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Re: O-Rings

Posted By: SVP Neon Equipment
Date: Wednesday, 31 March 2010, at 9:02 p.m.

In Response To: Re: O-Rings (Dana)


> Thanks for that tip. Since I use your merc
> traps, there seems to be about 6 of this
> size in my vacuum chain. Replacement solves
> the problem quickly, but they are pretty
> valuable if you buy them from the wrong
> place.

Agreed. Some others take the same approach.

> Some of the o-rings are in places that an
> old one (in my opinion) just shouldn't be
> re-used, especially when coated with
> expensive grease.

I assume the expensive grease you are referring to is Apiezon M (the dark amber stuff). Unlike Dow Corning silicone grease, Apiezon is hydrocarbon based grease. As such, O-rings that have Apiezon on them may be soaked in hot soapy water, after which rubbing them between your fingers or using an old tooth brush should remove any grease. Its a judgment call whether or not its worth the time to clean them or just replace them.

While on the subject it is important to mention that the O-rings of the compression fittings should not have any grease on them. Unlike the stopcock O-rings, which should have a touch of lubricant on them, the compression fitting O-rings should be used dry. If the connection is not leak-free then there is something wrong somewhere and the problem should be found and resolved. (There is a troubleshooting guide on my website). Applying grease to it in an attempt to fix the leak is only a band-aid fix.

> A Transco technician emailed me saying to
> make sure the tubulation glass is fire
> polished first, which you have also said to
> save the rubber from getting sliced when
> joining them together.

In addition to fire polishing the cut ends of the tubulation it is also important to wipe off the end that will be inserted into the compression fitting with a lint free tissue or even your shirt tail to remove any dust or dirt before sliding it into the compression fitting. This is a common oversight: Tubulation glass is often laid on the bending or pumping table where it picks up dust and dirt. It is then picked up and used without thought to the dirt that was picked up from the table and is on the outside surface of the glass. If not removed before inserting it in to the compression fitting, the dirt will be deposited on the inside diameter of the O-ring thereby causing a leak. Many people replace the #7 O-rings thinking they are damaged because there is a leak when all they need to do is to clean the O-ring, which may consist of nothing more than wiping it off.


SVP Neon Equipment

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