Our pipe resonator array is a proven technology for reducing turbo compressor noise at the source. Last year, we successfully tested a 30-inch pipe array, the largest ever built, in Le Havre, France.
Turbo compressors are, by nature, a loud noise source because of the high power and speed. Most compressors produce a strong tonal noise component that varies over a wide frequency range from 1,000 Hz to 4,000 Hz, depending on the speed of the compressor and the number of impeller blades. In a centrifugal compressor, noise is generated primarily by the impellers and their aerodynamic interaction with the stationary components.
Reducing this noise can be beneficial in many ways. Historically, engineers addressed this compressor noise problem by treating the sound transmission path and applying devices such as sound enclosures and sound insulation. Neither method requires much understanding of the noise source, nor can they be considered in the design phase.
Control Noise – At the Source. Today, the preferred technique is to attenuate, or reduce, the noise at its source. Our most significant technology to produce quieter machines is the pipe or diffuser duct resonator array, designed to absorb acoustic energy. This D-R® duct resonator array has undergone extensive testing and confirms that such arrays can reduce noise by 10 dB with no adverse effect on compressor aerodynamic performance. As noise level is a logarithmic scale, a 10 dB reduction equates to a 90 percent sound power reduction on a linear scale – a significant achievement. Furthermore, the advanced design of these resonator arrays is effective in reducing associated vibration that can cause structural fatigue failures and damage piping and instrument connections.
Dresser-Rand Develops and Tests 30-inch Pipe Resonator Array. Last year, Statoil asked us to perform a noise test for the largest pipe resonator array ever produced, a 30-inch pipe, to validate and confirm the estimated noise attenuation. The compressor is located on a platform in the North Sea, approximately 40 miles west of Statoil’s Kollsnes gas processing plant.
The project involved two complete compression trains with DATUM® D18 centrifugal compressors. In order to reduce noise emissions from the compressor, Statoil asked us to install all necessary components. This included a diffuser resonator array at the first and last stages of the compressor and a pipe resonator array installed on the inlet and discharge process piping.
“We can install an internal resonator array in the diffuser region or an external array on compressor flanges or into a client’s process piping,” said Scott Wisler, director, Centers of Technical Excellence at Dresser-Rand. “The initial choice was to use internal diffuser arrays, but Statoil asked us to also install pipe resonator arrays on their 28- and 30-inch pipes.”
The actual test was conducted at the Dresser-Rand facility in Le Havre, France. The facility includes a dedicated acoustic resource and state-of-the art technology in acoustic analysis and testing. To verify the attenuation of sound by the array, sound pressure levels were produced by a loudspeaker and measured in ducts upstream and downstream of the array. The measurements included a comparison of the sound level with a straight pipe spool piece and a pipe resonator array.
Results showed that the pipe array could achieve more than 10dB attenuation for the frequency range corresponding to the speed range of the compressor.
For clients looking to control noise at the source, Dresser-Rand’s D-R duct resonator array technology provides an excellent means of reducing noise pollution. It can be applied to new or installed compressors, including compressors built by other manufacturers.