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Draq

Vacuum leak detector question

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I am going to have the Nauticam vacuum system installed in my E-M5 housing.

 

I know vacuum systems like that are designed to verify seal integrity and alert the user to a problem pre-dive and during the dive. Beyond that, do these systems provide any meaningful protection against flooding? I am wondering if placing the housing under that kind of "negative" pressure pre-dive makes it less likely to flood at the surface such as in a rough shore entry or having to giant stride off a boat.

 

 

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I am wondering if placing the housing under that kind of "negative" pressure pre-dive makes it less likely to flood at the surface such as in a rough shore entry or having to giant stride off a boat.

 

Yes, it does... Not just from rough seas or giant stride entries, but just from simple knocks and bangs.

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No it makes no difference. If you crashed your housing would eventually flood the housing faster because of the delta pressure

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Many floods happen in the rinse tank or at the surface, where there is no water pressure to help keep the back and port in place. The vacuum is equivalent to only a few meter of water pressure, enough to increase resistance to dislodging forces but not enough to noticeably reduce the max depth limit. Close to the surface it may speed the rate of flooding if there is a leak, but it there was a leak the pre-dive check should have caught it.

 

Bart

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I had one on a Nikonos V, the pressure did help prevent leaks. Seats the O rings and applied pressure to them.

 

The Nic V had a problem with the 15 mm lens on the surface. The lens had some wiggle in it and could leak at the surface. At depth it was fine as the lens was pushed against the O rings. The vacuum eliminated this problem.

 

On the negative side, the alarm would sometimes go off and you could not fine a problem. It seemed there could be a gradual loss of pressure that would set off the alarm, but not be enough to actually cause a leak.

 

I ordered one for a GX 7 housing.

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Interceptor 121 is just plain wrong. It preloads the o-rings and helps prevent dislodgement at the surface. As far as "delta pressure" *snort* if you pump your housing down to negative 10 inches mercury, you would need to knock 10 feet off of your max depth rating.

Edited by diverdoug1
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Am not sure where you base your observations diverdoug

One thing is progressive flooding by failure of an o'ring or a small part that is not sealing (rare and would be detected by the leak detector before you even enter the water)

The other is when the housing gets knocked by shocks and bangs, those have little to do with moving an oring but could crack a port or the lcd viewer and in that case because of negative pressure your housing floods faster than it would normally

If your housing is water tight that 200mbar negative vacuum applied makes no difference whatsoever and does not make the housing more watertight than it already is however if you had to crack a port and your housing is damaged to get less watertight the vacuum floods it faster

Eventually if you crack a port your camera is fried in either case vacuum or not

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Am not sure where you base your observations diverdoug

One thing is progressive flooding by failure of an o'ring or a small part that is not sealing (rare and would be detected by the leak detector before you even enter the water)

The other is when the housing gets knocked by shocks and bangs, those have little to do with moving an oring but could crack a port or the lcd viewer and in that case because of negative pressure your housing floods faster than it would normally

If your housing is water tight that 200mbar negative vacuum applied makes no difference whatsoever and does not make the housing more watertight than it already is however if you had to crack a port and your housing is damaged to get less watertight the vacuum floods it faster

Eventually if you crack a port your camera is fried in either case vacuum or not

Diverdoug (and the others) are quite right

 

An o-ring will only seal correctly when under pressure, this pressure can be created either mechanically (e.g by clamping down the latches on the back of a housing and by the surfaces of the housing being forced together as the housing is submerged) and/or through fluid/air pressure (e.g through sucking air out of the housing, or by submerging the housing in water)

 

A pressure based leak detector assists with this by both pulling the surfaces of the housing together creating a higher mechanical pressure, and by applying air pressure by creating a pressure differential between the inside and outside of the housing.

 

If a camera and housing is left bobbing on the surface untouched then unless it's very poorly made or has a fault then I doubt very much it would flood. However that's not what happens in the real world, housings naturally get banged by waves, against the divers person etc. As the o-ring has minimal activation through pressure at that point, all of those physical knocks can break the seal and cause a flood. You only have to look at the amount of cameras that get flooded when left in the dunk tank after a dive to get an idea.

 

On the flip side, add a pressure based leak detector to your housing, you wont be able to open the housing at all once the negative has been pulled.

 

http://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf

Edited by bottlefish
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If the oring does not seal mechanically it won't seal by sucking vacuum.

 

Vacuum only increases the negative pressure already inside. If there is no seal there is no vacuum in fact this is why you have a lead detector

 

When you use a vacuum system you don't need to put it in the rinse tank at all. But if you did it would be just marginally less prone to flood as a normal system without vacuum.

 

Leak detectors are not high vacuum system typically 200 mbar over 1000 so only 20% less pressure equivalent to putting a normal housing in 2 meters of water which is far away from a strong vacuum and becomes almost irrelevant as you dive at normal working depths.

 

There is some extra vacuum but that should not make you forget the normal precautions. It may make you feel better as you have spent $300-500 but the additional advantages are all fairly marginal, the main purpose is to be able to check integrity without putting the housing in a rinse tank in a much more efficient fashion.

 

So it may make it somewhat more resilient but not a great deal, to the same extent that if you had to crash the port it would flood marginally faster but not a great deal

 

 

So giant strides off the both and rolling in with the camera remains risky business

Edited by Interceptor121

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So it may make it somewhat more resilient but not a great deal, to the same extent that if you had to crash the port it would flood marginally faster but not a great deal

 

Great, so you're now also saying that it makes a difference.

 

Glad we all agree :)

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It does make some difference but not the question the op asked which was can I giant stride in or am I allowed more rough entries?

 

I have a vacuum system myself and the housing opens even without releasing the vacuum this is not a high vacuum system the integrity is provided by the oring and not by the vacuum and is not designed to resist shocks or vibrations so that piece of documentation on engine oring in aircraft is irrelevant in most part only the static part is somewhat relevant

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I have a vacuum system myself and the housing opens even without releasing the vacuum

 

Hmm. That's surprising. When I pull my housing down to -10hg, I absolutely cannot open the housing. I can release all the latches, pick it up and shake it hard and the back will not come off. I didn't do that with the camera inside by the way :D I might be able to pry it apart with a screwdriver (I'm not going to try that!), but my housing is absolutely "sucked" together and cannot be opened without releasing pressure first.

 

Also, I can rotate the port if I put a lot of effort into it, but I cannot pull the port off when it's under negative pressure.

 

I'm using Backscatter's airlock system on an Aquatica housing, what housing / vacuum system are you using?

 

JP

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I didn't mean to cause controversy...

 

FWIW, I already decided to get the vacuum installed for its intended benefit and don't plan on treating the housing differently than before. I try to have the housing handed down to me from a boat. I was just wondering if there was any valid reason to believe a leak was less likely due to the vacuum at times when the housing is not otherwise under pressure. Curiosity more than any sort of buying decision. I am not really concerned about a cracked port or viewfinder. I see those as fairly unlikely for me and I suspect with or without the vacuum, such damage would most likely mean game over.

Edited by Draq
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BTW, I have done many giant strides with an Aquatica housing while snorkeling with Whale Sharks. I tried to hold it high near my head to minimize the surface shock, but had no issues at all. I'm sure the Nauticam is equally good for doing entries with housing. My opinion is it will be even safer under negative pressure. It would take a helluva shock to knock a port loose with a vacuum system and I have actually never seen a flood caused by a "damaged" housing/port.

 

It's always an o-ring not seated or a port coming unscrewed, both of those occurrences are exactly why you want a vacuum system.

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Hmm. That's surprising. When I pull my housing down to -10hg, I absolutely cannot open the housing. I can release all the latches, pick it up and shake it hard and the back will not come off. I didn't do that with the camera inside by the way :D I might be able to pry it apart with a screwdriver (I'm not going to try that!), but my housing is absolutely "sucked" together and cannot be opened without releasing pressure first.

 

Also, I can rotate the port if I put a lot of effort into it, but I cannot pull the port off when it's under negative pressure.

 

I'm using Backscatter's airlock system on an Aquatica housing, what housing / vacuum system are you using?

 

JP

 

I've used the Gates system, which again went down to about -10hg, and now use the sentinel on Amphibico Genesis, as with you, not a chance in hell of me opening the housing up without applying a lever and a serious amount of brute force.

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The leak sentinel works on 200bar or 5.9 hg alert. 10 is over 150% more vacuum so you would feel a difference of course

Anyway the op has already decided is not changing the practice and I don't think anybody manufacturing those system would say that they make the housing less prone to leak

 

In the specific of the nauticam em5 if you had to hit the latch you can easily open the housing even under vacuum

Housing with clamps would resist more

Edited by Interceptor121

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BTW, I have done many giant strides with an Aquatica housing while snorkeling with Whale Sharks. I tried to hold it high near my head to minimize the surface shock, but had no issues at all. I'm sure the Nauticam is equally good for doing entries with housing. My opinion is it will be even safer under negative pressure. It would take a helluva shock to knock a port loose with a vacuum system and I have actually never seen a flood caused by a "damaged" housing/port.

I know of one poor chap who had two catastrophic floods (once midway through a Galapagos trip :(), both on 5d Mk II housings, both caused by the port dropping off the front in shallow water.... (obviously no leak detector fitted)

Edited by bottlefish

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How much does it cost to retrofit one onto NA-EM5 in general? Maybe I could get it installed once it is maintenance time...

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How much does it cost to retrofit one onto NA-EM5 in general? Maybe I could get it installed once it is maintenance time...

$220 plus the valve is another $220 unless you need an offset valve which is more. If you combine the install with maintenance there is a discount on the maintenance. I think the discount is $80.00 worth of O rings.

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BTW, I have done many giant strides with an Aquatica housing while snorkeling with Whale Sharks. I tried to hold it high near my head to minimize the surface shock, but had no issues at all. I'm sure the Nauticam is equally good for doing entries with housing. My opinion is it will be even safer under negative pressure. It would take a helluva shock to knock a port loose with a vacuum system and I have actually never seen a flood caused by a "damaged" housing/port.

 

It's always an o-ring not seated or a port coming unscrewed, both of those occurrences are exactly why you want a vacuum system.

 

I always put a vacuum on my Aquatica housing now and it just recently saved me a flood when I inadvertently unscrewed my flat port during some decompression stops in heavy seas. I did not notice until I was on the boat. I have no doubt in my mind the port would have come off considering the sea conditions if I had not had it sealed with a vacuum.

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I use now more than 2 years two Hugyfot housings and made approx 200 dives with their vacum leak detector system called HugyCheck.
I never had any problem with water entring inside and it is impossible to open the housing while it is vacuumized.

I belive that the neagtive pressure inside the housing sucks the o-rings in their position providing a better seal on the surface

where non vacuumized housings may have the o-ring not perfectly sealed, what is the reason that the leak on the surface.

 

Any slight seal will trigger the alarm after about a half an hour and as i load my housing at home before i leave to the harbour

this is enough time that the alarm will trigger.

 

Chris

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Hugyfot was one of the pioneers in the vacuum check arena. I don't recall hearing any negative comments about their system. I am currently using a Backscatter electronic system on my preferred U/W rig (Aquatica AD800), and have been very pleased with it.

Edited by diverdoug1
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There are differences between the nauticam vacuum system, the backscatter airlock and the leak sentinel. Whilst the airlock has a gauge on the pump the other two systems don't. This means that with the backscatter system you can take the housing down to 350+ mbar or 10hg and effectively lock the system, the nauticam system and the leak sentinel give you a green light at 200 mbar or ~5hg which is sensibly less. This is still sufficient to avoid a port to drop but is not sufficient to keep the housing closed if you accidentally hit the locking hatch that most of medium and smaller nauticam housing have. This latch system is very secure however you could hit the red button and rotate and the torque easily breaks the nauticam housing open. Probably if you pump enough vacuum it will become very hard however the nauticam system itself will not tell you the actual pressure inside the housing and it is not recommended to pump more vacuum as the system is temperature controlled so creating more vacuum does actually make the in water alarm less effective

The nauticam system currently is the most advanced leak detector and with the integrated circuit is 100% reliable in water. The backscatter does not have an in water alarm and the leak sentinel can give false reading in case of heating up of the equipment inside the housing. My nauticam housing can't be retrofit but if it could i would get their system.

Leak sentinel had also a temperature sensor but currently this is not used by the software

Edited by Interceptor121

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We have a leak sentinel on our Amphibico Genesis housing. As said earlier in this thread, you haven't got a rats chance in hell of opening the back of it without applying a serious amount of brute force and ignorance once the pressure has been reduced.

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