Manafold

[Guest Mal]

I would like some advice on weather it is ok to make a Neon pumping manifold in copper . any advice would be much appreciated.

[B.O.P.]

I would like some advice on weather it is ok to make a Neon pumping manifold in copper . any advice would be much appreciated.

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There are numerous reasons why metals should not be used. The most obvious is the safety factor. You will be in close proximity to high voltage. (And please no one give me the argument about "proper grounding". This only induces bombarder flashback, not prevent it). Peak voltages on the order of what a bombarder is capable of producing can go to more than one ground path simultaneously. If you are in contact with the manifold when a bombarder flashback occurs you may be enough of a ground potential to attract some of that voltage. It has happened before with a "properly grounded" metal manifold. Although the operator survived, he did suffer serious medical problems.

Some not so obvious reasons are:

Mercury, which will eventually get into the manifold via vapor form even if you have a good trap, will amalgamate to copper and brass. In the case of stainless steel it will etch the surface after extended periods of exposure.

Copper will have to be soldered together. Unless it is OFC grade (oxygen free copper) the solder joints will eventually start to oxidize causing micro pipes (microscopic leak paths). When this happens the manifold will never pump down sufficiently and will always leak. The leaks will be next to impossible to find without the use of a helium leak detector. You will not be able to use the spark tester to check for leaks.

High vacuum metal valves are expensive compared to glass high vacuum O-ring valves and you will have the same problem with mercury. Further, high vacuum copper valves do not exist to my knowledge.

You cannot visually see when a metal manifold should be cleaned. And when cleaning you cannot tell if the cleaning was successful. In the instance of mercury amalgamation to the surface, it will require some serious chemicals to remove it, which usually have an adverse affect on the metal.

There are other reasons, but this should give you an idea.

The best choice for neon manifolds is Pyrex. Pyrex provides a stronger, more durable structure and allows more compact and intricate fabrication designs than soft glass. Borosilicate glass (Pyrex) has superior outgassing properties compared to soft glass, metals and metal surfaces. It is easily cleaned (provided you use a hydrocarbon based lubricant and do NOT use silicone grease) and the effectiveness can be visually seen. Glass is an electrical insulator, so it adds a safety margin to working closely to high voltage.

IMO, any neon person who is considering a metal manifold should re-examine what they are considering.

Mark@SVP

www.svpneon.com

[Erik Sine]

I can't imagine using anything else other than pyrex. :D

*added

....I just had a thought the person who told you to use a conductive err, metallic surface may have a hidden agenda against you

[B.O.P.]

....I just had a thought  the person who told you to use a conductive err, metallic surface may have a hidden agenda against you 

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Nah, some people just don't know any better :D

[Guest Mal]

There are numerous reasons why metals should not be used. The most obvious is the safety factor. You will be in close proximity to high voltage. (And please no one give me the argument about "proper grounding". This only induces bombarder flashback, not prevent it). Peak voltages on the order of what a bombarder is capable of producing can go to more than one ground path simultaneously. If you are in contact with the manifold when a bombarder flashback occurs you may be enough of a ground potential to attract some of that voltage. It has happened before with a "properly grounded" metal manifold. Although the operator survived, he did suffer serious medical problems.

Some not so obvious reasons are:

Mercury, which will eventually get into the manifold via vapor form even if you have a good trap, will amalgamate to copper and brass. In the case of stainless steel it will etch the surface after extended periods of exposure.

Copper will have to be soldered together. Unless it is OFC grade (oxygen free copper) the solder joints will eventually start to oxidize causing micro pipes (microscopic leak paths). When this happens the manifold will never pump down sufficiently and will always leak. The leaks will be next to impossible to find without the use of a helium leak detector. You will not be able to use the spark tester to check for leaks.

High vacuum metal valves are expensive compared to glass high vacuum O-ring valves and you will have the same problem with mercury. Further, high vacuum copper valves do not exist to my knowledge.

You cannot visually see when a metal manifold should be cleaned. And when cleaning you cannot tell if the cleaning was successful. In the instance of mercury amalgamation to the surface, it will require some serious chemicals to remove it, which usually have an adverse affect on the metal.

There are other reasons, but this should give you an idea.

The best choice for neon manifolds is Pyrex. Pyrex provides a stronger, more durable structure and allows more compact and intricate fabrication designs than soft glass. Borosilicate glass (Pyrex) has superior outgassing properties compared to soft glass, metals and metal surfaces. It is easily cleaned (provided you use a hydrocarbon based lubricant and do NOT use silicone grease) and the effectiveness can be visually seen. Glass is an electrical insulator, so it adds a safety margin to working closely to high voltage.

IMO, any neon person who is considering a metal manifold should re-examine what they are considering.

Mark@SVP

www.svpneon.com

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[Guest Mal]

Thanks for the advice . I was only wondering about a copper manifold because i use a system over here called a Barton pump bench and it is all copper,and the high vacuum taps (brass) are a third of the price of O ring high vacuum Pyrex taps. I prefer a Pyrex manifold so your advice settles it for me thanks Mal

[B.O.P.]

Thanks for the advice . I was only wondering about a copper manifold because i use a system over here called a Barton pump bench and it is all copper,and the high vacuum taps (brass) are a third of the price of O ring high vacuum Pyrex taps. I prefer a Pyrex manifold so your advice settles it for me thanks Mal

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A brass valve rated for high vacuum (not just vacuum - there is a difference) for a third the cost of a Pyrex O-ring valve? Either you found a great deal on the brass valves or someone is trying to hose you down on the Pyrex ones. What sizes are you comparing?