Abstract: An inspection device for use in scanning the interior of a pipe at a remote location is accurately centered within the pipe at the required location by two spiders. Each spider has three sickle-shaped arms which can be extended and retracted between operative and inoperative positions. The six spider arms are interconnected by a crank mechanism which ensures that all the arms move in unison between their limit positions.

Abstract: A pneumatically operated pipe crawler for transporting inspection equipment along the interior of a pipe comprises an elongate cylindrical tube of flexible resilient material, such as latex rubber, the tube being partitioned by longitudinally spaced plugs which are hermetically sealed to the wall of the tube thus defining three longitudinally separated chambers. The inspection equipment is mounted at the leading end of the crawler. To advance the crawler along the pipe, air or other gas is supplied to the chambers and exhausted therefrom in repeated cyclic sequence for sequentially expanding the chamber wall portions into clamping relation with the pipe, each wall portion recovering to its axial length upon deflation of the chamber, thereby to propel the tube step by step along the pipe.