In order to obtain the installation posture of flange end faces in multi-branch welded pipelines quickly and accurately

 a flexible measurement tool

 together with a calibration procedure

 is proposed for visual inspection. Each flange end face is fxed by the measurement tool’s claw

 whose scalability could adjust to various types of pipelines with different diameters. In addition

 the measurement tool possesses a good self-centering capability. A number of visual target points are laid on the bottom of the measurement tool. By visually measuring the target points on the calibrated measurement tool

a measurement coordinate system can be built up

 which could represent the normal vector

 the location of center point and circumferential position of the flanges. The experiments show that the absolute location accuracy of the flanges end faces is 0.070mm

and the double standard deviation of repeated positioning is 0.044mm.