What requirement does Annex M of API 650 specify for tanks?

• A. For tanks with a maximum design temperature exceeding 150F
• B. For tanks with a maximum design temperature exceeding 200F but not exceeding 300F
• C. For tanks with a maximum design temperature exceeding 200F but not exceeding 500F
• D. For tanks with maximum design temperatures exceeding 500F

Answer: (C)

Annex M of API 650 pertains specifically to tanks designed for elevated temperatures and places particular importance on material selection, design considerations, and the integrity of welded joints when operating under these conditions. The correct answer indicates that this annex applies to tanks with maximum design temperatures exceeding 200°F but not exceeding 500°F, which encompasses standards for assessing the performance and safety of welded tanks in environments where higher temperatures can influence the properties of construction materials.

This requirement is crucial because as temperatures rise, the mechanical properties of materials can change significantly, potentially impacting the tank's ability to safely hold liquids over time. Therefore, the guidelines in Annex M ensure that tanks built within this temperature range are properly constructed to withstand the conditions while maintaining structural integrity and safety in operations.

The other choices reflect ranges of temperatures that fall either below the threshold specified in Annex M or above it, which would be addressed by other standards, leaving the correct option as the one that aligns with the temperatures that Annex M explicitly covers.