NIKONOS O-RINGS AIN'T JUST BLACK RUBBER BANDS (PART 2)
Text and Photos by Bob Warkentin
Acting on a Nikonos O-Ring
Typically, any O-ring will be affected by any one (or a combination) of four things: (1) temperature during use, (2) chemical interaction with the O-ring's rubber, (3) fluid (or gas) pressures during use, and (4) the design and amount of pressure (compression) provided by the O-ring's seating environment. There are other factors to consider such as the design of the gland (we call it the "channel") and whether or not the O-ring seal is in dynamic operational use (being opened and closed or performing some operational movement of O-ring-sealed parts during use).
Temperature-wise, the typical range of storage/use for your Nikonos equipment is between sixty and one hundred degrees Fahrenheit, which is well within the "no effect" range of the rubber O-ring compound.
The "fluid" to which the Nikonos O-rings are exposed is typically water (fresh or salt) and the materials dissolved in it. While it's true that some "waters" can affect rubber, it requires a very prolonged and continuous exposure to cause such an effect (run your finger over the rubber ballcock which has been in your toilet's water tank for several years, and notice all the black coming off of it). Since you're prevented from staying submerged indefinitely, and you don't store your camera equipment in water in your closet, there is insufficient exposure over time to cause deterioration of your O-rings. Other items such as spray cans of oil, vinegar, and other seemingly harmless household "chemicals" will damage and destroy the useful life of your O-rings, not to mention other parts of the equipment. But the most harmful "chemicals" of all are sunlight and ozone; so just keep your equipment out of prolonged exposure to the sun (and away from electric motors).
So now we're down to the last two items affecting O-rings, both of which are pressures. There are only two pressures capable of acting on any O-ring within a Nikonos product: that from being confined within the space of the three O-ring channel walls and the fourth sealing surface, and the pressure exerted by a fluid (water). Let's take the case of the effects of the fluid first just to get it out of the way. If they were used as static seals in a high pressure pipeline, the type and quality of O-ring seals used in Nikonos equipment could be used at continuous pressures of 800 psi and up and at temperatures of several hundred degrees with complete success. However, this increased pressure and/or temperature would affect the O-ring material itself, causing it to shift and deform within the O-ring seating area (caused by pressures of the fluid) and/or swell (caused by temperature, or a chemical reaction due to the fluid in the pipeline), improving the O-ring's sealing ability.
But what are the conditions of this fluid we dive in? Generally, the temperature ranges from seventy to ninety degrees Fahrenheit, air included. This is normal for the O-ring and doesn't cause changes. Likewise, the chemistry of water generally has no effect on the seal.
What's left, then, is the effects of 160 feet of saltwater pressure (about seventy-two psi). In short, the effects from this low fluid pressure are insufficient to cause the O-ring to further shift and seal better within the O-ring environment of your equipment. So if you've ever heard someone talking about the fact that Nikonos O-rings deform into "kidney bean" shaped seals due to diving water pressures and seal better the deeper you go, ask them what they've been inhaling.
Nikonos O-rings are "low pressure" O-rings designed to provide sealing at continuously changing diving pressures of zero to seventy and back to zero psi without leaking at either zero feet or 160 feet. They are designed for the "dynamics" of opening and closing and other operations by human hands (not wrenches or other tools). Therefore, what's left that you can rely on, and must rely on, is that only the amount of rubber which extends out beyond the two vertical walls of your O-ring channel will be available to be compressed when the item is mounted onto or into the camera, strobe, or lens. It is this rubber and the condition of this rubber coupled with its clean bearing surfaces and those of the parts in which the O-ring is to be used, along with your proper lubrication, that spell a successful, nonflooding diving experience. This, and your awareness of the facts concerning "memory compression."
Note: If you are diving in extremely cold areas such as the Antarctic, have high temperature use requirements above 300 degrees Fahrenheit, have diving requirements beyond the rated 160 feet, require the use of medical disinfectants, or require any information that is for a nontypical use for a Nikonos, please contact me for additional information.
People generally worry only about cleaning their O-rings and the channels and applying whatever they consider is a "proper" amount of grease. To them, this is all there is to O-ring maintenance, and they believe if they clean and grease, the O-ring will last forever.
Well, rubber O-rings must be compressed to do their magic. And in the process of doing their "compressed" water-sealing work, the rubber of the O-ring retains some or all of this compression as a permanent memory. This harmless-sounding term "permanent memory" really means that the O-ring is now permanently flattened and that it has lost part of its elasticity, resulting in a loss of its ability to seal out water.
Along with cleaning the O-ring and its environment and using O-ring grease when dealing with O-ring sealed equipment, you must also consider one more thing: compression as a fact of an O-ring's useful life.
Cleaning and greasing a flattened, compressed O-ring is no different from cleaning and greasing a bald tire on your car. While it looks pretty and shiny to you when you use it in a wet area, you ain't got no traction!
Another point to remember: Every week an O-ring remains under compression in your closet is one less week of diving life for this O-ring! More on this later.
As O-rings become flattened by compression, they lose their ability to "reach out" and seal tightly between two surfaces. As these surfaces are opened and closed frequently for film or battery changing, lens replacement, or strobe changing, these greasy user-serviceable O-rings and their greasy environment are exposed to tiny particles of contamination which can become lodged on the bearing surfaces of the O-ring and the bearing surfaces of its environment. In essence, your O-ring now has to try to provide a watertight seal over and around these tiny "speed bumps."
A new O-ring with full strength will give you a better chance (if any really exists) of providing a seal in a contaminated area than a weak, flattened seal. The reason is that full-strength rubber capable of giving a tight seal over a wider area of an O-ring channel is all across the widened, compressed surfaces of a new rubber O-ring. If the particles are small, the seal can usually engulf the particle fully and not allow channeling" of water under the O-ring to occur. But if the O-ring has memorized its flatness, well, you fill in the answer!
The Third Problem: Dynamic Internal O-Rings Which You Can't Replace
These seals are made of the same material as your user seals, installed in their own compressed environments and undergoing the same process of flattening (see photo 4 again). While the obvious difference is that you're not required to remove O-ring-sealed parts like the shutter speed dial or the trigger just to change film or the switch knob of your strobe just to change batteries, don't think that these areas can't become contaminated as badly as user seals or that they can't cause a flood! These seals are "dynamic"; that is, there is a movable operation going on within and around this O-ring seal (like using the film advance lever, rotating the ASA dial, etc.). This dynamic operation allows contaminants to wiggle their way down between the O-ring and its sealing surfaces, causing "speed bumps." Good seals mean water tightness: weak, compressed seals mean leaking or flooding.
I know some people are going to misquote me on this when they try to tell someone else their opinion. If you're in a position where this question comes up all the time, please try to have other people read this information for themselves.
First, my cop-out: This question is difficult because of all the individual variables in how people use and maintain the equipment. And now to the answer: replace them at least annually (if you're a two-week-a-year sport diver), at least every six months if you're commercial, and certainly every three to four months if you're in rental! But whatever you do, don't just rely upon my calendar; rely upon what you know and see (and read and recognized in the pictures of O-rings in Part 1). Use proper cleaning and greasing and periodic professional servicing (just like your regulator and BC). Remember, every week of closet time for a user O-ring is one less week of diving time!
Isn't this overkill? Probably! But there are so many different sizes of O-rings in different pieces of equipment and under different degrees of compression that some will flatten faster than others. So use the "weak link" concept: when you determine one O-ring is flattened, all seals should be replaced even if the time period is less than that given above. Also, there are other factors to consider, including cleaning and preventing corrosion to the metal parts or abrasion to the plastic parts.
But the most important thing to remember is that user O-rings are constantly being opened and closed for changing the film, batteries, lens, and flash cable, and this is just on your camera body (think about your other pieces of equipment and their "user" O-rings). If they were left in place and the camera never needed to be opened, they'd probably last longer (except for corrosion buildup on the metal parts) because their O-ring-sealing surfaces (and the sticky grease) would not be directly exposed to contamination from particles of sand, towel fibers, tiny pieces of camera case foam, or grains of dried salt water. So, as your O-rings build up weeks of closet time flatness while losing weeks of diving time plumpness, the greater the chances are that your cleaning will not get everything, leaving something behind that will cause a flood.
The owner's manual from Nikon says once a year. You may convince yourself that this, too, is overkill, especially in light of the fact that you can't change these seals yourself but must have a professional do it for you. You must relinquish your equipment to someone for some time, and the cost of such servicing is more than the nine- or ten-dollar bag of user O-rings you can buy anywhere. Just remember these are seals you can neither get to, to see and examine nor get to clean, but they get the combined total of closet and diving time. So for these O-rings, you've got to use both the above calendar and professional servicing. Nikonos equipment is dive equipment; maintain it the same way!
Nikonos equipment isn't just a land camera, lens, or strobe; they are pieces of diving equipment just like your other pieces of diving equipment which are used in salt water. So like your mechanical regulator and BC which must have periodic (annual!) professional servicing to keep their moving parts in good, safe, operational condition and control corrosion and pitting of metal parts, your Nikonos equipment must be afforded its diving-related servicing. During the initial servicing of your equipment, you should consult your professional Nikonos service technician to establish a proper program of maintenance for your needs (one year may be too short or too long a period between service appointments, based upon your maintenance, or lack thereof).
Reprinted with permission from Bob Warkentin's Southern Nikonos Service Center, Inc.
9459 Kempwood, Houston, TX 77080 713/462-5436