What is Electromagnetic Locating?
Electromagnetic locating is a versatile method of locating underground utilities. It is used by OzDetect technicians every day and is their essential locating tool. When there is a conductive or metallic utility onsite, we put a current into the underground service and trace the location, direction, and depth of the service within a specified area. This is a cost-effective way to gain an accurate location of the services that may conflict with construction works within the area.
Importance of locating
Any excavation, irrespective of size, has the potential to damage assets located around the worksite, leading to service interruptions, delays to the project, costly repairs, and in the worst-case scenario, injury or death.
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If you are on a Worksite, Residential Property, Sporting Ground, School, or Park of any kind and need to penetrate beneath the ground’s surface, it is your responsibility to lodge Utility Plans. Contact us to arrange a time and place to pinpoint exactly what is beneath the ground.
In electromagnetic line locating, electromagnetic fields are used to locate underground utilities or other buried conductive materials. There are three primary methods of electromagnetic line locating:
- Passive Locating:
- Power Mode: This method detects the 50 or 60 Hz electromagnetic fields that are inherently produced by live electric cables. Utilities that are energised will naturally emit a certain frequency, and this can be detected passively without putting any signal on the line.
- Radio Mode: In this mode, the locator detects VLF (Very Low Frequency) radio waves that may be naturally re-radiated by buried conductive utilities. These waves are typically between 10 kHz to 30 kHz.
- Active Locating:
This involves introducing a specific signal or frequency into the utility or line that you’re trying to locate. This can be done in several ways:
- Direct Connection: A transmitter is physically connected to the utility, and it sends an electrical signal down the line. The locator then picks up on this signal at the surface.
- Induction: If a direct connection isn’t possible, the transmitter can be placed on the ground directly above the utility. It will send a signal to the utility without a physical connection. This method might not be as accurate as a direct connection because the signal can also be induced into other nearby conductive materials.
- Clamp Method: For utilities like gas or water that might have insulated sections, a signal clamp can be used. This clamp is placed around the utility, and it induces a signal into the line.
- Sonde Locating:
A sonde is a small transmitter that can be placed inside non-metallic utilities, like drains or sewers, and then tracked from the surface as it travels along the utility. Sondes emit a unique signal that can be tracked, which is useful for locating non-conductive utilities that will not naturally re-radiate radio frequencies or carry a signal as metallic utilities do.
To ensure the highest accuracy and verify utility location, a combination of methods should be used when line locating.