PREVENTING AMMONIUM SALT CORROSION IN HIGH PRESSURE FLASH GAS LINES

With  increased  requirement for deep desulfurization to meet market demand , old refineries are facing higher risk of corrosion by ammonium salts. The problem is compounded if ERW pipes were used in such application.

The paper describes failure of an ERW pipe in a high pressure flash gas line  through which  gases from Hydrocracker and Hydrotreating units are sent  to a centralized amine treating unit. To prevent similar failures  a two prong approach has been made . First to minimize  ammonium salt corrosion, specific limits of critical parameters have been  developed which are being monitored on a regular basis and  corrective actions are taken as required to maintain the parameters. Secondly  risk  analysis for all ERW piping in the refinery has been carried out  and depending on risk rating of a piping, a replacement/inspection  strategy  has been developed. Key words. Ammonium salt corrosion, ERW, Hydrotreaing, Hydrocracker, Flash Gas, Risk analysis replacement strategy