For this reason the section of pipe in front of the dent and the dent remains in neprokontrolirovannym. Intratubal magnetic inspection Flaw PII Ltd. (U.S. Patent US 6,538,431) contains a number of bars mounted on the body flaw. In each bar of a pair of magnets and magnetic field sensors.
Magnets mounted on steel brushes. Each bar pivotally connected to the housing by means of three levers. Here, the first lever is connected to the front of the bar and the movable unit mounted on the body flaw and are able to move along the body axis of the flaw detector, the second lever is connected to the rear of the bar and the second mobile unit mounted on the body flaw and are able to move along the axis of the body flaw. The mobile nodes are connected with springs that provide a clamp sticks to the inside surface of the pipeline. The third lever is connected to the rear of the bar and the body flaw.
The advantage of this flaw is that the mobility of the bars relative to the body flaw in radial direction provides the cross-over restriction, regardless of the length of the pipeline sticks brushes. And the mobility of nodes along the axis of the body allows rounding dent the pipe. The main drawback of this flaw is that in the event that the motion inside the pipe flaw detector encounters an obstacle, for example, with the edge welded to the pipe-line frame, this leads to conflict front of the bar with an obstacle that affects the bar in the opposite direction of the flaw.