Subject
A freespanning beam or pipe is susceptible to vibration through continuous and/or recurrent inducements such as wave or wind loads. So long as the vibration frequency is not close to the natural frequency of the pipeline, excitation is not expected and failure is unlikely.
This problem can occur in any pipe, beam or structure spanning a gap that is exposed to free flowing or gusty fluid (air or water), or attached to vibrating equipment. The consequences of a structural failure of this type can be at worst; devastating and at best; expensive.
DnV generated its Guidelines No. 14 (June 1998) to address this issue for submerged pipelines, SubSection 3.7.2 of which is dedicated to defining the expected natural frequency based upon either constant horizontal fluid flow (e.g. current) or pipeline (submerged) weight including the effect of axial tension or compression along with recommended coefficients for end conditions.
Calculator
Mode 14 calculates the natural frequency of a submerged pipe according to DnV's guidelines No. 14 for free spanning piplines, including the effects of axial tension or compression in the pipe due to the combined effects of laying, internal and external pressure differential and temperature when exposed to fluid flowing accross the pipe (current deflection load option) or simply due to the pipe's own submerged weight (weight deflection load option)
The mode 14 calculator also provides you with guidance on the appropriate use of DnV's recommended bending, axial and sagging coefficients (C₁, C₂ & C₃)
Mode 14 can be used to ensure that a pipeline’s natural frequency does not coincide with:
1) a sensitive piece of vibrating equipment
(see CalQlata's Engineering Basics, Rotary Balancing, Vibration Damping, Shafts calculators), or
2) the effects of a fluid flowing across it
(see CalQlata's Vortex Shedding)
Note: This calculator has not been officially endorsed by DnV. It is CalQlata’s interpretation of the guidelines
For help using this calculator see Technical Help
You enter: 
and the mode 14 calculator will provide: 


natural frequency

C₂.Sᵉᶠᶠ/Pᴱ

L/D

pipe second moment of area

outside diameter

inside area

outside area

effective mass per unit length

effective unsupported length

effective axial force

Euler buckling load

fluid flow load per unit length

mass load per unit length

Check minimum system requirements