A slip-on flange, also known as a SO flange, is a type of flange that is used to connect two pipes or fittings by sliding the flange onto the pipe end and then welding it in place. The inner diameter of the slip-on flange is slightly larger than the outer diameter of the pipe, allowing for a smooth transition and easy installation. The flange has a flat face or raised face and is typically used in low-pressure applications.

Sock weld flanges, on the other hand, are similar to slip-on flanges but have a recessed area or socket in the flange that allows for the pipe to be inserted into the flange. The pipe is then welded to the flange, resulting in a stronger and more secure connection than a slip-on flange. Sock weld flanges are commonly used in high-pressure and high-temperature applications, such as oil and gas pipelines, chemical processing plants, and power generation facilities.

Both slip-on and sock weld flanges are available in various sizes, pressure ratings, and materials, including carbon steel, stainless steel, and alloy steel. Proper installation and welding of the flange are crucial to ensure a tight and leak-free seal. The welding must be done carefully to prevent damage to the flange and to ensure that the connection is strong and secure.