On Sunday April 13, 1997, the transfer pipe for CO; gas from Ammonia Plant NII exploded. There were no injuries, but 850 meters of the line was totally destroyed and a large number of glass windows were broken. The line was temporarily out of service, and the investigation team concluded that the trip system had been disabled prior to the explosion, hydrogen enriched gas had entered the pipe line, nitrogen urge had not been effective, air had leaked into the line and formed an explosive mixture, and the mixture had ignited.