Pipe tube connection

Question

Pipe tube connection

helpyou (Automotive)

(OP)

7 Nov 22 16:25

Hi ,

I have a 3/4 pipe closed at one end.. I need to connect a isolation valve for venting purpose. What are the best connection type to connect the pipe and the valve without having to weld (just cut the closed end and connect)? What fittings are required ?

Can you refer to any standard that talks about this subject?

Your comments please.

Thank you

danw2 (Industrial) · Answer 1 · 2022-11-08 16:13:07

Tube fittings are designed so the ferrule fits the O.D. of the tubing and tubing is sized by its O.D. Pipe is sized by its nominal ID, so Tube fittings are not a solution.

You don't mention pressure, but given that most small valves are available with pipe thread process fittings, why not thread the pipe and screw on a valve?

TugboatEng (Marine/Ocean) · Answer 2 · 2022-11-08 16:43:14

Pipe has a nominal OD as well, the trouble is that the surface roughness and roundness of the OD of pipe is not controlled enough to support the use of swaged fittings.

helpyou (Automotive) · Answer 3 · 2022-11-08 17:07:20

Hi guys

Thank you for your replies. The application is nitrogen from cylinders to a downstream system. The pressure is 200 barg. It may not be possible to thread the pipe at site neither remove it and take it to workshop.

Apart from welding ..any good connection to a pipe that is not threaded or screwed?

Thank you

IRstuff (Aerospace) · Answer 4 · 2022-11-08 17:47:56

As Tugboat alludes, swaged fittings are the only other option, but it'll depend on what specs your actual piping adheres to. https://products.swagelok.com/en/c/straights/p/SS-...

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TugboatEng (Marine/Ocean) · Answer 5 · 2022-11-08 18:27:48

Swagelok fitting are not available to fit over pipe dimensions, tubing sizes only. Pyplok is the only compression type fitting for NPS or pipe that I know of that can withstand that pressure.

Threading is likely not an option if the pipe does not have sufficient wall thickness.

thebard3 (Computer) · Answer 6 · 2022-11-09 19:06:54

Flare fittings could also be considered

Brad Waybright

The more you know, the more you know you don't know.

TugboatEng (Marine/Ocean) · Answer 7 · 2022-11-09 19:28:01

Also not available for pipe diameters.

3DDave (Aerospace) · Answer 8 · 2022-11-09 19:34:23

What is the pipe schedule - or - what is the exact ID and OD?

What is the pipe material?

What is the cap configuration?"

Why can't it be threaded on site? If you can cut off the closed end and attach a valve you should have access to thread the pipe.

Oh - wait - is this a game where the pipe if fully embedded in concrete so that none of the pipe is actually exposed except for the part that can be cut off?

Now an answer requires on-site photos with a visible ruler with side, top, and front views from far enough away to see all the obstacles.

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Pipe tube connection