Allen C. Fagerlund

Piping noise transmission loss calculations using finite element analysis

The prediction of noise radiated by piping downstream of a control valve is subject to various uncertainties. One of the significant sources of uncertainty is the pipe‐wall transmission loss. Due to the difficulties in experimentally measuring pipe‐wall transmission loss accurately, and practical difficulties of taking into account pipe length and boundary conditions, an analytical approach for the calculation of transmission loss is required. The feasibility of uncoupled structural‐acoustic finite element based calculations of transmission loss is being investigated for this purpose. By developing the use of finite element based calculations of transmission loss, it is hoped to provide a simple analysis procedure to quantify the effects of pipe length and boundary conditions on the noise level downstream of control valves in practical piping systems. It should also assist in the refinement of analytical/statistical calculations of transmission loss and noise radiation.

Identification and Prediction of Piping System Noise

In a power plant environment, the piping systems form a network that extends throughout the facility. Various components can be major sources of in‐plant and community noise, both the pipe and the contained fluid can be propagation paths, and radiation can occur from the external surface. Though the basics of these phenomena may be understood, the translation into workable predictive tools has been slow. Too often, source, propagation, and radiation effects are treated as separate entities without allowing for the interactions that exist. The spectral characteristics of the sources will govern the type of response by the system. Pipe transmission loss models will change in pipe to duct transition areas. The status of these concepts will be reviewed with a discussion of current and possible future efforts to improve existing models.

Piping System Noise Issues: Multiple Noise Sources

Noise levels in power plants continue to be exceeded on occasion in spite of recent developments such as industry wide use of the International Electrotechnical Commission (IEC) control valve standard 534-8-3. There are several reasons for this related to the specific piping system under consideration. This paper presents flow test data showing the addition of sound powers and the resultant increase in noise due to multiple control valves discharging into a common manifold pipe.Copyright

Strain Based AIV Evaluation

A framework for Acoustic Induced Vibration (AIV) evaluation is outlined which is based on estimating the pipe surface strain for an evaluation framework of structural fatigue. Critical to this approach is that the assessment is implemented with frequency based formulations. The frequency based formulation allows for more accurate determination of the pipe’s structure response and combining different sources, such as the valve and piping elements. The approach relies on internationally recognized standards as the core technology, in particular the IEC 60534-8-3 control valve aerodynamic noise prediction standard and the fatigue assessment in design codes, such as the ASME Boiler and Pressure Vessel code. These are augmented with system noise predictions using a non-dimensional testing based model for piping component noise predictions. Components of this approach have been described in previous papers and are presented here in a more complete form.Copyright

AIV Evaluation With Sound Pressure and Fabrication Quality Standards

Criteria for evaluating acoustic induced vibration damage (AIV) has been based on available data, often referred to as the Carucci-Mueller approach1. The Carucci-Mueller approach has been developed with several variances, but all approaches apply the internal sound power formula used with that original published data. However, the equation is an approximation to sound power which is used in very few other applications. This paper will show a correlation between the Carucci-Mueller data and the related design curve to one generated using the IEC 60534-8-3 Control Valve Aerodynamic prediction noise standard2. Additional corrections for fabrication quality will be reviewed. Using internal sound power and the coupling to pipe wall vibration, the resulting external sound pressure can be directly related to strain and thus fatigue failure criteria which are material based. Utilizing the IEC noise standard as well as standards which give corrections for fabrication quality can move the AIV evaluation techniques to methods that are documented in international standards.Copyright

Noise generation and propagation effects on piping system components

In power plants and petrochemical plants, the piping systems form a network that extends throughout the facility. Various components in a piping system can be major sources of in-plant and community noise, both the pipe and the contained fluid can be noise propagation paths, and noise radiation can occur from the external surface of the piping. Though the basics of these phenomena are often understood, the translation into workable predictive tools has been slow. Several possible piping system noise sources are described and the experimental test program being undertaken to generate the required non-dimensionalized spectral data is outlined. The accuracy of pressure fluctuation scaling for pressure and flow rate is also reviewed based on the equal tee test program.

Measuring high frequency valve noise to evaluate interference with ultrasonic flow meters

Ultrasonic flow meters are installed in lines with particular concern on the location of flow noise sources, such as valves and other geometry changes and restrictions in a piping system. The ultrasonic flow meter operates with a tone burst, typically in the range of 100 to 300 kHz. While this frequency range is far above the typical range for noise control in piping systems, there is good evidence that the flow noise sources generate sound in the operating frequency range of the ultrasonic flow meter. The goal of the work was to establish a procedure to measure the noise generated by piping elements in the frequency range of the ultrasonic flow meter operation. The flow disturbance is placed upstream of the ultrasonic flow meter. The internal noise spectrum are measured at three locations: one upstream of the flow disturbance, one between the flow disturbance and the flow meter, and one downstream of the flow meter. Some available results in the literature will be reviewed along with presenting the exper...

Dynamic Stress Predictions of Acoustic-Induced Pipe Vibration Failures

The dynamic stress prediction methodology developed by Norton [1] for broad-band acoustic-induced vibration of piping systems is applied here to the failure data of Carucci and Mueller [2]. Proprietary noise and vibration prediction technologies are used in order to improve the accuracy and robustness of the predictions. This results in generalized dynamic stress predictions that clearly delineate the cases of acoustic fatigue and satisfactory operation documented by Carucci and Mueller, unlike other failure prediction procedures traditionally used by industry. Other advantages of the dynamic stress approach include (i) a theoretically sound approach to account for pipe wall thickness, pipe diameter and internal density; (ii) direct consideration of material fatigue properties and stress concentration effects; and (iii) the potential to evaluate fatigue life for transient blow-down conditions.Copyright

Blow-Down Valve Noise and Interactions With Downstream Orifice Plates

In a blow-down situation as might occur at a natural gas processing facility, noise levels are very high and significantly exceed the noise levels one would normally associate with a control valve. As the blow-down operation is an infrequent event, this may be permissible but requires consideration of the duration of these high noise levels to ensure that occupational noise exposure limits and acoustic fatigue limits are not exceeded. Tests of noise levels due to an 8-inch control valve in a 12-inch pipeline under blow-down conditions are compared here with noise level predictions based on the IEC standard. Consideration is also given to the impact of placing an orifice plate downstream of the control valve as is often done to reduce pressure drop across the valve in the expectation that control valve noise levels will be reduced. Simple orifice plates often installed by plant operators to achieve this goal are shown to have an adverse impact, and it is shown that a multi-hole diffuser or low-noise control valve should instead be used.Copyright