Hi

could anyone tell me how to calculate the minimum virtual anchor length for an underground pipeline?

thanks in advance

Hello Pooria,

In the SOIL MODELER input "TEMPERATURE CHANGE, Install-Operating" value. Then after converting, CAESAR II will calculate VAL automatically (see the conversion report).

Hi Farhad,

thanks for the reply, I already knew that. my problem is; I am dealing with a 10km buried pipeline and I am looking for a good estimation so I can only model the pipeline up until the virtual anchor point. this pipeline is a jacketed one with so many internal supports. modeling the whole system is pretty time consuming.

regards
Pooria

Pooria,

The formula is:

VAL = [E α Δtemp t + (P D / 2) (0.5 - v)] / [μ ( 2 ρs H / π + ρp t + ρf D / 4 )]

where:

Coefficient of friction, μ
Soil density, ρs kg/mm3
Buried depth, H, mm
D, diameter pipe, mm
E, N/mm2
α, mm/mm/C
Δtemp, degC (Coldest temperature to ambient)
t, pipe WT mm
v = 0.292
P, pressure bar
Pipe density, ρp kg/cm3
Fluid density, ρf kg/cm3

π IS it PI

yes.

Hello Farhad ,

can you please mention the reference (may be some book or code) from where you taken the above formula virtual length calculation.

Thanks,


kind regards,
Sammar Adhikari

you can find, a procedure in Pipe stress Engineering, Peng.

B. regards.

LFC

Hi:

I use this formula to calculate the virtual anchor lenght, with a Marston theory for friction force between pipe and silt; but when I use the buried pipe model of Caesar II, I get another value for VAL. Caesar II: 220m vs Formula with Marston: 450m

Any ideas for the difference???

B. Regards,

LFC

The analytical formulas are based on the "guessed" linear behavior from "fully restrained" to "unrestrained". As I know Caesar II get the VAL based on "springs" that simulate the friction on cylindrical surface(of course, not only this friction, the model is far more complex...).

By the other hand it may be a matter on how you've constructed your model to get 220 m value for VAL. How much pipeline straight length you considered in your model?

Hi,

I solve my problem, I confuse the friction coef. of internal soil and between soil and pipe. I insert all the pipeline in Caesar II.

B. Regards,

LFC

Hi,
I' trying to understand how Cii will treat pressure elongation in VAL calculation.
I changed the system pressure but it didn't affect the VAL which is surprising to me but also confusing as I'm new in pipeline analysis.
Is it required to convert the system pressure in to equivalent temperature (as suggested by PENG) to address this issue?
Could you please shade some light on this?

As a first step, to include he structural deformation due to pressure you must activate the "Bourdon effect in translation only".