If you're new to cable pressurization or have been working pressure for a number of years using the same tools and techniques, then this newsletter has reached the right hands. In this article we describe the important leak locating tools being used today that can make your job easier and your time in the field more productive. Several of the items discussed are probably familiar to you; others may not be. But by taking the time to re-assess what's available, you may discover that the tools which can save you the most time are the ones you're not using.
Circuits and Software
Undoubtedly, you've already heard about the benefits of the PressureMAP software and 289H LSS monitoring equipment. These are the two flagship products provided by System Studies, and together they represent the industry's most advanced cable pressurization system analysis, dispatching and diagnostics tools. PressureMAP regularly calls the 289H LSS for transducer readings, analyzes changing pressure and flow conditions, and dispatches you to problem areas. Analysis can also be performed on device pairs remotely via the 289H monitor using PressureMAP's 289H Diagnostics program. This capability, plus access to a comprehensive, user-oriented database, helps you to more quickly and easily find leaks in your air pressure system.
Logging on to PressureMAP from the field requires specialized equipment. With a laptop computer as an on-the-job tool, you'll be able to make better use of PressureMAP and the 289H LSS. Whether from a utility hole ladder or the front seat of your truck, you can access key device information, take realtime readings, and run diagnostics on transducer pairs.
To provide even greater proficiency in leak locating, laptops can be loaded with a copy of the Leak-o-Matic Gizmo, which is a software program that provides leak calculating and graphing information. You can obtain a copy of this utility, free of charge, by calling System Studies or by downloading a version from our website. The Gizmo includes the Zero Leak Projection (ZLP), Air Flow Calculation, Back projection, Pressure vs. Distance Graphs, Pneumatic Resistance Charts and more.
Hand Tools and Instrumentation
Making the right decisions in the field requires accurate pressure and flow readings and knowledge of modern leak locating techniques. A C Pressure Gauge, whether digital or analog, provides the pressure readings needed for several of the commonly used leak locating calculations. But be aware that there are many pressure gauges that only read down to one tenth of a Pound per Square Inch (0.1 PSI). For greater precision in leak locating, you should make sure that yours reads in hundredths (0.01 PSI).
The Flow Gauge (developed by System Studies to read Flow Finders) or the Portable Flow Rater are used to take flow readings at central office panels, along the air pipe (where Flow Finders are installed), and at field manifold locations. With the modern emphasis on air flow measurement and analysis, these tools are clearly two of the most important ones available to you. If you're working in a utility hole where cable pressures are closely equalized (due to interlacing, for example), you can use a Direction of Flow Indicator to confirm which one of the cables is leaking. This device is also handy around pressure plugs in the field and in the central office vault to determine whether or not they're losing air.
Visually checking cables and splice cases for leaks requires specialized "old school" equipment: specifically, a soap bucket and brush. This irreplaceable leak locating tool makes it possible to check for leaks in each of the utility holes you enter. When you soap a cable or splice for leaks, by the way, make sure that you apply a liberal amount of soap solution to as much surface area as possible. If you don't soap the back of the splice case, you're not likely to have much luck finding a leak(s) back there.
When leak locating efforts have reduced the search area to a cable section between two utility holes, the Ultrasonic Leak Locator and Helium/Hydrogen Leak Detector are two more tools that you should have on hand. The ultrasonic can be used with a duct probe to help you listen for a leak that's located a short distance up a duct. It measures inaudible high frequency sounds, like those created by pressurized air molecules forcing their way through a sheath opening. The Leak Detector measures a small portion of tracer gas, either helium or hydrogen, that is placed in the leaking cable. This instrument makes it possible to walk along the cable path at street or ground level and check for the highest concentration of gas. Both tools are excellent for confirming the location of leaks that are first determined by using standard graphing techniques or pressure drop per foot calculations.
Troubleshooting transducer pairs and other line problems requires two additional tools: a Volt/Ohm Meter and a Transducer Test Meter. The first device, which measures the electrical resistance on a pair, is used for troubleshooting resistive type pressure and flow transducers. The other tool measures electrical current and is used for checking System Studies' 4-20 milliamperes (mA) transducers.
A set of worksheets is available for recording information taken during the leak locating process. These Leak Locating Worksheets not only provide step-by-step procedures for performing a specific leak locating task, they also include information boxes, which represent utility hole or pole locations. The worksheets allow you to become more organized in the leak locating process and, perhaps even more importantly, they make it easy and convenient for you to record your readings and calculation results. A Pocket Pressurization Calculator and Pneumatic Resistance Charts are also a must for anyone not using the Leak-o-Matic Gizmo.
Some of the other tools used by successful air pressure technicians are:
While certainly not all of the tools described above are required for each specific leak locating task, we suggest that you carry as many of them as possible on your maintenance truck. A large measure of your success as a leak locator depends upon the tools you have available, and your knowledge of how and where use them.
If you'd like more detailed information about these leak locating tools, give us a call. And don't forget, System Studies can supply you with just about any cable pressurization tool or piece of equipment you need.
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