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CSA Z662 Flexibility and stress analysis — Stress design for unrestrained portions of pipeline syste

4.8.1 Unrestrained portions of pipeline systems shall be designed to have sufficient flexibility to prevent thermal expansion and contraction from causing excessive stresses in the piping material, excessive bending and unusual loads at joints, and undesirable forces and moments at points of connection to equipment, anchorage points, and guide points. 4.8.2 Where thermal expansion and contraction are expected to occur, flexibility shall be provided by the use of bends, loops, or offsets, or provision shall be made to absorb thermal strains by expansion joints or couplings of the slip joint or bellows type. Where expansion joints are used, anchors or ties of sufficient strength and rigidity shall be installed to withstand end forces due to fluid pressure and other causes. 4.8.3 The stresses due to thermal expansion for those portions of pipeline systems without axial restraint shall be combined in accordance with the following formula:

4.8.4 The thermal expansion stress range, based upon 100% of the expansion, shall be limited in accordance with the following formula:

SE ≤ 0.72 S × T


SE = thermal expansion stress range, MPa

S = specified minimum yield strength, MPa

T = temperature factor (see Clause 4.3.9)

4.8.5 The sum of the longitudinal pressure stress and the total bending stress due to sustained force and wind loading (see Clause 4.2.3) shall be limited in accordance with the following formula:

0.5Sh + SB ≤ S × F × L × T


Sh = hoop stress due to design pressure, MPa, as determined using the formula given in Clause 4.6.5

SB = absolute value of beam bending compression stresses resulting from live and dead loads, MPa

S = specified minimum yield strength, MPa

F = design factor (see Clause 4.3.6)

L = location factor (see Clause 4.3.7)

T = temperature factor (see Clause 4.3.9)

4.8.6 The effects of restraints, such as support friction, branch connections, and lateral interferences, shall be considered in the stress calculations. The coefficient of friction of steel-to-steel contact for support design shall be a minimum of 0.4 unless special measures are implemented to reduce friction. 4.8.7 Stress intensification and flexibility of components shall be considered in the stress calculations. Note: In the absence of more directly applicable data, the flexibility factors and stress intensification factors given in Table 4.8 should be used.

4.8.8 Specified dimensions of pipe and fittings shall be used in flexibility calculations. 4.8.9 In addition to the thermal expansion of the piping itself, the linear and angular movements of the equipment to which it is attached shall be considered. 4.8.10 Where cold-springing is used, the reactions R′ shall be obtained as follows from the reactions R, derived from the applicable flexibility formula as follows:

Read More:

CSA Z662-15 (Oil and gas pipeline systems)

Located in Calgary Alberta, We offer our Pipeline Engineering Services across Calgary Alberta Canada. To get our Piping Stress Analysis Services, please contact our Engineering firm at:



3705 Fonda Way #18 Southeast Calgary, T2A 6G9


+1 (587) 802-4050

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