Guideline for AIV

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Guideline for AIV

INERTANCE Inc. has assessed piping for risk from acoustic fatigue, which to be evaluate the critical data such as process condition, calculated sound power level, geometry information in order to calculate LOF (Likelihood of failure) value. AIV (Acoustic Induced Vibration) assessment has been performed in accordance with below code and standards;

  • ASME Paper 82-WA/PVP-8 “Acoustically Induced Piping Vibration in High Capacity Pressure Reducing Systems” by V. A. Carucci and R. T. Mueller
  • CONCAWE Report No. 85/52, “Acoustic Fatigue in Pipes”
  • “Designing Piping Systems against Acoustically Induced Structural Fatigue” by F.L. Eisinger
  • U.S. Patent 5711350, “Piping Systems Providing Minimal Acoustically-Induced Structural Vibration and Fatigue” by F.L. Eisinger
  • Energy Institute, “Guidelines for the Avoidance of Vibration Induced Fatigue in Process Pipework” 2nd Edition Jan 2008
  • API 521, 6th, 2014, Pressure-Relieving and Depressuring Systems
  • IEC 60534 8-3, 2010-11, Industrial process control valves, Part 8-3: Noise considerations-Control valve aerodynamic noise prediction
  • BS 7608; 2014, Guide to fatigue design and assessment of steel product, BIS Standard Publication

CONCAWE ASSESSMENT

It is based on predicting the sound power level generated by a control valves, pressure relief valves, etc. and then using empirical criteria, assessing the downstream pipework for the possibility of as AIV failure. The sound power level and pipework diameter are the critical factors, with all modification then based on increasing the pipewall thickness. As a guide, acoustic fatigue screening of relief pipework is only considered necessary for valves with a predicted high sound power level.

CONCAWE Assessment Guideline
[ CONCAWE Assessment Guidelines ]

EISINGER’s ASSESSMENT

This method is based on CONCAWE assessment but has been modified to take account of the pipewall thickness, as well as the pipework diameter using D/T method and Energy method. In this way, it may be considered a more refined and in general, less pessimistic methodology.

Energy Institute Guidelines

This method predicts a likelihood of failure (here in after LOF) value, which takes into account the incident sound power level (suitably attenuated to account for the distance downstream from valve), the pipe diameter and wall thickness, and connection design. With the high sound power levels associated with operation of specific relief and pressure valves, it shall be considered likely that additional modifications would also be required. AIV calculator has been developed by INERTANCE, which is typically used for detail engineering, and could propose and recommend the AIV control measure at main pipe and small bore connections.

LOF Calculation for AIV, guideline, EISINGER
[ LOF Calculation for AIV ]

API 521 6th, 2014

API 521-2014 introduces how to calculate the sound power level, which acoustic noise level is occurred from pressure safety valve (PSV). Those equations are identical one with CONCAWE assessment method, and it is suggested to apply the control measures, in case the sound power level is estimated higher than 155 dB.

IEC 60534 8-3, 2010-11

IEC 60534 8-3 provide the assessment methodology, how to estimate the noise level with discrete frequency for control valve. On this calculation, the compressible fluid services are applicable for control valve. It is possible to calculate the acoustic peak frequency on downstream pipe, which is necessary as one of major input data for acoustic excitation during finite element analysis.

BS 7608; 2014

BS 7608 provides the fatigue design guide for welding point of steel structure. The application approach is distinguished as per geometry of steel structure, and D, TJ classes are generally used for acoustic induced vibration assessment.

Weld
Class
Location on potential crack initiationApplicationNon-propagating stress range
DAt the toe of bevel buff of fillet welded attachmentReinforcing pad
O-let to main pipe
Support to main pipe
Branch (≤2″Pipe) to main pipe
53 MPa(P-P)
TJAdjacent to the toes of full penetration weldsBranch(<2″Pipe) to main pipe
O-let to branch pipe
67 MPa(P-P)
[ Weld Class, BS 7608 ]

INERTANCE has a full capability regarding related noise and vibration engineering as listed in below, and feel free contact us at (mountain@inertance.com).


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