Model CL & CCS Series - Centrifugal Compressor Silencers
Centrifugal compressors are noisy and require noise control. Just as a pump raises the pressure on a liquid, a compressor raises air or gas pressure. Centrifugal compressor noise is produced primarily by blade-tip turbulance which is a function of horse power, speed, discharge pressure, piping velocities, number of stages of compression, type and number of blades etc. The high speed rotation of vanes or impellers generates noise which primarily consists of discrete tones interdispersed over a broad-band frequency spectrum of lesser intensity. The maximum amplitude occurs at the blade passing frequency and its second harmonic. The high frequency noise generated is in the audible range and requires treatment for achieving noise control.
The importance of proper sizing of intake and discharge piping cannot be overemphasized. Both intake and discharge silencing is normally required. These silencers are absorptive type silencers which are essentially a high frequency, low pressure drop attenuator. It depends on sound absorbing material to dissipate the acoustical energy and are usually straight thru designs. All silencers should be coupled as close as possible to the compressor to prevent excessive pipe radiated noise.
The centrifugal compressor silencers are normally selected on the basis of maximum allowable pressure drop at rated flow and the silencing criteria. These silencers are usually sized for around 5000 to 5500 FPM velocity but not exceeding 7500 FPM velocity to prevent excessive self generated noise and aerodynamic noise generation.
While selecting the centrifugal compressor silencer, it must be ensured that the flow area throughout the silencer is sufficient to accomodate the air flow without imposing excessive restriction.
The following table indicates the maximum recommended air flow in CFM for respective silencer size in accordance with the above guidelines.
Select the silencer based on the air flow from above table.
Refer to the formulas given here for calculating the pressure drop for the silencer size selected. Check this pressure drop against the maximum allowable pressure drop. If the pressure drop is too high, select the next larger size and recalculate.
(These calculations assume air as the flowing gas. For other gases, density and other corrections may be required. Contact our engineers for assistance)
- Air Flow Rate (Actual CFM)
- Temperature (°F)
- Pressure (PSIG)
- Maximum allowable pressure drop (inches of water)
If this pressure drop is higher than the maximum allowable pressure drop, then select next larger size and recalculate.
Various options for acoustical absorption materials are available with temperature limits ranging from 325°F to 1000°F. Please consult our engineers for your specific applications for selecting suitable absorption material suiting to your requirements.
The silencers described herein are designed to a maximum operating pressure of 15 PSIG. For applications where pressure exceeds 15 PSIG, the silencers can be designed to ASME Code, Section 8, Div. 1 for pressure vessel construction. The dimensions are similar to standard models, but the material type and thicknesses are selected to meet code requirements. Consult our engineers for pricing and design information.
Noise attenuation curve showing insertion loss at each frequency is shown here. This represents the insertion loss for airborne noise under average conditions. The resultant silenced noise level will depend on a number of other factors therefore this curve should be used with discretion and can be used as a guideline for evaluating the noise levels after the silencer installation.
We specialize in custom designs and also provide various nozzle orientations to suit your specific requirements.