Which of the following is considered a limit for the rules of API 650 standard?

• A. The first sealing surface for proprietary connections
• B. The first joint in a threaded connection
• C. The face of the first flange in bolted connections
• D. All of the above are limits

Answer: (D)

The consideration of limits within the rules of the API 650 standard encompasses various critical points of a welded tank's design and construction, which include the first sealing surface for proprietary connections, the first joint in a threaded connection, and the face of the first flange in bolted connections.

These elements represent the key transition points where the integrity and performance of the tank can be significantly affected. The first sealing surface for proprietary connections is vital because it determines the effectiveness of the seal that prevents leaks. Similarly, the first joint in a threaded connection is crucial for maintaining strength and leak prevention, as it represents a potential weak point in the assembly. The face of the first flange in bolted connections is significant because it is essential for maintaining the pressure boundary and ensuring a secure connection between components.

By considering all these points together as limits, API 650 sets a comprehensive framework to address possible vulnerabilities in welded tank constructions, thus ensuring safety, reliability, and adherence to standards in oil storage applications. Addressing each of these elements ensures that the tank achieves its operational specifications while minimizing risks of failure.