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Re: HELP!!! I Screwed-UP

Posted By: SVP Neon Equipment
Date: Friday, 29 December 2006, at 9:43 p.m.

In Response To: Re: HELP!!! I Screwed-UP (John Anderson)

> Well, the hight voltage is already there.
> And you can't reasonably "float"
> an entire manifold and pumping system.

Unless you process using the open stopcock method you shouldn't have to worry about it. And I'm not sure what you mean by "reasonably float an entire manifold and pumping system". If there is nothing grounded in the manifold and you don't open the main stopcock while the bombarder is on where is the voltage going to go? From one electrode to the other.

> The pump itself is grounded (or should be) and
> it's not uncommon to see flashbacks going
> all the way back through a manifold, dif
> pump, and back to the mechanical pump.

If that is the case, then it is time to stop bombarding with the main stopcock open.

> It wreaks havoc on guages, o-rings, pumps, and
> it's outright dangerous IMO.

I agree, it is dangerous, but avoidable. And I don't mean by putting some type of ground in the system IMO

> Even things you think are "floating" become
> capacitively coupled to ground via the air
> around them with high voltages.

Not if there is no ground to go to.

> That's the big problem: your metal manifold parts are
> ALREADY slightly grounded by just being
> exposed to the air around them. In reality,
> it's often much worse as guage electronics
> and power supplies provide additional
> coupling. They will happily complete the
> circuit to ground for you! I say no thank
> you!!!!

I think it is safe to say that metal manifolds are a moot point between you and I.

> One person told me they isolated their
> belt-drive pump, and during a flashback the
> pulley was actually sparking between the
> motor and pump! This kind of nonsense is
> unacceptible - and entirely preventable.
> Granted, this person mostly likely had other
> contributing problems.

That is why I recommend using the cheapest belt you can find - one that does not have a metal core like the better belts do. Even so, I can see where static created by the belt may cause a problem. Yet another reason to keep the main closed whenever the bombarder is on.

> Back to Mr. Neon's unit: had his gauge tube
> been well-grounded - he'd most likely still
> have a working gauge right now.

I disagree. It's a crap shoot. I have seen gauges that have been destroyed even with a ground wire on the gauge tube. Peak voltages from an over loaded bombarder, which it would be in a flashback situation, are quite sufficient to follow more than one ground path at the same time.

> I see grounding electrodes (doesn't have to
> be an "electrode") as controlling
> a flashback discharge and putting it in a
> safe place.

I see them as a hopeful band aid fix that gives the operator a false sense of security. JMO

> I have ALWAYS had one between my
> unit being pumped, and the manifold itself.
> I now just have a piece of dumet wire
> hanging down. I never get flashback to it
> unless something goes wrong, or there is a
> lapse of attention with the spark-coil, etc.

I have NEVER used a ground of any kind exposed to the main manifold during bombarding and have never had a problem either. As for the lapse of attention, that was Mr. Neon's problem. Nothing is 100% failsafe. Accidents happen and things get broke. And I am wondering why your ground wire did not take care of your implied problem with the spark coil?

> It in no way interferes with the normal
> processing of tubes. Discharges never make
> it back to my gauges. And as I mentioned,
> you shouldn't get flashback during normal
> pumping procedures.

I agree, you should not get flashback during normal pumping procedures. But IMO having a ground inside the manifold increases the likelihood of it happening, even with a good processing procedure.

> I've visited many shops - in several
> countries. Most with a safety ground path
> and none with problems caused by it.

I have been in many shops in several countries too. And the shops that used a grounding electrode are the ones who were having flashback problems. That's just my experience.

> Just my .02 - for the safety of my
> equipment, my employees, and myself - I'd
> never operate a manifold without an
> emergency ground path.
> John

If you are that concerned about it install a redundant momentary push button 2-3 feet from the first one so the processing operator has to push each one with a separate hand. Unless they lay on the manifold (and I've seen that too) there is no way they can come in contact with the manifold while the bombarder is on. Flashback or not, they won't be near it.

(A redundant contactor is a good idea too in case one freezes in the closed position).

> I should add too:

> In Mr. Neon's case, it really doesn't matter
> where you stand on grounding electrodes
> since he normally isolates his gauge with a
> stopcock. I assume it's not even exposed to
> the manifold during bombarder operation.

> A well-grounded gauge tube would only have
> provided ground-path during a mishap, like
> the one that just occurred!!

And a well grounded gauge tube may cause a healthy flashback on a regular basis too!

Stay safe and have a great weekend and Happy New Year!

Mark

SVP Neon Equipment

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