Vacuum leaking on ROV

Hello.

My BlurROV is currently leaking too much and i cant seem to find out where it is? I’ve taken out all O-rings and changed all orings expect for the ones on the battery chamber since i do not have replacements for them. I’ve cleaned all the grooves with alcohol and greased the rings and put them back and remounted everything. Still it is leaking a bit fast. About 0.01PSI pr 7-8th second.

Time passed: 252 sec of 900
Current pressure is: 4.83 (Started at: 4.5)

Time passed: 368 sec of 900
Current pressure is: 4.96

And test fails at 4.5PSI:

ROV seems leaky, internal pressure did pass 5PSI during the test period.
It hit 5.01 in only 411.577 seconds… Starting point: 4.5PSI

Release pressure before you continue then press ‘Confirm’ then check for leaks

And it should be under 5PSI after 900 seconds. How can I find the leak without dismantling the whole thing again? Any tip? Been looking for days now. The oring seems tight around all the fittings

@thorleif,

You just might have air coming up the battery cable from the Battery WTC.

I had this happen to me so I pull a vacuum on both the Control WTC and the Battery WTC at the same time.

Regards,
TCIII AVD

Hi, I test both chambers at the same time. So should not be that afaik.

Visually check all of the cables. I’ve nicked one by accident cutting a cable tie.

Regards,
Ken

Hi @thorleif Interesting that you’re having sealing issues, sorry about that!

Something you can try is to apply a slight positive pressure to the inside of the WTE via the vent penetrator port and applying a soapy water solution to the areas around your penetrators and other seals. Also apply it to where the cables are epoxied into the penetrators. If you see bubbles, then that points to the location and defective part.

The other more painful way of doing this is to remove a penetrator at a time, blank it off, and re-conduct the vacuum test. A process of elimination will most likely find your defective penetrator.

If you find the location and it is a manufacturing defect, please e-mail us at support@bluerobotics.com and we can get you a replacement component.

@thorleif What program are you using to test the pressure?

@jwalser: I am using the internal barometer BMP180 on i2c for raspberry pi. Have a custom “pressuresafe” batterypack to run the ROV’s internal up and closes it up then i do the pressure. As soon as it hit belov 12PSI the pressure test starts once it reches 4.5 it starts a count, if it reaches 5.01 before 900 seconds it fails.

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@thorleif Can I ask if you found the leak, and how? Did you have to go penetrator by penetrator ?

I have a similar situation, and can’t seem to find the leak.
At 30-50 m there was water ingress so I know there is a leak.

Checked visually all cables, penetrators, dome etc, nothing.

Vacuum test @ 15 in hg for 30 min, no change. Sudden and slight drop when I checked 20 minutes later.
Submerged in water with 0,3 bar over pressure, no air bubbles.
Vacuum test @ 15 in hg for 1 hour and no change.
Submerged in water with 0,5 bar over pressure, no air bubbles.

have you tested the vacuum pump itself? Some are not as good as others

Yes, I’ve used 3 pumps from 2 different brands with the same results.
Maybe the hole or crack is just small enough for a leak at depth, but not big enough to affect the reading on the vacuum pump.

I could try a quick dip to 30-40-50 meter with an immediate re-surface, and then check for water ingress.

More to try if You hav´nt:
-Move cables, penetrators etc manually while pressure/vacum testing
-Could Temperature be a factor? (colder in water then test bench?)

hi
I use an ultrasonic transducer and detector, place transducer in the pressure vessel and seal as normal then use the detector to find the smallest of leaks. no vacuum needed unless you need to use it to help seat the O rings.

Do you have a link for the device? Or is it Arduino based?

Hi,
This is the amazon link in the uk, there is a better one in the US but much more expensive. The cheaper one really works.

https://www.amazon.co.uk/Ultrasonic-Detector-Pressure-Accessory-Detecting/dp/B07ZVDSQKR/ref=sr_1_12?keywords=ultrasonic+leak+tester&qid=1575406366&s=kids&sr=8-12

Ricci

i had a similar problem, putting overpressure inside the ROV showed that air is passing trough the penetrator all the way down the sonar cable and finally exiting from the sonar attachment… I would have never expected or found this one.

I think I found the problem… my land-rov might finally touch water again. After a lot of trying and failure my last resort was to pull all the plugs and electronics from bottom again. Seems like the O-rings have been flattend (using the first bulkheads with thick o-ring). So i am going to try to get some fresh orings they are sure 5 years old atleast… From the release of the bulkheads…

But I’m tempted to swap for the new connectors. But these are epoxied. So my question is, anyone done a swap from old bulkheads to new? Need to cut the cable possible? And if so can I change the cable to the thruster easily? Or is it epoxy all the way ?

I’d recommend reading through this post for some tips on swapping from potted penetrators to the new WetLink ones :slight_smile:

That depends whether you’re wanting to just change the penetrator, or if you’re wanting to actually swap the cable for a different one. See this comment for some details :slight_smile:

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