B31.3 Chapter 9 High Pressure Piping - Fatigue Analysis

[jay165]

I would like to use Chapter 9 to design some facility piping consisting of some large diameter - 12.75" OD high pressure applications - 8000 psig. The operating temperature is ambient - 30 - 95 deg F and I can calculate thermal, weight and prssure stresses with available software. Other than pressure fluctuations, there is no "fatigue" - ie the pipe is connected to a centrifugal pump and is heavily supported.

What does one do to comply with the code requirement ofing a "fatigue analysis"? Is there some specific software available for code compliance, such as the programs for code calculations for ASME pressure vessel wall thicknesses, etc?

Thanks in advance!

 

[LSThill]

Hi jay165 (Mechanical)

ASME SECTION VIII DIV 2. and you have to check your design

The Application Software is FE-PIPE by Paulin Research Group

http://www.paulin.com

The Home of FE-PIPE and BOS FLUIDS.

Leonard@thill.biz

http://www.thill.biz

 

[MJCronin]

jay165,

I am very curious about your question and your system design......I cannot help myself....and I must know the following:

-Is the piping system operating at 8000 psig ?..... this number is not an alllowable stress or something is it ?

-What kind of centrifugal pump are you using in an 8000 psig piping system ?

- If the pressure cycles are severe and frequent ( say 4000 to 8000 psig several times per day) you will get some fatigue cracking at pipe fittings and severe cracking at welded branches.

(My company saw much of this on a Canadian de-scale spray system (steel mill) with 8"NPS piping operating from 2000 to 6000 psig.... the branch connections all failed)

- I calculate a pipe wall thickness of about 2.5 inches, according to ASME B31.1/B31.3..this is way, way beyond commercially available pipe schedules....where are you going to get this piping ????!!!?

Can you let us in on some more details ????

You are not making some kind of big gun.....or, are you ????

MJC

 

[mohd]

hi,

very interesting. MJCronin... plz elaborate about your descale sys. piping... and what type of pipe mat. you use. how did you confirm its flexibility/rigidity?
thx

 

[jay165]

This is for a waterflood project in offshore GOM. THe pressures are on the high side, however 5,000 to 6,500 has been done before. The pump is a barrel type. It requires
about 12,000 HP.

The materials we use are typically super duplex or other high strength steel.

Hope that answers your questions, MJ.

 

[davefitz]

a possible alternative to Section VIII div 2 is the english version of the german boiler code, TRD 301 annex 1 ( or anlagen 1), available online from

http://www.ili-info.com.

Of course, there is code case N-47, if you want a nobel prize for your efforts. But since there is a plethora of finite element programs out there, it should be a simple matter to hire a consultant that is familiar with using these for a fatigue analysis.

If the branch connections are cast instead of forged, it will probably be nessesary to search to see if there is a fatigue strength reduction factor which must be applied.

 

[MJCronin]

jay 165,

The "fatigue analysis" that you refer to in your original post is something beyond the capabilities of the average "journeyman pipe stress analyst".

If your system has many large pressure cycles (you haven't said anything about this) you may experience failures at the branch connections.

If you can contact a Mr. John Breen (a frequent contributer to this forum) he can help you. John has decades of vessel/piping stress analysis experience.

Additionally, A Mr. Ron Haupt of "Pressure Piping Associates" has experience with high pressure cyclic loading of system and possible branch piping failure.

See

http://www.ppea.net

for more info.....

My opinions and ideas only.....

MJC