Oldschool, my apologies; I'll put that one to reading too fast and my blended lenses. ;-)
So far as the silicone grease on O-rings, that has been a fairly common practice for many, many years by some of us.
Herman, you make good points here. I was just saying what I have done with my regs over the years. And, they still work.
Luis, the micro cracks may or may not be there. I agree that old O-rings that have not been maintained will probably have those cracks, and need replacement. Thanks for the information; that's what forums are about, exploring our gear and understanding it better.
SeaRat
PS: tonight I took apart my Healthways Scuba Star and my Sherwood Magnum Blizzard, both piston first stages. The Sherwood Magnum Blizzard did need an O-ring change for the big O-ring. It had become flattened on the outside. But the Scuba Star, by far older, did not need a changed O-ring. I lubed them both, and changed the main O-ring (lubed it too with silicone grease, then wiped it off to get any excess off). They are both together and holding pressure just fine. The Scuba Star was my second regulator, probably about in 1962. This particular one dates from that era, but was not my regulator. I bought it from E-Bay about 3-4 years ago. In contrast, the Sherwood Magnum Blizzard was bought by me new, in the 1980s. Maybe it has tighter tolerances.
John, maybe I am wrong, but it sounds to me that you are still trying to justify a bad advice.
IMHO, trying to justify a bad advice that has no science behind it, just because you got away with it or from a few observations, is just bad practice and maybe even a bit irresponsible. Your observations are casual at best… you are not testing the actual material properties of those O-rings, such as: tensile strength, durometer, etc. All you tested was a very limited application.
That is almost like using the example that some cigarette smokers do live to an old age.
I apologize if I am coming a bit too strong, but this is just bad advice.
From the
Parker O-Ring Handbook:
2.6 Aging
Deterioration with time or aging relates to the basic nature of the rubber molecule. It is a long chain-like structure consisting of many smaller molecules joined or linked together. Points at which individual molecules join are called bonds. Bond sites and certain other areas may be particularly susceptible to chemical reaction. At least three principle types of such reactions are associated with aging.
They usually occur concurrently, but in varying degrees:
a. Scission — The molecular bonds are cut, dividing the chain into smaller segments. Ozone, ultra-violet light, and radiation cause degradation of this type.
b. Crosslinking — An oxidation process whereby additional intermolecular bonds are formed. This process may be a regenerative one. Heat and oxygen are principle causes of this type of aging process.
c. Modification of Side Groups — A change in the complex, weaker fringe areas of the molecular construction due to chemical reaction. Moisture, for example, could promote this activity.
Note: all mechanisms by which rubber deteriorates with time are attributable to environmental conditions.
It is environment and not age that is significant to seal life, both in storage and actual service. While selection and application of synthetic rubber seals to provide acceptable service life is the primary subject of this handbook, our concern in the next paragraph will be with seal life as it relates to storage conditions.
Storage recommendations from Parker:
following conditions are suggested for maximum life:
1. Ambient temperature not exceeding 49°C (120°F)
2. Exclusion of air (oxygen)
3. Exclusion of contamination
4. Exclusion of light (particularly sunlight)
5. Exclusion of ozone generating electrical devices
6. Exclusion of radiation
Buna-N (Nitrile) rubber does age in all but the most benign environments (like sealed in an oxygen free enviroment), and all the preservatives and treatments can do is temporarily delaying the aging. If you don’t know the history of the O-ring, there is no practical way to accurately tell how much aging has occurred.
There is NO treatment that will restore the structural properties of any rubber normally used on O-rings. The effects of aging on elastomers, as described above, can not be reversed.
Silicone grease on O-rings is a lubricant... it does not restore its properties. This has been confirmed by several chemical engineers and materials engineers that I have worked with in the past.
In non critical or benign applications (see note), it is true that O-rings can have a relatively long life. I have seen Buna-N O-rings in regulators that are 40 years old that look like they are good… but they have still aged.
Note: Scuba regulators live in a relatively benign environment (as compared to O-ring in machinery in an industrial environment, automotive, aerospace, etc.), but it is not totally benign.
Within reason, I am not normally too concern about the age of most O-rings in a regulator because most failures just start with a small leak and are not critical (and I know the history of any regulator I rely on).
Most O-rings failure in regulators are not catastrophic, they just create a small leak… I don’t subscribe to the big drama of “life support system”, but taking a calculated risk is totally different than offering public advice telling the world that grease is an acceptable repair for aged elastomers in O-rings.
