Replica-Q9

An inspection engineer responsible for the operation of petrochemical plant boiler observed a significant pressure drop which indicates that the boiler tubes might have experienced some damage problem. Preliminary report by process engineer states that the tubes were operated since 15 year ago. For temporary period, they decide to implements the fitness for service inspection to certify that boiler system component was fully ready to operate reliably.

1. Taking into consideration the microstructural condition of boiler system component in the aged petrochemical plant, propose the best assessment technique to certify that boiler system component was fully ready to operate reliably
2. Give your reasons for the above proposed method.
3. Recommend the best interval inspection package on boiler system component that would satisfies the plant engineers.
4. If you decide to perform replica assessment, identify the important information needed from plant engineers for assessment interpretation

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i) The condition assessment shall be implemented by in-situ metallography or replication
assessment method.

ii) This in-situ metallography method will be ensure;

• The fitness for service for the safety of operators/ workers/ contractors and/ or local communities as well as environment

• All equipment operates reliably

• Remaining life of metal structure or component which help the prediction when equipment should be re-inspected for the long-term & continuous productive operations

• Degree of overheating or other damage mechanisms manifested by microstructural changes.

• Assessment of surface flaws to determine if there are any cracks presented on boiler system component which help predicting the root cause of failure resulted by damage mechanism such as creep, fatigue, stress or corrosion.

• Information that supports emerging conditions to ensure optimal use of plant & resources

iii) The best practice of interval inspection is according to Nordtest Method. NT NDT 010: High Temperature Components in Power Plants: Remnant Lifetime Assessment, Replica Inspection. based on Neubauer microstructure evolution as shown in Table below.

Grade/ Class		Microstructure Characteristic	Recommendation Action
0/1		No cavity	No Action
2		Single cavities	Reinspect after 20,000hrs of operation/ inspection interval 3-5 years
3		Coherent cavities	Reinspect after 15,000hrs of operation/ inspection interval 1~1.5 years
4		Microcracks <2mm>	Repair/ Replace of reinspect after 10000 hrs of operation/ inspection interval 0 - 0.5 years
5		Macrocracks >2mm detected by NDT	Immediate Repair/ replace

iv) The important information needed from plant engineers for assessment interpretation are as follows;

• Objective of In-situ metallography; in this case - condition assessment,

• Material of construction with exact specification

• Location of replication with sketch

• Process parameters and design parameters

• Service life of the component at the time of replication.

• Any history of previous failures at the location of replication.