Nauticam Vacuum valve - how much vacuum?

Cooler water will cause the pressure inside to drop, but the housing electronics attempt to compensate for that - the only thing I can think of is that this compensation may not be exact and it's enough to trigger the alarm as you are too close to the trigger point. Does it come on straight away or after you reach a certain depth?

How many pumps do you make after the green light? I generally make three pumps after the light first goes green and find the light stays green in the water. As I noted above I do not think the extra vacuum will be an issue, one because it it is not that much lower and two is that air leaks faster than water. If the light stays green for an hour or two the housing is tight and not going to leak. The only time the extra pumps might be a concern is if you jump into the water 5 minutes after pumping it down.

 

Just experienced the same as trickster and Bevan. The strange thing is, why does getting into water that's cooler than the air temperature cause this to happen? I would think that environmental cooling would enhance, not reduce the partial vacuum inside the housing. Oh well, gave me a nice scare, and prevented a blue ring photo!

I think 4 degrees is a very limited range to really create any meaningful effect. Assuming that the volume is fixed 4 degrees are 3.8% of pressure change which is not something the temperature monitor would handle easily

There is one situation that can generate false positives and cannot be handled by any system which is when you prepare the housing in a very cold environment possibly an air conditioned room and the you go in warmer water this can generate up to 10% change of pressure and it will generate a false positive. So in general it is not a good idea to have a significant delta temperature between the preparation room and the water what would be ideal is to have very dry environment at the same temperature

Even if the water is slightly cooler especially if you take video there is a lot of heat generated in the housing that is far more important than the cooler water

So if you have the alert either you have a slow leak or a significant delta temperature between preparation and operating temperature of the camera

Even a 10° change in temperature is actually only a 3% pressure change. the pressure change is proportional to absolute temperature in kelvin so 20°C = 293K and 30°C = 303K If you start at 1 bar absolute the new pressure on heating 10° is 1.03 bar. (P2 = P1 x T2/T1). If you reach 0.1 bar vacuum when you pump down which is 0.9 bar absolute the pressure would change to 0.93 bar when heated 10°C. (Kelvin = °C + 273)

The problem could be simple. Presumably the system as it goes from blue through yellow to green is in a state where it is monitoring pressure and reporting that through LED colour and when it reaches target vacuum switches to a different state where it is monitoring pressure and temperature and is ready to alarm when it detects a change which can't be accounted for. When it does this the system alarms and is supposed to show red. It is quite simple to account for a 10° change with the ideal gas laws. Even a 20° change should not be a problem .

If you watch what happens when pumping it goes yellow and often flickers green- yellow for one or two strokes. The fact people are reporting the light returns to yellow indicates to me this is the case. If it detects an actual loss of vacuum or air/water leaking in the LED should flash red.

I always give it 3 pumps after I first get solid green and have never had this issue. As Is stated in my post above I believe people are over thinking this - air leaks in at a higher rate than water so pump it down and leave your housing sit for an extended period and you will be fine.

A few observations with mine.

I often prepare in a 20c room then dive in water 28 to 31c after that.

I also sometimes have the housing (accidentally) in direct sun in the tropics.

I've never had the vacuum fail or a warning when going to or from these environments.

It is very sensitive though. It picked up a hair on an O ring in about 20 mins and triggered after a few hours when my electrically connected ikelite strobe minus the battery (which was charging) created a tiny leak path through the cable and strobe.

So I think the circuit may well be temperature compensated or similar. It seems to behave with environmental changes but still very sensitive to actual leaks.

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I expect when the housing hits cold water it shrinks slightly, so the pressure inside increases slightly...same amount of gas in a smaller volume.

I would guess that the CTE of aluminum being what it is (20 ppm/degree) the size change is negligible for any practical calculation.

Bill

You are right about temperature being a small effect, but if the back of the housing, for example, bends in from the pressure, then there is less volume inside and the air pressure inside thus increases. I'm trying to find a reason why the vacuum light would turn yellow, not that I've ever seen that. I don't believe it is a changing temperature of the air inside....that would be a very slow process.

I've had (presumably) false positives from most of the continuous monitoring vacuum systems.

For me, this is a flaw in the philosophy. Back in the pre-vacuum days, most people were able to avoid housing leaks by looking after the seals and sealing surface. Now we have continuous monitoring, we seem to be incapable of reverting to this technique!

In my opinion, the monitor should really only be used to "double check" that you have successfully sealed the housings. Once it has done so, there is no need to continue to monitor the vacuum. You could perform the test and then switch the monitor off, but most continuous monitoring systems require you to open the housing in order to disenage it, which kind of defeats the purpose of vacuuming it

There is a benefit in maintaining a vacuum in the housings as it helps to keep the seals engaged, prevents ports rotating and helps avoid sand ingress into the seal. I'm not convinced that there is much benefit in monitoring it though.

The worst case is when the monitor (due to pressure changes or any other reason) gives a false positive. Typically, we spend significant amounts of money on traveling to destinations in order to take pictures. Some times, we also actually need to be taking pictures underwater in order to satisfy clients, and not being able to do so has a direct financial impact.

Adam

Like Adam I’ve had the occasional false positive underwater.

Other than the near heart attack, I’ve usually persuaded myself that all’s well. The housing would have been pressurised for a good while on the surface with the valve showing a green light - and there would have been no problems in the early stages of the dive which I reckon are the critical moments.

So, yeah, I’ve just carried on. Praying of course to St Ohcrap and maybe not enjoying the dive quite so much.

First of all I agree that checking the O-rings and sealing surfaces for cleanliness is vitally important, you really don't want to have a leak and need to open up again to try to find the problem .

I note that the OP and one other refers to the LED flashing amber. When I open the housing and release the vacuum, my Nauticam system flashes RED, not amber. The only time I see amber/yellow is when I'm pumping it down. I think the issue there is that the monitoring system has not switched from indicating sufficient vacuum to monitoring for a change in pressure.

To Adam and Tim, when you say false positives are you seeing yellow/amber light or flashing Red light? Are trying to minimize the vacuum?

To those trying to minimize the vacuum that seems to be assuming there is an absolute value at which the system alarms. I think it is more likely that the system is monitoring for a change in temperature corrected pressure from the initial value, which to me would make more sense as the pressure achieved on pump down will vary quite a lot between different users.

I pump to 3 strokes beyond solid green and let the housing sit preferably at least 20 minutes to give time for enough air to leak in to detect a very slow leak. I have not had any false alarms.

 

To Adam and Tim, when you say false positives are you seeing yellow/amber light or flashing Red light? Are trying to minimize the vacuum?

 

I pump to 3 strokes beyond solid green and let the housing sit preferably at least 20 minutes to give time for enough air to leak in to detect a very slow leak. I have not had any false alarms.

Hey Chris

I'm using the Vivid v5. There's no amber on that so the lights go from red to green.

Like you, I usually pump about 3 times once I get a green light. And again, like you, I wait at least 20 minutes - often over night as I tend to open my housing at the end of the dive day to change battery and download the card - before the housing goes into the water.

I must have had a false positive 3-4 times over the last maybe 150 dives.

@Chris...

I have had false positives from a variety of continuous monitoring systems, and in each instance, they have triggered a "loss of vacuum" warning. This takes different forms with different systems.

I have tried to diagnose why and find that there seems to be a greater prevalence of them when going from a relatively warm room into very cold water. Saying that I have had false positives in many situations.

Perhaps (with the OP's permission) we should refocus this discussion to ask the question: What is the advantage of continuous vacuum monitoring once the housing is in the water?

Bluntly, I can see none and false positives cause significant productivity problems.

All the best

Adam

@Chris...

 

I have had false positives from a variety of continuous monitoring systems, and in each instance, they have triggered a "loss of vacuum" warning. This takes different forms with different systems.

 

I have tried to diagnose why and find that there seems to be a greater prevalence of them when going from a relatively warm room into very cold water. Saying that I have had false positives in many situations.

 

Perhaps (with the OP's permission) we should refocus this discussion to ask the question: What is the advantage of continuous vacuum monitoring once the housing is in the water?

 

Bluntly, I can see none and false positives cause significant productivity problems.

 

All the best

 

Adam

I agree with Adam technically it would be possible to switch off the monitoring by including a clock into the electronics. However if I recall correctly the Nauticam system is not just vacuum but also moisture detection. When water enters the system you get flash red and audible alarm.

I would think that if your vacuum system turns red yellow and you haven’t banged the camera you can ignore it

For systems like vivid behaviour will depend on having or not a separate moisture sensor

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The point I'm trying to make is the OP and another post mentions an amber warning - but the Nauticam system flashes red to alarm. To me this indicates that by playing with the vacuum to try to get bare minimum vacuum they have prevented the system going from vacuum measure mode (for want of a better term) to vacuum monitor mode.

I've looked at this before and it seems that the Nauticam system at least get down to about a 0.1 bar vacuum, possibly less. Atmospheric pressure can vary from 0.87 to 1.07 bar absolute at sea level, though mostly it would be about less than half that variation which is the same order of magnitude as the vacuum being achieved. I think based on this it is unlikely that the system goes green at a fixed absolute pressure, but a fixed differential to the starting pressure.

Similarly if you pump down an extra few pumps I believe the system monitors change from the starting pressure not the difference between the starting pressure and a fixed pressure. This way it can be made more sensitive to detecting small leaks and trying to minimize the vacuum achieves nothing except perhaps increased chance of false positives.

As to whether or not ongoing monitoring is required if the housing is undisturbed probably is not needed. I'm sure though that Murphy could find a way to take advantage of that. I've not had false positives- maybe I'm not diving often enough?

I have the Vivid v4 on my Nauticam housing. My housing is older (Canon 7D) and came only with the leak detector. Sending the housing back for upgrade was not in the cards, so elected to get the Vivid instead. I do love it.

One nice thing about the Vivid is that you can seal the housing, pull your vacuum, then turn the detector off. I only do this if I have to prep the night before, otherwise I seal things up before I head out and just leave it running the whole time until after I'm home and rinsed.

I got in the habit of pumping an extra 7 pumps after getting vacuum. Once you first get the vacuum, the light can flicker, so the extra pumps just ensure a full vacuum is there. With that small pump, we aren't talking much delta-P on 1, 3 or 7 pumps, so I just went for the bit more to be sure.

Reactivating this topic to pick brains.

i have a nauticam Nikon system and have had from new for 1.5 years and 200 dives+. Very occasionally it goes from green to the blue ‘standby’ when it hits the water. The first couple of times I aborted dives, but always found the vacuum to be intact on venting and once left it in the changed ‘blue’ stage for 6 hours before venting and it seemed to be completely intact with a full vent after 6 hours. Anyone have any ideas or similar issues? I’ve completed 3 dives with it in ‘blue stage’ after it changed from green as I hit the water or just beforehand...no leaks.

so, not ‘green to yellow’ but ‘green to blue’ and the blue is the standard slow flashing blue from when you reset the alarm prior to closing the housing and pumping... I have changed batteries several times.

Does it stay blue or flash blue like it does when first turned on?  To me that would be an indication that it has momentarily lost power going back to the initial state.  I would look closely at the connections to power and wiggle them to see if  I could reproduce the fault that way - of course with the housing open you can't stay green but if it were red like after depressuring and went to blue that is likely to be thesame cause.    Also check the battery is inserted properly and change it out to see if that changes behavior.

Stays blue..for a while and then returns to flashing blue...it’s a weird one. I really don’t think it’s the battery as I’ve had 3 different batteries in it over the time and it’s happened with all of them.

it doesn’t really bother me that much now as it clearly isn’t losing pressure, but the bloody annoying thing is that I don’t now if the alarm would ‘actually’ work if there was a leak..

I’m hesitant to wiggle stuff after I tried to remedy a TTL board issue with ‘wiggling’ and it ended up being expensive

thanks for your thoughts though. I just though someone may have had the issue and gotten to the bottom of it,  

Can you reproduce it in a bathtub or pool?  Maybe you could take a video of what happens and get Input from Nauticam.

@Minister: This is strange behaviour. I only had red/blue so far (I cannot remember the exact sequence of red/blue now), when the battery was weak. 4 years, two housings, approx 400 dives and the following problems arose:

#1.: Two alarms before immersion (green => red). I will never will know whether these were right or false alarms, but , of course, did not take my camera underwater (I think the vaccums were, at least weak after opening). I believe these alarms were right ones and prevented flooding...

#2.: Many false alarms upon switching on the system, before even applying vacuum (blue => red; NAEM5II and NAEM1II). This was not due to the vacuum system, but due to the moisture detector, that is, in my hands too sensitive (always occured when the humidity was high; e.g. in bow of a boat or at the equator during rainday). Cleaning, drying, alcohol, re-soldering of sensor - nothing helped. I could only solve the problem by clipping one wire leading to the moisture sensor - never had this problem any more. Some may find this method ruffianly, but the moisture alarm, in principle, still is working (I now have two moisture "sensors" in series ), but less sensitive. I regard the vacuum detector to be the real important alarm (and the vacuum holds the entire assembly together)...

Wolfgang