Bijlage 2-shell-ffs-reactor

CATALYTIC REFORMER UNIT (REACTOR FFS ASSESSMENT)

Copyright of Shell Global Solutions International B.V.

by Amin Muhammed

PTE-EMMI

2/9/2011 1

Shell Projects & Technology

CATALYTIC REFORMING UNIT

Copyright of Shell Global Solutions International B.V. 22/9/2011

HISTORY


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.


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

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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]

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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

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REACTOR F105 – STRESS ANALYSIS

FEA analysis performed to establish limit load and stress distributions


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


REACTOR F105 – TEMPERATURE

Operational temperature data available from 1998 onwards


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.

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Replica’s required to indicate as repaired condition




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

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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 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.

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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


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.

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Engineering

Bijlage 2-shell-ffs-reactor