Air Springs deploys its ultimate stealth fighters against industrial NVH

Mar 1, 2014 in March 2014, News 2014
Airsprings under a giant military sonar testing tank to keep out noise

Dwarfed by the sonar testing tank is an employee of Air Springs Supply Pty Ltd. The air springs used on the project can be seen at his foot level, protruding beneath the tank.

Industrial isolators that so effective they were used in Australia under a giant military sonar testing tank to keep out noise, vibration and harshness (NVH) are now being adopted for more peaceful purposes.

The Firestone Airmounts(™) from Air Springs Supply Pty Ltd suspended the towering sonar test tank containing nearly 500 tonnes of water for more than 15 years at Plessey in Sydney before passing into honourable retirement having continuously achieved an isolation efficiency of 99.7 per cent at 1500 CPM (cycles per minute).

Either permanently inflated or adjusted by standard factory 7 bar (100 psi) compressed air, the Airmounts can be used in applications as diverse as suspending tanks, pressure vessels and liquid containers in which delicate processes are undertaken, through to suspension of process control technology including mixing tanks and computer and production automation equipment. They can also be used to isolate the source of the NVH, suspending compressors, vibrating screens, bin hoppers, packers, blowers and stamping equipment that pass disruptive impacts into the area surrounding them.

Engineered from tough fabric-reinforced rubber, Airmounts are identical in construction to the Airride® air springs used in the suspensions of heavy trucks seen every day on Australian roads and the ubiquitous Airstrike actuators used in applications such as industrial metal stamping presses and conveyors.

Convoluted and rolling sleeve air springs
Convoluted and rolling sleeve air springs, left, and the same robust technology used as actuators to split a dragline, right.

“The great virtues of Airmounts are simplicity, durability and sustained high performance,” says Air Springs Supply National Sales and Marketing Manager Mr James Maslin. “According to our records, not one of the Plessey 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.”

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.

The enormously strong Airmounts have been used to permanently suspend an entire swimming pool in a luxury Sydney hotel so the paying guests downstairs would not be startled by the sounds of people jumping in and frolicking upstairs. They have also 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 the 65-level Governor Phillip Tower. 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 is as quiet as a library.

The whole Plessey project was testimony to the value of keeping things simple, says Mr Maslin. “The equipment being tested in the tank was about as high technology as you could get then, but the method of isolation was as simple as it is possible to be – just a layer of air in a hugely durable heavy duty balloon.

“There are great lessons to be learned today in the cost-effective simplicity of this, for all types of industrial isolation. It applies whether you’re mounting an entire tank, computer room or production automation cell to protect it from surrounding NVH – or, conversely, if you’re cutting off the problem created by a single troublesome unit, such as a metal stamping press, motor, compressor, conveyors, mixers or pumps. Such nuisance sources of NVH can all be simply and permanently isolated to protect their surroundings, or delicate equipment can be isolated to protect it from the nuisances.”

Air Springs Supply is Australia’s national distributor of Firestone Airmount isolators and complementary solid Marsh Mellow(R) springs used in response to the demands imposed by the expanding use of computers and electronic process equipment, and for workplace health and safety reasons (by reducing the levels of noise, vibration and harshness (NVH) to which staff are subjected), says air Springs Supply, which has more than 30 years experience in noise, harshness and vibration (NVH) protection.