Situation: A second stage cyclone inside a cat cracker had a failed outlet pipe. This was allowing catalyst to by-pass the cyclone into the flue gas duct. The electrostatic precipitator overloaded and catalyst was entering the atmosphere.
Operating Conditions: The flue gas was operating at 1250ºF and 15 psig. The duct was 67" in diameter and had a ½" carbon steel wall with 6" of refractory and longhorns.
Solution: Team designed and manufactured special equipment to install a 30" steel ball to plug the outlet pipe in a reducer. A 36" hot tap was made in a horizontal position on the vertical duct. This permitted the 30" ball to be lowered into the reduced section above the cyclone. Two-inch and one-inch balls then were inserted to form a bed for the concrete refractory, which completed the seal. The customer was able to continue operating the unit without a shutdown for two years.
