Type of Flanges

What code are you referring to?

If you use weld neck flange it needs a test if done correctly, hence it requires radiography or any other test. So it is the other way around!

Check out:

http://www.google.com/search?sourceid=navclient&aq=&oq=weld+neck+flanges+design+application&ie=UTF-8&rlz=&q=weld+neck+flanges+design+application

It is hard to get a good radiograph on the weld for a slip-on or socket-weld flange (too much material in the way). So the OP is right on that point. It does depend on which Code is to be followed.

Ok live and learn.

To elaborate more on it. My thinking is: You have to radiograph or test the weld one way or the other. Which requirement comes first I cannot tell. Found this. Seems a nice wrap up of things.

Found this too and this.

Sure. Lethal service? ASME B-31.3 ????

Q1: Preferred over what? slip-on or socket weld? I think high-temperature is another, maybe the most important, driver of weld-neck over slip-on. Another issue is crevice corrosion with socket weld. In my petrochem experience, under 2" was usually socket weld and over 2" was usually butt-weld (weld neck). 2" was sometime socket weld, sometimes butt-weld, and I have seen butt-weld down to 1/2". Only cooling water and similar service used slip-on.

Q2: What are reverse flanges and Nut stop flanges?

H2 does not necessarily have to be considered lethal fluid.

See ASME B 31.3 (Refers you to Chapter VII, Point 341.4 for NDE)

I recommend (Sorry) ensured flanged union with additional helium test.

WP

1.- Socket weld flanges (Small bore) will be checked with RT examination. (Fillet weld and gap verification)

2. RT for slip on is complicate but:

1.- Slip-on flanges will be provided with a vent and pneumatic test 1/8 inch NPTdrilled hole on the neck prior to welding.2.- A pneumatic test shall be done after welding of slip-on flanges, at a pressure of0,7 - 1,03 barg (10 - 15 psig), for, at least, 5 minutes.No leaks are permitted. Hole shall be filled with appropriate grease to prevent from

entering water

WP