According to API 650, how many specimens are required for impact testing of plates?

• A. Two specimens
• B. Three specimens
• C. Four specimens
• D. Five specimens

Answer: (B)

API 650 specifies that for impact testing of plates, a total of three specimens are required for each test. This requirement is established to ensure that the testing results are statistically valid and can provide a reliable indication of the material's toughness. By utilizing three specimens, it allows for the evaluation of variability within the material and ensures a more comprehensive understanding of how the material will perform under stress and at low temperatures.

Using three specimens also aligns with common practices in mechanical testing where a minimum of three samples provides enough data to assess the average performance and identify any outliers. This rigorous approach helps maintain safety and integrity in tank design and operation within the oil storage industry. The requirement fosters a material selection process that prioritizes reliability, ultimately contributing to the overall safety and functionality of welded tanks for oil storage.