Article 16

Improved Air Pipe Delivery

If you need to install additional air pipe but don't have any ducts to spare, why not borrow a trick from the water department?

Providing adequate air delivery pressure to underground cables in the field is one of the key priorities of a good air pressure system. Another priority, especially in congested downtown wire centers, is finding ways to get air out there. When multiple air pipes are required on a route and no ducts are available, either the system goes without proper cable protection or new conduit must be placed. Both of these options carry a huge price tag.

In this Gazette we'll introduce you to a new air pipe design, called the Power Pipe System, that solves the problem of limited duct availability. With an internal diameter of one inch, Power Pipe is approximately only twice the size of typical half inch CA3131 air pipe, but it distributes up to six times the flow capacity of the smaller pipe. It is the ideal solution for systems with normal to high air flow requirements and a shortage of ducts.

Like Water, Like Air
The design concept behind the Power Pipe System is similar to the one used by a municipal water department. Both systems rely on the use of a larger diameter distribution pipe to feed smaller pipes at locations farther away from the source. The Power Pipe is like a large water main, except that it supplies air to smaller sections of half inch CA3131 air pipe. Just as you wouldn't find a water department using a half inch pipe to distribute water to its entire system, now there's no need to continue using half inch air pipes out of the office when one or more space-saving Power Pipes will do the job. The Power Pipe System is the ideal way to supply optimum delivery pressure to the cables in the field especially those near the central office where air flow consumption is generally the highest.

Some Impressive Numbers
Although it is a relatively new design, the Power Pipe System has been catching on rapidly in large urban wire centers across the country. Three of the important reasons for its popularity are cost savings, easy installation and documented performance.

Steve Ekstrand, System Studies' Technical Services Department Manager, recently estimated savings for a Power Pipe installation in four large routes to be over $800,000. His estimate was based on a comparison of the costs for updating the telco's air pressure system using Power Pipe and the required hardware versus installing the equivalent amount of CA3131 air pipe and hardware.

In the proposed installation, only eleven Power Pipes were required to achieve the desired design objectives. A total of 58 CA3131 air pipes would be needed to provide the same level of cable pressure protection. While engineering costs for both alternatives were the same, the estimated savings were in three distinct areas:

Pipe Characteristics
With its one inch internal diameter, Power Pipe permits a much higher volume of air to be transported to the field than is possible by using multiple half inch air pipes. The reason for this is that there is very little pressure drop per foot in the Power Pipe. Tests show that even at 200 Standard Cubic Feet per Hour (SCFH), the pressure drop per 1,000 feet of Power Pipe is only 0.33 Pounds per Square Inch (PSI).

To simplify installation and help eliminate problems with transposed air pipes that often occur during new pipe installations. Power Pipe is available in wide varieties of colors (blue, orange, green, purple, etc.). The color variations also help technicians more easily identify a designated Power Pipe during routine maintenance and leak locating.

System Components
The Power Pipe System consists of a number of components that simplify installation and make it possible for the new design to mesh with existing CA3131 air pipe systems. The specially designed Power Pipe Panel serves a function similar to other pipe alarm panels. It carefully regulates air dryer output, provides a means for both manual and remote pressure and flow measurements, and it enables you to shut off air feed to the field. But it is the high range 475 SCFH Flow Finder and Dual (Pressure/Flow) Transducer that makes the panel unique. These tools provide important system measurement and monitoring information.

In the field remote pressure and flow readings can be provided at selected locations with the High Range Flow Measurement Assembly (see illustration). This device, which is installed directly in the Power Pipe, provides realtime warning of any leaks that may occur in the pipe.

Maximum Pipe Consumption
In a Power Pipe System design, one Power Pipe is typically designated to feed all of the manifolds and cables on a route that are nearest the central office. Additional pipes are used as express pipes (when needed) to feed manifolds and cables farther out in the field. The maximum flow rate per Power Pipe is based on the telco's allowable flow rate (SCFH) per manifold tube and the distance of the manifolds from the central office. Shorter pipes can feed more manifolds and cables than longer ones.

By calculating allowable air usage at various manifold locations and pressure drop over distance, it is possible to determine how many cables one pipe should feed before the endpipe pressure drops below the minimum pressure standard of 7.5 to 8.0 PSI.

Big $avings or Power Hype? You Make the Call
It's not everyday that a new design concept comes along that offers an alternative to either spending big dollars for new conduit or having to deal with inadequate cable pressure protection. But with Power Pipe installed in your system, you can see both immediate improvements in air pipe delivery pressure and lasting improvements in overall system quality.

There are many advantages to using Power Pipe. Some of the most important ones are listed here:

150,000 Power Pipe Users Can't Be All Wrong
OK. So, we fudged the numbers a little bit. But there are more and more Power Pipe Systems being installed all the time, especially in the older and larger central offices. Most importantly, these systems are performing as expected providing greater delivery pressure to the system and maximizing valuable duct space.

While the Power Pipe System may not be the best design for every air pressure system, it's certainly worth serious consideration if you need additional air pipes in your system but can't get them out into the field. So why not do what the water department does? Use a larger delivery pipe; use a Power Pipe.

To find out more about the Power Pipe design and how it can make a difference in your system, give us a call. We'll be happy to supply any information you need.


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