START-PROF performs local pipe wall buckling check according to the following codes:

- ASME B31.8
- EN 13941
- GOST 32388
- CJJ/T 81

Axial stress in the pipeline should be lower than critical buckling stress according to 833.10

D – outside diameter

E – Elastic modulus

P – Internal pressure

S – Yield Strength

t – Nominal wall thickness

Axial stress in the pipeline should be lower than critical buckling stress Sst

Do – outside diameter

E – Elastic modulus

tn – Nominal wall thickness

When analyzing vacuum elements
(with input negative operation pressure), the local stability of pipe cross-section
under **external** overpressure
*P*_{op}, as well as longitudinal forces *N*, transverse
forces *Q* and bending
moments *M*, must be analyzed. Analyses
are performed according to GOST 32388.

Total stability margin factor under
combined forces of *P*_{op}, *N,* *Q*, *M*
must be less than 1:

,

where *P*_{op} - **external**
overpressure (absolute operation pressure value for a vacuum element), N - value
of effective axial force in element, Q
- absolute value of effective
transverse (shearing)
force in element, M - absolute
value of effective moment in element, [P]
- allowable external pressure
based on stability conditions, [N]
- allowable axial force based
on local stability conditions, [Q]
- allowable transverse (shearing)
force based on local stability conditions, [M]
- allowable moment based on
local stability conditions. All
allowable values are determined according to GOST 32388-2013
+ rev. 1 and
2.

If the above stability conditions are not met, the corresponding cell in the table will be highlighted in red.

To increase stability under external
pressure *P*_{op}, various types
of stiffening rings can be inserted at set intervals along the pipe axis.
To consider them in the analysis,
select the ring type number in the "stiffening
ring type" field.
Clicking on one of the stiffening
ring property cells will bring up a dialog window, where properties can
be input (fig. 2).

Fig. 2. Dialog windows for inputting stiffening ring type and properties

Lateral Buckling of Above-ground Pipe

Upheaval Buckling of Buried Long-radius Bend

Upheaval Buckling of Buried Pipeline

After analysis: Output > Pipe Wall Buckling Check