Field Metallography Replication Technique to Assess Structural Integrity of Plant Equipment

Transcription

1 Corrosion UAE 2011 Abu Dhabi 27 th February -1 March 2011 Field Metallography Replication Technique to Assess Structural Integrity of Plant Equipment Prepared by: Dr.F. Habiby Reliability and Technical Support (RTS) Department, Arabian Petrochemical Company (Petrokemya- SABIC), Saudi Arabia v

2 Outlook Importance of Materials and its Structural Understanding Metallography (Destructive) Vs Non-Destructive Metallography Replica technique: Taking Laboratory to the field Case Studies Advances in Replica Techniques Question-Answer Sessions 2

3 CIVILIZATION Polymer and Composite? Materials and Human Civilization Silicon Age Steel Age Structure Iron Age Performance Bronze Age Stone Age Properties Processing Interaction between four component of Material Development. TIME IN YEARS 3

4 Importance of Materials Structure & Metallography Metallography allows to examine the structural details of materials. It mainly assists in carrying out: Structure- Property Relationship. Development of New Materials. Root Cause Failure Analysis (RCFA). Recognizing Early Signs of Failures. Color Microscopy: A Combination of Beautiful Image and Scientific Details A microstructure showing grain structure at high magnification (100X). 4

5 High Resolution of Materials Structure Apart from optical microscopy, structure of materials is also studies by high resolution microscopy to establish their properties. A high resolution electron micrograph taken by the author on a high strength aluminum alloy used in aerospace and nuclear industry. Magnification: 1 Million times or 100,000 times the average diameter of a human hair. An electron diffraction image of the above micrograph showing crystal structure. 5

6 Cutting Samples for a Laboratory Metallography Photograph of a HP steam pipeline from where representative samples were cut for destructive metallographic analysis to be conducted in a metallurgical laboratory. 6

7 Performing a typical metallographic analysis Following are the key steps required to perform a typical metallographic analysis: Selection of Sample. Sample Preparation. Grinding and Polishing.. Etching and Examining Under a Microscope. A variable speed controlled equipment used for grinding and polishing metallic samples in a metallurgical laboratory.

8 Example of Metallographic Analysis: Stress Corrosion Cracking A photo-micrograph of stainless steel tube heat-exchange confirming the failure had occurred due to stress corrosion cracking. [Magnification 200 times].

9 Realizing economic benefits of Root Cause Failure Analysis COST SR Cost of Root Cause Analysis Without Root Cause Determination. High Risk of Unplanned Shutdown SAVING With Root Cause Determination No Unplanned Shutdown SERVICE PERIOD Root cause analysis of plant equipment, assisted by microstructural analysis, provides significant benefits in terms of capital savings as well as improving a company s safety records.

10 Replica technique: Taking Laboratory to the field A step-by-step sequence of obtaining surface replica from a furnace tube without cutting a sample and impairing the tube further usefulness.

11 Case Study-I: Evaluation of Hotspot on a Reactor Location on the reactor (in circle) from where surface replica were obtained. A micrograph of replica showing unaltered pearlitic structure confirming absence of Hydrogen Attack.

12 Case Study-II: Corrosion Damage on a Steam Turbine Rotor Location on the rotor (tenon) from where surface replica were obtained. The replica results showed that the pits were formed due to corrosion-erosion mechanism, erosion being more prominent.

13 Case Study-III: Evaluation of Deformed Diaphragm Performed replica test on the deformed diaphragm to assess damage on the rotor due to probable rubbing during operation. Assessment of strength variation of the steam turbine diaphragm carried out and results conveyed for proactive actions. Analysis were made to determine the reasons of strength variation of the rotor due to high temperature exposure during suspected rubbing.

14 Case Study-IV: Creep Rupture Condition Assessment An overview of super heater tubes. The two shining spots (shown by white arrows) are locations where replicas were taken. Evaluation of material degradation of creep exposed components. Structural and Damage Features Assessment Creep exposed material with cavities. Creep exposure, isolated cavities. Numerous cavities without proper orientations. Creep damage with grain boundary separation. Primary Creep Secondary Creep Secondary Creep Tertiary Creep

15 Advances in Replica Techniques A state-of-the art system is now available that provides instant on-site electronic imaging with out the use acetate replica paper. The system claims to eliminate the deficiency of poor image quality of replica technique that normally uses acetate paper. Portable Grinder Portable Microscope Portable Electronic Imaging Station. A state-of-the art system that uses a portable microscope with 400 times magnifying power and an on-site electronic instant image recording and analyzing station driven by a computer software.

16 Advances in Replica Techniques : 3-D Replica In addition to enhanced capability of portable instruments, there has been significant advances in replica gel. A two-component rubber compound which is applied by a hand-held gun offer replica with 3-D capability and more microstructural details. A two-component rubber compound offers 3-D viewing details under a microscope. Metallic surface of copper alloy. Structural detail by replica. 200 times magnified image. 200 times magnified image.

17 Improvement in Replica s Quality and Details During past years, significant improvements have been observed in the quality and details of replicas as illustrated by the following micrographs: Replica of low alloy steel taken in year The structure is hazy with little details. Replica of low alloy steel taken in year The structure shows clear grain boundaries and microstructural details.

18 Thank You Thanks and acknowledge are due to Petrokemya Management for granting permission to publish some of the findings from inhouse failure investigations and analysis reports. Thanks are due to Sabic T&I Jubail for metallography support. M/s Al-Hoty- Stranger and M/s Cooper Heat are dully acknowledged for providing field replication services as well as interpretation of microstructural observations. 18

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