管道示踪线测试原理

Principle of pipeline tracing line test

铜包钢是由钢芯线和紧紧包裹在其周围的铜层组成的金属芯。外侧为PE防腐层。铜起传导微弱电信号的作用，钢丝起支撑作用。铜芯线一般由内层铜芯线、中间层绝缘护套和外层保护套组成。铜包铝由铝芯线和将其紧紧包裹形成金属芯的铜层组成，外层为PE防腐层。

Copper clad steel is a metal core composed of steel core wire and copper layer tightly wrapped around it. The outer side is PE anticorrosive coating. Copper plays the role of conducting weak electrical signals, and steel wire plays the role of support. Copper core wire is generally composed of inner copper core wire, intermediate insulating sheath and outer protective sheath. Copper clad aluminum is composed of aluminum core wire and copper layer tightly wrapped to form metal core, and the outer layer is PE anti-corrosion layer.

由于钢制燃气管道外层防腐层为塑料层或具有绝缘防腐性能的涂层，其结构类似于铜包钢、铜芯线、铜包铝和其他外层，它们也是具有绝缘和防腐性能的塑料层。.因此，我们采用两个等效物，采用PCM管道电流衰减率法来测试示踪线防腐层的平均绝缘质量。

As the outer anti-corrosion coating of steel gas pipeline is plastic layer or coating with insulation and anti-corrosion performance, its structure is similar to copper-clad steel, copper core wire, copper-clad aluminum and other outer layers, which are also plastic layers with insulation and anti-corrosion performance Therefore, we use two equivalents and PCM pipeline current decay rate method to test the average insulation quality of the anti-corrosion coating of the tracer line.

检测原理是向示踪线施加一定频率的电流信号，电流从示踪线传到远处会逐渐衰减。其衰减与示踪线塑料层的绝缘电阻率有关。示踪线塑料层的平均绝缘电阻率越高，电流衰减越慢，反之亦然。

The detection principle is to apply a certain frequency current signal to the tracer line, and the current will gradually decay when it is transmitted from the tracer line to a distance. Its attenuation is related to the insulation resistivity of the plastic layer of the tracer line. The higher the average insulation resistivity of the tracer line plastic layer, the slower the current attenuation, and vice versa.

管道示踪线试验方法

Test method for pipeline tracing line

为保证示踪线的导电性、强度、耐腐蚀性和耐用性，一般建议选用截面积大于2.5mm的多股铜线，并尽量将示踪线保持在铺设时管的顶部。在分支处，应剥去导线接头的绝缘层，将铜芯绞在一起数圈，然后在接头处缠上绝缘胶带，以保持良好的导电性。

In order to ensure the conductivity, strength, corrosion resistance and durability of the tracer wire, it is generally recommended to select multi strand copper wire with a cross-sectional area greater than 2.5mm, and try to keep the tracer wire at the top of the pipe when laying. At the branch, the insulation layer of the conductor joint shall be stripped, the copper core shall be twisted together for several turns, and then the joint shall be wrapped with insulating tape to maintain good conductivity.

示踪线应留有一定的线头余量，并避免线头被泥土或杂物覆盖。为了减少不能出地的示踪线末端的接地电阻，需要在剥去绝缘层后，将裸露的芯线30cm处做好接地。措施，定向钻孔铺设的PE管道，应使用较强的导体，以免施工过程中被拉断，导致无法检测定位；当导体的直径远小于埋深，而忽略地面介质和空气的介质变化时，示踪线可视为均质介质中的无限长线。

A certain amount of thread end allowance shall be reserved for the tracing line, and the thread end shall not be covered by soil or sundries. In order to reduce the grounding resistance at the end of the tracer wire that cannot be grounded, it is necessary to ground the exposed core wire 30cm after stripping the insulation layer. Measures: for PE pipes laid by directional drilling, strong conductors shall be used to avoid being broken during construction, which will make it impossible to detect and locate; When the diameter of the conductor is much smaller than the buried depth and the medium change of the ground medium and air is ignored, the trace line can be regarded as an infinite line in homogeneous medium.

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