Study of the Ventilation Effect to Reducing the Corrosion of the Main Concrete Sewer Collector line in the Vicinity of Dropshaft Manhole

Abstract

Corrosion is one of the major problems in utilizing sewage networks. In some points of wastewater networks, such as drop shafts, the corrosion intensity due to hydrogen sulfide gas accumulation is significant. In Arak main concrete wastewater collector line which transfers waste water from city to wastewater treatment plant the corrosion conditions of sewage pipe in the vicinity of the dropshaft were investigated with the help of sewer CCTV inspections. The occurrence of severe corrosion defects was monitored then intensity of hydrogen sulfide gas was measured. For reduce the intensity of hydrogen sulfide gas and the moisture content of the pipe atmosphere, stack ventilation and circulation pipes, were constructed then the values ​​of hydrogen sulfide gas were again measured. Maximum and minimum values of hydrogen sulfide were reduced 11.9 and 9.09 percent, respectively. The tensile strength test was performed on the last tie rod of ladder stairs. The yield stress of the last stair of ladder in dropshaft manhole was lower than the value of upstream and downstream manholes, that it indicates corrosion in dropshaft manhole was more severe. Due to the observation of the presence of hydrogen sulfide gas in the manholes and in order to investigate the effect of this gas on the metal of the manholes ladder, the tensile strength test of the last step of the manholes ladder and its upstream and downstream manholes was performed. Comparison of yield stress values showed the accumulation of hydrogen sulfide gas and the occurrence of Hydrogen Embrittlement in the ladder.

Keywords

• concrete pipes corrosion
• dropshaft manhole
• h2s
• camera raft robot
• tensile strength
• hydrogen embrittlement