ASME B31.5

[TeeAr]

Hi there,

hope somebody could help me or share his experience.
I am dealing with a B31.5 analysis of an heat exchanger, that may be classified as a piping.
What puzzles me is following issue.
If I utilize the straight tube formula as indicated in the standard, I get a burst pressure much lower than the one I am getting in experimental burst tests.
In shorts, according to the standard I should utilize an higher wall thickness that the one I would utilize if relying on experimental tests.
This puzzles me.
Please, has any of you got a similar experience ?

Many thanks for your help

 

[jte]

TeeAr-

You are designing a refrigerator or air conditioning system?

Which forumula, specifically, are you using? Are you sure it is not a design formula rather than one which would ostensibly predict burst? Are your experimental burst tests using materials with minimum properties (these would be difficult to procure)?

You should tell us much more about the system which you are designing if you expect to get a reasonable answer.

jt

 

[TeeAr]

Hello, apologizes for not being exhaustive.

I’ll try to be more clear.

I am dimensioning an heat exchanger, not a system neither a refrigerator. Considering the dimensions and pressure related, this heat exchanger can be classified as a pipe.
For this reason I am referring to ASME B31

In detail, I have to refer to 504.1.2, and the formula is
Pressure = 2 * allowable hoop stress/(pipe outside diameter – 2*coefficient*thickness).

The issue is: the pressure I get from this formula is lower than the one I would get from a burst test and then applying a safety factor.
Nevertheless it seems this standard has to be fulfilled.

Please, has anybody of you ever faced to this issue ?