FOUR-ARM CALIPER- FLAW DETECTOR FOR INVESTIGATION OF TECHNICAL STATE OF CASING PIPES AND TUBING STRINGS OF OIL-GAS WELLS Russian patent published in 2012 - IPC E21B47/08 G01N27/82 

FIELD: mining.

SUBSTANCE: four-arm caliper- flaw detector is equipped with electromagnetic flaw detector, centralisers with spring-loaded levers and four-arm caliper with converter of mechanical movement of levers to electrical signal. Four-arm caliper is combined with one of centralisers with levers tracking irregularities of the well walls. Four-arm caliper includes constant magnets installed in the middle of diametrically opposite levers and Hall transducer located on the flaw detector axis inside the centraliser housing made from non-magnetic material. At that, axes of constant magnets, when levers are folded, are perpendicular to flaw detector axis, and axis of maximum sensitivity of Hall transducer is directed perpendicular to flaw detector axis and lies in one and the same plane with axes of magnets. Besides, hall transducer is electrically connected to electronic circuit of flaw detector providing the reception and processing of signals from Hall transducer and their transmission to the surface.

EFFECT: improving measurement accuracy of inner diameter, reducing overall dimensions, simplifying the design of the instrument and enlarging its application field.

2 cl, 3 dwg