Power plants FG WILSON
Exhaust muffling
In most locations, excessive noise is undesirable. Since most of the noise is produced by the pulsating engine exhaust, this noise can be reduced to an acceptable level by using a muffler. The required level of attenuation depends on the specific location and may be regulated by law. For example, engine noise is undesirable in a hospital area, but is generally acceptable within an isolated pumping station.
Muffler selection
The muffler reduces the noise of the exhaust system by dissipating energy in the chambers and tubular baffles, thereby eliminating the emission of sound waves that cause resonance. The muffler is selected depending on the degree of noise suppression required to meet the installation conditions and applicable regulations. The size of the muffler and the exhaust pipe must ensure the value of the exhaust back pressure within the limits recommended by the engine manufacturer.
Depending on the degree of noise suppression, mufflers are divided into mufflers:
- low grade or industrial;
- temperate or populated areas;
- high degree or critical.
Low grade or industrial noise suppression – suitable for industrial areas where the background noise level is relatively high or for remote areas where partially suppressed noise is acceptable.
Moderate or populated areas – Reduces exhaust noise to an acceptable level in places where moderately effective noise suppression is required – such as semi-populated areas where there is always moderate background noise.
High or critical noise suppression – provides maximum noise suppression for housing estates, hospitals, schools, hotels, shops, apartment buildings and other areas where the background noise level is low and generator set noise must be kept to a minimum.
Silencers usually come in two configurations – (a) end-in, end-out or (b) side-in, end-out. The presence of these two types provides flexibility of installation, for example, horizontal or vertical position, above the engine, on the outside of the wall, etc. The side entry type allows a 90° change of direction without the need for an elbow. In any case, both configurations must include drain fittings.
The muffler can be located next to the engine, while the exhaust pipe goes outside after the muffler; or the muffler can be located outside the wall or on the roof. Positioning the muffler close to the engine provides better noise suppression due to the minimal length of pipe that fits the muffler. Placing the muffler inside simplifies its drainage and maintenance.
However, mounting the muffler externally has the advantage that there is no need to isolate it (although it must be surrounded by a protective shield). The job of insulating the exhaust pipe indoors is easier when the muffler is outside, and the insulation helps suppress the noise.
Since mufflers are large in size and weight, consider these parameters when designing the exhaust system. The muffler must have adequate resistance so that its mass does not exert pressure on the exhaust manifold or engine turbo pump. The muffler must be located in such a way as to avoid excessive bends in the exhaust pipe, which can create high exhaust back pressure. A side-entry muffler can be installed horizontally above the engine without the need to provide a large overall height.
Mufflers and exhaust pipes within the reach of personnel should be protected by fences or insulated. Indoors, it is desirable to insulate the muffler and exhaust pipe, as insulation not only protects personnel, but also reduces heat radiation into the room and also reduces exhaust system noise. Mufflers installed horizontally should be located at a slight angle to the engine exhaust manifold and provided with a drain fitting at the bottom point to drain the accumulated moisture.