Long Weld Neck Standard
Class 300 Long Weld Neck Flanges
MSS SP-97 long weld neck flanges for Class 300 service
Class 300 Long Weld Neck flanges serve medium-pressure vessel nozzles where the extended hub provides both structural support and insulation clearance. The Class 300 rating covers a broad range of process conditions, making these flanges one of the most commonly ordered LWN configurations in the petrochemical industry.
The forging process for Class 300 LWN flanges produces a continuous grain flow from the hub through the flange body, resulting in superior mechanical properties compared to a welded assembly of separate pipe and flange components. This is particularly important for cyclic service and applications where nozzle loads from piping thermal expansion are significant.
These flanges are frequently specified on reactor vessels, fractionation columns, and heat exchangers operating in the 300 to 700 psi range. Material grades include ASTM A105 for carbon steel and A182 F11, F22, and F304/F316 for alloy and stainless steel applications.
