Replica-Q14

What is the qualitative thermal degradation indexes considered in metallographic analysis?

• Tendency to pearlite/ bainite spheroidisation

• Coarsening of precipitates in the ferritic matrix and at grain boundaries,

• Broadening of denuded zones (no precipitates) along grain boundaries.

Replica-Q13

What is Creep or creed deformation?

Creep is a phenomenom of a sample to deform against time at particular temperature. Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to levels of stress that are below the yield strength or ultimate strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and near the melting point

Replica-Q12

What is Creep or creed deformation?

Creep is a phenomenom of a sample to deform against time at particular temperature. Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to levels of stress that are below the yield strength or ultimate strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and near the melting point

Replica-Q11

What are the deterioration mechanisms that could be detected by using in-situ metallography

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• graphitization

• spheroidazation of pearlite

• creep

• thermal fatigue

• hydrogen attack

• carburization

• grain boundary oxidization

• embrittlement of microstructure etc.

Replica-Q10

Why microstructural crack analysis is important?

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• Possible to make a correct determination of crack type.

• Important to determine whether the crack is the original defect or caused by service conditions or damage.

• Once the crack type is identified, the proper corrective action, such as

• Eliminating a corrosive environment

• Reducing stress levels

• Re-examine the services condition & make a preventive actions

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.

Replica-Q8

What are the Critical Point in Boiler Tubes ?

• Bends

• T-sections

• Reducting section

• Valves

• Rigidly-held pipes

• hangers

Replica-Q7

What are the components that subjected to in-situ metallography?

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• Boiler tubes

• Furnace

• Superheaters

• Steam piping

• Turbine

• Heat exchanger

• Pressure Vessel

Replica-Q6

There are wide differences in the techniques of in-situ metallography (replication technique) against laboratory metallography. These differences get highlighted when in-situ metallography is actually carried out. Together with your experiences in lectures, laboratory works and industrial training, list down on this issue.

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• The nature of metal and alloys under investigation,

• Field conditions,

• Geometry and location of area intended for in-situ metallography,

• Purpose of the in- situ metallography,

• Selection of polishing equipment and method,

• Selection of etching method,

• Technique of replication,

• The details required from the replica,

• Types of microscopy to be used,

• Technique of viewing the replica and

• Interpretation of results.

Replica-Q5

In-situ metallography is used on vessels or structures that have been exposed to temperatures in excess of their design limits, and materials that have been in a corrosive atmosphere. What does in-situ metallography reveal?

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• Displays flow pattern lines indicating hot or cold working

• Grain structure is viewable

• Characteristic structure such as pearlite’s lamellae

• Exposes whether alloys have segregated during solidification

• Microscopic characteristics give insight into macroscopic properties

Replica-Q4

The object of in-situ alloy metallographic method is to allow viewing of the surface microstructure of operating components. Elaborate the application of this non-destructive technique?

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• Remaining life of metal structure or component studies, which help predict when equipment should be re-inspected.

• Damage assessment from creep mechanisms or fire damage to determine if it an item is safe to use after being exposed to fire.

• Heat treatment condition evaluations to assess if the component has been properly heat-treated.

• Composition verifications.

• Classification of cast irons without sacrificing any components.

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

• Assessment of surface flaws to determine if they are cracks, laminations or seams.

• The cause of cracking which help predicting the root cause of failure where it resulted from corrossion, creep, fatigue, stress etc.

• Fitness for service to ensure that all equipment operates with safety and reliably

Replica-Q3

As an NDE technique, in-situ metallography is ideal for assessing the remaining life of power and petrochemical plants. Why this technique is important to industries?

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• To ensure the safety of operators/ workers/ contractors and/ or local communities as well as environment

• To ensure that all equipment operates reliably

• To ensures long-term & continuous productive operations

• To provide information that supports emerging conditions to ensure optimal use of plant & resources

• To be applied for microstructural analysis when examining large components that cannot be easily moved or destructive sample preparation is difficult or not permissible.

Replica-Q2

On field testing, metallography can be applied non-destructively by replication technique. Briefly explain, what is the replication technique and it objective?

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• Replication means, the act or process of duplicating or reproducing something.

• Replication in metallography, is the use of thin plastic films to nondestructively duplicate the microstructure of a component. The film is then examined at high magnifications using metallurgical microscope (or SEM).

• The object of this nondestructive testing method is to allow viewing of the surface microstructure of operating components.

Or the answer could be like this

• The sample is ground, polished, etched, replication & inspected in the field to identify microscopic defects

• Tests metals currently in use, instead of metals being mass produced

• Addresses potential failure problems of industrial equipment

• The objective is to determine the microstructural deterioration & damage of engineering alloys subjected to various environments

Replica-Q1

What is Metallography?

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Metallography is the science and art of preparing a metal surface for analysis by grinding, polishing and etching to reveal it's microstructure constituent