Material Selection & Properties Flashcards
7 cards from real BGE 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
Which material property determines how much a metal expands when heated, and why is it critical for pipeline design?
Answer: Coefficient of thermal expansion
The coefficient of thermal expansion dictates how much a pipe grows or contracts with temperature changes; expansion loops and offsets must accommodate this movement to prevent stress failures.
A BGE technician is selecting grounding electrodes for a new substation. Which material offers the best long-term corrosion resistance for buried ground rods in Maryland's soil?
Answer: Bare copper-clad steel
Copper-clad steel rods combine steel's mechanical strength with copper's excellent corrosion resistance in soil, making them the industry-standard choice for grounding electrodes.
What is the maximum allowable operating pressure (MAOP) classification for PE 4710 gas distribution pipe in a typical residential distribution system?
Answer: Up to 100 psi for medium-density PE in distribution class
PE 4710 pipe used in distribution-class systems is generally rated up to 100 psi, sufficient for residential and light commercial natural gas service.
Which transformer insulation system uses mineral oil as both a coolant and a dielectric medium?
Answer: Liquid-immersed oil-filled transformer
Liquid-immersed (oil-filled) transformers circulate mineral oil to dissipate heat and provide dielectric insulation between windings and the tank.
A gas line crossing a river requires a casing pipe. What material is specified in DOT regulations for the carrier pipe inside the casing?
Answer: Standard-weight carbon steel with external coating and cathodic protection
DOT 49 CFR Part 192 requires steel carrier pipe with external corrosion coating and cathodic protection for crossings through casings under water bodies.
What is the purpose of a zinc anode attached to a steel gas main?
Answer: To provide cathodic protection by sacrificing the zinc to prevent steel corrosion
Zinc is more electronegative than steel; it corrodes preferentially (sacrificially), protecting the steel pipe from electrochemical corrosion in the soil.
Which conductor property is expressed in circular mils (kcmil) on utility material lists?
Answer: Cross-sectional area of the conductor
Kcmil (thousand circular mils) describes the conductor's cross-sectional area, which determines its current-carrying capacity (ampacity).