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My Story: Phone cables often fail because of water intrusion

Rick Miller

So, you work for the phone company but you do not repair phone wires, you do not place new facilities, poles, reels of cable and you don’t even splice the new wires together. No, what you do is much more important, you provide and maintain a dry air system in all the phone cables and monitor by computer a network of flow and pressure transducers.

Phone cables often fail because of water intrusion, mostly in manholes that fill with water from the weather and other sources. The dry air system is a proactive measure to keep a positive pressure pushing out then the water would pushing in, killing phone service for all customers working in that cable.

That introduction being said, how does an air pressure technician find the location of a leak in-between 2 manholes or a manhole and a termination point, like more to my point, a bank. A real pretty well known bank about to lose all telephony inside because of a wet cable.

A tech. Has isolated the location of the cable section, say a 100 foot cable from the manhole to the bank. How do we find where the leak is? We need to fix the leak, break the beautiful bank’s fancy walkway at it’s entrance. We need to be precise to minimize damage which equals money, $1000’s of dollars.

Here is a nitrogen tank:

A pressurized tank like this will hold about 2500 pounds of pressurized nitrogen.

So, what the hell is my point? We know the problem now, how do we find the leak location.

The phone company in it’s infinite wisdom has two methods of location this leak, Isolate the cable and introduce helium gas into the cable and it will permeate the ground and using a helium detector, we know where the leak is by concentration, oh, there is one problem here though, the gas doesn’t go through the concrete walkway at the bank.

Not to worry, there is an other way, a sound device that is pushed up the conduit until the sound of the leak is identified and the leak is located. By marking the rod used to push the listening device at the duct entrance, the rod is pulled out and laid over the cable (oh, how do we know where the cable is?, induction and a radio cable locator, simple!). I know your tired of this, but wait (yet again) the cable is too big and there is no room for the probe, strike two!

Well this Tech. Was an engineering student and came up with an idea.

Isolate the cable with two plugs built with a liquid plugging compound, one on each end.

Cut a hole in the cable on each end and place a saddle over each hole with an air valve stem like you have on all of your car tires.

Place a nitrogen tank at each end and set the regulators to maintain ten pounds of pressure at each end. Place a tech. At each end of the cable with communication devices.

At the exact same time, turn off the nitrogen tanks and time how long it take to get to five pounds. This will give you a ratio that you can apply to the distance of the cable and locate your leak.

Example: when the tanks are shut off, tech one (on the left side) measured ten seconds to go from 10 pounds to 5 pounds, the tech. On the right measured five seconds. Now we have a 2:1 ratio. The leak is 67 feet from the left side.

The digging contractors found the leak dead on.

Plausible?

Rick Miller

rickym51@mac.com

Four Winds 10 - News