| 摘要 |
<p>An apparatus (14) is disclosed including first and second housing halves (16a, 16b) which are welded together to attach the apparatus (14) to a pup joint pipe (10) installed in an oil well casing pipe (12). The housing (16) includes a cylindrical portion (18) and first and second frustoconical portions (20) at opposite axial ends thereof. Axially extending L-shaped spacers (22) are secured to the inside surface of the cylindrical portion (18) and include longitudinal edges which abut with the outer surface of the pipe (10). Series of axially spaced, first and second, right parallelepiped shaped, magnets (28, 30) are sandwiched between the inside surface of the cylindrical portion (18) and the outer surface of the pipe (10), with the poles of the first and second magnets (28, 30) being reversed relative to the pipe (10). The housing halves (16a, 16b) are welded along their longitudinal free edges after being clamped together by a clamping band (32) with sufficient force to secure the apparatus (14) to the pipe (10) generally by frictional forces and being free of attachment to the pipe (10).</p> |
