Investigation of the ferroprobe coercitivity meter KIFM-1 with various shoes for inspection of tubes

The quality of the metal of carbon-st l pipes about 25 to 48 mm in diameter and having the wall thickness of about 1.5 to 9 mm may be controlled by the use of a KIFM-1 coercimeter together with an attached electromagnet (the cross-sectional area of a core of about 12x28 mm). So, the influence of occasional gaps on the coercimeter readings may be reduced by increasing the length of pipe mouthpieces. The optimum length of the pipe mouthpieces, corresponding to the minimum measurement error when the gap is varying from zero up to 0.5 mm, depends on the ratio of the diameter of the mouthpiece to the diameter of a pipe, and on the pipe wall thickness. The least optimum length of the mouthpiece at an invariable wall thickness of pipes corresponds to the case where the ratio of diameters of the mouthpieces to those of the pipes is close to unit