On the selection of exhaust silencers for steam boilers

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I. Under normal operating conditions at the site, the silencer provides a high level of noise reduction； II. The resistance loss or power loss caused by the silencer to the air/gas flow must be low, so as not to affect the normal operation of the equipment ； III. The silencer is durable, compact, lightweight, simple in structure, and easy to manufacture ； When selecting steam vent silencers for industrial boiler systems, more attention should be paid to the type of noise they are intended to suppress, such as those used for exhaust gas during boiler startup and ignition, as well as those for exhaust gas from the safety valves in the boiler system. These two are completely different. As is well known, the exhaust silencer of a safety valve releases a large amount of high-temperature, high-pressure steam instantly when the boiler is under load or when the pressure reaches the value preset by the safety valve; in other words, its force of release is quite strong. This is also why some manufacturers of silencers design such noise-reduction devices to be quite large in size. Moreover, such noise reduction devices are extremely difficult to adopt a structure based on throttling flow to reduce noise. As for the silencer used for exhaust gas during boiler startup and ignition, the operating pressure of this noise-reducing device is not as high as that of the silencer attached to the steam safety valve, resulting in no significant sudden force during exhaust. The Dongneng brand spray, resistance, and impedance composite silencer causes high-pressure steam to pass through a flow control mechanism within the silencer before entering a pressure-reduction chamber, where it expands in a large volume to become low-pressure steam before being ejected. During this process, part of the kinetic energy of the steam is converted into sound energy of a certain frequency, thereby significantly reducing the noise level. However, due to factors such as discrepancies between the actual exhaust frequency and the designed value, the exhaust noise remains above the **standard specified level. To address this issue, a double-layer structure containing sound-absorbing material* has been designed outside the noise-reducing unit; this structure is tailored to the spectral characteristics of the residual noise emitted by the noise-reducing unit, and it is capable of effectively absorbing that residual noise, thereby reducing the steam exhaust noise below the **standard value (GB12348-94). It utilizes the noise reduction mechanism of flow control, expansion, and absorption. For the silencers used to handle steam discharged from safety valves, Dongfan Power Equipment adopted a silencing mechanism that is entirely different from the one used in silencers for boiler startup steam discharge – namely, a mechanism based on expansion through large holes rather than using smaller holes for flow control. This design enhances the resistance to spray and noise reduction capabilities, allowing steam to be discharged smoothly while ensuring safety and keeping noise levels within the standards set by regulations. This is also why the noise reduction value of the steam safety valve silencer is much lower, at the same level, than that of the ignition exhaust silencer.