One of the challenges of servicing and replacing vibration isolators essential to industrial processes is that they can be located in confined and inaccessible spaces that pose OH&S issues and delays to production processes as a result.
Without fully functioning isolators – performing accurately to their original design specifications – machinery used in mineral processing, food and beverage processing, and materials handling can ultimately suffer long-term damage from failing springs.
"This can compound damage to production schedules, as maintenance staff work carefully within often confined spaces to replace beds of springs required to restart processes," says actuation, isolation, and suspension specialist Vinh Lam.
Where metal springs pose such issues, a compact and easily installed solution is being offered by Air Springs Supply Pty Ltd to address the problem of grit, powders, and damp environments wearing out metal springs over time – breaking down their isolation capacity that is essential to the reliability of crushers, grinders, conveyors, shakers, sorters, and vibrating screens and bins.
Warning bells
Air Springs Supply is Australian distributor for robustly engineered rubber-and-fabric Marsh Mellow™ springs manufactured by Firestone, which are in use worldwide in applications such as shaker screens, crushing equipment, vibrating bins, conveyors, and other equipment subject to vibration.
"Warning bells should ring for operations staff when individual metal springs start to break in isolator sets, because often springs installed as a set will break down as a set, within six months or so of each other, as they collectively exceed their service life."
This means that many old metal coil spring sets that came with OEM machinery will need to be replaced completely, preferably with isolators that are easy to fit, don't break, tolerate wet and aggressive environments and are compact and simple to replace," says Vinh, who is Technical Product Manager at Air Springs Supply Pty Ltd, distributor of Firestone Industrial Products.
Marsh Mellows do not require upkeep and don't need lubrication that can attract powders and grit to metal springs. They won't set (suffer permanent compression) like metal springs, which reduces efficiency and performance. Because of their belted rubber and fabric layer construction, they cannot crack or fragment catastrophically to bring entire processes to a halt. Plus, they are easy to install and replace.
"While no one spring design is ideal for all applications, Marsh Mellows offer considerable advantages over both conventional coils and solid rubber springs for many tasks, says Vinh, noting that both Marsh Mellows and Firestone's inflatable Airmount™ isolators and Airstroke™ actuators can compactly replace many types of isolators and actuators currently in use.
Marsh Mellows and complementary Firestone Airmount™ and Airstroke™ isolators and actuators are used worldwide in vibrating equipment. They can easily cross and substitute for Goodyear, Conti, Rexroth, Norgren and similar components incorporated globally by OEM manufacturers. Both types of rubber spring offer the OHS advantage of silent operation, while also providing very high isolation efficiencies, says Vinh.
The size of Marsh Mellows deployed will depend on the particular application, but generally fewer and smaller Marsh Mellows are required than conventional springs, reducing installation time and cost.
Marsh Mellows operate silently with more spring travel and greater load capacities than conventional coil springs, while outperforming all-rubber alternatives in many areas, such as greater load capacity and more compact size for comparable tasks.
The cylindrical Marsh Mellow springs 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. The spring's components (rubber, bias plies, size of centre) are combined in different ways to meet specific load and performance requirements (such as those of crushing and screening equipment).
This gives them great flexibility and precision, says Vinh, whose experience spans applications of both solid and hollow (bellows-type) air springs throughout Australia over more than 20 years.
One of the big advantages of Marsh Mellows is that they offer constant vibration isolation with changing loads. Their variable spring rate allows for a nearly constant natural frequency under the impact of such loads, says Vinh.
And because of the Marsh Mellows' greater deflection capabilities – and the load-carrying influences of the fabric reinforcement – it can carry a greater load when compared to a solid rubber part of the same modulus and dimensions.
Their ability to maintain a cylindrical shape while supporting greater loads means a smaller overall size can be used compared with an all-rubber springs of identical load capacity. This is important when considering an application with a small design envelope.
Marsh Mellow springs' high load capability also means fewer springs may be needed in an application, resulting in less overall cost.
Also, the lateral spring rate of a Marsh Mellow spring can be less than the vertical spring rate, resulting in a lower lateral natural frequency. The low natural frequencies mean Marsh Mellow springs provide excellent isolation of forced frequencies in the range of 800-1200 cycles per minute (13-20 Hz).
"In many cases, Marsh Mellows are the ideal substitute for OEM actuators and isolators that have outlined their usefulness. 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," said Vinh.
About us:
About Air Springs Supply Air Springs Supply Pty Ltd is Australia's leading supplier of air springs and associated pneumatic technology for industrial actuation and isolation and air suspension for heavy truck, bus, rail and hard-working light-to-medium vehicle applications.
Air Spirngs offers cost-efficient and reliable solutions for actuation and isolation systems employed in industries extending from construction, conveying and food and beverage and primary product processing through to mining and energy, metalworking, manufacturing, materials handling, NVH removal, production automation, safety, and testing applications.
