Using threaded fittings and welded fittings in the same piping system 3

[borobam182]

Hello all,

I just wanted to check this with someone in case I'm missing something obvious.....

I need to use a threaded coupling at one point in my arrangement to tie in with existing equipment. The connection is a 1" female thread. I am going to apply the required male thread onto my 1" pipe. I then need to create a tight S bend at the other end of my 1 " pipe, and this would be best achieved by going fitting to fitting with 2 off 90 degree welded elbows.

I cant any issues with this. All pipe and fittings are 1". I will be getting a 1" pipe and threading one end and welding something onto the other.......

Sounds easy.....maybe a little too easy?!

Is there a rule against mixing threaded pipe fittings and welded pipe fittings in the same system?

Any advice would be greatly appreciated.

Thank you

 

[SandCounter]

It is difficult to say if there is a rule against mixing pipe fittings without knowing the application, medium going through the pipes, and under which regulations you might be governed. In my experience, what is regulated is not mixing of fittings, but rather if threaded fittings are allowed in the particular application.

I used to count sand. Now I don't count at all.

 

[borobam182]

Thank you for your reply.

The media is only water for drainage.

 

[moltenmetal]

Does it matter if the thread leaks?

If so, you will need to turn the threaded joint one full rotation to get your welded parts to their desired orientation.

If leakage doesn't matter, you can use a good sealant system (heavy weight teflon tape AND anaerobic pipethread sealant is what we use, always), apply it carefully, tighten it carefully and hope for the best.

If not, a point of rotation (union or flange) is required so you can tighten the leaking threaded joint without messing up the orientation.

Nothing inherently wrong with combining threaded and welded piping elements, other than this.

 

[borobam182]

Thank you for the response.

I will feedback this issue regarding tricky installation with regards to maintaining correct orientation of the welded components. I think a union will be the best way forward.

Thanks again

 

[weldstan]

Treaded and weld fittings have been used in the same pipe systems. You can seal weld the threaded joints to prevent leakage.

 

[mk3223]

Verify what it's said in the piping specification for the service. If the thread connection is allowed in the spec, then there is no need to use welded fitting.

 

[borobam182]

Thank you for the feedback

 

[MJCronin]

https://www.eng-tips.com/viewthread.cfm?qid=202265

MJCronin
Sr. Process Engineer