Pipe Thickness Calculation for Underground Pipe 2

[DEEPBLUE76]

Can anyone help me out with a detail procedure or may be a spread sheet to calculate the Pipe thickness for underground pipes as per AWWA need it very urgently please help pipe material API 5L

 

[BigInch]

RConner,

OK, makes sense. My estimate was made for offshore installations where X52 is usually a good maximum value to prevent exactly what happened above. The extra wall thickness needed for X52 helps collapse pressures and the high installation loads from the stinger tensioners often leaves about a 400 ft depth margin before collapsing stress is reached. With that poor D/t ratio, I can see where it could very easily have been an external pressure collapse. The LOWER D/t limit for most pipelines is around 100, (ASME B31.8 has a limit, but I don't recall the exact value right now) for which a thicker wall thickness is usually needed for common internal pressures. Using the X-65 would give even a thinner wall for pressure than X52 or X60, so it looks at first glance exactly like it was designed only for internal pressure and NO engineer checked it for external pressure collapse!




BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[stanier]

Australian standard for buried pipe gives a safety factor of 2.5 for instability due to buckling. If the soil is weak the Fs is the same.

As for aboveground pipe the external pressure will not be as for this original case and could not exceed that of full vacuum.

Many engineers out there select pipe based on hoop stress alone. I think that is pretty risky. This particulalry so as in there ignorance they dont do a surge analysis. But that is another subject.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au