Failure analysis of the sulphur dioxide transporter pipe to the diffusion water producer tank in the sugar plant of Mashhad

The diffusion process in the production of sugar is a determining process which affects the final quality of sugar. The pH of water which is used in this process is being controlled by adding sulphur dioxide gas to the water. In this research، the reason of corrosion of the sulphur dioxide gas transporter pipe to the diffusion water producer tank has been studied. In this way، the quantometery analysis of the base metal and weld zone، and X-ray diffraction analysis of the corrosion products has been applied. In addition، the corrosion rate of the base metal has been determined by the potentiodynamic polarisation technique at the temperatures between 50 t 70°C and also the DLEPR method has been used for the weld zone. The Results showed that the main reason of the corrosion of the pipe was the accumulation of the gas in the bottom of the pipe and the concentrated sulphur containing droplets which led to the localised corrosion ofthe pipe. Finally، changing the position of the branch pipes، shelving the pipe and changing the material are being suggested.