Unique Problem With Air Tool...

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Joe AutoDrill wrote:

OK, stupid question time--is there any way that for this specific application you could use an O-ring either directly or with a machined adapter?
If so, then that opens up a lot of choices.
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I don't think so... But it is certainly one of the things I'm thinking about. It would have to be a pretty serious O-Ring to work in the existing groove... And then the tolerances are so tight between teh quill/piston and the cylinder wall (0.001" or so...) that a cup seal, which expands is usually more efficient. An O-Ring might squeeze in there but cause too much resistance even if it were a special substance.
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Joe Agro, Jr.
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You are breach-free in this instance. Cross-posting is preferable when the topic pertains to two groups as it will eliminate most duplication of answers.

As others have said, Teflon comes to mind first. Perhaps you can warm the Teflon to a more plastic state and slip it into place?
Wiki had this to say about PTFE: "Due to its low friction, it is used for applications where sliding action of parts is needed: bearings, bushings, gears, slide plates, etc. In these applications it performs significantly better than nylon and acetal; it is comparable to ultra high-molecular weight polyethylene (UHMWPE), although UHMWPE is more resistant to wear than Teflon. For these applications, versions of teflon with mineral oil or molybdenum disulfide embedded as additional lubricants in its matrix are being manufactured."
and this: "Other polymers with similar composition are also known by the Teflon name: * PFA (perfluoroalkoxy polymer resin) * FEP (fluorinated ethylene-propylene) They retain the useful properties of PTFE of low friction and non- reactivity, but are more easily formable. FEP is softer than PTFE and melts at 260 C; it is highly transparent and resistant to sunlight."
Your answer will probably be in there somewhere.
R
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Joe AutoDrill wrote: ...

Not on a direct solution, no...
Curiosity--is this in an actual medical device or used in the manufacture of a device? Might have bearing on how to approach, I don't know.
Only suggestions I would have would be (a) have you tried working w/ the FDA "advice/guidance for approval" side instead of enforcement? Same overall organization but different hats. Not my baliwick but coworker did some consulting work in medical device area and actually did get some useful feedback that way, and (b) any chance you could find somebody in local/state university w/ the med school/med-engineering school in the field that might talk to you?
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dpb wrote:

A medical tool company, operated by Rob Lee's father IIRC (of Lee Valley Tool Fame).
I don't see anything directly related to your issue, but they do have engineers and such that are familiar with surgical/medical equipment.
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Froz...

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Another lead I'll check out. Thank you.
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Joe Agro, Jr.
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The FDA allows food grade silicone in the main valve of Rainsoft water softeners. I've been using it for about 15 years.
Max
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Joe AutoDrill wrote:

I would try teflon rings for the seals. It sounds like this is something that is used under true sterile controls. I would assume it can be disassembled for autoclaving?

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Steve W.

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I doubt they cook it... In fact, I can pretty much guarantee they don't...
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Joe Agro, Jr.
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Joe AutoDrill wrote:

In that case you could likely use a split Teflon ring that has an overlapping joint.
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Steve W.

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"Joe AutoDrill" wrote:

Anybody looked at dry film lubricants?
Lew
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wrote:
Leaping in several hours too late, but...
PTFE piston rings or even cast iron piston rings. Cast iron may well be better.
If perfect sealing is vital, look up Clupet style piston rings. If perfect sealing is not a major problem, just use a split ring with a few thou of clearance.
Mark Rand RTFM
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Is it possible that the problem with the seals is that the surface of the seal has oxidized? If so using Nitrogen ( cheaper than Argon ) might be the answer.
You might also check with Exxon Mobile ( I consider them as world leaders in Lubes ) for food grade lubricants. Their best worm gear lube is a food grade synthetic.
Dan
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Hi, Joe. I understand your problem. We make cables on occation for a division of Respironics. NOTHING can be changed or deviated in the manufacturing procedure unless it is documented and approved by FDA. Years go we wanted to replace a machined delrin bracket with an injection molded bracket. No way!
My suggestion is to track down an engineer type, possibly chemical engineer, at the company you get the rubber seals from. Perhaps they can formulate a rubber seal material that is self lubricating. Or they may have a slightly different material mix that will let the seals last longer.
I bet an engineer would just love to work on your problem, but you have to get to the actual manufacturer, not just a rep or distributor. I hope the seals are US made. Not because foreign are inferior, but because you can''t be sure you will ALWAYS get the same mix of raw materials.
I a sure you will keep us informed.
Paul Drahn, President Jodeco, Inc.
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how about synthetic blood plasma?
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LOL. Maybe. Off to Body Depot in a few to get some to try it. :)
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Joe Agro, Jr.
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Joe, I am certainly not an expert, but I may have a solution. If possible, you should consider adding another seal or "O" ring, not to seal, but to lubricate. It is possible to get rubber that is molded with silicone imbedded in the rubber. You can occasionally see windshield wipers made with the stuff and they last much longer than standard rubber, but they also leave a microscopic film of silicone on the windshield that acts as a water repellant. Perhaps this is worth pursuing. Steve

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Joe
There is a product called Surgical Grease. Hospitals keep it on hand. I suspect that it simply is a good grease that is sterliized.
Bob AZ
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IIRC, it also will not burn. Important for O2 fittings.
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What do they lube one-time hypodermic syringes with, if anything?
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