Emerson develops silencer to reduce pipe noise

Industrial organisations have long searched for a solution to reduce process piping noise, but until now all solutions have generated significant pressure drop, reduced flow 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.

Emerson has now announced it has developed and released 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 dB 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.

The modal attenuator addresses piping noise and other issues with a drop-in solution, which is said to improve worker safety and regulatory compliance while reducing the risk of damage to downstream equipment due to high noise levels internal to piping. It consists of acoustic cavities of varying sizes surrounding a full-bore perforated tube. Each cavity generates destructive interference over a range of frequencies to provide noise reduction across a broad spectrum.

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 or where pigging is required for cleaning and maintenance.