Lateral Branches

[Metma]

Good afternoon.
We have to design a lateral branch with an angle of 20 degrees:
since ASME B31.3 allows to use an angle not lower than 45 degrees, while EN 13480 allows to use an angle not lower than 30 degrees, could you suggest an applicable code/standard?
Have you ever faced out this matter?
Thank you very much in advance for your collaboration.
Regards

 

[MJCronin]

Metma,

You seem to be in an area where the piping/pressure vessel rules require a unique evaluation/analysis of your particular component.

There are a few finite element codes specially suited to evaluate "odd" nozzle configurations and perform the required pressure reinforcement and detailed stress level calculations required. FEpipe and NOZZLEpro are well known(

http://www.fepipe.com/default.aspx)

Because of the additional fabrication cost and engineering effort involved in this type of detailed analysis, many companies decide to either: 1) simply ignore the issue and dump all reponsibility onto the newbie or 2) redesign the joint and use only standard geometry fittings.

Is there any possibility of a redesign/reconfiguration ?

What is the size of the joint, materials to be used, pressures, temperatures etc..??

Consider posting at the

http://www.COADE.com

website....

Regards

MJC

 

[JohnBreen]

Metma,

As Mike alluded to - don't do it! Think about it; there is a reason that the Codes limit the intersection angle. After a certain angle is exceeded you are taking away too much run pipe wall and you cannot effectively reinforce it using any practical method.

But your first questions was "could you suggest an applicable code/standard?" - and herein lies the real answer. You must design your piping to the Code MANDATED by your jurisdiction (the jurisdiction in which the piping system will be constructed). You cannot "shop around" to find a Code that allows you to do something that the MANDATED Code does not approve.

As Mike says, if you want to pursue this you will have to use a "design by analysis" methodology like FEA instead of a "design by rule" methodology like the Code book. But do not be surprised when you find that the reinforcing scheme makes the final design impractical. Are you sure you cannot make a 45 degree design work?

Regard, John.

 

[zdas04]

I'm sure there is a really good reason not to use a standard lateral and either a 15 degree hot bend or a mitered pup, but I can't imagine what it is. Could you share some of the rational that got you to this point just to satisfy the purient curiosity of a bunch of old farts?

David

 

[Metma]

Thank you all for your answers: on Monday, from the office, I will post a sketch and some details to share with you this matter.
Unfortunately I confirm you that there is no possibility of a joint redesign.
Regards

 

[MJCronin]

Metma,

In what country will this piping be installed ?

-MJC

 

[Metma]

I have collected some info.
The 20 deg lateral in subject (I attach a sketch) is used to collect polymer powder from different reactors and to carry it, through a vertical pipe, to a below reactor; the slope of 20 deg (from a vertical axis) is required in order to prevent powder from settling on the inclined pipe.

project design code B31.3 (maybe I am misled, but paragraph 304.7.2 allows design of unlisted components);
material LTCS;
design pressure 18.4 barg;
design temperature 38 C deg;
country in which the pipe will be installed: the Arabic peninsula.

What is your opinion?
Thank you and Regards.

 

[gr2vessels]

Can you use a 45 degree Y (which makes 22.5 degrees with vertical CL)?
cheers,
gr2vessels