Compensated blast joint for oil well production tubing

A carbide-sheathed oil well blast joint comprising a production tube having an internally threaded box joint at one end and an externally threaded screw joint at the other end, said blast joint comprising two sections of production tubing of approximately equal length joined end to end by a screw threaded flush joint, a plurality of axially short carbide rings of oblong rectangular cross section each having parallel opposed end surfaces at right angles to the longitudinal axis of the tube sections which end surfaces are continuously parallel from their inner to their outer periphery, said carbide rings being slidably mounted about said production tubing sections and extending in an assembled group in contact with each other from adjacent the screw threaded pin joint to adjacent the box joint, a slideable clamping collar adjacent each one of the free ends of the joined sections comprising a first clamping collar mounted on the tube adjacent the pin joint and a second clamping collar mounted on the tube adjacent the box joint, said carbide rings being slideably mounted on the tube between said first and second clamping collars, and a multiple wave spring embracing the tube adjacent the box joint end between the first collar and the adjacent end of the string of carbide rings, said first clamping collar being endwise adjustable along the production tube to engage and hold the wave spring in compression therebetween and the carbide rings, adjacent ends surfaces of the carbide rings being maintained by the wave spring under yieldable endwise pressure in contact with each other, the multiple wave spring yielding axially in response to endwise and angular motion of the carbide rings to accomodate stretch and flexing of the tube at down hole position and temperatures.

A carbide-sheath blast joint comprising a length of oil well tubing,

• collars embracing said tubing and fixed thereto adjacent each end thereof,
• a series of contiguous abrasion-resistant carbide rings co-axially mounted on said tubing between said collars,
• said carbide rings being of uniform oblong rectangular cross section and each having an axial length not substantially greater than one inch,
• the end walls of said carbide rings being disposed planar and parallel continuously from their inner to their outer peripheries, and
• a set of discontinuous annular wave springs embracing said tubing and held in compression between one said collar and the nearest carbide ring, so as to maintain the carbide rings with their end surfaces in close contact,
• said wave spring being transversely slotted each by a single slot which allows for contraction and expansion, and
• the carbide rings being maintained by said wave springs in contact with each other and under yieldable endwise pressure to accomodate stretching and flexing of the tubing at down hole positioning and temperatures.