I grew up around these patterns since my dad is a welder. He doesn't use them much these days since most of his work is large-scale natural gas transmission (so usually around 18-24" pipe), but he started in chilled water/mechanical systems and has always done little personal projects (porches, trailers, smokers/grills) where he used a lot of 1.5 and 2".
I believe he called them "saddles", or maybe the term was "saddling the pipe", I forget, but he still has a lot of these in different sizes. I know he's made some of his own but I've seen a lot of store-bought ones around as well.