Sophisticated new outside plant tools have been developed that improve efficiency and cut labour by combining several powerful functions in a single device. Some utilities are now adopting integrated locating equipment that combines sheath fault location, cable tracing and marker location in one unit. As multiple tasks are consolidated in fewer test devices, the craftsperson is able to work more effectively with a smaller capital investment. The key issue is locating, repairing and qualifying outside plant troubles as quickly as possible to minimize customer outages as well as field costs.
The Locating Challenge
It is a common paradox in underground utilities that the time required to locate a cable, splice, or other underground component can be greater than the time it takes to do the actual repair. While buried outside plant conditions vary from company to company, there is a basic need for rapid and accurate locating to minimize digging effort, avoid unintentional damage to other services, and maximize service to customers.
The challenge of fast and precise location is particularly complicated when there is a high concentration of utility services within a small right-of-way. Inaccurate documentation and unmarked facilities add to the problem.
Passive electronic markers, in use for more than 20 years, are important to the field efficiency of the utilities. They allow quick location of buried facilities such as manhole covers, hand holes, buried splices, branch splices, buried service drops and conduit stubs.
Technicians can be quickly trained to use electronic marker locating systems and can then easily use the equipment in the field. Since passive marker location is not affected by nearby metal objects, electrical power fields, or adjacent passive markers that are tuned to other frequencies, locating is simplified for the technician.
Passive markers are supplied in different frequencies so that each utility - telecommunications, gas, power, CATV, water and waste water - has its own unique electronic identification. Marker colours are based on guidelines established by the American Public Works Association.
The full range marker, with an intended burial depth up to eight feet, was developed first and since then the electronic marking concept has evolved into a complete family of marking devices.
After the full range marker, the next design was the circular mini-marker, which has spokes to help stabilize it in the correct position for pinpoint locating accuracy. This device is intended for burial to six feet. Then a ball-shaped marker was developed for use in cable trenches at depths to four feet. This spherical unit contains a free-floating antenna suspended in a non-toxic water/propylene glycol solution, keeping the tuned circuit in a horizontal position when the ball is dropped into a trench or hole. This ensures accurate location of "lost" facilities.
Later a small, near-surface marker was developed for easy marking of underground and street access facilities that are just below the surface. Near-surface electronic markers make it easy to relocate access points even after re-landscaping, or under conditions of snow cover. All passive marker styles can function for the life of the buried plant because they require no external source of power, and can withstand underground conditions including moisture, chemicals, minerals, and temperature extremes.
According to Wayne Campbell, a technical support specialist for 3M Telecom Systems Division, it has become common for construction engineers to mark locations on outside plant drawings for crews to place passive electronic markers during construction. "The most common spots are at splice points, cable branches and turn points, laterals, road crossings, and other points that can't be easily found with a conventional locator," he said. "In many companies, the field crews place markers routinely whenever they place a splice or work on any underground facilities."
Advanced Locating Equipment
The locators used to find passive markers are portable, hand-held units that transmit a pulsed radio frequency signal into the ground. When in the vicinity of a marker, the signal is reflected back to the locator. The locator receives this secondary signal, and gives the operator an audible tone and visual display that indicate proximity to the marker and lead the user to a spot directly over the marker.
Electronic marking system transceiver units are now available for contractors and outside plant crews allowing them to locate and identify markers of any utility. This helps contractors and multi-utility companies learn the location of any nearby utility services for damage prevention.
The integration of all frequencies into a single marker locator unit allows users to eliminate the need for six different marker locators. Utility workers concerned only with their own network components can use a single-frequency locator to detect only their own markers.
When using a cable/fault locator that is capable of detecting the markers of all utilities, some equipment allows the operator to simultaneously trace a cable path while finding buried markers along the way by using the marker alert mode. The Dynatel brand 2205/2206 Marker Locating Accessory from 3M is one product with this capability.
The functionality and portability of these new outside plant tools are due in large part to the use of digital signal processing and the power of microprocessor control. Unlike earlier devices, they incorporate display screens, help functions and memory features that assist the user in making sophisticated locations with speed and accuracy.
With the passive marker system and integrated cable tracing and fault locating equipment, workers can pinpoint a spot accurately, easily distinguish electrical facilities from gas, telecommunications, CATV, water and waste water facilities, and cut locating time. That's music to the ears of cost-conscious utility managers as well as their busy customers.
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