How does Underground detectable warning tape work?
Simply put, its working principle is similar to a "warning sign buried underground", which sends out signals through special materials and is recognized by metal detectors on the ground, thereby warning of important pipelines below and avoiding accidents caused by blind excavation.
Below we will analyze its working process step by step:
1、 Composition of warning tape
Underground detectable warning tape is not an ordinary plastic tape, it is a composite material usually composed of two layers:
◉ Warning layer (upper layer): usually a bright plastic film (such as red representing gas, yellow representing electricity, etc.) with prominent text and graphic warnings indicating the type of pipeline below, such as "Gas pipeline below, excavation strictly prohibited", "CAUTION GAS LINE BELOW", etc. This layer is for manual excavators to see, and if they reach this layer, they must stop immediately.
◉ Detectable layer (core layer): This is the key to the functioning of the warning tape. It is usually embedded in a plastic substrate with continuous metal foil (such as aluminum foil), metal wire (such as copper wire), or conductive layer containing metal powder. When this layer of metallic material is excited by an electromagnetic field of a specific frequency, it produces a strong and detectable response signal.
2、 Workflow
Its workflow can be divided into two stages: "laying" and "detection".
Stage 1: Laying (burying)
◉ When laying underground pipelines (such as cables, optical cables, gas pipelines, water pipes), not all soil will be immediately backfilled during the pipeline construction process.
◉ After the pipeline is laid in place, parallel lay this detectable warning tape at a depth of about 30 to 50 centimeters directly above it.
◉ Then continue with the backfilling work, burying the warning tape and pipeline underground together.
Why is it laid above the pipeline? The purpose of this design is that any excavation work carried out from the ground will first encounter warning tapes before touching deeper pipelines, providing a valuable "buffer warning" space.
Stage 2: Detection (positioning)
Before carrying out any excavation work such as road construction, greening, or building construction in the later stage, the construction party must conduct an "underground pipeline exploration".
◉ Using instruments: The staff will use a device called a "pipeline detector". This type of instrument usually consists of a transmitter and a receiver.
◉ Emission signal: The transmitter will emit electromagnetic wave signals of a specific frequency to the ground.
◉ Generate response: Electromagnetic wave signals penetrate the soil and act on the metal layer in the warning tape. The metal layer will generate a secondary induced electromagnetic field under the action of an alternating electromagnetic field. This secondary magnetic field responds much stronger than the surrounding soil.
◉ Receiving signal: Technicians hold receivers and move them on the ground to scan. When the receiver passes directly above the warning tape, it will clearly capture this strong secondary magnetic field signal.
◉ Warning: The receiver alerts the operator through sound (beep becoming louder, tone increasing) and visual display (signal bar peak, reading increasing): "There is something below.
◉ Accurate positioning and marking: Technicians can follow the path with the strongest signal to accurately outline the direction of underground pipelines, and mark them on the ground with paint or flags to warn excavators that there are important pipelines below this area. Large mechanical excavation is prohibited and manual excavation must be carried out carefully.
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