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Re: HELP!!! I Screwed-UP
Posted By: John Anderson In Response To: Re: HELP!!! I Screwed-UP (SVP Neon Equipment)
Date: Friday, 29 December 2006, at 5:37 p.m.
> Sorry, I have to disagree with those
> recommendations. Grounding wires attached to
> metal gauge tube body's and grounding
> electrodes in the manifold system induce
> high voltage discharge to unwanted areas,
> not prevent it.Well, the hight voltage is already there. And you can't reasonably "float" an entire manifold and pumping system. 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. It wreaks havoc on guages, o-rings, pumps, and it's outright dangerous IMO. Even things you think are "floating" become capacitively coupled to ground via the air around them with high voltages. 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!!!!
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.
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 see grounding electrodes (doesn't have to be an "electrode") as controlling a flashback discharge and putting it in a safe place. 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. 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 realize there are strongly differing opinions on providing a safety ground path in the manifold - there always have been. It sparks passions similar to the old metal vs. plastic conduit wars. I happen to be in the camp that strongly feels they are necessary. I've visited many shops - in several countries. Most with a safety ground path and none with problems caused by it.
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
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