Which type of flange is welded to the pipe in two locations?

The correct choice, a slip-on flange, is designed to slide over the end of a pipe. It is then welded in two places: first, a circumferential weld on the outside where the flange meets the pipe, and second, a second weld on the inside of the pipe, creating a secure connection. This double-welded design enhances the strength of the joint and minimizes the risk of leaks, making it ideal for applications where a robust seal is required.

In contrast, a threaded flange does not involve welding; it is connected to the pipe through threading, which can limit the pressure and temperature applications to which it can be subjected. Blind flanges are solid and used to seal the end of a pipe, meaning they are not connected in a manner that involves welding to the pipe itself. Socket weld flanges are similar but differ in that they are designed for use with a pipe that fits inside the flange and is single-welded on the outside, not in two locations as with the slip-on flange. Understanding these distinctions is crucial for proper selection depending on the mechanical or pressure demands of a piping system.