009, at 1:15 p.m.

In Response To: Bombarding question (caliph23)

> I'm working with some (new to me) equipment.
> 12.5kva daco bombarder, variac choke and
> alcatel pump. After preheating the tube and
> when I begin to process the tube, the
> initial arc stream isn't constant, kind of
> stumbles or pulsates. The stream evens out
> as the tube heats up or if the beginning
> pressure is less than 2mm.
> Is this normal with the variac? I never saw
> this with my old slide choke and 7.5kva. The
> vacuum pump and manifold are performing well
> and the the tubes seem to process fine.

> One other question. Can someone recommend a
> better manufacturer of ball valves? Tired of
> the cheap made in china from Lowes.
> Thanks

KVA ratings can be very misleading, depending on how the bombarder manufacturer (or equipment supplier) rates the duty cycle of the bombarder among other things. Instead of the claimed KVA, I am more interested in the secondary voltage and maximum short circuit secondary current. These are the main factors in determining the length and diameter of glass that can be processed.

Another factor to consider is, as you mentioned, what type of choke you are using. A slide choke will typically reduce bombarder output by 1% to 2%, while a DC reactor (variac choke) will reduce bombarder output by as much as 10% to 12%.

The Alcatel vacuum pump will not affect how big of a unit you can bombard, but it will affect how fast that unit is evacuated after it has been bombarded.

You did not mention the diameter and length of the unit or units you are having this problem with, so it is difficult to give any specific recommendations. However, based on what you did say it sounds like you are trying to process too much glass at one time for the particular bombarder/choke combo you have.

Mark

SVP Neon Equipment

Messages In This Thread

• Bombarding question -- caliph23 -- Monday, 16 November 2009, at 9:31 p.m.
  • Re: Bombarding question -- SVP Neon Equipment -- Thursday, 19 November 2009, at 1:15 p.m.
    • Re: Bombarding question -- caliph23 -- Thursday, 19 November 2009, at 2:39 p.m.
      • Re: Bombarding question -- SVP Neon Equipment -- Thursday, 19 November 2009, at 5:41 p.m.

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