pipe collapse 3

[pgmmce]

I am trying to determine the parameters and sizing criteria to determine the collapse strength for a large diameter pipe.(Exterior pressure). Can any one steer me to a good refence or source?

 

[MikeHalloran]

ref 1: "Tubing Limits for Burst and Collapse", Tech Note, CTES, L.C., Conroe TX

http://www.ctes.com

ref 2: "Effect of Initial Eccentricity on Collapse Pressure of Circular Beam Tubes", S. Yadav
Fermi National Accelerator Laboratory, Batavia IL

http://www.flab.gov

Mike Halloran
Pembroke Pines, FL, USA

 

[doct9960]

For process piping, see para. 304 of ASME B31.3. For straight pipe under external pressure, refer to para 304.1.3

 

[doct9960]

pgmmce,

I just noticed that your profile shows "civil/environmental". If you are looking for info about buries pipes, search the forum. Here's one that discusses buried pipe... thread378-175239

 

[GregLamberson]

You didn’t mention if this was a subsea pipeline or not?

Design for the internal pressure is primarily based on the tensile hoop stress within the pipe wall, while external pressure is based on buckling phenomena of the pipe cross section.

The net ext presure is the pressure difference between the max ext pressure acting on the pipeline and the min internal pressure.

The potential for collapse of the pipeline is affected by 4 primary factors: 1) the net external pressure, 2) D/t ratio of the pipeline, 3), stresses other than external pressure within the pipe wall, and out of roundness of the pipe.

Our-of-roundness of thje pipe cross section is one that may be overlooked, but needs to be considered for external pressures. Internal pressure with its uniformly distributed pressure will tend to decrease the out-of-roundness of the pipe, but thw affect of external pressure is just the opposite. External pressure tends to increase the out-of-roundness or collapse the pipe surface.

You will also need to look at pipe stresses during installation as tipicaly and especially in deep water he stresses in the pipeline during installation are higher than those during operation. It is generally the installation stresses which determine the required pipe grade and wall thickness.

If it is offshore you will need ot factor in wind, waves, currents and what about seismic? bottom soil movements? These ar both installation factors. To determine the magnitude of these loads for design purposes it is important to know the method by which the pipeline will be installed and operated.

And don’t’t forget when determining the required strength of a pipeline - MAOP and temperature.


Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[JohnBreen]

Someone should have mentioned the ASME B&PV Code paragraphs UG-28 and UG-29.

 

[doct9960]

Hi John,

ASME VIII-1 UG-28 through UG-30 was specifically mentioned in ASME B31.3 para. 304.1.3 as the procedure to be followed in determining pipe wall thickness and stiffening requirements for straight pipes under external pressure. The exception to the use of the ASME BPVC is for pipe with Do/t < 10, where the allowable stress S to be used should be in accordance to the value specified in para. 304.1.3. But this is for process piping designed to B31.3.

It would have been helpful if pgmmce stated the piping code, material, service, etc. to which his pipe is designed to.

cheers

 

[pgmmce]

Thanks for the post. Can you suggest a source for information on "Buckling phenomena of a pipe cross section"
which would give formulas and calculation procedures for determining failure stress ,deflection, etc.

 

[BigInch]

I have one old doc from US Dept Energy showing Sturm's formula and L ratio chart for the K values,

I placed it where you can download it here,

http://rapidshare.com/files/25162745/pipe_collapse_pressure_dpst72386.pdf.html

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com