Guidelines for Acoustic Induced Vibration (AIV), Flow Induced Vibration (FIV) Analysis

► Noise Vibration

► Vibration Damping

► Vibration Welding

► Vibration Testing

8/28/2014

Guidelines for Acoustic Induced Vibration (AIV), Flow Induced Vibration (FIV) Analysis

4.1 Acoustic Induced Vibration a) Acoustic Induced Vibration – AIV De finition Acoustic Induced Vibration (AIV) is generally applicable to lines in gas service. In a Gas System, high levels of high frequency acoustic energy can be generated by a pressure reducing device such as a Relief valve, Control valve or Orifice plate. The amplitude of this energy is governed primarily by the Flow rate & Pressure drop. Excitation due to this can lead to fatigue failure of welded downstream connections. Piping downstream of Pressure reducing devices as below is prone to Acoustic Induced Vibration AIV.

Relief Valves. Blow Down valves & Restriction Orifices. Pressure reducing Valves. Compressor recycle Valve. Choke Valve. b) Impact of Acoustic Induced Vibration – AIV

Acoustic Induced Vibration can lead to Fatigue failure at Small Bore branches. c) Mitigation of Acoustic Induced Vibration – AIV

Detailed Acoustic Induced Vibration – AIV study shall be carried out by AIV Consultant based on the Multidiscipline responsibility Matrix as  per Appendix-1. The study recommendations shall be incorporated in the design of Piping Systems. Generally the study recommendations will be available at a later stage of the Project. In order to minimize the modifications due to Acoustic Induced Vibration AIV Consultant’s recommendations, the following guidelines shall be followed during initial design of lines prone to AIV. Process to identify Acoustic Induced Vibration AIV Prone lines in Line list, at early stage of the Project. A separate Pipe Class may be used for Flare system. Generally after Acoustic Induced Vibration AIV study, the Consultant comes up with typical recommendations such as increase of Pipe wall thickness particularly, for low wall thick Flare lines, Sweepolet branch fitting in place of weldolet, forged lateral/ 90 Deg Tee in  place of stub –in lateral/ 45 Degree connections, Full encirclement pad for supports at PSV outlets etc. In case of reinforced Stub-in connection, consideration shall be given to Clause 304.3.5 (b) of ASME B31.3 regarding use of Tee fittings or complete encirclement types of reinforcement for branch stub-in connection. As this will have impact on material procurement & design, the study shall be expedited & provision for incorporation of such recommendations shall be kept to the extent possible in preliminary piping design itself. For high energy level PSVs like Slug Catcher/ Export Line PSVs, in low wall thick piping, D/T (Diameter/Thickness) ratios of pipes shall  be reviewed & D/T