Pipeline vibrations – Measurements under difficult conditions

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Pipeline vibrations – Measurements under difficult conditions

Mon, 02/11/2019 - 14:24
Kötter Consulting Engineers
Kötter Consulting Engineers

In many technical applications pipelines are used for the transport of potentially flammable or hazardous gases and liquids. Vibration problems at pipelines often depend on the volume flow. Vortex shedding is a typical result of flow induced pulsations and may cause severe piping vibrations and failures. Another excitation source for critical pulsations or elevated vibrations is the use of compressors or pumps due to their unsteady working principle.

Measurements of pulsations and pipeline vibrations are important for the assessment of dynamic material loadings. In addition they often allow a comprehensive root cause analysis in case of elevated vibrations. In some cases it is not possible to install standard measurement equipment at the area of concern. Then special measurement technics and investigation methods have to be used. These different methods are presented in the following two case studies.

The first case study deals with a flow induced vibration problem at a grid gas manifold. Obvious vibrations occurred randomly during high volume flow in winter time. A long-term measurement was performed to determine the characteristic behavior. Spectral analysis and volume flow correlations enabled a precise characterization of the critical vibration phenomenon. On this basis a simple well working mitigation measure was identified and realized.

In another case elevated vibrations occurred in the reactor bay of a chemical plant, where a hyper compressor is used to compress ethylene with a discharge pressure of up to 3,000 bars. It was impossible to install extensive measurement equipment during compressor operation due to the hazardous conditions inside of the reactor. Therefore, a laser vibrometer was used to detect piping and steel construction vibrations from outside of the bay with distances above 100 m. A multitude of measurement positions allowed the detailed analysis of the vibration phenomenon. Finally, a measure was derived to improve the vibration behavior.

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