Zur erforderlichen Größe von Zinkdurchlauföffnungen feuerverzinkter Hohlprofilkonstruktionen

Required Size of ventilation openings of hot-dip galvanized hollow sections.

In order to avoid distortion and cracking during hotdip galvanizing a relatively high immersion speed should be chosen. For instance, in the new German standard to avoid cracking during hot-dip galvanizing DASt-Ri 022 a dipping speed of vE ≥ 0,8 m/min has been proposed. Especially for elements with hollow sections the dipping speed is strongly dependant on the size of the ventilation openings. However, it was found that the current rules on size and distribution of these openings are not sufficient. Therefore, the aim of the research described hereafter was to find out rules for size and distribution of ventilation openings that enable a safe galvanizing by providing enough freedom for a quick immersion. Basis of the derivations are the rules of hydraulics that furthermore are verified by experiments of the immersion of hollow sections. The results yield into a simple and reasonable algorithm to determine size and distribution of ventilation openings of hollow sections, contributing to a distortion- and crack-free structure. Finally a proposal in form of design a sheet is made available.