Noise and vibration emanating from compressors, pumps and rotating equipment in the refrigeration and HVAC systems of commercial and industrial buildings can be a source of disturbance to neighbours, workers and delicate electronic and data equipment.
While modern Heating, Ventilation and Air Conditioning (HVAC) plant is generally well engineered to eliminate Noise, Vibration and Harshness (NVH) issues, poorly sited or inadequately damped plant can create OH&S issues and disruptions that spread through walls and floors.
In its most disruptive form, this can interfere with automation and processing equipment (such as data processing facilities in commercial office buildings and computerised automation and processing systems in factories, food, beverage and agribusiness plants).
And as building space becomes more precious and specifiers are asked to deliver greater functionality within tighter areas and closer neighbour boundaries, refrigeration and HVAC systems can face greater demands to reduce NVH levels to avoid conflict with workplace NVH requirements on the one hand, and increasingly automated production and building control systems on the other.
“Even common screw compressors, for example, can be an issue, and typically operate in noise ranges of 40-90dB. Where noise levels reach or exceed the upper level in this instance, being exposed for longer periods of time can be considered dangerous for hearing,” says James Maslin, Technical Product Manager for pneumatic isolation specialists Air Springs Supply Pty Ltd.
Where NVH issues cannot be adequately damped by solid rubber mounts or flexible pads of elastomers, cork, dense foam or laminate materials, something better is called for to preserve good workplace and good neighbour status.
Two solutions to such NVH issues are offered by Air Springs Supply, which is national distributor for Firestone isolation technologies used globally in commercial and industrial applications by architects, engineers, specifiers and building managers:
Airmount™ air springs in capacities from a few dozen kilograms to more than 40,000 kg each. These hugely robust products from Firestone provide isolation efficiencies often exceeding 99 per cent – so good in fact they can be used beneath giant film projectors or hospital operating beds.
Marsh Mellow™ solid rubber-and-fabric isolators so tough that they are used beneath vibrating screens in stone quarries and mining facilities, as well as agricultural product materials handling facilities where they tame the shaking otherwise entering surrounding areas, while simultaneously eliminating the noise that previously dominated the workplace.
Airmount™ isolators have been called into service as passive or semi-passive isolators to provide isolation efficiencies of up to 99 per cent for applications such as:
- HVAC and chiller equipment
- Nearby computer and data processing floors (especially those affected by ambient traffic)
- Floor mounting of delicate automation equipment,
- Emergency generators and rotating plant in buildings (so the building doesn’t shake when they start up, particularly alarming in high-rise)
- Scientific research equipment sharing space adjacent to HVAC and other building services. Airmounts have been used beneath laboratory, educational and testing equipment (including an entire 500-ton sonar testing tank, where they continuously achieved an isolation efficiency of 99.7 per cent at 1500 CPM (cycles per minute).
“A great virtue of our single, double and triple-convoluted Airmount isolators is low-or no-maintenance simplicity. They are highly engineered balloons, carefully constructed to deliver a range of outstandingly sensitive NVH performance across a very broad spectrum of needs,” says Mr Maslin.
Capable of virtually indefinitely supporting weights from a few kilograms to 40,000kg each, they are manufactured by Firestone to the same standards as the Air Springs used as OEM equipment in the suspensions of trains, buses and heavy trucks used to carry coal, rock and precious cargoes over outback roads.
Marsh Mellow isolators, meanwhile, have also demonstrated they also can easily carry the weight of the compressors, pumps, chillers and HVAC systems typically installed in applications such as food and beverage plants and primary processing facilities including meat, poultry and fish processing plants.
All such places encounter the issue of vibration that occurs in all rotating or reciprocating machinery because of forces generated within it. Sometimes the vibration is intended – as in vibrating screens and vibrating conveyor sections, for example – and sometimes it is caused by imbalances in rotors, bearings, springs and gears as vibration migrates from the source to surrounding structures and wear-prone components.
Cylindrical Marsh Mellows provide a simple, robust and effective means of solving vibration and isolation problems created by such equipment as well as for quiet isolation of machinery vibration and for general shock absorption throughout industry.
Marsh Mellows give consistent performance regardless of changing loads, while offering high lateral stability and compact size. Marsh Mellow springs are constructed of a solid rubber core with a hollow centre and several plies of fabric-reinforced rubber as an outer cover. The plies provide the springs with stability as well as a consistent cylindrical shape.
Marsh Mellow springs are quiet in operation, unlike steel springs which readily transmit high frequency structural noise and often suffer from coil chatter. A failing coil spring may crack, causing fragments of the coil to damage equipment, resulting in expensive downtime. This problem is eliminated with Marsh Mellow springs, which are tolerant of overload and, if they ever do fail, do not fail catastrophically, says Mr Maslin.
The quiet performance of Marsh Mellows – and the fact that they resist water and grit – means they are ideal for applications where high levels of workplace safety and hygiene are essential. Such applications can range through to primary processing, timber and paper and food and beverage HVAC and refrigeration plants where an isolation solution must provide durable, maintenance-free performance under conditions that may be grimy, damp and confined. In such circumstances – which can kill standard isolators – Marsh Mellows can excel.
Certified to ISO 9001: 2008 Quality Management Systems – Requirements, Air Springs Supply has more than 30 years’ experience in pneumatic engineering, with a long-established national sales, service and technical support network to help provide solutions for industry