connected which in turn includes electrical components connected to the cable 31 a central tubular extension 58 is integrally formed in the nozzle head 13 and envelopes the extension 52 providing a reinforced extension for the reduced diameter tubular member 52 as shown in fig5 and 7 vent passages 55 vent a chamber 60 in the upper portion of the lance structure shown in fig4 as best shown in fig6 and 9 the nozzle head 13 includes an outer cylinder wall 56 with which the pipe extension or wall 49 provides a cooling chamber 57 the extension or stub 58 is connected to the pipe extension 49 by means of circumferentially spaced walls 59 fig1 discloses a modified nozzle arrangement generally indicated at 65 the nozzle 65 includes an outer cylindrical wall 66 substantially similar to the lower pipe 36 39 of fig6 and has connected thereto at its lower end a skirt portion 67 welded thereto as indicated at 68 the skirt has a tubular stub portion 69 which is connected to a sensor support member 70 having an upwardly extending tubular extension 71 connected to the central pipe 22 by a weld 73 the pipe 39 includes the lower extension 47 also shown in fig6 which is in relative sliding engagement with the pipe portion 48 a lower pipe section 74 is welded to the pipe portion 48 by means of a weld 75 the cable 31 of course.