Actual Depth Rating of PT-010

I have taken my PT-010 to 36m without cracks appearing. Dave was with me with his PT-009 to the same depth without problems.

Anyone took the housing deeper?

If you search for depth in this forum, you will find several entries.

My personal record is 47m (several times at 40+m) without problems.

Deepest picture was taken around 44m, everything worked well.

Sabine

I was told that the depth rating on the Camedia housings varies. Some housings are pressure tested @ 40m and some @30m.

WORD OF CAUTION:

DON'T PUSH THE HOUSING'S DEPTH RATING TO AVOID FLOODING.

Here's another point of view, which I believe has merit, but I'm not an engineer. This came up in a discussion on the U/W Photo group on Yahoo:

You need to be VERY careful using any underwater product rated at only  

30m/100ft for scuba diving. That rating can be misleading, because it is  

based on uniform static loading. The real world is VERY different from a  

test tank slowly pressurized to 100fsw. Dynamic loading, which is what  

equipment faces in the real ocean, is a whole other thing.

 

Although the real physics of dynamic loading is best left to a college  

engineering course, the basic principal as applied to underwater equipment  

is pretty simple. When you move an object through air or water, pressure  

builds up on the side facing the direction of motion, and a low pressure  

zone forms behind the object. So if you have approximately 100fsw  

hydraulic pressure on an object when at rest, you will have higher than  

that on one side, and lower than that on the other, when you move the  

object through the water. How much difference depends on speed,  

acceleration, and how hydrodynamic the object is (and lots of other factors  

if you're an engineer, but that's enough for us). But whatever the  

difference, if you're at 100ft, and you move, you've exceeded the rated  

pressure limit.

 

And then what happens when you accidentally descend to 105ft? Well,  

there's probably some wiggle room in the rating, right? Sure, until you  

move it. In fact, if you're safely at 95ft, and your movement alters the  

pressure on any part by only 10%, you've just subjected it to 105fsw  

pressure.

 

OK, but if you're careful about depth, never take the gear too deep, you're  

fine, right? Not necessarily, because of those nasty o-rings. O-rings  

deform under pressure. That's a good thing, because they deform and fit  

themselves to the shape of the cracks and grooves in the equipment that you  

want them to seal. But it's a bad thing if the pressure is uneven, like  

when you move the equipment through the water. The o-rings and equipment  

are made to tolerate the pressure differences and still hold a seal, but  

only up to a point. If you're already anywhere near the rated limit of the  

equipment, differential distortion of any o-ring in the system will mean a  

flood.

 

That's why my Nikonos V o-rings are "rated" to 160 psi (about 100m/300ft),  

and my Citizen Aqualand is rated to 200m (>600ft), even though both are  

made and marketed to be used only for recreational diving, to 130ft or less.

 

Bottom line: gear rated at 30m is basically snorkeling gear, especially if  

you are going to count on it to keep hundreds of dollars worth of camera  

electronics dry.

I don't know the name of the author of this post, but I know the concept holds true for watches.... just food for thought.

Richard

Many thanks to those who replied. Much appreciated. More relaxed now if I have to take that critical shot somewhat deeper than usual.

Jorge

In the beginning i didn't take the camera with me when we planned a dive deeper than 30m and i always stayed around 30m when i had it with me.

Then we dived at a place where a pygmy seahorse was known to live in a gorgonian at 37m. Fortunately we had planned several dives there, so i decided to take the empty housing with me for the first dive. I took it down to ~ 42 m and watched it carefully.

Everything seemed to be ok and so i took it with me on the second dive.

Since then i have taken the housing down to 40+ meters several times, but only if i knew for sure that there was something to photograph that was worth taking the risc.

The 47m depth were not planned that deep (but there were sharks) and i'm glad the housing survived.

Otherwise i prefer to do deeper dives without camera - for me and my buddys safety as well as for the camera.

Richard's quote is very interesting but i suppose that a housing that is depth rated to 30m should be able to survive this depth (and probably a bit more) no matter how you move it. If it was the pressure alone it should read pressure rated to 40bar.

Another question is strong current. What about hitting a very strong current in ~20m. I'm not an engineer but woudn't that put more pressure on the current-ward side of housing and less pressure on the other side too ?

Sabine

Depth rating for housings is for dynamic pressure, not static. Otherwise, all our housings would have been flooded a long time ago, pushing all those buttons, and swimming with the camera inside.

Loco,

I am an engineer, so I'll chime in.

The discussion you posted in basically crap. (Not to shoot the messenger)

You need to be VERY careful using any underwater product rated at only  

30m/100ft for scuba diving. That rating can be misleading, because it is  

based on uniform static loading. The real world is VERY different from a  

test tank slowly pressurized to 100fsw. Dynamic loading, which is what  

equipment faces in the real ocean, is a whole other thing.

This isn't dynamic loading, this is differential loading. Dynamic loading is time dependent. i.e. how fast do you apply pressure to the camera body.

Although the real physics of dynamic loading is best left to a college  

engineering course, the basic principal as applied to underwater equipment  

is pretty simple. When you move an object through air or water, pressure  

builds up on the side facing the direction of motion, and a low pressure  

zone forms behind the object. So if you have approximately 100fsw  

hydraulic pressure on an object when at rest, you will have higher than  

that on one side, and lower than that on the other, when you move the  

object through the water. How much difference depends on speed,  

acceleration, and how hydrodynamic the object is (and lots of other factors  

if you're an engineer, but that's enough for us). But whatever the  

difference, if you're at 100ft, and you move, you've exceeded the rated  

pressure limit.

This person needs to take the course he recommends. You cannot create enough speed for this problem to manifest itself. In the practical world, this never occurs.

And then what happens when you accidentally descend to 105ft? Well,  

there's probably some wiggle room in the rating, right? Sure, until you  

move it. In fact, if you're safely at 95ft, and your movement alters the  

pressure on any part by only 10%, you've just subjected it to 105fsw  

pressure.

Others have had these housings below 140 feet with no problems, so there must be some margin. No one engineers exacally to the limit. That would be foolish.

OK, but if you're careful about depth, never take the gear too deep, you're  

fine, right? Not necessarily, because of those nasty o-rings. O-rings  

deform under pressure. That's a good thing, because they deform and fit  

themselves to the shape of the cracks and grooves in the equipment that you  

want them to seal. But it's a bad thing if the pressure is uneven, like  

when you move the equipment through the water. The o-rings and equipment  

are made to tolerate the pressure differences and still hold a seal, but  

only up to a point. If you're already anywhere near the rated limit of the  

equipment, differential distortion of any o-ring in the system will mean a  

flood.

This guy needs to read up on o-rings. O-rings don't deform under pressure. O-rings are seated the moment some differential pressure is applied to the system. If your housing does not leak in a few feet of water, it won't leak ever until you exceed some structural limitation. If your housing deforms excessively you could open up the o-ring groove causing a leak. ( i.e push down on the center of a tupperware lid, you will see the edges curl up). Else, at some point, you will extrude the o-ring out of the groove (at about 2000 to 40000 psi!).

That's why my Nikonos V o-rings are "rated" to 160 psi (about 100m/300ft),  

and my Citizen Aqualand is rated to 200m (>600ft), even though both are  

made and marketed to be used only for recreational diving, to 130ft or less.

O-rings aren't rated to any specific depth. The system may have limitations. You generally loose functionality of the pushbuttons before any signs of mechanical degradation. O-rings, in properly designed grooves, are good for thousands of psi. As an example, look at the ones in your regulator and tank.

Now, all this said, is there a problem with polycarbonate (lexan) housings? Sure. Poycarbonate hates cold temperatures and scratches. It gets brittle at somewhat cold temperatures. I think that freezing is OK though. It is also notch sensitive ( has poor strength in the presence of notches and scratches). If you scratch your plastic housing significantly, I wouldn't dive with it. (i.e. getting it gouged by rocks in the surf). Fortunately, the scratches would be on the compression side of the housing mitigating any effects.

Polycarbonate also doesn't like solvents. Keep it away from Toulene, Xylene and such. I would also keep it away from petroleum products. Don't pack it in the same bag with your wetsuit repair kit (wetsuit glue fumes) or your toiletry bag.

Sorry this is so long winded.

Michael

Don't be sorry at all. There is so much information floating around out there, that it's refreshing to hear from someone that knows whereof they speak.

As I said, I know nothing of the author of that quote, or his level of expertise, I just thought it was an interesting take on this thread. In fact, he went so far as to email me outside of that forum to expound these theories, when I suggested the PT-xx housing for a newbie looking for an economical digital setup.

Thanks again for your insights.

Richard

Even though I'm an engineer I would not be proficient at designing a camera housing. Just because an engineer is degreed in a field, doesn't mean they have expertise in a particular sub-field. The same degree is equally used by hydraulics designers and steel fabricators. Though, I wouldn't use a hydraulics designer to design big steel.

I have some passing knowledge of pressure vessels and o-rings. I can do light engineering of these things. I would have to dig deep into my mind to be confident on the details.

My big interest right now is "why do we need two o-ring lubricants". OLY recommends one grease for buna rubber and a different one for silicone rubber.

I think I can get a single lube for both. Then, you don't have to worry about contamination between your strobe o-rings and your housing o-rings.

Incidently, you don't know if the OLY o-rings are silicone rubber or flurosilicone either. And you can't tell by the color since color is not standardized across the industry.

Life is too short to experiment with different compounds of O-rings and chemical compatibility of the lubricants that are supplied by each manufacturer. Do you have the different O-rings and lubes that you can use for possibly destructive testing? Are you prepared to spend that kind of money?

Some people who have used a different manufacturer's lube on their O-Ring have experienced catastrophic failure (read: flood) due to cracking, swelling, or other unpredicted result of the O-ring.

If you want to read up on the subject, I recommend the Parker O-Ring Handbook.

The problem is that we do not know exactly which elastomer each O-Ring is made of and thus its chemical compatibility.

Cheers,

You are correct that we do not know the exact elastomers used in the o-rings.

I am familiar with the Parker O-Ring catalog as it sits on the shelf in my office (though its a little old). I have ordered the current catalog just to get the latest.

Parker does have a lubricant that is compatible with buna-n, silicone, flurosilicon, etc. It should work with anything.

"Destructive" testing is too involved. You need to do absorption testing, durometer testing, strength testing as a minimum.

One should weigh the odds of changing to a "universal" lubricant with the odds of having two or more lubricants in your kit and using the wrong one. I have one lube for the flash, one for my dive lights, another for regulator parts, and another for the camera housing.

I like the idea of striving for one universal lubricant.

I would not recommend this approach to others unless they feel comfortable pouring through engineering documents. I have not yet made a decision to go this route yet, but am looking into it.

One thing is getting a usable quantity of lube. Parker sells this stuff in a two ounce tube. This would last a lifetime for a boat load of divers. I would want to repackage it in a dive kit size in a watertight container. Don't know the price yet or the best way to buy. Got to find a distributor if I get serious.

Maybe we should start with Cristolube 111 because that is quickly becoming the standard for most regulator manufacturers.

Shall I send you the MSDTs?

With dive lights, I wouldn't really consider the lube to be so critical, unless you are talking about my cannister light...

At the minimum, you would have to test the lube with the O-ring to check if there wasn't any swelling or deformation, or cracking/drying out. Personally, I don't have the time or parts to waste trying this out. Also, a lot of manufacturers aren't forthcoming about this information or just plain don't know.

I think all those different 5 gram tubes of grease won't hurt to carry around...YMMV.

Whats a MSDT? I know what a MSDS is, but that wouldn't have the info one would require. They are safety related.

I would care about what I put on my dive light. Those o-rings can be pricy too.

You minimum isn't minimum enough. There is a standard for this type of testing, but I haven't read it in a number of years. The equipment required isn't excessive, but unless you have test lab, its not worth getting. Also, the testing is slow. Months to get data that you can use in long term aging studies.

If Parker says "this lube is compatible with pretty much everything" I would be confident in its use. But, like I said, I haven't got that far in my research yet.

Obviously OLY probably won't be forthcoming with info, but other manufactures like ikelite may be more helpful.

Generally most of these o-rings are buna-n, just because its cheap and does the job. The only really odd one is the new OLY o-ring, and that is likely either silicone (as advertised) or flurosilicon. Silicone absorbes petroleum products (i.e. grease). Flurosilicone not so much.

Additionally.....

Thanks for the reference to Christo

Lube MCG-111. Apparently used in Scuba Regulators because its compatible with the o-rings and is O2 safe. Don't know what else the lube is compatible with (Yet). Not too expensive either. This would make a good "universal" lube as well if it is campatible with a wide selection of materials. I will look further...

I also found out that some regulators use Viton seals. This makes sense since Viton works well at cold temperatures. Viton is also much more expensive.

Yes, I meant MSDS (Material Safety Data Sheet, for those of you who don't know).

That's exactly my point about the testing! We don't have a testing lab and not enough time and money to do such testing.

If you don't know the elastomers in questions, it turns out to be a lot of trial and error testing, so why bother?

Viton is used in regulators mostly for oxygen compatibility. Opinions from various manufacturers vary on using Viton. Christolube is widely recommended as the standard lube due to its O2 compatibility.

You have the Parker catalog, there are more elastomers than you can shake a stick at, although I doubt the Olympus O-rings are an exotic like ATLAS or even Viton...too expensive.

Good luck,