We want to use 1-1/2" 6000# threade 1

[rmillier]

We want to use 1-1/2" 6000# threaded half coupling welded into a 4" sch 80 pipe and use it for a level control float style switch. The half coupling interferes with the float movement. Can we reduce the length of the non threaded end of the coupling by 0.25" as long as we do not reduce the length of internal threads? If so how much of the non threaded end can we remove?

 

[XL83NL]

What is your design code, ASME B31.3? What are your design conditions, like pressure and temperature? What is the medium, fluid service, material of construction, etc.?

One important aspect is the area reinforcement calculation. As per para 304.3.2 (b), calculation is required for this opening in the run pipe. Removing the end may make the fittings a non-listed one, requiring analysis per para. 304.7.2, but I think that's overkill. In the end, you couldve also made this modified half coupling from pipe. The 1.1/2" half coupling roughly equals a 2.1/2" Sch XXS pipe. Either way, you satisfy Code requirement as long as the calcs show there´s sufficient reinforcement. I dont see a problem with removing the 0.25" end. Make sure the internal weld reinforcement doesnt protrude too much into the half coupling causing the level switch to jam when inserting it.
Another aspect to consider, which cant be answered from your OP, is the service with respect to use of threading. B31.3 has provisions for the application of threads. However, the Code doesnt consider all aspects of your service. Therefore, threading should not be considered for certain critical services, like high temperature, lethal service, cyclic, etc.

 

[jte]

I think what XL83NL is trying to say is... Hire a mechanical engineer with experience in piping component design to do your piping design work. As you may have perceived from that response, there is a bit more to piping design than meets the eye. That is one reason engineers are required in many states to practice only in their areas of competency. For example, in Texas, the first sentence here pretty much says it all:

The Texas Engineering Practice Act and Rules Concerning the Practice of Engineering and Professional Engineering Licensure require that licensed professional engineers (PE) only practice engineering in their area of competence.

It's been said here before and is worth repeating: The value of the advice you get from the internet is worth every penny you paid for it.

 

[GenB]

Buy the ASME b16 code for threaded calponents. I think the coupling is already listed with the thread deducted. And yes you can cut it . but do the dligence. Good luck

 

[Duwe6]

Gotta love watching someone reinventing the wheel. IMHO, O'Lets are the best for Branch Connections. These are designed & tested for this use; as opposed to guessing what plumbing item can be cut up and forced to serve as a boiler & pressure vessel item

http://www.bonneyforge.com/products.php?pg=branch&subpg=thredolet

Notice that these items are Full-Penetration welded, and do not infringe on the ID of the main line. You've gotta stop using plumbers to build your pressure systems.

 

[LittleInch]

what on earth are you trying to do here?

A half coupling is designed to connect pipe to a screwed end.

It is not designed to connect a curved object ( your 4" pipe) to a screwed connection.

This is called a "threadolet" or a threaded integrally reinforced connection as per duwe6

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[XL83NL]

Welding a half coupling on a run pipe as a means for a branch to connect e.g. an instrument makes perfect sense, imo. Although it depends on service and service conditions, and those conditions should always be reviewed and considered for a proper assessment.
Attaching a threadolet is overkill, and in some designs even inferior to a half coupling from a construction and cost point of view. Think of all those layers of weld metal that are needed. And what if the run pipe is 4" Sch 10S stainless steel? The pipe will show excessive deformation due to heat input. Just make sure the Code requirements for area replacement are cosnidered and that due consideration is given for the aforementioned service conditions.

 

[LittleInch]

The OP quotes the connecting pipe as 4" Sch 80. He is trying to use it to connect "a level control float style switch." Whilst we have no drawing or sketch or operating temp or pressure, it seems to me that the section of the coupling entering the pipe is the bit the OP wants to "reduce", i.e. turning it into something like a weldolet(!)

Hence, like many things here "It depends". I note your further points about review and area replacement etc, but without knowing all these crucial details is it not better to advise doing something which is more technically correct, safer and more robust?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[XL83NL]

Without the right context of the OP´s situation it´s always guessing. Going the conservative way is safe and robust, yes, and hence safe practice. Good (and still safe) practice would, I think, be to get more details on the service, and it's conditions and requirements. And then decide. Often we find that in these situations our customers/end clients (quite often those companies who write all those specs we often debate about here) tend to overspecify such design details and therefore end up with systems that arent only more costly than required, but are also not fit for purpose and down the road introduce their limitations, because the overall picture hasnt been considered.

 

[LittleInch]

I agree we're guessing - I think it was when the OP says he or she is welding a 1 1/2" coupling onto a 4" Sch 80 pipe. That's a big hole in a small pipe and with a lot of curvature. It's also #6000. Implies there is some pressure behind it otherwise why not use #3000?

A 1 1/2" on say a 24" line / vessel would be much more like it or even just a reducing tee for heavens sake.

There's too much doing things just because someone thinks its easier / cheaper / faster when in fact it's actually harder / costlier / less safe than doing it properly.

Anyway it's all IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[NBrink]

It's also #6000. Implies there is some pressure behind it otherwise why not use #3000?

Never underestimate the power of "whatever happens to be laying around in the fittings bin".

But I agree, from what I can ferret out, an olet or reducing tee is the way to go...

Nathan Brink