Mounts for Generators
Generators can be one of the most bothersome noise sources aboard any vessel. Because they run during transit and at rest, the constant nature of even low levels of noise are often a source of noise complaints. Structureborne noise from the generator can be heard in spaces far removed from the equipment. Good isolation of your generator is essential to a quiet installation.
Generators typically run at 1,800 rpm (US) or 1,500 rpm (EU) which results in a dominant frequency between between 38Hz and 90Hz. These low frequency tones require a high deflection mounting to provide effective isolation and noise reduction. Often the best solution is a double mounting where two sets of isolation mounts are installed below the generator.
Often you will want to consider a double isolation system like the one shown below. Double isolation takes advantage of the mounts that come, often built-in, with the generator, but add a second set of mounts below the plate or pan at the bottom of the generator. Like many effective insulation systems, this applies the benefits of layers to an isolation solution, with two sets of flexible mounts absorbing vibration.
In some cases, adding a plate or heavy plywood under the drip pan will improve performance by creating a solid, stabilizing platform between sets of mounts. Usually, the ideal weight for this intermediary is half the weight of the equipment being mounted. So a generator weighing 1,000 lbs would be double mounted to a 500 lb plate.
For the most optimized generator mounting solution, Soundown can perform a Finite Element Analysis (FEA), which finds the natural frequencies of the element to make sure that what noise is not mitigated by the mounts is not escaping at an excitatory frequency. Some escaping vibration will create sound that’s amplified in other spaces, while other vibrations will dissipate. It depends on the frequency and the naturally resonant qualities of surrounding materials. The analysis may suggest mounts of a different size or stiffness, to produce a slightly different and less harmful frequency.
Soundown’s most common mounts for generators under 200 kW include TR004, BRB or Ring Bushing Mounts. For larger generators RD Conical Mounts are often the best option. If you can provide us with a generator drawing that shows the weight and center of gravity we can provide options for the most effective solution.
For more complete information on reducing generator noise please review our generator noise control page.