Characteristic of Magnetic Fluctuation of Underground Passing Pig Labeled with Magnets

Table 1

The influence of each parameter on the magnetic anomaly.

Model parameters	Range	With the increase in the parameter
Pipeline buried depth (mm)	2-3.5	Fluctuation decreases
Existence of permanent magnets	Nonexistent-existent	Obvious fluctuation
Pipeline outer diameter (mm)	500-700	Fluctuation decreases
Pipeline wall thickness (mm)	4-10	Fluctuation decreases
Pipeline length (m)	60-75	Fluctuation almost remains the same
Pipeline permeability	100-900	Fluctuation decreases
Number of permanent magnets	2-6	Fluctuation increases at the center of the measuring line and almost unchanged at both ends
Polarity of permanent magnets	Horizontal-vertical	Fluctuation is negligible
Magnetic intensity (nT)	21000-69000	Fluctuation almost remains the same
Magnetic dip	−80°~80°	Fluctuation decreases first and then increases
Magnetic declination	−25°~25°	Fluctuation almost remains the same
Detection height in the experiment	0.5 m-1.2 m	Fluctuation decreases