CATALYTIC REFORMER UNIT (REACTOR FFS ASSESSMENT)

Transcription

1 CATALYTIC REFORMER UNIT (REACTOR FFS ASSESSMENT) by Amin Muhammed PTE-EMMI Shell Projects & Technology Copyright of Shell Global Solutions International B.V. 2/9/2011 1

2 CATALYTIC REFORMING UNIT Copyright of Shell Global Solutions International B.V. 2/9/2011 2

3 HISTORY Copyright of Shell Global Solutions International B.V. 2/9/2011 3

4 HISTORY Reactor vessel F-105 was commissioned in 1971, construction material is 1.25 Cr 0.5 Mo material to BS -1515:1965 code First reported damage goes back to 1999, at that time the damage had been ground out and unit was put back in service. In 2009 crack like damage was reported; but not contributed to creep damage, damage had been ground out. In April 2009, additional damage had been found close to original damage. An creep assessment was conducted on the reported damage in Reactor F105 top/bottom nozzle welds. Consumed life to date 326,446 hours. Current operational cycle 6 years. Next TAR 9/2009; first replacement opportunity for reactors 2015 Copyright of Shell Global Solutions International B.V. 2/9/2011 4

5 REACTOR F105 SCOPE 2009 Reported Damage/repair situation Top Nozzle head - plate inclusions/fabrications defects, no evidence of active service-related propagation; ground out to 12mm depth Bottom nozzle - gas porosity/welding related hydrogen cracking; nozzle weld repair/service related creep damage. Excavated, profiled and left in place on the basis of previous life assessment [note: low (2 yrs min) initial remaining life estimate] Copyright of Shell Global Solutions International B.V. 2/9/2011 5

6 REACTOR F105 SCOPE Copyright of Shell Global Solutions International B.V. 2/9/2011 6

7 REACTOR F105 SCOPE Establish level of prior damage (see NDT, replication results etc) Derive appropriate stresses from FE analysis compare with classic flat plate solutions Provide life assessment Copyright of Shell Global Solutions International B.V. 2/9/2011 7

8 REACTOR F105 STRESS ANALYSIS FEA analysis performed to establish limit load and stress distributions Copyright of Shell Global Solutions International B.V. 2/9/2011 8

9 REACTOR F105 STRESS ANALYSIS Reference stress based on FEA results rather than flat plate solution resulted in a ref. stress of 50MPa approx compared to 68 MPa with flat plate solution Copyright of Shell Global Solutions International B.V. 2/9/2011 9

10 REACTOR F105 TEMPERATURE Operational temperature data available from 1998 onwards Copyright of Shell Global Solutions International B.V. 2/9/

11 REACTOR F105 REMNANT LIFE? Predicted rupture life using R5 Rupture life has been consumed at this point. Future damage is likely to develop slowly and progressively. Creep data scatter and unknown material properties make remnant life predictions for safe operation difficult. Copyright of Shell Global Solutions International B.V. 2/9/

12 REACTOR F105 REMNANT LIFE? Replica s required to indicate as repaired condition Copyright of Shell Global Solutions International B.V. 2/9/

13 REACTOR F105 REMNANT LIFE? Copyright of Shell Global Solutions International B.V. 2/9/

14 REACTOR F105 REPLICA POST REPAIR Replica result after defect removal suggests very little creep damage in base metal, but need confirmation from weld metal and HAZ Copyright of Shell Global Solutions International B.V. 2/9/

15 F105 SUMMARY/CONCLUSION Vessel life assessment of the basis of stress analysis and creep rupture data alone is inconclusive, as a result of the variability in the available data; Lower bound remaining life estimates indicate that locally creep life is exhausted and this is consistent with inspection findings to date. Remaining creep life will depend on the condition and integrity of the remaining wall, post grinding. Inspection on the basis of replications shows no creep cavities to date, however service conditions inherently imply that the creep life is at least partially consumed. Copyright of Shell Global Solutions International B.V. 2/9/

16 F105 SUMMARY/CONCLUSION A best estimate, on the basis of available data would suggest that life consumption is probably in the region of 50%. Based upon experience of life estimation on the basis of replica investigations, a prudent initial inspection interval would appear to be 2 years from the date of the last inspection. Care should be taken in planning and scheduling future inspections to ensure sufficient time is available for vessel replacement in the event that future degradation occurs at a faster rate than presently anticipated. This fact has also been considered in arriving at the recommended inspection interval such that at least two future inspection opportunities are likely to be available as the basis for understanding long term vessel degradation. Copyright of Shell Global Solutions International B.V. 2/9/