The three general types of flange connections are the screwed, the Van Stone and the _____ .

The correct answer, welded, refers to one of the three general types of flange connections. In a welded flange connection, the flange is permanently attached to the pipe or fitting using a welding process. This method creates a strong and durable connection that is capable of withstanding high pressure and temperature conditions, making it suitable for many applications in refrigeration and other industries.

Welded flanges provide a seamless and leak-proof bond, which is especially important in refrigeration systems that handle refrigerants or other fluids where leaks can be problematic. This type of connection is favored in situations where a permanent, robust joint is required.

The other types of flange connections, such as screwed, Van Stone, ring joint, raised face, and bolted, serve different specific purposes and have their own advantages, but in the context of the question, welded is one of the primary methods used alongside the other two specified types. Understanding these different types of flange connections is essential for ensuring reliable and efficient system designs in refrigeration and HVAC applications.