Eugene L. Broerman

Acoustics In Pumping Systems

This tutorial will explain the pumping system speed of sound concept (how to account for acoustic velocity changes due to pipe wall flexibility and liquid properties), the definition of quarter-wave, half-wave, and higher order acoustic mode shapes, the importance of each mode shape, and examples of how to estimate these mode shapes and frequencies. The use of basic acoustics to identify and resolve pulsation and vibration issues in liquid pumping systems using acoustic filters will be described in this tutorial. Some simple examples of acoustic pulsation problems with the corresponding mode shapes and frequencies will be presented. Examples of pulsation control in liquid pumping systems using acoustic filters will be given. This tutorial will conclude with some recommended practices and guidelines for the application of acoustic theory and practice to the design, review, and problem avoidance or resolution in liquid pumping systems.

Identifying and Mitigating Flow-Induced Vibration in Recycle Loop Gas Piping at a Centrifugal Compressor Station

The South East Supply Header (SESH) is a relatively new pipeline placed into service in September of 2008. The 42″ /36″ pipeline originates near Delhi, Louisiana and ends near Coden, Alabama. The pipeline has a nominal capacity of 1 BSCFD and includes three (3) mainline compressor stations, two (2) booster stations and numerous meter stations.Copyright

Helmholtz Absorbers: Experiments in Controlling Resonant Pulsation Without the Use of Orifice Plates

Pressure drop has been used for more than half a century to control resonant pulsation in reciprocating compressor piping. Although avoiding these resonances is the preferred method, this is not possible in many high-speed/variable-speed installations. In these cases, resonant pulsation is often managed by using orifice plates to dampen the response. Helmholtz absorbers are an old technology, used to improve the acoustics of ancient Greek theaters and modern recording studios alike. Although their application in the field of piping acoustics has been well documented, this paper presents new ways in which they have not yet been applied. In this paper, experimental data is shown for a self-tuning Helmholtz absorber, or Side Branch Absorber (SBA) used to cancel a piping length resonance, and for a Virtual Orifice that is used to reduce cylinder nozzle pulsation. These devices open up new doors for controlling pulsation with reduced horsepower costs in reciprocating compressor installations.Copyright

Development of a Predictive Method for Quantifying Vortex-Shedding Pulsation Amplitudes in Compressor Piping Systems

One of the design criteria for centrifugal compressor piping systems is the prevention of piping and valve failures from high pulsation amplitudes and vibration caused by vortex-shedding induced (VSI) pulsations of gas flow past closed piping branches (stubs). Most vortex-shedding analyses are performed on the basis of frequency avoidance. If a coincidence is predicted between the acoustic natural frequency of a piping segment and the flow induced vortex shedding frequency, piping changes must be made to avoid the coincidence, since there is currently no known method for accurately predicting the severity of the resulting pulsation amplitudes and, therefore, the possibility of piping failures. Often, these piping changes are expensive and time consuming and likely unnecessary for smaller bore piping (10-inch or less), assuming the flow-acoustic coincidence does not coincide with a mechanical resonance.The majority of research performed to date on vortex-shedding excitation of piping stubs focuses on predicting the frequencies of excitation using an experimentally determined Strouhal number or range of numbers for a given geometry or piping feature. However, to properly design a piping system using a combination of support structures and piping changes, reliable prediction of the pulsation amplitude is essential for determining the shaking forces acting on the piping system and the resulting vibration and stress amplitudes. Due to the expense of experimental testing and availability of equipment, it is difficult to obtain accurate amplitude measurements of VSI pulsations of fluids at Reynolds numbers typically associated with natural gas transmission.This paper describes a series of experimental tests performed to record vortex-shedding induced pulsation amplitudes in three test facilities. Three different process fluids were utilized varying the operating conditions to obtain gas flows with Reynold’s numbers between 1e5 and 2e7. Steady state flow, temperature and pressure data was recorded with ASME PTC-10 compliant instrumentation. Transient pressure data was taken with dynamic pressure transducers installed at each stub end as well as in the main piping near the tee. The geometry configurations, pulsation amplitudes, and calculated Strouhal numbers associated with each test configuration are presented. Comparison was made between the test results and several previously published formulas. From the test results, a predictive method was developed to best represent the limit of the pulsation amplitudes.Copyright