shown in the drawings in which a guide pipe moves in the radial direction through the furnace wall 2 of a blast furnace 1 and is fixed to a case 4 two pulleys 5 and 5 39 are attached to the inner wall of the end of the guide tube 3 in a manner to rotate freely and an opening 6 is formed in the lower portion of the tube 3 adjacent both pulley 5 and 5 39 a looped portion 8 see fig2 is formed in an end of a wire rope 7 running through the guide pipe 3 one end of the loop 8 passing around the pulley 5 and the other end around the pulley 5 39 and the looped portion hanging down into the furnace through the opening 6 and passing through the eye hole 10 formed in a plumb 9 to locate the plumb 9 always at the mid point of the two pulleys 5 and 5 39 for the purpose of preventing swinging during the shifting of the guide pipe 3 the wire rope 7 is wound around a wire drum 13 installed in the case 4 after passing around a pulley 12 which is installed in a load detector 11 fixed in the case 4 the wire drum 13 is.