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Re: Grounding Electrodes

Posted By: SVP Neon Equipment
Date: Wednesday, 30 March 2011, at 12:05 p.m.

In Response To: Grounding Electrodes (Dana)


This board has been almost dead lately, so why not...

> I have never experienced a flashback
> situation and I am sure the grounding
> electrode is the reason.

Are you sure you would have a flaskback without the grounding electrode? If there is no path to ground, why would you? As you stated, what you are seeing now is a "controlled flashback." Personally, I prefer not to have ANY flashback, which is why I don't have a grounding electrode in my system and why I don't recommend them. But using one or not seems to be personal preference more than anything. If having a controlled flashback makes you feel safer than not having any at all, then you should use a grounding electrode.

> Connection of KF fittings is merely a
> channel-clamp that maintains slight pressure
> on an ‘O’ ring between ground-face parts
> so there is virtually no stress of compression
> on the parts.

I disagree with "there is virtually no stress of compression on the parts". Have you ever looked at a clamped glass KF flange with a polariscope? You should. You may change your opinion about there not being any stress in the glass. Any clamped piece of glass will have induced stress. The question is, how much stress? That depends on how much the clamp is tightened, how well the clamp "fits" and/or is positioned around the flange and how well the flange was annealed when it was made. (Neither Transco nor Eurocom - the two companies who use glass KF flanges on their manifolds - use a correct glass flange clamp). If you tighten the clamp enough to make a good seal, which should be enough to obtain at least a 20% compression factor, there will be a significant amount of stress in the glass flange.

Btw, the "face" of a glass KF flange is not ground. It is tooled, unless they have realized the error in their ways and have started lapping them after they have been tooled. And if the tooling is not clean, or is worn, etc., the face of the flange will not be smooth enough to make a good seal unless it is lapped. But this is easy enough to check. Just look at the face of the flange in good light. If there are tooling marks on the face rather than perfectly smooth glass you will see them. And if the face has been lapped it will have a dull frosted looking appearance.

Mark

> Some comments on an old subject?

> Because my Transco manifold was setup that
> way, it came with a grounding electrode
> installed by default on the debris trap.

> It connects directly to the ground, which I
> provided a dedicated dual 8’ copper
> electrode system connected with #6 wire.

> I have never owned one without it, but it
> seems to me by having this sort of
> 'controlled flashback' it would prevent a
> possibly dangerous situation.

> When the tube is first heated, there is an
> obvious arc stream to the electrode and as
> it is heated the stream begins to drop away.

> I have never experienced a flashback
> situation and I am sure the grounding
> electrode is the reason.

> Transco manifolds – they use KF fittings
> between major parts. This has proven to be
> one of the finest features of the unit. It
> makes it completely expandable with standard
> vacuum fittings. I imagine it added several
> dollars to the cost of the glasswork, but
> the serviceability is greater.

> Connection of KF fittings is merely a
> channel-clamp that maintains slight pressure
> on an ‘O’ ring between ground-face parts so
> there is virtually no stress of compression
> on the parts.


SVP Neon Equipment

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