API Tension and Burst - Work

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Basic Tubular Buckling, release 5, issued 16 May 2008. Work version.

This worksheet exists in two versions. They are identical apart from the way they are formatted. The Work version hides intermediate calculations and allows the user to see the results just below the inputs. This is useful for quick “what-if” games, changing various inputs to see what works best. The JIT version displays all intermediate calculations, plus adds tutorial text to explain the methodology.


This worksheet takes a bunch of inputs for a tubular and it’s parameters. It uses the accepted engineering formulae to calculate the Axial Force Fa and the Stabilising Force Fs which arise from the axial (tensile/compressive) force and the internal and external pressures. These two forces added together make the Effective Force, Feff. Either of the two component forces can be negative and where the Effective Force becomes negative, it is possible for the casing to buckle. With thin walled tubes like casings and tubings, it is assumed that the tubular has no mechanical resistance to buckling.

If both ends of the tubular are fixed (such as in a cemented casing), a temperature or internal pressure increase will decrease Fa and if this decreases Feff to below zero, then buckling can occur. The temperature increase can be entered in this worksheet and the results calculated, allowing options to be explored to avoid buckling due to changes in temperature.

User input

4.5″ 9.5 ppf4.5″ 10.5 ppf4.5″ 11.6 ppf4.5″ 13.5 ppf4.5″ 15.1 ppf5″ 11.5 ppf5″ 13 ppf5″ 15 ppf5″ 18 ppf5″ 21.4 ppf5″ 23.2 ppf5″ 24.1 ppf5.5″ 14 ppf5.5″ 15.5 ppf5.5″ 17 ppf5.5″ 20 ppf5.5″ 23 ppf5.5″ 26.8 ppf5.5″ 29.7 ppf5.5″ 32.6 ppf5.5″ 35.3 ppf5.5″ 38 ppf5.5″ 40.5 ppf5.5″ 43.1 ppf6.625″ 20 ppf6.625″ 24 ppf6.625″ 28 ppf6.625″ 32 ppf7″ 17 ppf7″ 20 ppf7″ 23 ppf7″ 26 ppf7″ 29 ppf7″ 32 ppf7″ 35 ppf7″ 38 ppf7″ 42.7 ppf7″ 46.4 ppf7″ 50.1 ppf7″ 53.6 ppf7″ 57.1 ppf7.625″ 24 ppf7.625″ 26.4 ppf7.625″ 29.7 ppf7.625″ 33.7 ppf7.625″ 39 ppf7.625″ 42.8 ppf7.625″ 45.3 ppf7.625″ 47.1 ppf7.625″ 51.2 ppf7.625″ 55.3 ppf7.75″ 46.1 ppf8.625″ 24 ppf8.625″ 28 ppf8.625″ 32 ppf8.625″ 36 ppf8.625″ 40 ppf8.625″ 49 ppf9.625″ 32 ppf9.625″ 36 ppf9.625″ 40 ppf9.625″ 43.5 ppf9.625″ 47 ppf9.625″ 53.5 ppf9.625″ 58.4 ppf9.625″ 59.4 ppf9.625″ 64.9 ppf9.625″ 70.3 ppf9.625″ 75.6 ppf10.75″ 32.75 ppf10.75″ 40.5 ppf10.75″ 45.5 ppf10.75″ 51 ppf10.75″ 55.5 ppf10.75″ 60.7 ppf10.75″ 65.7 ppf10.75″ 73.2 ppf10.75″ 79.2 ppf10.75″ 85.3 ppf11.75″ 42 ppf11.75″ 47 ppf11.75″ 54 ppf11.75″ 60 ppf11.75″ 65 ppf11.75″ 71 ppf13.375″ 48 ppf13.375″ 54.5 ppf13.375″ 61 ppf13.375″ 68 ppf13.375″ 72 ppf16″ 65 ppf16″ 75 ppf16″ 84 ppf16″ 109 ppf18.625″ 87.5 ppf20″ 94 ppf20″ 106.5 ppf20″ 133 ppf

Short RoundLong RoundButtress NormalButtress Special ClearanceOther

Select a casing



Enter the temperature at the depth of interest. Temp =


Enter the number part of the steel grade eg for L80, enter 80 (units are kpsi). Gr =


Enter the design factor for burst. DFb =


Enter the design factor for tension. DFt =

Click here when any values are modified to update the result.


Maximum possible pipe OD within API tolerances

Minimum possible pipe OD within API tolerances

API nominal wall thickness

Minimum possible wall thickness within API tolerances

API nominal ID

ID for minimum CSA within API tolerances

API Drift Dia

Nominal cross sectional area

Temperature Correction Factor

API Minimum Yield Strength, nominal, ambient

API Minimum Yield Strength, with TCF and DF

Pipe body API Minimum Internal Yield, ambient

Pipe body API Minimum Internal Yield, with TCF and DF


Worksheet references

API Specification 5CT, 5th Edition, April 1 1995 “Specification for Casing and Tubing (U.S. Customary Units)”.

API Bulletin 5C3, 6th Edition, October 1 1994 “Bulletin on Formulas and Calculations for Casing, Tubing, Drill Pipe, and Line Pipe Properties”, also ISO/TR10400:2007 which is expected to replace API 5C3 during 2008.

API Bulletin 5C2, 21st Edition, October 1999 “Bulletin on Performance Properties of Casing, Tubing and Drill Pipe”.

Formulae for Temperature Correction Factor taken from the Exxon Casing Design Manual.

SG of steel from http://www.simetric.co.uk/si_metals.htm taken as 7.85.

Version 1 of this worksheet released on 11 January 2008.

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