Half Coupling Note in Mechanical Drawing 2

[vhmech]

In an NPT half coupling, one of the diameter of the coupling is larger than the other side.

In my project, the half coupling must be welded in the proper direction.
How do I address this in a mechanical drawing?
In other words, what note should I write in the drawing to show that the larger diameter of the hole has to be in the bottom and the smaller one has to be in the top and not the other way?

Thank you,
vh

 

[MikeHalloran]

Show the thread in a side view or section as a pair of hidden lines with a greatly exaggerated taper. That's all.

You shouldn't need a note unless you're doing something completely counter-intuitive to an experienced fabricator, e.g. welding the half-coupling to the bottom surface of a tank in such a way that a nipple can be screwed into it from inside the tank, e.g. to make a standpipe.





Mike Halloran
Pembroke Pines, FL, USA

 

[chicopee]

Show the half coupler as part of the assembly or sub assembly drawing, then using a thick circular phantom line around the coupler and part of the assembly or sub assembly attach a balloon as reference to an expanded view on the same or different sheet. As pointed out above increase the scale of the expanded view and attach notation but make some symbol to indicate notation for the proper orientation shown or assumed in the expanded view.

 

[vhmech]

Thank you for the replies.

Exaggerated taper is a good idea. I also increased the scale to make it look more clear.

 

[PeterStock]

Maybe just use a note: "THREADED END TO OUTSIDE"

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[RoarkS]

Looking at the drawing where it shows that it is not a thru thread, Agreed a "THREADED END TO OUTSIDE" note with a leader arrow on the end of the part with the threads.

If your really worried about it, maybe go as so far to note
"NPT ADAPTOR ORIENTATION CRITICAL" as well in the prints note section. It's your print/contract to get your point across, there isn't a symbol for everything.

 

[MikeHalloran]

If your shop is _that_ stupid, maybe you should just use a full coupling, so they can't get it backwards.





Mike Halloran
Pembroke Pines, FL, USA

 

[jte]

Well... I do have photos of alloy piping flanges with the raised face side welded to the pipe...

But I have to agree with Mike. Anyone running a shop welding half couplings on who can't figger out which end the pipe goes in to... Well, they won't be getting a lot of repeat business.

jt

 

[IFRs]

I wanna see those pictures!!!

 

[jte]

Here ya go.

jt

 

[IFRs]

Love it!!

 

[MikeHalloran]

They're halfway decent welds, too.

I'm guessing they were done that way by an experienced fabricator as some sort of 'malicious obedience'.



Mike Halloran
Pembroke Pines, FL, USA

 

[MintJulep]

"Just fillet weld the flanges to the pipes."

 

[RolMec]

That's not easy, to do a well centered weld joint on that side of the flange. Very good pic, shall keep it in mind!
Thanks.

R.

 

[jte]

I've tried but failed to identify the facility in which this was done. I have several "not in my facility" responses - the colors looked similar to one in particular but I'm assured by good sources that it didn't happen there.

A few notes, aligned with the comments above. * A junior welder on the job for his first day would not be allowed to touch alloy piping. This stuff looks like some flavor of stainless or higher.
* Fitup looks good.
* Weld quality looks ok.
* Even an apprentice welder would (should?) have seen a flange pair before and would be expected to have an understanding of the mechanical assembly of flanges.

Thus, it is my opinion that this was the job of a senior welder within a week of retirement or quitting. Perhaps in a response to a junior engineer telling him exactly how to weld the flanges to the pipe. As per Mike's eloquent phrase above, 'malicious obedience.'

jt