How to size the concrete anchor?

[Petroleumman]

Dear Everyone;

ASME B31.4 434.17.2 State:
Scraper traps on mainline terminations and tied into connection piping or manifoldding shall be anchored below ground with adquate concrete anchor when required and suitable supported above ground to prevent transmission of line stress due to expansion and extraction to concerning facilities.

According the above stipulation, the concrete anchor shall be set near the Above ground/Under ground point. And who can introduce how to calculate the thrust force abosorbed by concrete anchor? Thank you at advance.

 

[GregLamberson]

Petroleumman

The key word is "when required". Anchor blocks should be avoided whenever possible (and generally can be avoided).

There have been some lively discussions on the subject in previous threads - do a site search on "pipe stress" and "stress analysis" and you will get more information than you could possibly want.


Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[GregLamberson]

Petroleumman

I didn't mean to put a damper on the thread, I thought others would jump in. Most have quite an aversion to anchor blocks, myself included and hate to see them used, preferring to see them designed out.

That being said, basically you need to calculate the forces on the pipe and design the block with enough mass to hold it. Section 419 of 31.4 deals with expansion and flexibility.

The net longitudinal compressive stress due to the combined effects of internal pressure and temperature rise are calculated from the equation from section 419.6.4(b) of 31.4 (I have the 2002 edition). Section 421 deals with design of anchors.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[Petroleumman]

GregLamberson:

Thank you very much.

However, our client require to install the concrete anchor for the buried pipeline. For the calculation, only net longitudinal compressive stress due to the combined effects of internal pressure and temperature rise can not be used to size the concrete anchor, because the soil friction force shall be taken into consideration together. Is there any soil friction force equation?

 

[GregLamberson]

Petroleumman

You can check the geotech data, but generally the soil cohesive and friction forces will form an anchor and you only really need to be concerned with un-restrained pipe.

It sounds like the client is requiring an anchor block, not asking if one is needed. If the calcs show it is not needed and they want one anyway, I don't really see where the size is an issue. I would stick with the longitudinal & tensile stresses as per ASME's methodology above and would not worry with the soils.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[LSThill]

Petroleumman (Petroleum)

Reference: Piping Stress Analysis Design Guide:
Title: BURIED THRUST BLOCK sizing in cohensionless soils

METHOD OF CALCULATGION: the calculations performed are classical civil engineering soli equations, which were taken from INTERDUCDTORY SOIL MECHANICS AND FOUNDATIONS, GEROTECHNICAL ENGINEEERING, 4TH ED. GOEORGE F. SOWERS


L S THILL