Hello Forum members,

Consider a hot reheat line that is 37.50 inches O. D. with a wall thickness of 1.906 inches. The line operates at 565 psig and 1005 degrees F. The material is A335 P22. The line has been in service continuously since 1992. In 1998 the staff at the Utility's Generating Station noticed that the constant support hangers in the basement (one level below the turbine operating floor)that support this hot reheat line were all sagging and at the bottom of their travel. The "fix" that the Utility's staff came up with was to add more supports. My contention is that the line is no heavier now than when it was first installed and what is being seen is the irreversible effects of thermal creep.

I am inclined to think that the line should have random metallurgical inspections of the grain structure (by replication) to ascertain what the degree of creep progression in the metal. These inspections can be at planned outages every year. If it is determined that there is still 150,000 to 200,000 hours before advanced creep damage sets in, then continuing to add supports to the reheat pipe might be a solution until advanced stages of creep damage are spotted. When advanced stages of creep damaged are picked up by metallurgical micrography then you replace the pipe.

Does any of this make sense and is this a prudent approach ?

I would apprciate this forum's comments


Thanks


Pat LaPointe