Checking of metal tubes for faulty internal coatings - is based on measuring resistance between tube and metal mandrel which is driven by V=pulley

摘要

The method is for testing internal protective layers such as lacquer layers on tube blanks and is based on measuring their resistance so that a flaw is indicated by values below a nominal value. The testing device (10) consists of a mandrel (11) rotatably mounted on an arm (12) which can move to and fro. The mandrel is driven by a V-pulley (13). For testing the end of a tube blank (15) remote from a screw nipple (16) is pushed onto the mandrel. A pressure roller (20) is urged against the tube blank which is caused to rotate. The electrical resistance between the tube blank and the mandrel is measured. An insulating head member (22) and circumferential ring (23) prevents short circuits at the tube blank ends.