Read the passage below:
Engineers retrofitting an auxiliary marine propulsion unit replaced standard copper-nickel heat exchanger tubes with thin-walled aluminum alloy tubing. During trial operations in brackish coastal waters, salinity readings in the closed condensate return line climbed steadily while external hull seals remained intact. Simultaneously, auxiliary boiler operational pressure fell below normal thresholds, and technicians discovered localized pitting concentrated exclusively along the contact surfaces between the aluminum tubes and the heavy bronze mounting plates.
Based on the implied cause-and-effect relationships in the passage, match each observed condition to its unstated underlying cause or outcome.
- Rising salinity in the closed condensate return lineExternal brackish cooling water penetrating compromised heat exchanger walls
- Drop in auxiliary boiler operational pressureLoss of working fluid volume within the closed steam generation circuit
- Localized pitting at aluminum-to-bronze contact pointsElectrochemical degradation between dissimilar metals in a conductive fluid
Answer
Rising salinity in the closed condensate return line matches external brackish cooling water penetrating compromised heat exchanger walls; Drop in auxiliary boiler operational pressure matches loss of working fluid volume within the closed steam generation circuit; Localized pitting at aluminum-to-bronze contact points matches electrochemical degradation between dissimilar metals in a conductive fluid.
Each match correctly links an observed symptom to its necessary unstated cause or consequence based solely on the passage facts: the salt in the closed line implies external water entered through perforated tubes; the localized pitting at bronze-aluminum interfaces implies galvanic reaction between dissimilar metals; and the boiler pressure drop reflects the resulting loss of fluid containment.
Step-by-Step Solution
Key Concept
Recognizing unstated causal links between physical interventions, material properties, and operational failures in technical passages.
Estimated Time:1m 15s