BURIED LBV DISPLACEMENT

[B.L.Smith]

Dear Sirs,

I've performed stress analysis on a buried pipeline which includes a Line Break Valve(LBV) before the pipeline become aboveground.
According to my analysis, the displacement of the LBV is about 110 mm. Is this displacement allowable? What is the allowable displacement of the LBVs or pipelines?
It should be mentioned that the pipeline diameter is 20", Min soil Temp. 15 C and operating temperature is 47 C. I have not placed any anchor support at above and underground interface.

 

[LittleInch]

That's quite a lot of movement. How have you worked it out?

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

 

[B.L.Smith]

According to the soil data which has been received from civil department, I modeled the pipeline route by CAESAR II software. I used CAESAR II Basic modeler for modeling buried pipeline. CAESAR II Basic Modeler uses Peng. method for calculating virtual anchor and the pipeline movement.
The temperature I used for my calculation is:
∆T=47(operating Temp.)-15(Min. Soil Temp.)=32 °C
Also, pipeline material is API 5L Gr. X60

 

[BigInch]

I'd expect to have about 1/2 of that movement. That movement at that temperature gives an anchor length of about 600m. In reality it is rarely over 300m maximum and usually about 1/2 of that. It appears that the soil is rather weak in cohesion, or not enough friction is present in a cohesionless soil. Increase the burial depth to help get more friction, or use a better friction factor. Sand values typically used do not account for grain wedging as movement occurs and can often be up to twice the customarily values.

 

[LittleInch]

Do I read that right? Operating temperature minus 15 C??

Movement of your valve will be least of your problems as you grow a large ice bowl around the pipe....

Once you start to grow ice you change everything and essentially it becomes an anchor.

Something isn't right here - provide more info.

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

 

[BigInch]

That's what I thought at first, then I realized he was doing the calculation for you. It is 42 - 15. The min op temp is not -15.

 

[LittleInch]

Ok got you, start temp 15 C, operating 47C, Delta T 32C.

Don't think that's going to give you 110mm unless you've built this in some sort of super slippery slime?

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