Nipoflanges are used for branch a pipeline by 90 degrees and are basically a combination between a weld neck flange and a nipolet (forged o'let). A nipoflange is a forged product, made out of one solid piece of steel (i.e. the flange and the nipolet are not welded together). The nipolet is welded on the run pipe and branches the pipeline. On the other side of the nipolet, the flange connects the pipe to other devices (example anoter pipe or a valve). Nipoflanges are available in multiple materials from carbon to stainless steel. Nipoflanges are also available in the reinforce type.
Weldoflanges are similar to nipoflanges, as that they are a combination between a weld neck flange and a branch connection (a weldolet in this case). Weldoflanges are made out of a single piece of solid forged steel.
Other less common types of flange-olets (combination of weld neck flanges and forged o-lets) are: elboflanges (flange + elbolet for 45 deg. branched connections), latroflanges (latrolet + flange).