GB283256A - Electro-magnetic testing of steel wire ropes - Google Patents

Abstract

283,256. Wall, T. F. Oct. 1, 1926. Magnetic tests.-A method of testing steel wire ropes &c. for flaws comprises a magnetic circuit system with parallel branches comprising a laminated iron structvre, the common limb of which is surrounded by a coil excited by alternating current, one parallel branch consisting in part of laminated iron and the specimen under test, while the other branch consists in part of laminated iron and a piece of standard rope. In Fig. 1, the exciting coil E is wound round the central limb of a set of laminations L formed from H- stampings riveted together. The rope R to be tested passes through clearance poles in the projecting limbs L<1>L<1> of the stampings. Removable blocks of stampings C may be secured by bolts B to the ends of the limbs. Guide pulleys P are provided for the rope R. In a corresponding position on the other side of the coil E a piece of sound rope D similar to the rope R is fitted, and this may be placed under the same. tension as the rope R. Two search coils S1S1 connected in series are arranged to link with the flux through the rope R, and are connected in opposition to two similar coils S2S2 linking with the flux through the rope D. If the whole system is balanced, the total resultant EMF induced in the coils is zero. If a flaw exists in that part of the rope R in the magnetic circuit, the EMF induced in the coils S, will he diminished and that in the coils S2 increased, and this disturbance of the balance may be measured by means of a voltmeter or ammeter. An amplifying arrangement such as a thermionic valve system may be used in order to detect small flaws. In a modified form there are two series of channel-shaped stampings and two coils excited from the same source. In this form the flux changes occur only in that series through the rope to be tested passes.