Prevention beats cure when eliminating noise, harshness and vibration from industrial and commercial buildings

Feb 1, 2015 in March 2015, News 2015
Airstroke Actuators & Airmount Isolators

Simple, silent and soothing – a broad variety of commercial and industrial plant can be mounted on Firestone Airmount® isolators, left. Uses extend from vibrating HVAC units and generators through to motors, shakers, crushers, compressors and computerised and telecommunications technology.

One of the most direct ways to cure noise, vibration and harshness (NVH) issues in commercial and industrial buildings is to cut the problem off at its source.

Before investing in extensive sound-deadening materials – or requiring staff to wear personal protection equipment in affected areas – facility owners and managers should look at relatively inexpensive ways to isolate the source of the trouble with simple inflatable or solid rubber mounts.

These inflatable Airmount® Air Springs and complementary solid engineered fabric and rubber Marsh Mellow™ springs are already proven globally in applications ranging from extreme isolation of operating tables in hospitals and computer and electronics installations, through to outstandingly effective dampening of the din and shaking created by huge and heavy shakers, crushers, metal stamping, compressors and generators in Industrial plant.

Isolation efficiencies of up to 99 per cent have also been attained beneath common sources of NVH in buildings, ranging from emergency electricity generators and HVAC plants in high-rise buildings, through to, in one Australian instance, a swimming pool in an exclusive hotel. The entire pool was mounted on air springs to ensure its glassy surface is isolated  from disruptive trains rumbling by in nearby tunnels and other heavy vehicle traffic (and also to ensure that the sounds of diving and aquatic carvorting don’t transmit through to the hotel rooms below, often costing more than $1000 a day).

Generator mounted on Airmount air springs

Generator mounted on Airmount air springs (bottom, in silver mountings)

“It just makes sense to look at prevention before cure – preventing noise happening, and preventing vibration spreading,” says James Maslin, National Marketing Manager for isolation and actuation specialist Air Springs Supply Pty Ltd, which is the long established and highly experienced national distributor of Firestone industrial products. (www.airsprings.com.au).

The NVH problem is almost universal throughout the design, engineering and construction of industrial and commercial buildings: It is not only a workplace hazard to the human occupants of buildings, disrupting employee comfort and safety (the number of claims for industrial deafness has doubled since the start of the decade).  But also it can, where the problem is really bad, disturb the daily function of instruments and computerised building systems, including automation systems and process control and materials handling systems.

“Years ago not many building specifiers and their clients gave a second thought to environmental NVH – it was just typical background noise in just about every industrial plant or commercial building,” says Mr Maslin.

“All that has changed radically over the last decade or so. Not only have State governments become aware of the health issues involved, but also a huge amount of electronic equipment has gone into industrial and commercial buildings as companies strive for efficiency and automation.

“Instead of being an afterthought, a quieter environment free of vibration and shock has become a necessity in many buildings which are heavily dependent on electronic equipment and computerised production,” said Mr Maslin.

Air Springs has an extensive range of inflatable Airmount isolators, responding to designer and industry needs for simple, reliable and highly efficient ways to tackle NVH.

Weights up to 40,000kg a unit

Airmounts are available in an expanded range of sizes which can individually support weights extending from under 100kg up to more than 40,000kg. Models range from palm-sized to nearly a metre across, which have been used as actuators to lift mining draglines for maintenance.

“One of the beauties of isolators as simple as the Airmounts is that they contain no internal moving parts to wear, or metal springs or surfaces to corrode or break,” says Mr Maslin. “They are extraordinarily tough, being manufactured by Firestone in exactly the same way as the Air Springs used in the suspensions of luxury coaches, heavy trucks, and express trains such as NSW’s XPTs and France’s TGVs.”

Air Springs Supply’s single, double and triple-convoluted Airmount isolators – as well as rolling sleeve models and complementary Marsh Mellow (R) isolators – have been refined to achieve isolation efficiencies exceeding 99 per cent in some instances.

“In essence, Airmounts highly engineered balloons – balloons which are carefully constructed and permanently installed to deliver a range of performance demanded across a very broad spectrum of needs. This can extend from suspension of  a 30kg computerised control panel,  for example, to total suspension of the entire 100-tonne bulk of a huge motor, crusher,  press or production line or, in the case of a commercial building, entire generators and HVAC plants.

Examples of uses   

Recent examples of Airmount applications include:

  1. Simple mounting of a top-heavy control box on a mezzanine floor of a manufacturing plant (the same techniques can be used for mounting of racks and other types of cabinets). The control box was mounted on high-efficiency, rolling sleeve Airmounts, mounted vertically beneath the box and inflated individually via reinflation valves. To counteract any horizontal instability, smaller (1M1A) Airmounts were used horizontally to brace the box at the sides and rear (the Airmount bracing also minimising transmission of vibration from surrounding machinery).
  2. Mounting of an entire sub-floor for a computer room – a typical application in buildings which have a self-contained computer room or control room surrounded by vibrating or stamping equipment. In this case, the sub-floor was mounted on larger Airmounts to provide the major shock absorption, while smaller Airmounts (again, 1M1As) were used to provide wall isolation and stability (where Airmounts are used horizontally to provide stability for a structure with a suspended floor, they can, for mounting convenience, be applied at heights up to, and including, the top of the wall. The isolation provided protection against heavy processing equipment, including cutting and debarking machinery, being used at a timber processing plant.

    Airmounts/Airide units used to suspend HVAC unit graphic-airmount

    Single convoluted Airmounts/Airide units (centre, with graphic right) used to suspend HVAC unit

  3. HVAC units at the headquarters of an international accounting firm. Suspended above the heads of hard-working partners and staff in the national HQ of the international accounting firm, heavy building plant is in constant motion 24 hours a day. But even the top floor staff closest to the twin heat exchanger plants don’t know it is there, thanks to an Airmount air suspension system has achieved isolation efficiencies of 97 and 98 per cent respectively under the 3100kg 4726kg Carrier HVAC units.
  4. Built-in protection against disruption and discomfort in one of Australasia’s telecommunications headquarters. The Firestone Airmount isolators were used beneath two units of Carrier chiller units in the HVAC equipment in the plant room atop the organisation’s national headquarters in Auckland New Zealand. The total assembly, weighing 12,000 kg including the chillers, was suspended on a total of four model 21-2 double-convoluted Airmounts mounted on posts at chest height (as seen top right below) to give a lower centre of gravity and enhanced stability for the installation, which operates on a floor just metres above the heads of people working below.double-airmounts Double convoluted Airmount Graphic


    Double convoluted Airmounts, left, mounted at chest height for additional stability, right

  5. Mounting of disruptive industrial processing equipment (such as the shaker, above) to curtail metal spring noise and to isolate vibration from surrounding workplaces and from nearby computer and/or automation equipment.
    Mounting of disruptive industrial processing equipment
  6. Mounting of an electron microscope in a research facility. Because the microscope not only had to be isolated from surrounding vibration, but also maintained in a perfectly level configuration, a three-point levelling system was specified, incorporating a built-in compressor and three-point levelling system (Three-point systems, with each point feeding clusters of air springs, are recommended in preference to multi-point systems. The use of three points prevents excessive “hunting” by levelling valves as they allocate air pressure to individual Airmounts to ensure the load is maintained in a level configuration).

Simple Mounting

Airmounts are typically mounted in the four following ways, each of which involves the fabrication of metal brackets to connect the air spring and its load. The brackets are usually fixed to bolts ramset into floors or walls, and the Airmounts are bolted onto them by way of studs protruding from the air spring’s metal heads. The Airmounts, in turn, are bolted to the equipment which they are isolating.

  1. The simplest way is to mount the load to be isolated on sealed air springs equipped with a valve (just like a tyre valve). Airmounts used this way are inflated individually and each must be checked periodically, as part of a routine maintenance programme, to ensure they retain the correct operating pressure and, hence, isolation efficiency.
  2. Alternatively, individually inflated Airmounts can be linked to a compressed air tank via a regulating valve which ensures they maintain a pre-set pressure by drawing on the compressed air as any leakage occurs (leakage is a very gradual process – similar to the deflation of a car tyre)
  3. More sophisticated and maintenance-free is a three-point regulated system, using which Airmounts are connected directly to a typical industrial (100psi – 7 Bar) compressor via pressure regulating valves. This eliminates the need for periodic inspections. The Airmounts involved are connected in clusters with the load supported by three regulators to ensure even distribution of load.
  4. The most sophisticated of the mounting systems in general use is a three-point levelled system connected to a compressor, as above, but also incorporating levelling valves, actuated by sensors, to ensure the load is maintained precisely in the desired position.

And an alternative: Marsh Mellows®

Firestone Marsh Mellow® tubular isolators

Rugged, solid Firestone Marsh Mellow® tubular isolators, which are suitable for low maintenance heavy plant

A product which is complementary to Airmounts (and also engineered by Firestone) is MarshMellow® springs, are tubular isolators which comprise a solid rubber core surrounded by bias layers of fabric engineered to the needs of particular applications.

Simpler again than Airmounts – they don’t even need to be inflated – Marsh Mellows are one of the latest isolation techniques to achieve international acceptance.

Marsh Mellow springs are a simple, robust and effective means of solving industrial shock and vibration isolation problems that can be encountered when using using metal spring isolation, including noise, short spring life, corrosion, abrasion, bottoming-out and high maintenance costs with lengthy downtime.

Information about the full range of Airmount isolators can be obtained through the website of Air Springs Supply Pty Ltd, www.airsprings.com.au which is one of Australia’s most comprehensive guides to pneumatic actuation, isolation and suspension.