Pig for measuring the shape of a pipeline

摘要

The object of the invention is to measure, surely and in a stable condition, the orientation of a pig body in the pipe of a pipeline thereby to correct errors caused by measuring the linear shape of the pipeline by means of a gyroscope sensor. A three-axis gyroscope sensor unit 4 is placed in a pig body 2 such that one of measuring axes of the gyroscope sensor unit 4 is parallel to the center axis of the pig body 2 and is fixed so as to prevent the gyroscope sensor unit 4 from being shifted in position with respect to the pig body 2. Two sets of six distance measuring means 5-10 and 11-16 are arranged on the outer periphery of the pig body 2 at two positions in the back and forth direction (in a direction of travel) , respectively, and the six distance measuring means of each set are arranged at equal intervals in the circumferential direction of the pig body 2. Deviation between the center axis of the pig body 2 and the center axis of the pipeline is calculated from the outputs of the distance measuring means 5-10 and 11-16 and the output of the three-axis gyroscope sensor unit 4 is corrected based on the deviation. In this manner, errors caused by the orientation of the pig body 2 are corrected and hence the correct measurement of the linear shape of the pipeline can be performed. <IMAGE>