Underwater Installation

[loop 0]

I have a client who uses a a remote controlled underwater vehicle to clean large drinking-water pools. He's running 150M of RJ60 Coaxial cable for the transmission and controlling the self-made sealed P/T camera that is attached to the vehicle. Together with it he runs some 220V and 380V cables for the vehicle's engines.

My client couldn't get a reasonable picture until he was advised to install the following unit:

http://www.sctltd.co.uk/acatalog/info_EXT4.html

 

Now he can get a clear picture, but when vehicle's engines are working he gets interference. The interference gets severe as more cable is inside the water.

 

I'm thinking of redesigning the system and change cables/transmission technology, and looking for something that will not be affected by the environment (water) and the magnetic field that the power cables produce. I'm thinking about fiber, but am not familiar with the technology or pricing.

 

I would like to ask you for your ideas/experienced advice about this.

 

Thanks.

[Cooperman 0]

Interesting problem you have there loop.

 

I've custom built underwater housings for industrial process monitoring cameras (about 10 metres depth), but I've no experience of having 220 / 380v cables being used in such close proximity.

 

On the last project, we actually used a somewhat 'unconventional' co-ax, CT 100 RBS, which is a co-ax + a 100% copper foil screen sealed in a plastic armoured outer layer. It's quite heavy (except in water ) has a diameter of about 10mm from memory, and is very resistant to snagging or tight bends. I had to use 2 seperated IP68 rated cable glands to minimise the risk of water ingress.

 

Although I actually used a line powered camera for the last project, personally I would avoid using power down the co-ax if you can, and perhaps use a seperate pair of conductors in the multicore, or localised adaptor to convert to 12v DC for the cameras supply.

 

Fibre would certainly solve your interference pick up problem, but most fibre cables are not really suited to constant movement. Lay them down and they'll last a lifetime, but if you start twisting them about, you risk breaking the fibre and then the whole cable has to be junked.

 

The 'loose tube' fibre cable used to be available with heavy plastic armouring and, aluminium foil barrier and kevlar strand reinforcements, but it's certainly not cheap (I've still got a load of it lying around somewhere ) and it's not the easiest stuff to handle.

 

If you can get hold of some heavy duty plastic armoured, foil screened co-ax to try on perhaps a 50 metre length test, I think that might do the job.

[XXX 0]

The first thing that came to my mind was to use a flooded category 5e cable using some of NVT's products.

[loop 0]

Thank you both for your replies. I haven't used anythning else than coaxial cables for installation, so if you can link or provide more information about those cables, and what makes them good for the task.

[wahloon 0]

have you used direct burial cable, they have better insulation so that should cut down on your signal lose.

[Cooperman 0]

hey loop,

 

I've just done a quick check on current cable types and whilst CT 100 is still readily available (in its basic form it is widely used for satellite work), there is a variant called WF 100 which uses a solid foam dielectric to prevent the possibility of internal water problems.

 

I don't know whether this is available in 'RBS' plastic armouring, but the CT 100 and CT 125 are both available with the extra outer protective layer. Incidentally, the number corresponds to the diameter in mm's for the central conductor, so CT 125 has a 1.25mm copper conductor, and generally very good characteristics for colour video signal transmission over hundreds of metres. Larger diameter versions are also available, but you really wouldn't like the price (or the weight).

 

You'll probably need to contact a few cable suppliers locally, as the only sites I've come across, don't really give any useful technical information (other than the price!). If I can find my cable book (it seems to have gone walkies) I'll get back to you.

[loop 0]

Wahloon, do you have any expirience with direct burial cables?

Interesting Cooperman. Please PM me some links and prices, since I don't think I can find those here in Israel. By the way, I currently reading something about using fiber for underwater vehicles equiped with cctv cameras, and it seems to become a standard in these kind of applications.

[XXX 0]

Wahloon, do you have any expirience with direct burial cables?

Interesting Cooperman. Please PM me some links and prices, since I don't think I can find those here in Israel. By the way, I currently reading something about using fiber for underwater vehicles equiped with cctv cameras, and it seems to become a standard in these kind of applications.

 

I was talking about using "flooded" direct burial cable. I would use direct burial fiber. It has a thick outer casing with two fiberglass rods that run down the length of the cable. It is "flooded" with a gelatinous material. You shouldn't have any problem with the fiber in this application. You would have to break the fiberglass rods well before you would damage the fiber.

 

Berk-tek has this type of cable.

[rory 0]

guys our local cable internet company has fiber (or somthing real big an $$$$$) run from the USA to the Bahamas, in the ocean .... dont know what it is ..anyone ?

 

Company is called caribbean crossings .. may want to do a search and see what they use, or contact a cable internet/tv company ..

 

 

Edit - here is the info on what they use::

http://www.caribbeancrossings.com/

 

The System

The (BICS) system consist of over 1,000 km of high performance submarine fiber cable and another 600 km of terrestrial cable strategically placed to form a highly reliable integrated optical Network connecting the United States and the World to the Bahamas.

 

This passive long reach state of the art Optical Network does not utilize any active submarine components requiring remote power thus ensuring a very high performance reliable digital lightwave system. These integrated technologies enable Caribbean Crossings to troubleshoot and manage the Network remotely from our Network Operations Center in Nassau, ensuring reliability, performance and commitment to Customer Service Level Agreements (SLA).

 

Flexible Platform

The Integration of the BICS all Optical Network and the Service intelligent Terminal equipment, creates architecture to deliver industry-leading network-based and premises-based solutions for such services as Frame Relay, ATM, TDM, SONET, Ethernet and IP.

 

This Architecture allows conversion from the North American Synchronous Optical Network (SONET) to the European Synchronous Digital Hierarchy (SDH) for interoperability and connection with other International Carriers that serve the Caribbean.

 

Seamless Integration

The installed network multi-service provisioning platforms enable integrating the aggregation and transport functions from separate network elements into an integrated network system providing internetworking solutions. These unified solutions are also designed to blend multi types of traffic that are prioritized and enabled for quality of service (QoS) across common optical facilities.

 

DWDM

The BICS all Optical system is currently designed for DWDM for up to 80 wave lengths now and 160 in the future yielding digital bandwidths capacity of up to 12 Terabits per second and beyond.

 

Protection

The Caribbean Crossings BICS fibre-optic subsea network has route diversity and is self healing with less than 50 millisecond switching functionality.

[Cooperman 0]

originally posted by loop

Wahloon, do you have any expirience with direct burial cables?

Interesting Cooperman. Please PM me some links and prices, since I don't think I can find those here in Israel. By the way, I currently reading something about using fiber for underwater vehicles equiped with cctv cameras, and it seems to become a standard in these kind of applications.

 

The RBS cable I mentioned is actually used for direct burial. The U.K. manufacturer Raydex have some info on their site:-

http://www.cdt-uk.co.uk if you look up Television / Distribution Cables.

 

The CT 125 RBS is 9.6mm diameter, has 1.1db (5MHz) attenuation / 100 metres (328 feet), and weighs 82Kgs. (180 pounds). The Foamed FE would be preferable to the air spaced. Incidentally the picture on the website spec. page doesn't show the plastic armoured version.

 

Interesting that fibre is becoming 'de rigeur' for underwater work. I would imagine that in mission critical / military applications, it would be the cable of choice, particularly where cost is not an issue.

 

Maybe Rory can get hold of some cheap left over bits from the US fibre link to the Bahamas

[loop 0]

hehe,

 

Thanks Cooperman, i'll check this out.

[dusan 0]

hi

looks like your original problem was a power and ground loop problem

 

new video / power mux now have a rf noise leaky coax

http://www.biwave.com/

 

test a rechargeble battery power only for video camera ,dpdt relay switch to recharge battery power (or dc insulated floting power supply) ,in off position when in video use

tap from 220v so no need for extra power wire

and ground loop insulation cat5 / coax video adaptor

 

better is to go digital at the bottom ,so go mpeg4 video/ptz like SED-2100R

and if you need SED-3200 for decode

http://www.acti.com/corporate/contact.htm

 

network up no video noise ,use cat5 stranded shielded waterproof

 

dusan

[loop 0]

The problem seems to be exactly as you described.

found some info here:

http://www.epanorama.net/documents/groundloop/video_isolation.html

 

the image looks exactly as the one I get.

I will look more into it.

 

Thanks a lot.