Input variables

Generic variables

These variables can be found in virtually all reports as input variables

Design Pressure – Pc
Pressure assumed to be present in the component according to the design terms
Design Temperature – T
Temperature assumed to be present in the component according to the design terms
Name of selected material used for the construction of the component

Specific variables

These variables are component specific

Outside Diameter – Do
Outside diameter of the attached part. The diameter runs from the outside of the wall to the opposite outside of the wall, through the center of the circle.
Nominal Thickness – en
Thickness ‘as is’, meaning it is the design thickness taking into account corrosion and tolerance.
Corrosion – c0
Amount of thickness that accounts for the possible effects of corrosions.
Tolerance – c1
Tolerance in thickness for production
Infinite length – L′
The unsupported lenght of the shell is infitely long, meaning the external pressure can not collapse the shell.
Maximum unsupported length – L
Maximum length of the straight part of the pipe that is unsupported.

Calculated Values

Allowable stress at operating temperature – S
Stress in the component at which it is still allowed (without failure) to use the component.
Yield strength at operating temperature – Rpt
Stress in the component at which the component starts to plastically deform at operating temperature.
Modulus of elasticity – Et
Tendency to deform (tensile strain) along an axis when opposing forces (tensile stress) are applied along that axis.
Poisson's ratio – ν
(Negative) ratio of transverse to axial strain. An extension (or contraction) in the direction of a load corresponds in a contraction (or extension) in a direction perpendicular to the applied load. The ratio between these two quantities is the Poisson's ratio.
Number of circumferential waves – ncyl
Number of circumferential waves for an unstiffened part of cylinder. The value is an integer ≥ 2 to minimize the value of Pm
Critical strain – ε
Mean elastic strain at collapse
Yield pressure – Py
Pressure at which mean circumferential stress in cylindrical shell midway between stiffeners reaches yield point of material.
Critical pressure – Pm
Theoretical elastic instability pressure for collapse of perfect cylindrical shell
Critical pressure – Pr
Lower bound collapse pressure
Maximum Allowable Pressure – Pa
The maximum pressure at which the component can be used in operation. This value should be larger than the design pressure.


Can’t find material ‘MaterialName’ in database
Material could not be found in database. Select an existing material name, or select another material via the material selection window.


Restricted unsupported length: L = x mm
The unsupported length is restricted to a maximum: LL′

Calculation errors

Can't calculate maximum unsupported length for external pressure.
The shell has insufficient strength to determine the unsupported length.