Continuous drier on rotary offset printing presses and operation of such

Abstract

A continuous drier for drying a printed web on web-fed rotary printing presses operates during ongoing printing and blanket washing processes with control of the gaseous and vaporous constituents of the ink, solvent, and burner gases. An infrared beam path is installed in the drier to measure concentrations of gas vapors in the drier by an extinction method. The continuous drier process is thus controlled according to the rate of evaporation of volatile constituents. The infrared extinction measurement yields spectral measurements of vapors released by the printing ink during the printing process, or of solvent constituents released during the blanket cleaning process, each according to their characteristic band position and intensity. During the transition from printing to blanket washing, the user obtains an instant picture, based on the band intensities, of the current vapor concentrations. Depending on the concentration limits, he can then adjust the flow, heating and ventilation settings within the drier system or selectively adjust solvent dosages. In conjunction with rapid control interventions or preprogrammed adjustments, this undelayed on-line measuring system prevents explosions in the drier. The system also allows the composition of the printing ink, with its varying application rates, to be controlled based on the measured extinction values. Similarly, the burner settings can be controlled via the CO and fuel gas bands in the drier.