What is an Annular Plate as defined in API 650?

• A. A bottom plate welded to the shell that has butt-welded, substantially radial joints
• B. A type of reinforcement used in the upper section of tanks
• C. A plate used to create a thermal barrier
• D. A standard for determining tank design specifications

Answer: (A)

An annular plate, as defined in API 650, refers to the bottom plate that is welded to the tank shell and features butt-welded, substantially radial joints. This design is crucial because it plays a significant role in the structural integrity of the tank, ensuring that the loads and stresses are evenly distributed. The design of the annular plate allows for proper attachment and support of the tank shell, contributing to both the stability of the tank and its ability to withstand internal pressures.

Radial welding joints are particularly important as they allow for more efficient transfer of forces, reducing the likelihood of stress concentrations that could lead to failure. In the construction of welded tanks for oil storage, adherence to the specifications for annular plates as outlined in API 650 is essential for ensuring safety and compliance with industry standards.

The other options do not accurately describe the annular plate. For instance, while reinforcement is an important aspect of tank design, it does not fully encapsulate the primary function of the annular plate. Similarly, using a plate to create a thermal barrier or as a standard for determining tank design specifications does not reflect the specific characteristics and purpose of the annular plate as defined by API 650.