Likelihood of Failure (LOF)

Likelihood of Failure (LoF) can be calculated either quantitatively or qualitatively for a piping system.

LoF is used by the Energy Institute guidelines to determine the risk that a piping system will suffer a vibration failure. The LoF can be calculated in two ways, either Qualitatively or Quantitatively, for each type of vibration mechanism.

For the Likelihood of Failure due to Flow Induced Turbulence (FIT) both the qualitative and quantitative approaches are based on the kinetic energy of the fluid flow.

The qualitative approach then compares this kinetic energy to limits, to determine if there is a Low, Medium, or High risk of vibration failure due to Flow Induced Turbulence. Actions are then prescribed based on the risk. This approach is conservative compared to the quantitative approach.

In the quantitative approach the dimensions of the pipe, pipe supporting, and fluid viscosity are also accounted for together with the kinetic energy of the fluid flow. The likelihood of failure is then expressed as a value between 0 and 1.0. Design actions are then expressed depending on the value of the LoF. For example, an action may be recommended if the LoF ≥ 0.7.

Our instructor-led training course Pipework Vibration explains how to do an LoF assessment for your pipework system conform the Energy Institute guidelines.