Business profile Watching the detecting
The concept of electromagnetics is quite simple: a conductor buried in the ground will radiate an electromagnetic field as long as there is an electrical current flowing in that conductor
E
lectromagnetics have been used for many years to detect the presence of buried utilities. The first buried utility locators detected the electromagnetic field radiating from mains cables. This is still done today. The problem arises when there is no current flowing in the cable, for example where there is a disused cable, or a cable whose electrical currents are perfectly balanced. In these situations there will be no resulting radiated field (RF) to be detected. One other method of detecting a buried utility is to detect reradiated rf signals. These signals originate from low-frequency transmitters. Buried conductors will reradiate these signals which are detectable using a receiver tuned to that band of frequencies. Both these methods do not require the person locating the service to introduce a signal. However, locating a passive signal is reliant on factors outside the control of the operator and is therefore not always a reliable way to detect a buried utility. To overcome this it may be desirable to inject a signal current onto the buried service using a signal transmitter set to a precise frequency or selection of frequencies. This also has the benefit of focusing the locating signal onto one line and is particularly useful for tracing or identifying a specific utility line. ‘The introduction of transmitters has allowed developers to enhance the signal with the use of very selective filters ensuring only the desired frequencies are detected,’ says Steve Benzie, UK sales manager. ‘Further developments have seen multiple antennas that enable the gradient of the signal to be analysed, and depth measurements to be calculated. Identifying how much signal current is present on the service also aids the operator to ensure the correct utility is being detected,’ says Benzie. Vivax-Metrotech has over 40 year’s experience developing cable locators. Latest developments have seen the natural progression of integrating GPS into locators. Detecting utilities can be a time consuming and costly exercise. Mapping and recording the results ensure the data can be used time and time again without further site visits. Vivax-Metrotech offers a cost effective solution which consists of integrated GPS and internal data logging.
Page 192 April 2013
This low cost option has an accuracy of better than two metres, and has free management software enabling the retrieval of data to a base computer. More accurate GPS’s are available but can be costly.
Data can be saved as .shp, .kml, .xl, .csv files. For example if the results are saved as .kml files they can be e-mailed to colleagues who can view all the data, at each record point, on a Google Earth map. There are no registration or on-going costs and little or no setting up, the aim is to facilitate the free flow of data among colleagues. Vivax-Metrotech has recently opened up a sales office in Exeter, from where an experienced direct sales force ensures customers in the UK have access to the very best support. The office has stock, service and repair facilities and the full
support of its head office in Santa Clara, United States, and also from its dedicated manufacturing facility in Shanghai. In addition to its range of cable
locators Vivax-Metrotech offers push rod inspection cameras used to inspect duct and sewer systems. ‘Vivax-Metrotech has recently obtained full Network Approval for its vLoc2 locator and associated transmitters. This means that Network Rail operators and contractors now have access to the latest cable locator technologies ensuring a safer working environment for both operators and those in infrastructure,’ concludes Steve Benzie. For further information, contact Steve Benzie, UK sales manager, Vivax-Metrotech. Tel: 01392 368833. E-mail:
steve.benzie@
vxmt.com www.vivax-metrotech.co.uk
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