IJSTE - International Journal of Science Technology & Engineering | Volume 3 | Issue 07 | January 2017 ISSN (online): 2349-784X
Mitigations to Flow Induced Vibration (FIV) in Control Valve Piping System using Visco-Elastic Dampers & Neoprene Pads Mr. Bhagwat B. Kedar M. Tech. Student (CAD/CAM & Automation) Department of Mechanical Engineering Veermata Jijabai Technological Institute Mumbai, India
Ms. Jayshri S. Gulave M. E. Student (Heat Power) Department of Mechanical Engineering Matoshri College of Engineering & Research, Nashik, India
Abstract The control valve piping is vibrating due to high flow rate and high velocity, also this line is running at different flow rate condition. The generic calculations based on Energy Institute Guidelines [1] indicate that the flow is Turbulent and Likelihood of Failure is more than one. This number is alarming and detailed analysis considering change in flow, pipe route, supports etc. is recommended to be performed. This Paper aims to study the 12-inch Control Valve Piping Vibrations observed at site due high flow rates and high velocity. and also attempts to find probable cause of the vibration and the solution to minimize these vibrations. Keywords: FIV, CAESAR II, LOF, Visco-Elastic Damper, Vibration Pads ________________________________________________________________________________________________________ I.
INTRODUCTION
Pipe will exhibit a series of natural frequencies which depends on the distribution of mass and stiffness throughout the system, and the distribution are influenced pipe diameter, material properties, wall thickness, location of lumped masses (such as valves), pipe supports and also fluid density. Each natural frequency will have unique deflection shape associated with it, which is called mode shapes, which has the locations of zero motion (node) and maximum motion (Antinodes). The response of the pipe work to an applied excitation is dependent upon the relationship between the frequency of excitation and the system’s natural frequencies. Vibration generated in the pipe work may lead to high cycle fatigue of components (such as Small bore connections) or the failure at welds in the main line itself. II. FLOW INDUCED VIBRATION Flow-induced vibration, or vortex shedding, is due to high flow velocities and High mass flow rates such as in a piping dead leg of a centrifugal compressor system. with certain flow conditions, piping systems will develop high levels of noise and vibration that can damage the pipes and related systems such as tube bundles, side cavities, and bluff or tapered bodies in flow streams. Pipe damage compromises plant safety, forces shutdowns, increases maintenance, and reduces efficiency and capacity.
Fig. 1: Example of vortex shedding from an object in the flow stream.
III. VISCO-ELASTIC DAMPER Viscoelastic dampers reduce vibrations by converting kinetic energy into heat thus damping the motion of the system. Damping, as a method to reduce unwanted vibrations, is most effective in cases where the vibratory system is excited with a frequency close to its natural frequency. [3] Viscoelastic dampers may be used to solve very different vibration problems. A typical example is the damping of operational vibrations in an industrial piping system e.g. in a power plant. Whenever the piping systems cannot be isolated from the source of vibration, damping might be an adequate measure to reduce the motion of the piping to an acceptable level. The Construction and mounting of the Visco-Elastic Damper is shown in Fig. 2.
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