Material Selection & Properties Flashcards
7 cards from real AEP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Material Selection & Properties flashcards as text
In transformer manufacturing, why is the insulating oil treated to reduce moisture content before filling?
Answer: Even small amounts of moisture dramatically reduce the dielectric strength of transformer oil
Water in transformer oil reduces dielectric strength exponentially; even 50 ppm of water can reduce the breakdown voltage of oil by over 50%.
What is the primary reason stainless steel (e.g., 304 or 316) is selected over carbon steel for chemical piping systems in power plants?
Answer: Stainless steel has a chromium-oxide passive layer that provides superior corrosion resistance
The chromium content (minimum 10.5%) in stainless steel forms a self-repairing passive chromium oxide layer that prevents corrosive attack in most chemical environments.
Which non-destructive testing (NDT) method is best suited for detecting subsurface cracks in non-magnetic austenitic stainless steel welds?
Answer: Ultrasonic testing (UT)
Ultrasonic testing uses high-frequency sound waves that penetrate the material and reflect from internal defects, making it effective for subsurface flaws in non-magnetic materials.
When selecting lubricants for electric motor bearings operating in high-temperature environments, which characteristic is most important?
Answer: High dropping point and oxidation stability at elevated temperatures
Grease with a high dropping point ensures it remains in consistency and does not liquefy and run out of the bearing housing at elevated operating temperatures.
What is the purpose of using a sacrificial anode (e.g., zinc or magnesium) in cathodic protection systems for buried pipelines?
Answer: To intentionally corrode in place of the protected metal structure
A sacrificial anode has a more negative electrochemical potential than the protected structure, so it preferentially oxidizes (corrodes), providing cathodic protection to the pipeline.
In the context of power plant piping material selection, what does the ASTM designation 'A106 Grade B' specify?
Answer: Seamless carbon steel pipe for high-temperature service
ASTM A106 Grade B is a standard specification for seamless carbon steel pipe intended for high-temperature and high-pressure service in power plants.
Which material characteristic is described by the Charpy V-notch impact test?
Answer: Notch toughness (energy absorbed during fracture at specified temperatures)
The Charpy V-notch test measures the energy absorbed by a notched specimen when broken by a swinging pendulum, indicating a material's toughness and susceptibility to brittle fracture.