Ir. Harmen Slot
Unacceptable pulsations and mechanical vibrations in process facilities may result from flow, even in the absence of compressors and pumps. At high flow velocities turbulence will cause broadband pulsations. Large tonal pulsations occur when vortex shedding couples with an acoustic or mechanical resonance, for instance in a pipe T or at tubes in a heatexchanger. These phenomena should be analysed in the design stage of an installation.
If unsteady flow excites acoustic or mechanical resonances, large pulsations and vibrations will occur especially when an interaction occurs with an acoustic or mechanical resonance. This may affect the pipe system integrity or have an impact on instrumentation like flow meters. In some cases we have measured and analysed systems that showed unallowable vibrations and failures. Vortex shedding occurs at distinctive frequencies, which increase with flow velocity. In addition to vortex shedding, broadband flow noise is an unwanted result of flow-induced pulsations. It is good engineering practice to address these issues in the design phase of a new installation, which results in much more time and cost efficient modifications then modifying the system on site.
TNO provides flow-induced pulsation (FIP) analyses, both in the design phase of a new installation and as a root cause analysis for troubleshooting at existing facilities. The objective of the FIP analysis is to avoid or eliminate pulsations (and excessive vibration, stress and sound radiation) excited by vortex shedding at T-joints with closed side branches in the piping system. This analysis should be carried out in the design phase of a new installation, because required modifications to eliminate FIP problems can be implemented relatively cheap and time efficient.
When pulsation or vibration problems occur or have lead to the failure of an existing installation, TNO provides root cause analyses to identify the problem and recommend modifications to eliminate future problems in the installation. Both analyses can be applied in the entire value chain of the oil and gas world: upstream, midstream and downstream. All types of gasses and liquids can be analysed with our in-house developed software tool PULSIM. Besides numerical analyses, we also have experimental facilities for scale testing.