News Releases

October 2005

We'll pay that one: accountants discover Airmount heaven for offices, shops, factories.

Suspended above the heads of hard-working partners and staff in one of the latest international HQs of accounting firm KPMG, heavy building plant is in constant motion 24 hours a day.

But even the top floor staff closest to the twin HVAC (heating, ventilation and air conditioning) heat exchanger plants don't know it is there, thanks to an air suspension system engineered by Airpro Mechanical Ltd for Stephenson and Turner NZ.

Using the same type of Firestone Airmount" isolators used under beds in operating theatres, Airpro Mechanical has achieved isolation efficiencies of 97 and 98 per cent respectively under the 3100kg Carrier 30GX102 and 4726kg Carrier 30GX182 HVAC units.

"Heat exchangers never sleep. They are integral to the HVAC systems of all new office, shop and factory buildings and work hardest when people are present. They are up there industriously pumping and compressing liquid and gas 24 hours a day, if high-pressure or multi-shift businesses need that," said Mr Darrell Whitehead, Project Manager for the HVAC installation designed to achieve optimum noise, vibration and harshness (NVH) isolation in the new KPMG six-level headquarters at Viaduct Harbour Way in Auckland.

Using simple and cost-efficient Airmounts available throughout Australia and New Zealand, the installation addressed an issue facing many owners and operators of buildings containing high technology equipment: how to ensure ambient noise, harshness and vibration do not disrupt delicate electrical, electronic, computer and telecommunications installations (or the staff operating them).

"Rather than using metal springs or solid rubber suspensions, the specifiers for the installation were seeking the ultimate isolation available through Airmounts. In essence, these are ruggedly engineered rubber and fabric balloons so effective they are used beneath beds on operating theatres and in weapons guidance systems."

The Airmounts , distributed in Australia by Air Springs Supply and in New Zealand by Bridgestone, were used in different ways for each Carrier HVAC unit:

• 30GX102: Four mounting points were selected to cope with quite substantial variations in load encountered with the lighter unit. Single-convolute Model 116-1 Airmounts were chosen, each doughnut-shaped unit being capable of supporting more than 1100kg at 7 bar with a natural frequency of 2.26HZ.
  
  
• 30GX182: Eight mounting points were used for the heavier unit, with two different model Airstrokes used to cope with the variations in load. In five places a new model 160 Airmount was used, while the 116-1 was used in the three remaining heaviest loading points.

Bridgestone Product Manager Mr Jim Hine says isolation efficiency of the installation was greatly assisted by the Airmount isolators having a variable spring rate.

The variable spring rate is due to air spring geometry, internal air pressure, and changing effective area. The effect of this variable spring rate is that an Airmount isolator can perform with constant efficiency through a wide range of loads. It also means that a single style of air spring can often be used at multiple mounting points of machinery or systems that are unevenly loaded - without sacrificing this efficiency at any of the mounting points.

"Traditional constant spring rate isolators such as coil springs do not have this ability to operate with constant efficiency through a wide range of loads. In fact, a coil spring designed to operate at a given height loses isolation efficiency with even very small decreases in the supported load."

"Given that a lower system natural frequency provides superior isolation and that less variability in natural frequency provides more constant isolation, the Airmount installation selected for KPMG has considerable benefits."

Permanently inflated for ongoing low-mainteance operation, Airmounts they can be pumped up just like car tyres of vehicle air suspensions if they ever require such attention.

Their reliability is assured by a construction that is identical to that of the air springs used in the supensions of heavy trucks, trains and advanced 4wd and limousines.

Airmounts deliver a range of very high isolation efficiencies across a very broad spectrum of needs, typically achieving isolation efficiencies of more than 99 per cent. Importantly, they achieve this extreme performance with reliability across a wide weight range. Their uses can extend from suspension of a 30kg computerised control panel, for example, to total suspension of the entire tonnage of common industrial plant such as motors, crushers and vibrating screen conveyors.

Airmounts 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.

For more information in New Zealand, Jim Hine Product Manager, Industrial Products at Bridgestone NZ Ltd can be contacted at Ph:06 355 0928, Fax:06 3577198, Mobile: 021 963979, email: jim.hine@bridgestone.co.nz.

For more information about Air Springs Supply's Australian distribution and technical support network, please contact Air Springs Supply Pty Ltd, 137 Bowden St, Meadowbank, Sydney 2114, ph (02) 9807 4077, fax (02) 9807 6979, sales@airsprings.com.au

Darrell Whitehead can be contacted at Airpro Mechanical Ltd, 5 Winston Place, Henderson, Auckland, New Zealand, ph (09)836 4441, fax (09) 837 3020, mob 029 283 5089, darrell@airpro.co.nz.