Waterblocking
It may be that when you read the title of this blog, "Waterblocking" that you thought to yourself, "Isn't ALL jacketed wire and cable waterproof?" The answer is "No." Almost every jacket compound, from PVC to Polyethylene to Teflon® is at least water resistant, so they can get wet and then dry out and they cables would probaby be okay. It really depends on how much time they spend in water, and what kind of exposure they might have. For example if your cable is on the outside deck of a ship, that would require a lot more waterblocking protection than inside a rack room. The real problem is when a cable is in standing water which doesn't go away. An example of this could be a conduit filled with water goes all the way to a lake in a theme park. Water is often called the 'universal solvent': given enough time, it will get through anything. Water can easily work its way through polyvinyl chloride (PVC) which is the most common cable jacket material. A cable underwater with a PVC jacket maybe has weeks, or a few months, before it fails. The first step toward long-term waterblocking is a better jacket material such as polyethylene (PE). This is much more water resistant, especially if it is high-density PE, and may last many months, even years, underwater. But there is one more step you can take, and that is to specify that the cable has a 'waterblocking' layer.
There are two kinds of waterblocking, dry waterblocking and gel waterblocking. Dry waterblocking is another layer in the cable, under the jacket but over everything else. It's an impregnated cloth that is wrapped on the core of the cable. If there is a hole or cut in the jacket, and water touches this layer, it will swell up and block the water. Because it is just a cloth layer, it has no effect on the performance of the cable or on the connectorization. Just cut that extra layer and put on connectors as usual. Dry waterblocking will double or triple the life of a cable where water is a problem. However, if that is not enough you can always ask for the ultimate in waterblocking: gel. This material is added to a braid shield or extruded on top of a foil shield. Because it is a gel, it tends to flow and fill in any gaps or openings that appear. But gel-filled waterblocking is hard to work with. Once you strip the cable, you have to remove the gel before you can put on a connector. (The gel is not conductive.) You can remove gel with special wipes for that purpose such as alcohol wipes or citrus wipes. Wipes used to clean fiber can also work here such as D'Gel-FO made by PT Technologies/LPS Worldwide, and many others. But gel-filled waterblocking is the ultimate in long-term protection.
Belden makes a number of waterblocked cables, and you can find many of them by putting the word 'waterblock' in the search box of our eCatalog on our web page (www.belden.com). Our web page shows many of our waterblocked cables such as our Waterdog™ line of cables. These are dry waterblocking, as are our multipair analog audio snake line 1814WB-1818WB. We also have a single analog audio pair waterblocked, 9451WB. We even have giant Class 1 speaker cables 8810WB and 8808WB, which commonly might be buried in a stadium or theme park and could be wet a lot of the time. We also have 1694WB which is our most rugged waterblocking digital video cable. With the same performance and distance as regular 1694A, it has both a high-density PE jacket and a gel waterblocking layer for our ultimate long-term water protection.
The one thing I haven't mentioned is connectors. If the connectors are not intended to be used outdoors, then your waterblocked cable has to come into the building before it is connected. And there lies another problem, because many of these cables have no fire rating. The NEC code says very clearly that any installed cable must have a fire rating, even if it is installed in conduit. Waterblocked cables with PE jackets have no rating. Fine for outdoor applications but not for indoor. The NEC code says you can go 50 ft. into a building with unrated cable before you have to change to a fire rated cable (CM, riser, plenum etc.). There are a few connectors available for outdoor, weatherproof, applications such as rugged XLR connectors in the Neutrik line (for analog or digital audio balanced lines), or Belden's new watertight BNC connector 1694ABHDLW.
Do you have any questions regarding your waterblocking options? Leave a comment or drop me a line at steve.lampen@belden.com.
About the Author
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Steve Lampen, RCDD, worked for Belden for 25 years with his latest role being the multimedia technology manager and product line manager for entertainment products. In 2010, he was named “Educator of the Year” by the National Systems Contractors Association (NSCA). In 2011, he was named “Educator of the Year” by SBE. His book, The Audio-Video Cable Installer’s Pocket Guide, was published by McGraw-Hill.