Sound Zorber Technical Guidelines and References
SoundZorber is a brand under General Rubber Corp. representing our complete line of noise and vibration control products, as well as seismic restraints. Our original product was a simple rubber flanged pipe, pre-dating the spherical expansion joint, used to reduce the noise and vibration generated from mechanical equipment including pumps, chillers, compressors, fans, heat exchangers and cooling towers. Today’s SoundZorber product line includes resilient mounts, hangers, pads and bases, as well as seismic restraints, making it a complete isolation package for the same group of mechanical equipment.
Noise and vibration can represent a serious problem, some finding it more objectionable than poor heating or cooling. This is because an individual can add or remove clothing or use local space heaters or fans when needed. The same individual can do little to dampen noise and vibration. The use of SoundZorber® products can effectively eliminate these problems and at a remarkably small cost, typically less than 1/10 of 1% of the mechanical budget.
The SoundZorber® products are used for both simple and demanding applications. For example, when the building structure is considered stiff, as in the case of ground floor mechanical rooms, the theoretical efficiency equation works well. The efficiency or amount of vibration isolated is based on this relationship between the disturbing frequency fd and the natural frequency of support fn. fd is typically the lowest RPM of the equipment and fn is based on the operating deflection of the resilient support. 90% efficiency solves the vast majority of noise and vibration problems and is simply obtained by selecting a resilient support with a fn 1/3 of fd. All rubber supports work well isolating higher frequencies, where as the addition of coil springs improve the range of frequencies dampened.
More demanding applications exist when the support structure is not considered stiff, as in the case of mid-floor mechanical rooms or roof mounted equipment. Essentially the deflection of the support structure will negate some of the theoretical efficiency. With a trend to lighter construction and larger spans between supports, this more demanding application has become common. Complicated equations can be used to theoretically solve these applications, however simply adding a portion of the allowable beam deflection to the calculated static deflection of the resilient support will generally accomplish the same result. Our engineers are pleased to review mechanical equipment tables and make recommendations regarding minimum deflection based on type of equipment and location. Structural steel or concrete bases are available for rigid support of equipment. Concrete bases have the added benefit of being more rigid and thinner than structural steel bases. Their additional mass also helps to lower the amplitude or oscillating deflection that tends to occur with equipment that has a high unbalanced force SoundZorber® bases are available both custom fabricated or modular bolted construction.
Seismic restraints can be applied to both rigid and non-rigid mounted systems. An analytical method for seismic restraint design is used to calculate the seismic force (Fp), applied to the center of gravity of the equipment in the horizontal direction. While many seismic building codes only require inspection of the horizontal loads, we will always inspect the vertical loads as well. Keeping the system in place and avoiding a life threatening situation is the primary purpose for most seismic building codes. Unfortunately, little importance is often placed on the likely damage to the system as a result of the seismic event. We anticipate that the survivability of the system will become a more important design goal in the near future, particularly for utilities and municipalities providing essential services. Seismic Survivability of Piping Systems is the subject and title of the linked paper presented at the National Earthquake Conference. A case study was sighted in the paper where the California Transportation Authority specified expansion joints that would accept the anticipated forces and displacements of a seismic event. The paper also outlined the use of a dynamic response computer analysis to model the system. The program verifies the equipment’s restraint, as well as its survivability based on allowable fragility levels. Snubbers, restrained mounts and seismic restraint cables work well in this passive design. An air gap between the restraint and the resilient support is needed for the resilient support to operate under normal conditions. A rubber stopper is typically incorporated in the restraint to decelerate the equipment as it is restrained.
SoundZorber noise and vibration control products including our resilient mounts, hangers and pads can virtually eliminate objectionable noise and vibration. Our seismic restraints are designed to protect both life and property in the event of an earthquake. The experience and capability of General Rubber can effectively utilize these products in even the most demanding applications. In consideration of our products, you are assured that every aspect of your project will be our priority.
Thank you for your consideration.