Virtual Anchor Length

Hi Guys,
Can somebody help me to calculate the virtual anchor lengths in the pipeline?
Regards
Bikram

Dear Piper 78,

Is it for burried pipeline?
Total weight of pipe use lb/ft
Friction resistance = mu*total weight (lb/ft)
Longitudial stress = Sl = [E*alpha (T1-T2)] - [v.P(D-2t/2t)]
Thermal expansion force = Ft = Sl*Metal area

Distance of no movement from point of burial:
L= Thermal expansion force / Friction resistance

Might also be worth looking at the Peng papers.
http://www.pipestress.com/Pages/PEpapers.html

(of course you'll have to decide how useful they are)

piper_78

It is not just a matter of the length of the piping. The popular opinion is that there must also be at least three changes in direction (e.g., bends) between the "virtual anchor" and the point where your analysis model begins. The use of a "virtual anchor" is not codified but you can get some useful information if you reference the WRC document "Technical Position on Piping Installation Tolerances, Welding Research Council Bulletin 316, July 1986 and also the EPRI document "Guidance for Piping System Reconciliation", (NCIG-05, Electric Power Research Institute, EPRI-5639, May 1988 (note that these two documents ARE NOT CODES).

ASME B&PV Code, Section III, Nonmandatory Appendix "T" might also interest you but it does not answer your question.

John.

Piper 78,

Give your email address, and I shall send you the calculation method.

There are two reasons for elongation of the pipe. Thermal and pressure. These elongations are countered by the resistance of the soil. with increasing length of the buried pipe the resistance increases, and finally at some point in the length of the pipe these two elongating forces cancel each other. That point is the virtual anchor point. (Sorry about imperfect English - not my native language).

Don't know what kind of pipe your dealing with, but this is especially important when you are using GRE piping with coulings.