Remotely pretensioned threaded tubular connections

A tubular connector comprising:

• (a) a first hub having a through bore, a first end and an externally threaded exterior section proximal the first end;
• (b) a second hub having a through bore, an outer surface, an interior end, and a shoulder opposed to the interior end;
• (c) a coupling nut having
• an internally threaded proximal end adapted to threadedly engage the externally threaded exterior section of the first hub, and
• an internal shoulder distal to the threaded proximal end engaged with the shoulder of the second hub to provide axial and radial position control for said coupling nut,
• wherein tightening the coupling nut forces the first end of the first hub towards the interior end of the second hub;
• (d) a heating element attached to said coupling nut;
• and
• (e) torquing means for transmitting torque to the coupling nut to tighten or loosen the nut;
• whereby when the heating element increases the temperature of the coupling nut sufficiently the coupling nut is expanded and less torque is needed to achieve a predetermined pretensioning of the tubular connector.

A tubular connector comprising:

• (a) a first hub having a through bore, a first end having a sealing surface traverse to the through bore, and a plurality of external threads proximal to the sealing surface;
• (b) a second hub having a through bore, an outer surface, and an interior end having a sealing surface traverse to the through bore;
• (c) a coupling nut having a plurality of internal threads at a proximal end, the threads adapted to threadedly engage the external threads of the first hub;
• (d) mounting means for coaxially mounting said coupling nut onto the outer surface of the second hub, said mounting means for providing axial and radial position control for said coupling nut;
• (e) selectably controllable heating means for heating a length of said coupling nut, said heating means positioned distal to said proximal end;
• (f) seal means for sealingly engaging the sealing surfaces of said first and second hubs when said internal threads of the coupling nut sufficiently engage the external threads of the first hub;
• and
• (g) torquing means for transmitting torque to an external surface of said nut to tighten or loosen said nut;
• whereby a pressure-containing connection is effectuated between the first and second hubs by a combination of applying torque to said nut and applying and then removing heat from said nut.

A method of prestressing a threaded connection comprising:

• (a) selecting a tubular connector to connect two lengths of tubing, the connector comprising:
• a first hub having a through bore, an interior end and an external surface, wherein the first hub has a plurality of external threads on a portion of the external surface;
• a second hub having a through bore and a first end;
• a coupling nut coaxially mounted on the second hub to limit axial movement of the coupling nut along a length of the second hub, wherein the coupling nut has a plurality of internal threads adapted to threadedly engage the threads on the external surface of the first hub, wherein tightening the coupling nut forces the interior end of the first hub towards the first end of the second hub;
• and
• a heating element for heating the coupling nut;
• (b) aligning the internal threads of the coupling nut for engagement with the external threads of the first hub;
• (c) applying an initial torque to the coupling nut to engage the external and internal threads to form a connection between the first hub and the coupling nut with a first level of tension on the connection;
• (d) thermally expanding the coupling nut;
• (e) applying a secondary torque to the coupling nut to provide a second level of tension on the connection;
• and
• (f) allowing the coupling nut to achieve ambient temperature to achieve a third level of tension on the connection.

A method of establishing a pressure-containing threaded connection comprising:

• (a) selecting a tubular connector to connect two lengths of tubing, the connector comprising:
• a first hub having a through bore, a first end having a sealing surface traverse to the through bore, a second end attached to a first length of tubing, and a plurality of external threads proximal to the sealing surface;
• a second hub having a through bore, an outer surface, an interior end having a sealing surface traverse to the through bore, and an exterior end attached to a second length of tubing;
• a coupling nut having a plurality of internal threads at a proximal end, the threads adapted to threadedly engage the external threads of the first hub, wherein tightening the coupling nut forces the first end of the first hub towards the interior end of the second hub;
• mounting means for coaxially mounting said coupling nut onto the outer surface of the second hub, said mounting means for providing axial and radial position control for said coupling nut;
• selectably controllable heating means for heating a length of said coupling nut;
• seal means for sealingly engaging the sealing surfaces of said first and second hubs;
• and
• torquing means for transmitting torque to an external surface of said nut to tighten or loosen said nut;
• (b) aligning the internal threads of the coupling nut for engagement of the external threads of the first hub;
• (c) applying an initial torque to the coupling nut to engage the external and internal threads to form a connection between the first hub and the coupling nut with a first level of tension on the connection;
• (d) thermally expanding the coupling nut;
• (e) applying a secondary torque to the coupling nut to provide a second level of tension on the connection;
• and
• (f) allowing the coupling nut to achieve ambient temperature to achieve a third level of tension on the connection sufficient to force the seal means to engage the sealing surfaces of the first and second hubs and prevent the egress or ingress of fluid through the seal means.