Connection types (FF, RF, RTJ, NPT) 1

[Pmatherne]

What do you use to determine what type of end connection you will use on a fitting.
For instance when do you use ring joint instead of a raised face or flat face
What about NPT connections?
The reason I am asking is I have seen some use 600# RTJ and then use 600# RF later.
My initial thoughts are the smaller sizes use NPT because a flanged connection would be impractical


Future PE Engineer
Pet project I am working on to help other engineers, not much yet hoping to get it grow as I learn more

http://www.peexamquestions.com

 

[LittleInch]

Just search RF RTJ on this forum for plenty of ideas. This is a typical exchange

http://www.eng-tips.com/viewthread.cfm?qid=343642

FF is only for cast iron, low pressure stuff #125, #150 or plastic flanges where low bending stress is allowed

RF goes from #150 upwards. Where you stop is more depenadnat on who you work for or what your plant piping spec says than anything else.

You don't often see #600 RTJ, but some companies love them so put them on #300 flanges. NPT is more common for instruments and items of 1" and below as flanges of that size get bulky and weigh a lot compared to the pipe size.

You will find as many ideas and thoughts as there are people commenting here....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way