Vacuum Leak Test

  • It Used To Be Not If, But When!

    Anything taken underwater that has an air-space within it will have a tendency to leak. This sad fact of life used to be never more true than with cameras. There was even the once ironically named Society of Nikonos Flooders! So the philosophy of underwater photography combined with the realism of the likelihood of a flood coined the advice, “It’s not if, it’s when.”

    So why does something that is designed to keep the water out, let the water in? Well, it’s all down to the fact that you need to access a submarine housing from time to time, whether it is to renew a battery or replace a memory card. The seal at the point of entry is usually effected by an O-ring that sits it a groove and abuts another surface when the unit is closed up. If the point of contact between the O-ring and these surfaces is not scrupulously clean and smooth, free of any foreign bodies like hair or grit, the seal will be broken and water at the pressure of depth will hose through the so-caused gap.

    The O-ring must be lightly greased. This does not help it seal but simply allows the O-ring to flex and move as the two surfaces are offered up to each other. Too much grease can in itself cause a leak. You should just put on enough to make it glisten.

    Passing a clean O-ring between your lips can help you detect if it has any grit or hair clinging to it and you might do this before you re-grease it. O-rings are often supplied with camera housings as spares but the original will never wear out. You would need to damage it with a sharp object for it to need replacing.

    So keeping the opposing surfaces smooth and clean and placing a clean lubricated O-ring between them should maintain a perfect seal – but bad things can still happen. Using the wrong type of grease can cause a leak. If you use silicone grease on a silicone O-ring, it can cause it to swell or start to dissolve. Use the right grease - an environmental silicone - even on neoprene O-rings.

    Don’t leave your rig in a fresh water rinse tank. Other divers may not be so careful about your precious kit and a careless collision with another object being rinsed could cause some catches to come undone.olympus_tg4_package_1

    Isn’t there a better way? Well, yes there is. If you want a compact camera, what about the Olympus TG4 in an Olympus housing? You will need to maintain the main O-ring of the housing in much of the same way as you would any other make of housing but the TG4 has a second line of defence in the event of an ingress of water into it. The Olympus TG4 is itself an amphibious camera and can be used down to 15 metres deep just as it is. Put it inside it’s housing and, should the housing be found to leak, you will only need to ascend to 15 metres deep and later, open the housing and rinse it in some fresh water and dry it, before you are ready to reinstall it in its housing, first having discerned what caused the leak in the first place.

     

    nauticam_na_g7xIf you go for a compact in a more elaborate housing, buy a Nauticam and spend the additional £191 on a vacuum leak-test kit. These vacuum leak test are available on bigger more expensive Nauticam housings for bigger and more expensive cameras and nobody in their right mind would eschew the chance to never suffer another leak again.

    The vacuum leak test as an integral part of a housing was first introduced by Hugyfot. These housings are available only for more expensive cameras but when they were first introduced many years ago, several owners suffered flooded cameras. The problem was that these housings are securely sealed and locked using bolts. These bolts were sometimes not fastened tightly enough and when the clamshell housing was pushed together by the intense pressure found at depth, the bolts could work loose. When the diver ascended to a lesser pressure, the two halves of the clamshell housing could become loose and a flood was the result. The Hugyfot vacuum leak-test was the answer to this problem (now included as standard equipment on all Hugyfot housings) and Nauticam has more-or-less adopted a similar system.hugyfot_canonmk3_front

    This is how it works: The camera is sealed inside the housing with a lightly lubricated O-ring to seal out water, as usual. A pressure sensor within the housing confirms it is working and a (red) LED signals that the air inside the housing is at the same pressure as outside.

    The air is then vacuumed out of the housing via a special one-way valve using the pump provided. The pressure sensor inside detects that the air pressure is suitably reduced and a green LED shows. Green is good.

    The user then waits to see if the green light remains or whether a red light will show instead. It is recommended to wait around 20 minutes. If no air has leaked in, no water will leak in. Depressurizing the interior of the housing has a secondary benefit. Outside air pressure pushes the two parts of a clamshell housing together so firmly that you need not do up any bolts or close catches (should you forget) and you literally cannot prize the two parts apart without letting air back into the housing via the valve provided.

    nauticam_5dsrSo this cured at one stroke, the problem of Hugyfot users not fastening the housing bolts sufficiently, as well as ensuring there was going to be no leak. Hugyfot cured this design/user defect at one stroke.

    Underwater photographers find that winking green light to be very comforting on a dive and never open the valve to let air into the housing until they are out of the water and done using the housing. Now it’s not not-if-but-when, it’s green ensures your costly camera will survive!

     

     

     

  • Vacuum Leak Tests

    Photographing a Dugong in Egypt The Author photographing a Dugong in Egypt
    In a career as an underwater photojournalist spanning twenty-one years I made around three-hundred individual dive trips. That amounts to more than six-and-a-half -thousand dives and virtually every one was made armed with a camera. Would it surprise you to know that in the process I flooded a couple? Well, you might think that two floods in that many dives is not a bad average but I can tell you that every one left me cringing. It’s not just the cost of replacing the camera but it’s the cost of missing out on the pictures while you are so disarmed. How do floods occur? Inevitably it’s a case of user error. All you need is a badly seated main O-ring or some foreign body to drop on to it just as you close up the housing and it’s “Goodnight, Nurse!” Putting the camera into its housing after reloading a freshly charged battery of a new memory card should be straightforward. It is if you are in a clean environment such as a well-lit hotel room and nobody distracts you while you do it. However the world is not a perfect place and substitute those idyllically serene conditions for the rolling deck of a dive boat in a rough sea or the gloomy interior of an island hut and operational accidents can happen. Some people take their housings into the sea for a first dive without their camera installed. I see little point in this since the housing must be cracked open in order to install the camera later and that is when O-rings might pop unobserved or  a stray strand your girlfriend’s hair might float into the place where it can cause chaos. As a busy professional, I always carried a duplicate camera and lens with me in case the worst happened. I might see tell-tale bubbles escaping from the housing while underwater and lose a dive but at least I could carry on afterwards. To flood two cameras on the same trip is tantamount to carelessness.
    The author photographing a Great Hammerhead (Picture by Bob Semple) The Author photographing a Great Hammerhead shark (Picture by Bob Semple)
    With a little compact camera in a transparent plastic housing you can always check for a leak by gingerly immersing it in the fresh water rinse tank. The sight of a few drops of water that can be removed before they do any real damage will reveal a leak. Not only that but a cursory examination of the O-ring in its groove through the transparent plastic will show up any break in the watertight seal. Not so with machined aluminium housings. One just had to be fastidious in preparation and have faith in your ability to do it right. A leak detector merely sets off a loud siren should it detect water inside the housing. By then it is usually too late and only adds more crisis to the drama as you try to get back to the surface before the precious camera inside is lost for good.
    Leaksentinel unit Nauticam Vacuum Valve
    Gradually I evolved from shooting on 35mm film to digital cameras and from there inevitably ended up working with full-frame DSLR cameras. These became so expensive to buy that there was no way I could warrant the expense of doubling up but technology came to my rescue in the form of the vacuum leak-test.
    Nauticam Leak Detector In Use Pumping out the Air from the Housing
    Instead of testing for leaks with water that will ruin the camera should you get it wrong, you test for leaks prior to diving using non-destructive air. This is by and large how they work although different makes of equipment have intermediate lights using different strategies. After sealing up the housing with the interior full of air at ambient pressure, a warning light indicates that. It is red. You then pump out the interior through a special valve in the bulkhead of the housing using the pump supplied. Once the interior pressure-sensor determines that a suitably low pressure has been reached, the indicator light shows green. Green is good.
    Nauticam traffic lights Indicator Lights. Green is Good, Red is Bad!
    Leave the housing for at least twenty minutes. If any air leaks back in, the warning light changes to red. Red is bad. If that happens you should reopen the housing and see what is amiss. It’s not a test of the housing. It’s a test of how well you closed it up after installing the camera. During the last seven or so years that I had the benefit of the vacuum leak test on my camera housing, I never lost a camera. Twice in that time I got a red light but was able to rectify the problem before it was too late. In previous years I would only have discovered the fault once I was under water with depressing results.
    Leaksentinel by Vivid Housings Sentinel Vacuum Leak Test
    I recommend anyone with a valuable camera to get the advantage of a vacuum leak test installed. Both Hugyfot and Nauticam, makers of camera housings, can supply them although it is an extra cost with Nauticam. There is also and after-market version called the Leak Sentinel that can be fitted to a wide range of housings. I can confirm that I always slept well in my cabin or hotel room while that little green light winked all night but I woke up with a start both times a red light began to flash. Green is good. A by-product of depressurising the housing is that the fittings are pulled tight and it is impossible to open unless you purposefully release the air-input valve. This means that both lens port and back are secure from accidental opening, for example in the fresh-water rinse tank, the site of many an accidental flood. I recommend you get a housing with a vacuum leak test or get one fitted and be released from the stress of waiting for a flood. After all, the saying goes, it’s not ‘if’ but ‘when’. John Bantin is the author of Amazing Diving Stories.

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