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;
(2) aligning the internal threads of the coupling nut for engagement with the external threads of the first hub;
(3) 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;
(4) thermally expanding the coupling nut;
(5) applying a secondary torqueTIJUANA, Mexico -- The United States closed off northbound traffic for several hours at the busiest border crossing with Mexico to install new security barriers on Monday, a day after hundreds of Tijuana residents protested against the presence of thousands of Central American migrants.

The U.S. also closed one of two pedestrian crossings at the San Ysidro crossing in a move apparently aimed at preventing any mass rush of migrants across the border.

The installation of movable, wire-topped barriers threatens to complicate life for Mexicans using San Ysidro, where about 110,000 people enter the U.S. every day in 40,000 vehicles.

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Long lines backed up in Tijuana, where many people have to cross the border to work on the U.S. side.

Such inconveniences prompted by the arrival