Emerson has introduced the Fisher™ WhisperTube Modal Attenuator for noisy gas or vapour applications in a wide range of industries. The modal attenuator is a full-bore device offering 15-decibel sound suppression to reduce noise inside pipes produced by sources upstream, such as control valves or other devices. It is installed downstream of these types of devices in place of a pipe spool piece, generates no additional pressure drop, and has no impact on process flow.
Industrial users have long searched for a solution to reduce process piping noise, but until now all solutions have generated significant pressure drop, reduced flow, and/or introduced obstructions. This has led some users to install acoustic insulation to pipe sections to reduce noise, but this can be very costly and cumbersome to install, and it does nothing to reduce internal piping noise. The modal attenuator addresses these and other issues with a drop-in solution, improving worker safety and regulatory compliance, while reducing the risk of damage to downstream equipment due to high noise levels internal to piping.
Leading applications for the modal attenuator include those where upstream process flows are changed by control valves, pressure relief valves, pumps, compressors and other devices that generate noise. Many of these devices must be installed in lengths of piping with no flow restrictions downstream, and the modal attenuator works particularly well in these applications because it introduces no such restrictions.
Unlike other noise suppression solutions, the modal attenuator does not introduce an obstruction into the piping, so it can be used in applications where particulates are suspended in process flows, and/or where pigging is required for cleaning and maintenance.
The exact amount of noise reduction depends on the frequency of the noise and the velocity of the flow. Estimates regarding the degree of sound suppression can be provided by Emerson experts prior to purchase and installation.
WhisperTube devices are offered in sizes from 2 to 12 inches, with American Society of Mechanical Engineers (ASME) flange ratings of Class 150, 300 and 600. Pressure ratings match the flange rating sizes, and the maximum temperature is 700° F (371° C).