Flange Selection Guide

At OneHydraulics, we know that there are many styles of flange to choose from, and it's not always clear why you may use 

one style over another. We've compiled the guide below to make your flange selection just a bit easier. 

Butt Weld Flanges

Butt weld connections allow the pipe to ‘butt’ against the end of the flange. The two pieces are then welded around the outside beveled perimeter. 

 Butt weld connections are often favored over socket weld connections since there is greater weld penetration which results in a stronger connection.

Socket Weld Flanges

Socket weld connections allow the pipe to slip inside the socket of the flange. The connection is then welded at the base of the connection where the pipe makes a 

90 degree connection with the flange. While the weld penetration is not as deep as would be with a butt weld connection, it is often favored because it is easier to weld.

Saddle Weld Flanges

Saddle weld flanges are used to ‘tap into’ an existing piece of pipe or new pipe assembly to create a new flange connection port. 

 The existing pipe must be drilled in the appropriate location and cleaned to remove any debris or metal shavings. 

 The saddle weld flange is then placed over the hole and welded around the perimeter.

Captive Flanges

Captive flange are available with either drilled bolt holes for o-ring side connections or tapped bolt holes for flat face side connections. 

They are often used on new tube or pipe assemblies because they are confined to the assembly and will not be lost when the equipment is serviced in the future.  

Split Flanges

Split flanges are only available with drilled holes and is simply a captive flange that is drilled in half.  They are preferred for most o-ring flange head 

connections because of their ease of assembly and disassembly. They are commonly used with hose and split flange adapter fittings (flange heads) 

because it is often not possible to fit a captive flange over the outside diameter of the fittings. Split flange simply slide around from the outside.