NVH challenges intensify as new infrastructure and industry projects are packed closer together in crowded cities

Bridge, road, rail and tunnelling projects throughout Australia will generate jobs while posing environmental issues

Noise, vibration and harshness (NVH) challenges are increasing in industrial, commercial, and infrastructure applications, as large construction and production projects with heavy machinery operate in neighbourhoods where projects are packed ever closer together as a result of urban consolidation.

The challenges posed to engineers, architects, operations managers and civil and construction professionals are expanding as Governments promote infrastructure and new industrial projects to accelerate economic recovery – while also insisting that people and property are protected against harm and hazards, including building cracking and damage from preventable disruption, as well as OH&S threats to hearing from noise on busy worksites.

One proven highly effective solution to NVH issues is provided by Firestone Airmount® pneumatic isolators, which can support up to 40 tons per unit and typically achieve isolation efficiencies of more than 99%, producing noise levels as quiet as a library just metres from major machinery. These ultimate actuators, distributed nationally by Air Springs Supply Pty Ltd, not only silence intrusive NVH from machinery and plant mounted upon them, but also are also suitable for mounting beneath entire structures and building and electronic facilities to protect them against NVH created by passing rail and road traffic, civil engineering machinery and other ambient NVH.

Firestone Airmounts® have been used for applications as diverse as mounting heavy industrial machinery (including generators, screens and HVAC plant and motors) through to protecting building occupants and their electronic equipment from ambient NVH from adjacent disruptive sources including road and rail traffic and tunnels.

Firestone Airmount isolators are the answer to noise, harshness and vibration

Silent and deadly to disruption – Firestone Airmount™ isolators, above left, are the ultimate answer to noise, harshness and vibration created by industrial infrastructure, conveyors, crushers, motors and civil engineering and construction projects.

Firestone Airmount isolators are the answer to noise, harshness and vibration

“As urban expansion and infrastructure development brings more infrastructure and engineering projects closer together – and industry operates closer than ever to expanding urban communities – there is a rising demand for isolators that can protect against increasing ambient NVH sources such as heavy machinery and nearby rail, road, tunnelling, civil works and construction equipment” says Air Springs Supply National Sales and Marketing Manager Mr James Maslin.

“In many cases, Airmounts can virtually eliminate sources of NVH to which nearby residents and site staff are subjected by heavy industrial equipment, such as vibrating screens, conveyors and rowdy process equipment suspended on clattering metal springs. These outstanding isolators are also effective with bin hoppers, packers, blowers and stamping equipment that pass disruptive impacts into the area surrounding them.”

Airmounts deliver a range of very high isolation efficiencies across a very broad spectrum of needs, while achieving their isolation efficiencies of typically more than 99 per cent. Importantly, they achieve this extreme isolation efficiency across a wide weight range. Their uses can extend from suspension of a 30kg computerised control panel, for example, to total suspension of entire structures, process equipment, tanks and typically noisy industrial plant, such as motors, generators, pumps, crushers and vibrating screen conveyors.

Super-silent Airmounts – either permanently sealed or fed by standard industrial compressor equipment – range from palm-sized to nearly a metre across, individually supporting weights extending from a few dozen kilograms up to more than 40,000kg. They are available in single, double and triple-convoluted types as well as rolling sleeve models in Australia’s leading range of such technology, comprehensive stocks of which are housed in Air Springs Supply’s expanded headquarters in Sydney. They are distributed nationally by a supply and technical advice network built up over more than 40 years.

HVAC equipment and the sonar testing tank
HVAC equipment (left) suspended on the black doughnut-shaped Airmounts. At right the huge sonar testing tank.

Engineered from tough fabric-reinforced rubber, Airmounts are identical in construction to the air springs used in the suspensions of heavy trucks seen every day on the toughest Australian roads. They are also used beneath passenger railway locomotives and rolling stock, where they withstand grime and shock while providing the outstanding ride and isolation properties required.

“The applications in truck and train suspension show just how tough Airmounts really are. Their great virtues are simplicity, durability and sustained high performance,” says Mr Maslin, giving the example of the sonar testing tank suspended on air springs for 15 years. “According to our records, not one of the sonar testing air bags ever needed to be replaced. There was no wear, no unexpected leakage or maintenance, beyond the need to keep the air levels at the correct level, in much the same way you do with your car tyres.”

Air Springs Supply's headquarters
Air Springs Supply’s expanded national headquarters, from which it supplies its national service network with high levels of stocking of product, range and security of supply

Containing no internal moving parts to break or wear, Airmount isolators range upwards in size from the tiny palm-sized 1M1A model, which features a 35mm stroke, minimum (collapsed) height of fewer than 50mm and isolation efficiency of 97.8 per cent at 1500 cycles a minute. At the other end of the scale, huge triple-convoluted Model 348-3 isolators, measuring a metre in diameter, can support nearly 40,000kg and achieve isolation efficiencies of 99.3 per cent.

Large Airmounts have been used to suspend four 16-tonne 2000kV diesel emergency generators only metres above the heads of top-level executives working in the highest floors of a Sydney CBD high rise. Big generators can produce up to 140dB in a confined space, when they are being tested, so the Airmounts had to produce a level of just 35-40dB in the floor immediately below, which was as quiet as a library as a result, says Mr Maslin.

“Using Airmounts to achieve outstanding isolation of building plant is almost as simple as it is possible to be – in essence, Airmounts provide a layer of air in a hugely durable heavy-duty balloon,” says Mr Maslin.

Air Springs Supply is Australia’s national distributor not only of Firestone Airmount® isolators, but also structurally identical Airstroke® actuators and complementary solid rubber-and-fabric Marsh Mellow® isolator springs, which are also used internationally in response to the demands imposed by expanding commercial building and infrastructure as well as workplace health and safety issues.

Marsh Mellow isolatorsanswer to NVH created by production
Marsh Mellow isolators, left, provide another low-maintenance answer to NVH created by production, packing and distribution centres

Firestone’s fabric-reinforced solid rubber Marsh Mellow® isolators provide a complementary low maintenance alternative for quiet isolation of machinery vibration and for general shock absorption throughout industry. Marsh Mellows 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. give consistent performance regardless of changing loads, while offering high lateral stability and compact size. The low natural frequencies of Marsh Mellow springs mean they provide excellent isolation of forced frequencies in the range of 800-1200 cycles per minute (13-20 Hz).

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.

“Their high load capability means fewer springs may be needed in an application, resulting in less overall cost,” said Mr Maslin, adding that Marsh Mellow spring elements can be custom-engineering to meet customers’ specific load and performance requirements.