Because so much bulk handling, materials processing, mining and quarrying equipment is prone to high levels of damaging impact vibration and noise, plant engineers are giving increasing attention to OHS and reliability issues.
This is particularly the case with production components that are a vital link in the production chain, such as conveyors, vibrating screens associated with them and mixers, motors, compressors, crushers, blowers and bins that abound in the production line.
Not only can excessive vibration cause noise and component failures, but also it can disrupt sensitive computers and electronic equipment now being widely adopted by the industry to automate production, says isolation and actuation specialist Mr James Maslin of Air Springs Supply Pty Ltd.
One solution to NVH (noise, harshness vibration) problems is contained in expanded ranges of compact and highly efficient Marsh Mellow® isolators that are being introduced by Air Springs Supply to eliminate damage and production interruptions. Manufactured by Firestone, Marsh Mellow® springs are engineered for immense strength and longevity with a hollow centres surrounded by a solid rubber core and fabric ply reinforced body to deliver constant vibration isolation with changing loads, says Mr Maslin.
Their unique construction delivers low natural spring frequencies to provide excellent isolation of forced frequencies in the range of 13-20-HZ (800-1200 cycles a minute). This outstanding performance - and a maximum load range now extending from 1.4 kN up to 88 kN (on special order) - makes them particularly suitable for vibration isolation applications beneath equipment commonly used by the materials handling, mining and quarrying industries.
Marsh Mellows also make ideal shock absorbers for conveyor and primary product and other materials handling applications, particularly in situations where their corrosion-resistant durability means they will survive damp and corrosive environments in which standard coil springs may fail, says Mr Maslin, who is National Sales and Marketing Manager for Air Springs Supply.
"Marsh Mellows have no moving parts and require no maintenance or lubrication, so they are ideal of applications in grimy and demanding environments. "And because they reduce structurally transmitted noise caused by vibration, Marsh Mellows have considerable OHS and comfort benefits by being quiet in operation - unlike coil springs, which often suffer coil chatter and readily transmit high frequency structural noise.
“Their terrifically rugged rubber construction eliminates the problem with coil springs of cracking to allow fragments of metal to damage equipment and cause costly downtime. Additionally, Marsh Mellow springs exhibit exceptionally high overload characteristics and offer some support even during failure.”
Other advantages of Marsh Mellows include:
- High load carrying capacity because of their superior deflection capabilities and the load carrying influences of the fabric reinforcement. This means they can carry a greater load than an all-rubber part of the same modulus and dimensions at a superior natural frequency.
- Increased stability at higher percentages of compression. As height compresses, the fabric-reinforced rubber plies pantograph and the diameter grows. This supports the rubber core laterally even in an emergency at 30-40 per cent compression.
- Lower cost. Marsh Mellow springs’ higher load capability means fewer springs may be needed in an application, resulting in less overall cost.
The spring's components (rubber, bias plies, size of centre) are combined in different ways to meet specific load and performance requirements. This gives them great flexibility and precision, says Mr Maslin, whose Air Springs engineering team's experience spans several hundred applications of both solid and hollow (bellows-type) air springs throughout Australia over more than 30 years. (Details of applications can be researched on Air Springs' website, www.airsprings.com.au.)
Naturally different types of springs have different performance characteristics suited to particular tasks. These should always be discussed with suppliers having wide experience in the particular area of application being considered.