1.Weld Neck Flange (WN)
Has a tapered hub and is butt-welded to the pipe. Commonly used for demanding pressure, temperature, and cyclic service when properly designed.

2. Slip-On Flange (SO)
Slides over the pipe and is generally fillet-welded at the inside and outside. Often used in less demanding services where permitted by the design code.

3.Blind Flange (BL)
Has no bore and closes a piping end, nozzle, or opening. It is used for isolation, testing, or future connections when the system design permits.

4.Socket Weld (SW) and Threaded (TH) Flanges
Socket-weld flanges accept a pipe inserted into a socket before welding. Threaded flanges connect to compatible threaded pipe without a pipe-end weld.

5.Lap Joint (LJ) Flange
Used with a compatible stub end. The flange can rotate to simplify bolt-hole alignment and is useful in some piping systems requiring frequent dismantling.