Jump to content


Photo
- - - - -

New Housing "Airlock" Vacuum from Backscatter


  • Please log in to reply
195 replies to this topic

#161 roshanzamir

roshanzamir

    Hermit Crab

  • Member
  • Pip
  • 3 posts

Posted 16 July 2013 - 10:22 PM

very helpful. 

 

thank you...



#162 aquanomad

aquanomad

    Sea Nettle

  • Member
  • Pip
  • 14 posts

Posted 03 September 2013 - 12:51 PM

Im about to buy a leak check. Either the backscatter or sentinel. The sentinel looks more streamline is almost half the cost! Any reason to shell out double the money for the backscatter?



#163 NikonKidF3

NikonKidF3

    Starfish

  • Member
  • Pip
  • 9 posts

Posted 03 September 2013 - 01:22 PM

Im about to buy a leak check. Either the backscatter or sentinel. The sentinel looks more streamline is almost half the cost! Any reason to shell out double the money for the backscatter?

Just returned from another successful week of diving in Key Largo, using the Leak Sentinel on my Aquatica AD90.  It adds a tremendous level of confidence and eliminates much of my anxiety when the camera hits the salt water.  

 

I always assemble my rig in my hotel or condo before leaving for the boat, and don't have to open the enclosure to replace data cards or batteries between dives.  I pump the enclosure down about 1/2 hour before leaving, and make sure the blinking green light is on before I leave for the boat.  

 

Diving the Spiegel Grove, I did find that the light went from blinking green to alternating blinking red-green, the caution condition. I noticed this at about 90 feet.  I didn't see any water in the port or the back window, and thought it very likely that the enclosure was being squeezed to a slightly smaller volume at 90 feet than at the surface, thus raising the internal pressure very slightly.  This turned out to be the case, and upon ascending the line at the end of the dive, the light went to straight blinking green at about 60 feet.  There was not a hint of water in the enclosure when I opened it up at the condo that afternoon.  I have taken to pumping the enclosure a bit further down than before: 8-10 strokes on the pump instead of 4-6, and that seems to have taken care of the false alarms.

 

Ergonomically, the Leak Sentinel LED is positioned right at the top of the housing for me, in the second strobe bulkhead port, placing it at eye level every time I swing the enclosure up to shoot.  I can't help but see the light and check that it is blinking green (it looks yellow underwater) throughout the dive.  Battery life appears to be very long, certainly more than the 24 hours I spent underwater and leak checking my enclosure in the condo (I pump the enclosure down and leave it blinking overnight if I make any changes such as removing the port or replacing a bulkhead).

 

I think any vacuum leak detection system makes a huge difference in reducing anxiety about your equipment.  The Leak Sentinel does the job for me with no fuss, no muss, no sticky mess.  I think the other systems would do a fine job as well.  

 

Willis



#164 diverdoug1

diverdoug1

    Eagle Ray

  • Member
  • PipPipPip
  • 392 posts
  • Gender:Male
  • Location:Sarasota, Florida
  • Interests:UW photography, Cave diving, Trimix, Spearfishing, Saltwater fishing, Freshwater fishing, Skiing

Posted 16 September 2013 - 01:06 PM

Gates housing vacuum check system uses the same valve. Gates uses a battery powered pump. This system has been around for a long time for high end video housings. I have my own version for DSLR for over 8 years on request from customers. Not one had serious problems. No electronic is a plus. The pump with the gauge is all you need. It is only partial vacuum like -0.5 bars which simulates about 5m depth. User could either leave vacuum in or purge it. Very unusual to have a sudden o-ring seal failure when the housing is under equal hydrostatic pressure from the water column. Unless user decide to whack the port on a rock. I had over 8 years and more than 60 people with these vacuum valves for both DLSR or video housings. I know they work. Keep it simple. Electronic only adds more stress.  The seal is checked on land and if seal is not working then the gauge will drop. Sort out the o-rings and then check again. O-ring either fail or working. They don't just decide to fail halfway. Anyway Backscatter version looks simple enough. Its the way to go for peace of mind.

 

Cheers

David

I put a hair across my main o-ring, and pumped down my system to 10" Hg.  It took almost 10 minutes for the vacuum to fall below 5" Hg.  So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.


Edited by diverdoug1, 16 September 2013 - 02:10 PM.


#165 ianmarsh

ianmarsh

    Triggerfish

  • Member
  • Pip
  • 43 posts
  • Gender:Male

Posted 17 September 2013 - 09:11 AM

I put a hair across my main o-ring, and pumped down my system to 10" Hg.  It took almost 10 minutes for the vacuum to fall below 5" Hg.  So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.

Doug,

 

Good point, indeed.

 

I have the non electronic version... seems like a solid piece of gear. Very reassuring, but:  With that model, a STABLE vacuum reading is critical.

 

If the vacuum is changing, the housing is leaking.

If you start out at -10in/Hg and it "drops" to -5in/Hg the absolute value doesn't matter. It doesn't start to leak when it gets to 0in/Hg.

The ∆ indicates a leak, and if its leaking air, it is leaking water.

 

The point is, with a non monitored system, stability of the initial reading is key. Don't fool yourself into thinking a small change doesn't matter. It does.

 

However, be aware of temperature/pressure fluctuation.

 

ian



#166 pointy

pointy

    Moray Eel

  • Member
  • PipPip
  • 81 posts
  • Gender:Male

Posted 19 September 2013 - 06:45 AM

Why do divers hate ideas that are obviously good? You will ALL be using vacuum leak tests (complete with flashing green lights) within a decade, apart from the dinosaurs among you!

 

A leak check system is a good thing, but people are paying a lot for flashing lights to indicate either enough, or not enough vacuum. Such basic two point  monitoring could fail to detect a slow leak, so we should hope to improve on that over the next decade. 

 

An altimeter within the housing gives constant assurance that the housing is tight. Some Swiss Army knives come equipped with tiny altimeters, so maybe housing manufacturers will design better and cheaper vacuum monitoring.

 

John McCracken



#167 diverdoug1

diverdoug1

    Eagle Ray

  • Member
  • PipPipPip
  • 392 posts
  • Gender:Male
  • Location:Sarasota, Florida
  • Interests:UW photography, Cave diving, Trimix, Spearfishing, Saltwater fishing, Freshwater fishing, Skiing

Posted 19 September 2013 - 08:52 AM

I plan on pumping my system down to -7''Hg, then if it goes from green to yellow in the time it takes me to get ready to dive, I will be alerted to a leak.  I will keep in mind that a significant increase in internal housing temperature may give me a "false positive" leak test.



#168 Nicool

Nicool

    Wolf Eel

  • Member
  • PipPip
  • 172 posts
  • Gender:Male
  • Location:Antibes, France

Posted 20 September 2013 - 03:52 AM

Hi Folks,

 

I used to be more tempted by electronic vacuum checks, I mean the ones with a LED like Hugycheck, Leak Sentinel, Airlock electronic.

However I got troubling situations with my Leak Sentinel several times: the LED was green on land, and after a dive was no more (and it didn't return to green later). In another occasion I left the housing ready at home for a few hours, it was still green, and when arriving on the dive site, no more green. This did not sound logical to me so both times I did dive (closely watching the moisture alarm), and the housing didn't flood.

From above discussions it seems those "fake warnings" could be due to temperature changes. Maybe, but I am missing the purpose of feeling calmer when taking my gear underwater...

If I understood well the above talks, if I get a stable pressure after 30 minutes of vacuum, then it won't move no more, a leak would have been detected. Then I don't need any LED, right?

Actually there's one situation where I'm in doubt: what if your vaccuumed housing gets a shock, e.g. in the dive boat, let's say on your macro port. Any risk the vacuum between port and housing gets jeopardized? Then I'd see a clear interest for continuous feedback LED.

 

cheers

Nicolas



#169 John Bantin

John Bantin

    Sperm Whale

  • Industry
  • PipPipPipPipPip
  • 1859 posts
  • Gender:Male
  • Location:Teddington/Twickenham UK
  • Interests:former Technical Editor of
    Diver Magazine (UK) and www.divernet.com
    occasional contributor
    SportDiver (Aus)
    Undercurrent
    Author of Amazing Diving Stories (Wiley Nautical)

Posted 20 September 2013 - 04:52 AM

Sounds like you've got reliability issues with the electronics. The only time I got a false red on the Hugycheck (two different housings owned and a great many dive trips) was when I took it from a cold environment where I closed up the housing into a very warm pool. I wouldn't countenance a housing without it now. (Nauticam's will be available any day now)

 

I've had two red lights, both with the D800.

1/ I arrived in Cyprus and put my housing/camera together for an early morning start, in my hotel room. I went for dinner with green flashing. When I came back I had a red. Reassembled the camera and woke up in the night to see a comforting green light.

 

2/ Went to Malpelo. I assembled the housing/camera during a rough crossing. Went for dinner. Came back to find a red light.

 

That's twice I might have lost a D800 and lens. It's very comforting to see the green light reflected on a cabin ceiling and helps you get a good night's rest!


Edited by John Bantin, 20 September 2013 - 04:58 AM.

I buy my own photographic kit. Diving equipment manufacturers and diving services suppliers get even-handed treatment from me whether they choose to advertise in the publications I write for or not. All the equipment I get on loan is returned as soon as it is finished with. Did you know you can now get Diver Mag as an iPad/Android app?

 

#170 diverdoug1

diverdoug1

    Eagle Ray

  • Member
  • PipPipPip
  • 392 posts
  • Gender:Male
  • Location:Sarasota, Florida
  • Interests:UW photography, Cave diving, Trimix, Spearfishing, Saltwater fishing, Freshwater fishing, Skiing

Posted 20 September 2013 - 06:52 AM

Going from a 71 degree airconditioned room to 85 degree water caused my vacuum reading to go from -10"Hg to -7"Hg.  If it had caused a slightly greater decrease in vacuum, my indicator light would have flashed yellow.


Edited by diverdoug1, 20 September 2013 - 07:45 AM.


#171 MarkD

MarkD

    Lionfish

  • Member
  • PipPip
  • 52 posts
  • Location:Cardiff, Wales, UK

Posted 21 September 2013 - 08:08 AM

I have just come back from the Red Sea with my bulkhead Housing Sentry equipped housing. I strongly support the reassurance that the flashing green light provides although of course this is no substitute for careful assembly procedures. After one rather rushed equipment change in my hot and dark resort room, the housing was de-pressurised but it seemed to take longer than usual to reach the green light pressure. As I put the housing into it's carry bag a few minutes later, the flashing changed to red. Reassembly of all the o rings traced the probable leak to salt crystals on the main housing o ring/seating, with no subsequent problems on re-cleaning and reassembly. I believe that in all probability, Housing Sentry saved an expensive flood and a disappointing photography trip. No matter what we all believe about our own careful and methodological procedures, we are all susceptible to human error, especially when under pressure or in suboptimal conditions.

 

A quick plug for Housing Sentry - I discovered that the electronic module was not functioning properly during preparations shortly before this trip. An exchange of emails between myself, Bill and Mary at Underwater Camera Stuff led to the electronics speeding back across the Atlantic, being repaired (threshold components replaced), exhaustively tested and express couriered back to the UK FOC, all in 8 days door to door. Remarkable service and back-up for their kit.

 

Mark



#172 John Bantin

John Bantin

    Sperm Whale

  • Industry
  • PipPipPipPipPip
  • 1859 posts
  • Gender:Male
  • Location:Teddington/Twickenham UK
  • Interests:former Technical Editor of
    Diver Magazine (UK) and www.divernet.com
    occasional contributor
    SportDiver (Aus)
    Undercurrent
    Author of Amazing Diving Stories (Wiley Nautical)

Posted 22 September 2013 - 09:47 AM

Some day all housings will be equipped this way....:)


I buy my own photographic kit. Diving equipment manufacturers and diving services suppliers get even-handed treatment from me whether they choose to advertise in the publications I write for or not. All the equipment I get on loan is returned as soon as it is finished with. Did you know you can now get Diver Mag as an iPad/Android app?

 

#173 drsteve

drsteve

    Manta Ray

  • Member
  • PipPipPip
  • 483 posts
  • Gender:Male
  • Location:Santa Barbara, CA

Posted 22 September 2013 - 11:52 AM

I don't want to be a shill for Backscatter, but I bought one of their systems and am very happy with it.  It was a bit pricey but the peace of mind is worth it.  Besides no one is suggesting that a vacuum system is a substitute for regular maintenance and careful inspection during assembly.  Being able to measure the housing integrity sure beats looking for bubbles in the rinse tank. 

 

It also solves one of the things that has bugged me about my housing for years.  That is that the main housing o-ring is intentionally under compressed by design.  If you go to any o-ring catalog or consult the Machinist's handbook, there are very clear design guidelines that date back nearly a century.  Face seal o-rings are supposed to be clamped tightly enough that the two metal surfaces come into contact, with the o-ring trapped in the groove.  Every housing I have seen violates this design rule.  I believe that it is because the clamping force required for such a large o-ring would require bolts, and housing vendors perceive that this would be too annoying. Instead, for convenience, they use suitcase style cam-latches, which cannot provide enough force to complete the face seal.  That is one of the reasons there are so many floods in the rinse tank.  An under-compressed o-ring seal can flood when bumped.  Most housing vendors explain away this design decision by saying that the water pressure causes the housing to "seal better" when you take it diving.  This is certainly true, but it is really an acknowledgment that the seal is marginal at the surface!  Perhaps someone can correct me, but I think that only Hugyfot uses bolts instead of suitcase clamps.

 

Another benefit from a real face seal, is that if you shore dive with your housing (which I rarely do), the gap between the two surfaces can allow sand to enter.  It doesn't necessarily compromise the seal, because it is outside the o-ring, but as you descend, it gets ground into the surface as they are pressed together under pressure.

 

The vacuum check system solves this problem.  The partial vacuum provides the additional pressure to complete the face seal.  It also locks the ports.  I love it!


...STeve
www.flickr.com/photos/drsteve/
Canon EOS 5D3, Aquatica Housing, Inon Z220+Z240 strobes, Sea&Sea TTL, ULCS Arms


#174 ChrigelKarrer

ChrigelKarrer

    Great Hammerhead

  • Member
  • PipPipPipPip
  • 796 posts
  • Gender:Male
  • Location:Playa Herradura-Costa Rica and Sardinia-Italy

Posted 22 September 2013 - 12:37 PM

Perhaps someone can correct me, but I think that only Hugyfot uses bolts instead of suitcase clamps.

 

Yes, Hugyfot uses bolts to tighten with a allen wrench.
I am not sure if this closes the housing better nut i am sure that this avoid a semi-closed / unlocked latch snapping open under water.

Chris


Nikon D800 + Sigma 15mm + Nikon 105mm Micro VR + Hugyfot Housing + 3 Inon Z-240 strobes + 2x2 8'' ULCS arms - Panasonic LX100 + Nauticam Housing + SubSea +10 diopter
Nikon D90 + Ikelite housing + Ikelite DS125 strobe (for sale) - Nikon D7000 + Hugyfot housing (for sale) 
Canon G1X + Canon OEM housing (sold) - Canon G12 + Patima aluminium housing  (for sale) - - Fuji E900 + Ikelite housing (for sale)
Visit My Costa Rica Website - Visit My Italy Website


#175 John Bantin

John Bantin

    Sperm Whale

  • Industry
  • PipPipPipPipPip
  • 1859 posts
  • Gender:Male
  • Location:Teddington/Twickenham UK
  • Interests:former Technical Editor of
    Diver Magazine (UK) and www.divernet.com
    occasional contributor
    SportDiver (Aus)
    Undercurrent
    Author of Amazing Diving Stories (Wiley Nautical)

Posted 24 September 2013 - 02:59 AM

http://www.undercurr...ests201304.html


I buy my own photographic kit. Diving equipment manufacturers and diving services suppliers get even-handed treatment from me whether they choose to advertise in the publications I write for or not. All the equipment I get on loan is returned as soon as it is finished with. Did you know you can now get Diver Mag as an iPad/Android app?

 

#176 adamhanlon

adamhanlon

    Harbor Seal

  • Admin
  • 1944 posts
  • Gender:Male
  • Location:Lancaster, UK

Posted 24 September 2013 - 01:38 PM

I, like a few others, can't seem to leave this thread alone!

 

As I understand it, if an O ring seal is to be tightened until metal to metal contact is ensured, a soft O ring of 50 or 60 shore is required. Unfortunately, this softness of O ring would deform and need replacing after almost every use. The reason this features in machinists handbooks and the like is that most engineering applications for O rings are for permanent installations, rather than situations in which the seals are regularly disturbed.

 

Even with a bolt type closure, the only way to guarantee metal to metal contact would be to specify a torque to do so. 

 

Firmer, harder O rings, located in a suitably deep groove, have sufficient material hardness to form a seal that will not extrude despite the metal not meeting. There are quite literally millions of examples of this in action-not least of which would be the O ring sealing your regulator onto your tank!

 

Just to emphasise again, I would imagine that few underwater photographers rely on "gingerly dipping" their housings in a rinse tank. Cleaning, inspection and careful preventative maintenance are the key. Vacuum detectors simply prove that you have followed these procedures correctly.

 

I think I need to stop following this thread:)

 

Adam


Adam Hanlon-underwater photographer and videographer
Editor-wetpixel
web | Flickr | twitter | Linkedin | Facebook


#177 drsteve

drsteve

    Manta Ray

  • Member
  • PipPipPip
  • 483 posts
  • Gender:Male
  • Location:Santa Barbara, CA

Posted 25 September 2013 - 04:18 PM

Adam, you are partially right, but you have confused the hardness of the o-ring material (durometer) with the o-ring resiliance, which is the tendency to become permanently deformed.  The durometer rating is related to the clamping pressure required to make the seal, whereas the resilience depends primarily on the material used and the percent compression. If you have enough clamping pressure (ie bolts) you don't need to use a soft material.  For example Buna-N o-rings are inexpensive and have good resilience, which is why they are so commonly used.  A face seal using a 70 durometer Buna-N o-ring with a 15% compression is good for over 3000psi without even trying.  If you use bolts, you get plenty of clamping force.  You don't need a torque wrench, you can simply tighten the screws until you hit the hard stop of the two surfaces touching.  The problem is that the suitcase clamps can't do this, so the housing vendors rely on an incomplete face seal and let the water pressure complete the seal.  To me this is a poor trade-off and explains the tendency for housings to flood in the rinse tank.  Frankly, the pressures experienced in recreational diving are trivial for a good o-ring design, so unless the o-ring is physically damaged, issues like compression set should be almost irrelevant.  If you are interested, there is more than you ever wanted to know about designing seals at  http://www.logwell.c...er_Handbook.pdf

 

I too need to give this thread a rest.


...STeve
www.flickr.com/photos/drsteve/
Canon EOS 5D3, Aquatica Housing, Inon Z220+Z240 strobes, Sea&Sea TTL, ULCS Arms


#178 John Bantin

John Bantin

    Sperm Whale

  • Industry
  • PipPipPipPipPip
  • 1859 posts
  • Gender:Male
  • Location:Teddington/Twickenham UK
  • Interests:former Technical Editor of
    Diver Magazine (UK) and www.divernet.com
    occasional contributor
    SportDiver (Aus)
    Undercurrent
    Author of Amazing Diving Stories (Wiley Nautical)

Posted 26 September 2013 - 11:38 AM

I, like a few others, can't seem to leave this thread alone!

 

As I understand it, if an O ring seal is to be tightened until metal to metal contact is ensured, a soft O ring of 50 or 60 shore is required. Unfortunately, this softness of O ring would deform and need replacing after almost every use. The reason this features in machinists handbooks and the like is that most engineering applications for O rings are for permanent installations, rather than situations in which the seals are regularly disturbed.

 

Even with a bolt type closure, the only way to guarantee metal to metal contact would be to specify a torque to do so. 

 

Firmer, harder O rings, located in a suitably deep groove, have sufficient material hardness to form a seal that will not extrude despite the metal not meeting. There are quite literally millions of examples of this in action-not least of which would be the O ring sealing your regulator onto your tank!

 

Just to emphasise again, I would imagine that few underwater photographers rely on "gingerly dipping" their housings in a rinse tank. Cleaning, inspection and careful preventative maintenance are the key. Vacuum detectors simply prove that you have followed these procedures correctly.

 

I think I need to stop following this thread:)

 

Adam

 

 

Adam, The Nauticam version will arrive any day and then you can sleep soundly in the knowledge!


Edited by John Bantin, 26 September 2013 - 11:39 AM.

I buy my own photographic kit. Diving equipment manufacturers and diving services suppliers get even-handed treatment from me whether they choose to advertise in the publications I write for or not. All the equipment I get on loan is returned as soon as it is finished with. Did you know you can now get Diver Mag as an iPad/Android app?

 

#179 Deep6

Deep6

    Great Hammerhead

  • Member
  • PipPipPipPip
  • 885 posts
  • Gender:Male
  • Location:Broomfield, CO

Posted 26 September 2013 - 11:48 AM

Adam, The Nauticam version will arrive any day and then you can sleep soundly in the knowledge!

Oh thank you John for that reassurance!  :dancing:


Carpe carp - Seize the carp


#180 adamhanlon

adamhanlon

    Harbor Seal

  • Admin
  • 1944 posts
  • Gender:Male
  • Location:Lancaster, UK

Posted 27 September 2013 - 10:20 AM

Hi John,

 

I know it is a big ask, but if you read my reviews, you would know that I have been using the Backscatter one for some time! I don't find that it affects my sleep in any way at all. 

 

http://wetpixel.com/...zen-dp-100-port

 

http://wetpixel.com/...ty-check-system

 

I should also point out that it was kindly supplied by Backscatter free of charge for review purposes. There are now other similar units available from many other manufacturers and suppliers, including the one that John espouses in his Undercurrent article.

 

For what it is worth, rinse bucket O ring leaks are normally due to O rings not being located properly,being damaged or being dirty. A correctly installed, undamaged and clean O ring will not leak in a rinse bucket ( or anywhere else!) If it was common, most underwater photographers (including John before he saw the "light") would have flooded their housings many times over. Housing leaks are not caused by poor design or engineering, but by user error.

 

Even so, I can't find any reference to face to face contact in static seals being necessary in the text above....Perhaps I missed it.

 

Adam


Adam Hanlon-underwater photographer and videographer
Editor-wetpixel
web | Flickr | twitter | Linkedin | Facebook