Horizontal Directional Drilling (HDD) Code Compliance with ASME B31.8

[NathanielBabiak]

Hi,

(I've never posted before, but have found this forum to be quite useful. I've been doing facilities work for about 9 years now, and just moved into pipeline. I've already searched the site and haven't found anything relevant.)

I have a question about horizontal directional drills post-installation. Specifically, about the residual stress on the bent pipe string. I read the 1995 edition of PRCI PR-227-9424 available in Technical Toolbox and also David Willoughby's HDD book. Both take care to show that this consideration is significant, but check for code compliance with B31.4, not B31.8. I'm not sure how to check if an HDD design is compliant with ASME B31.8, as this topic doesn't seem to be within the code's scope.

So here's my question(s):

Which paragraph in ASME B31.8 considers the HDD post-installation residual stress of bending?
As a follow-up question, how does this consideration compare a *design* stress or strain to an *allowable* stress or strain?

Thanks in advance,

~Nathaniel

 

[LittleInch]

I think it's section 833 in ASME B 31.8 dealing with longitudinal stress.

Normally the issue is that there is some level of permanent elastic bending in the pipe which results in a positive and negative longitudinal stress to add to the other stress on the pipe.

Different stresses or combinations of stresses have varied maximums compared to the SMYS of the pipe. You need to look at each section in turn.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[NathanielBabiak]

Thanks LittleInch,

I appreciate the speedy response! I had read through 833.4, Combined Stress for Restrained Pipe, but got confused at 833.4(f), which states: "The biaxial stress evaluation described above applies only to *straight* sections of pipe" (emphasis added).

I had thought that the bending residual stress would make it not *straight*... maybe not though?

What do you think?

 

[EdStainless]

By straight they mean 'more or less intended to be straight', as opposed to deliberately curved.

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P.E. Metallurgy, Plymouth Tube

 

[NathanielBabiak]

Thanks Ed,

I think I was just over-thinking it. Appreciate your response!