Analysis of production of glass tubes by vertical nondebiteuse drawing

In the nondebiteuse method of producing glass tubes for industrial pipe lines, a repeat anneal is considered to be an obligatory operation. This distinguishes this process unfavorably from the vertical drawing of flat glass where annealing is done directly in the shaft of the machine. This is explained by the higher speeds (3-4 times) by comparison with flat glass used in the drawing of glass tUbes and also by the different characters of the cooling of flat glass and glass tubes in the annealing zone.