Answer :
Final answer:
In HF service, carbon steel operating above 200º F should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400. The correct answer is D.
Explanation:
High-frequency (HF) service refers to the transmission of high-frequency electromagnetic waves through a pipe or pipeline to detect changes or anomalies in the material. Carbon steel is commonly used in pipelines for various applications. However, at high temperatures, carbon steel is susceptible to corrosion and may experience significant thickness loss, which can result in structural failure and leakage.
According to NACE International (National Association of Corrosion Engineers) Standard MR0175/ISO 15156, carbon steel pipelines operating above 200º F (93º C) should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400 or another suitable material.
The reason for choosing 200º F is that it is the temperature at which carbon steel begins to experience a significant reduction in its mechanical properties due to carbide precipitation. This can lead to hardening and embrittlement of the material, making it more prone to cracking and corrosion.
Therefore, it is important to monitor carbon steel pipelines operating above 200º F for thickness loss and consider upgrading to a more corrosion-resistant material such as Alloy 400, which has superior resistance to corrosion and temperature effects.
Thus option D is correct.
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