Production • Processing • Handling
with conditional and operational factors to predict the ‘likelihood of failure’ (LOF) for each pipe branch. Visual inspection is a quick and
effective method for identifying potential areas for concern. Many pipework vibration problems are simply the result of operators not following recommended good practice, and visual inspection by skilled assessors can quickly flag up areas for improvement relating to pipe infrastructure. Tis may include installing more effective pipe supports or replacing worn or damaged supports, proper bracing of SBCs, avoiding fretting and poor geometry, and allowing for thermal expansion of tubing.
Te basic piping vibration
measurement phase identifies areas of concern based on measured values of pipework vibration. In this phase specialist engineers will first use a single axis accelerometer connected to a portable data collector to take initial vibration
comparison with assessment criteria in the Energy Institute guidelines. If vibration is assessed as being at a concern or problem level, or for pipework with a higher frequency vibration of more than 300 Hz, the next phase used by vibration engineers is based on specialist measurement techniques. Here, a variety of more in-depth tests can be deployed depending on need. In addition, engineers can implement specialist predictive techniques, applying sophisticated tools and modelling to provide a more detailed assessment of the dynamics of specific pipelines throughout their lifecycles. Te final stage of any pipework assessment is to recommend corrective actions to reduce vibration levels and the likelihood of future failures. Tese actions vary from improving the support infrastructure around pipework including bracing and dampening, or modifying the process conditions themselves to reduce fluid loadings.
Te design of practical and
appropriate corrective actions is important in achieving cost effective yet thorough solutions, and often utilises FEA techniques to predict the effect of remedial repairs, alongside CAD software for mechanical design of supports and bracing systems. Strain gauging and FEA
are powerful tools in this analysis process and although they are often perceived as being distinct and alternative assessment technologies, AVT has long recognised the power of combining practical strain gauge work with theoretical FEA. AVT’s Pipework Vibration
Fig. 2. Corrective actions to reduce vibration vary from improving the support infrastructure around pipework, including bracing and dampening, or modifying the process conditions themselves to reduce fluid loadings.
levels, ranging from 1 Hz up to 300 Hz. Tese measurements are presented as vibration amplitude versus frequency and enable the vibration to be classified as acceptable, concern or problem, based on
Solutions service offers everything from initial on-site surveys and vibration diagnosis, to solution recommendation, design and installation. AVT’s service helps customers
reduce the risk of major incidents caused by pipework vibration, as well as underpinning HSE responsibilities under the COMAH and Offshore Installations (Safety Case) Regulations 2005. l
Neil Parkinson is technical director at asset integrity specialist AV Technology (AVT).
www.avtechnology.co.uk
www.engineerlive.com 75
“Proactive assessments can be used to routinely evaluate all pipework on a site, whether existing or planned, to ensure that best practice has been adopted and to identify possible areas of concern.”
Neil Parkinson, technical director, AV Technology
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