Engineering News

Ensuring the accurate and safe detection of underground utilities is both safety-critical and can help to reduce costs and save time on a project.  

A new probe designed to accurately pinpoint underground utilities and buried services up to 30 m deep, is said to have an accuracy to a depth of 6 m. The Amprobe UAT600 series from Comtest is designed to be rugged and durable. The locating kit comes complete and ready for use with a transmitter, receiver, test lead kit, batteries and additional fuses – all contained in a mobile, protective duffle bag.

The UAT-620 kit also includes a signal clamp for transmitting a signal, used when it is not possible to make electrical contact with the cable being traced. For applications where ground fault locating is required, the UAT-600 transmitter can be used in combination with an optional A-frame accessory.

Comtest explains that mines routinely use ‘Thumper’ technology for cable fault location, whereby a portable high voltage surge generator is used to apply a high voltage direct current surge into the faulty cable. This  leads to a high-current arc making a thumping sound at the site of the fault. Disadvantages of this method are that it is very time-consuming, exposing the cable to high voltage surges may lead to degradation and the need for reinsulation and it can also not be used to find short circuit faults.

The company highlights the case of a gold mine that had to urgently pinpoint a damaged cable. An external contractor used the Thumper method and diagnosed that the damaged cable was located at a length of 120 m. An excavation team dug to that length but no breach in the cable was found.  A new channel was then dug at 60 m and still no fault was found.  On the third tracing attempt the breach was located across the road and on a different cable. 

The consequence of the cable breach was numerous days of lost production and costs associated with the Thumper analysis and misdiagnosed detection.  Comtest asserts that if the mining company had used its cable locator instrument, it would have accurately and safely diagnosed the location and reached a solution within a day.

Main applications of the AMPROBE UAT-600 series:

• Locates energized 50/60 Hz cables carrying current
• Identifies the location of all metallic utilities: pipes, energized and de-energized cables. Tracing of non-metallic pipes and conduits is also possible after inserting metal fish tape or cable.

Three testing modes for a range of applications:

• Passive power mode (50/60 Hz): tracing energized lines conducting current (no transmitter necessary)
• Passive radio mode (RF): using surrounding radio waves to trace underground utilities (no transmitter necessary)
• Active mode: using UAT-600-T transmitter

Three active modes using the UAT-600-T Transmitter:

• Induction: the transmitter will automatically start to radiate a signal around it using an internal antenna, used for tracing individual cables where there is no access to the line to connect test leads or a clamp
• Direct connection with test leads: the most reliable method to trace an individual cable or a pipe
• Clamp (Included in the UAT-620 kit, optional for the UAT-610 kit): provides an efficient and safe method of applying a locate signal to a cable, where it is not possible or safe to gain access to a cable for making an electrical contact

Special applications:

• 2 frequency options: 8 kHz and 33 kHz
• Location of non-metallic pipes and sewer lines
• Take depth and current measurements
• Measure voltage, resistance and output current
• Advanced locating with two people
• Locate ground faults with the optional AF-600 A-frame accessory

In addition, the UAT-600 series has a CAT IV 600 V safety rating, which means that users are able to safely connect the transmitter directly to an energized line up to 600 V in a CAT IV environment, whereas previously, if a specific electrical line was being traced by transmitting a signal through it, the line had to be de-energized first, which could lead to delays and reduced productivity.