Standard Types of Flanges

the type of flange to be used for a piping application depends, mainly, on the required strength for the flanged joint. flanges are used, alternatively to welded connections, to facilitate maintenance operations (a flanged joint can be dismantled quickly and conveniently).

let’s now dive in the key types of flanges.

• welding neck flange

• slip on flange

• threaded flange

• socket weld flange

• lap joint flange

• blind flange

weld neck flanges

a welding neck flange (“wn”)features a long tapered hub that can be welded with a pipe.their integrity, performance in systems with multiple repeat bends, and the ability to use them in high-pressure and high-temperature systems make them a leading choice for process piping.

the absence of pressure drops prevents negative effects as turbulence and erosion/corrosion of the metals in the proximity of the flanged joints.

the tapered hub allows a smooth distribution of the mechanical stress between the pipe and the weld neck flange and facilitates the execution of radiographic inspections to detect possible leakages and welding defects.

slip-on flanges

slip-on flanges are found to be very common and also available in a wide range of sizes in order to accommodate the systems with high rate of flow and throughput. it is quite easy to install it by simply matching the flange with the outer diameter of the pipe in order to connect it. installing these flanges is bit technical as there is a need of fillet weld on the both side in order to secure the flange to the pipe.

threaded flanges

also known as a screwed flange, this style has a thread inside the flange bore which fits with the matching male thread on the pipe or fitting. the threaded connection means you can avoid welding in many use cases. simply match the threading to the pipes you wish to connect.

socket weld flanges

this type of flanges are usually used for smaller pipe wherein the diameters in low-temperature and low-pressure areas feature a connection in which the pipe is placed inside the flange in order to secure the connection with a single or multi-pass fillet weld. this is responsible for making the style simple in installing as compared to other welded flange types by avoiding the limitations that are associated with the threaded ends.

lap joint flanges

lap joint flanges feature a flat face and are always used in conjunction with a stub end.

lap joint flanges resemble, in shape, slip-on flanges except for the radius at the crossing of the flange face and the bore to accommodate the flanged portion of the stub end.

a lap joint flange slips over the pipe and seats on the back of the stub end and the two are kept together by the pressure of the bolts.

the use of lap joint flanges in combination with stub ends is a cost-effective solution for stainless steel or nickel alloy pipelines, as the material of the lap joint flange can be of a lower grade (generally carbon steel) than the material of the stub end (which has to match the pipe grade, as in contact with the conveyed fluid).

blind flanges

used for terminating or isolating piping systems, blind flanges are essentially boltable blank discs. when installed properly and combined with the correct gaskets, they can achieve an outstanding seal which is easy to remove when needed.