help for beginner - use of half couplings

Hello
I would like to know what is the use for a half coupling (threaded, socket welded). From one side you connect the thread or the pipe inside the socket, but what do you connect to the other side? thank you for the help.

What is the size of the header and the branch? What is the rating? What is the service?

Also go through cr4.globalspec.com/thread/29239/ ... s-Weldolet

I’m afraid I’m going to have to disagree with my colleague Mr. Jop! I work in the oil fields and we use half coupling all the time! It’s a much simpler branch connection (simpler = cheaper). Now in a strict piping environment type area then I think Jop is correct, but half couplings don’t require the amount of welding for attachment and for vessel and tank connections with internal coatings they are very good. I believe this is one of those “options” that a designer needs to know all the ramifications before using or NOT using. My $0.02

I understand Jop's point of view, better safe than sorry. However in low pressure systems the use of half couplings is common in paper and pulp industry for threaded connections off of main headers and the use of "stab ins" for welded. Cost factors and speed of construction seem to govern these applications. On high pressure systems I would defer to Jop's guidance.

Use the half coupling on vessels or odd branchings (is that even a real word or just my canadian accent talking ) such as a tap off a cap. It can be used as a branch off a pipe but needs to shaped, olets should be used there. I think the field guys like them instead of olets because there's less welding. Full couplings are for joining fittings ie pipe to swage (similar to a union). I hope that helps.