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Old 07-14-2009, 07:40 PM   #1
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Help with watertight fitting for "submerged" wire

Greetings everyone. I have a question that isn't exactly about aquariums, but I have hit a lot of dead ends in tying to find an answer, and it seems like aquarium lovers might be able to tell me what direction I should explore next.

I am a grad student, conducting research on the effects of wave action on sandy/clayey bottom surfaces. I have a large acrylic (1" thick) wave tank. It is sealed on top and during operation it is at about 6-7 psi inside.

I need to get a few instruments into the water column to measure water speed and sediment density. The instrument have cables roughly 1/2" o.d.

I am looking for some sort of fitting that will allow me to pass a 1/2" cable into the tank, then tighten around it to provide a watertight seal against 6 psi. I need to be able to remove the instruments, since I am sharing them with another research project, so I can't just epoxy them into a hole.

Functionally, this is the same problem as temporarily passing a heavy gauge extension cord into the bottom of a 12-foot deep aquarium. Has anyone here ever attempted doing so without entering through the water surface?

I greatly appreciate any help/suggestions you can give. I am sorry my query isn't quite aquarium-focused, but I can't think of anyone else who would have any experience with this sort of enterprise. I have tried Acrylics fabricators, hydraulic equipment vendors, plumbers and electricians with no luck.
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Old 07-14-2009, 09:25 PM   #2
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I did a quick search for watertight electrical connectors and from this site
Watertight Subsea / Underwater Electrical Connectors
came up with this type of connecter:



I think your best bet would be a bulkhead connection something like this.
That way you can dis-connect the sensors with ease to use on the other projects.

Here is the next one that came up.
http://www.odu-usa.com/?gclid=CNuIh8...FSgYagodElbxAA
I'm sure if you use these search peramiters, you can find what you're looking for.
I'm not in the States so I can't give you any specific companies, but if you go to marine electrical wholesalers you should have good luck.

Let us know how you do. You never know when something like this might be of use to someone else.

Rick



PS
Here is the type of fitting you actually asked for:

From this site:
http://www.hardwareandtools.com/icat...nduitliqtight/
I used:
pass through watertight electrical fittings
for the search.

I still think the first one would be better if you can use it.

This is another type of thing for multiple cables.
http://www.jastramtechnologies.ca/bst/bst-reg-1.htm
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Old 07-14-2009, 09:35 PM   #3
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Quote:
Originally Posted by Ruadh View Post
Here is the type of fitting you actually asked for:


From this site:
Liquidtight Connectors at HardwareAndTools.com
I used:
pass through watertight electrical fittings
for the search.

I still think the first one would be better if you can use it.
This one is actually the more likely to work - I said "cable" but one of the intruments in question is actually a bundle of fiber-optic wires - I have to leave them intact at the same length they came.

Thanks for the tip - I'll look into this further.
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Old 07-14-2009, 09:38 PM   #4
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I added another link to my post.
It might be better.
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Old 07-14-2009, 09:42 PM   #5
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It's awesome!

Quote:
Originally Posted by Ruadh View Post
I added another link to my post.
It might be better.
"Cable Transit" - exactly what I need. Thank you very much! I will post pics and a report when I get this working.
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Old 07-17-2009, 06:04 AM   #6
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Quote:
Originally Posted by juneappal View Post
Greetings everyone. I have a question that isn't exactly about aquariums, but I have hit a lot of dead ends in tying to find an answer, and it seems like aquarium lovers might be able to tell me what direction I should explore next.

I am a grad student, conducting research on the effects of wave action on sandy/clayey bottom surfaces. I have a large acrylic (1" thick) wave tank. It is sealed on top and during operation it is at about 6-7 psi inside.

I need to get a few instruments into the water column to measure water speed and sediment density. The instrument have cables roughly 1/2" o.d.

I am looking for some sort of fitting that will allow me to pass a 1/2" cable into the tank, then tighten around it to provide a watertight seal against 6 psi. I need to be able to remove the instruments, since I am sharing them with another research project, so I can't just epoxy them into a hole.

Functionally, this is the same problem as temporarily passing a heavy gauge extension cord into the bottom of a 12-foot deep aquarium. Has anyone here ever attempted doing so without entering through the water surface?

I greatly appreciate any help/suggestions you can give. I am sorry my query isn't quite aquarium-focused, but I can't think of anyone else who would have any experience with this sort of enterprise. I have tried Acrylics fabricators, hydraulic equipment vendors, plumbers and electricians with no luck.
What type of signals, voltages, and current are we talking about? And what type of cable are you using for the sensor?
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Old 11-24-2010, 02:06 AM   #7
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Quote:
Originally Posted by juneappal View Post
"Cable Transit" - exactly what I need. Thank you very much! I will post pics and a report when I get this working.
It's been a little while, but I finally am getting around to posting pictures. To recap, we need to put various cable through 1" plexiglass under 6 psi of pressure. The length of cable inside the tank needed to be adjustable, and they all had permanently affixed devices at the tips. The Roxtec cable transit has worked wonderfully. Thanks for the recommendation!:

Here' the tank. The cable went in through the top, in the center (right where the white return flow hose is sagging.



And here are two photos showing cables passing through the transit. There is a single metal rod that supports the probe tips on the three blue cables. We have put lots of different arrangements or cables and support rods in here - it is very easy to swap modules in and out, and we have had no trouble with leaking (for our purposes that means: When the machine is running, the pistons causes the pressure to vary between +6psi gage and -2 psig every twenty seconds. After swapping blue pieces in and out dozens of times over the course of a few weeks, we get no leakage when the machine isn't running, and less than a half cup an hour when it is. )






Thanks again for the recommendation! If anyone has any question about the cable transit, I will be happy to respond!
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