a. a flexible cylindrical conduit having insulation around an exterior surface thereof, and having a cylindrical inner surface defining a hollow internal cylindrical region;

b. a flexible metallic sheath provided coaxially inside said internal cylindrical region of said conduit such that a coaxial space is provided between an outer surface of said sheath and the cylindrical inner surface of said conduit;

c. an elongated heating element removably inserted into and extending along a length of an interior of said flexible metallic sheath; and

d. a temperature sensor attached to said heating element, the sensor being adapted for removable insertion into the interior of the sheath with the heating element;