ASNT Level III- Visual & Optical Testing

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5.1.3 Microstructural Interpretation To date, the greatest advances in the use of acetate replicas for nondestructive testing have come from their use in microstructural testing and interpretation. Replication is an integral part of visual tests in the power generation industries as well as in refining, chemical processing and pulp and paper plants. Replication, in conjunction with microstructural analysis, is used to quantify microstrain over time and to predict the remaining useful life of a component. Future applications are not limited by material type. In industry, tests are carried out at preselected intervals to assess the structural integrity of components in their systems. These components can be pressure vessels, piping systems or rotating equipment. Typically these components are exposed to stresses or an environment that limits their service life. Replication is used to evaluate such systems and to provide data regarding their metallurgical condition. Charlie Chong/ Fion Zhang
Microstructural replication is done in two steps: surface preparation followed by the replication procedure. Surface preparation involves progressive grinding and polishing until the test surface is relatively free of scratches (metallurgical quality). Depending on the material type and hardness, this can be obtained by using a I to 0.05 p.m (0.04 to 0.002 mil) polishing compound as the final step. Electrolytic polishing can increase efficiency if many areas are being tested. Surfaces can be electropolished with a 320-400 grit finish. The disadvantages of electropolishing are that (1) the equipment is costly, (2) with most systems only a small area can he polished at one time and (3) pitting has been known to occur with some alloy systems containing large amounts of carbides. Next, the polished surface is etched to provide microstructural topographic contrast which may be necessary for evaluation. Etchants vary with material type and can be applied electrolytically, by swabbing or spraying the etchant onto the surface. With some materials, a combination of etch-polish etch intervals yields the most favorable results. Charlie Chong/ Fion Zhang
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Page 7 and 8: SECTION 4: BASIC AIDS AND ACCESSORI
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Page 59 and 60: Temperature indicating sticks were
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6.3.6 Precise Post forming Heat Con
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Another example of handforrning is
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6.3.7 Pipeline Coatings Epoxy powde
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The most common use for temperature
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FIGURE 67. Temperature indicating s
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PART 7: CHEMICAL AIDS 7.0 General T
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7.1 Test Object Selection Figure 68
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7.2 Surface Preparation Preparation
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7.2.2 Removing Rust and Scale Rust
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If the required finish cannot be ac
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FIGURE 70. Example of contrast reve
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7.3.2 Safety Precautions Etchants a
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Etchant Safety Charlie Chong/ Fion
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Etchant Safety Charlie Chong/ Fion
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7.3.3 Containers Containers used wi
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1. add the acid or alkali to the wa
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7.3.6 Disposal Before disposing of
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7.4.2 Swabbing Etching may also be
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7.4.4 Test Object Preservation Rins
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7.5 Conclusion Visual testing is pe
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Cellulose Replica Sheets Charlie Ch
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Charlie Chong/ Fion Zhang
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ASNT Level III- Visual & Optical Testing

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