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Tuned Mass Dampers Using Wire Rope Isolators


Tall, steel, chimney stacks installed in windy regions are prone to violent vibrations that could lead to stack failure. The source of this vibration is due to the phenomenon called vortex shedding. Controlling the amplitude of vortex-induced vibrations is crucial to avoid catastrophic failure of the chimney and increase its lifespan. One widely accepted design for doing so is the use of hydraulic dampers installed between the top of the chimney and a steel ring. While this is an effective design at limiting a chimney’s vibration, it often requires maintenance, and its performance could vary based on temperature. A less known way of controlling chimney vibration is through the use of wire rope isolators (WRIs). When tuned to the proper stiffness and damping, WRIs can be very effective at controlling the chimney’s vibration. In addition, WRI-tuned mass dampers (TMDs) offer further advantages such as their maintenance free construction, temperature-independent performance, and extremely long lifetime. Our purpose here is to present a case study where the Socitec Group provided a WRI based TMD for a chimney stack. The simulation results show that just like hydraulic dampers, WRI TMDs can be very effective at controlling a chimney’s vibration.
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Using Wire Rope Isolators for Seismic Protection


Wire rope isolators offer distinct advantages over other installation methods for sensitive equipment in seismically active regions. The linked publication gives an overview of the general problem of protecting equipment from seismic events, and also details two case studies where wire rope isolators were applied.   Click Here to View Published Article
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reading a precision machinists level

Annual Preventative Maintenance Checklist for Press Installations


Check the level of your press. The level condition of the press should be checked annually because the floor/foundation supporting a press can shift and settle under the weight of the press. Changes in the operation or plant layout can also affect the settling of the foundation and require releveling of the press. If the press is installed on Vibro/Dynamics isolators, the releveling process is very fast, easy, and precise. For thorough information on the leveling process, contact Vibro/Dynamics to request a copy of the technical bulletin, M/L 647 – How to Level a Press Using a Precision Machinist’s Level. Clean debris from around the isolators. When slugs and other debris build up around the isolators, it’s possible for a solid connection to form between the isolator housing and the floor or pit wall, which could in effect “short-circuit” the isolators and reduce their performance. Check the isolator locknuts. The locknuts threaded on the isolator leveling screws should be securely fastened to the machine feet. If you need to adjust them, use a wrench to hold the head of the leveling screw while tightening the locknut. Check for any solid connections between the press and the foundation or building structure. Flexible connections are recommended for all plumbing and electrical conduit. Floor plates, walkways, railings, feeds, rolling bolster rails, etc…should not be attached to both the machine and the floor, foundation, or building structure. Hard connections will reduce isolation effectiveness. Inspect the machine feet and legs. Repair any cracks or damage. Check the condition of the isolator resilient members. Bulging of the resilient members is normal and it’s okay if they’re dirty. A problem may exist if there are rips, tears, or signs of the resilient member deteriorating. If you are concerned about their condition, send us a photo and we’ll analyze the situation. If there are any problems, individual isolator components can be replaced. Vibro/Dynamics also offers a reconditioning service for isolators, which brings the isolators into a like-new condition for less money than if you were to purchase new ones. To view all of Vibro/Dynamics’ installation instructions, please visit our documents page.
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Large Viscous Damped Spring Isolator

When Should I Consider Installing my Press on Spring Isolators?


For a majority of stamping press installations, Vibro/Dynamics elastomer isolators provide the best combination of vibration control, machine stability, ease of installation, and precision leveling. However, there are certain situations when installing a press on spring-type isolators would be a good or even the best choice. This article is intended to help you determine whether your press installation might be a good candidate for spring isolators. What’s the difference? – It’s important to understand the basic difference in performance between the spring and elastomer-type isolators. In a nutshell, while elastomer isolators provide excellent vibration control, spring-type isolators provide even greater vibration reduction. The trade-off is that spring isolators allow greater press motion, thus elastomer isolators are typically used to provide stability where maximum vibration reduction is not required. There is also often a difference in the size of isolator used for the same load. Since elastomer isolators generally support a larger load in a smaller area, spring isolators are typically physically larger for the same size press. Finally, grout plates are typically recommended under spring isolators, while elastomer isolators are installed directly on the concrete surface. Environmental Issues – Whenever a press is installed in an environment where maximum vibration reduction is important due to an existing or potential vibration problem, then the press should be analyzed to see if it can be installed on spring isolators. Examples include presses installed near residential or business neighbors, near sensitive machinery, or near office spaces. In most of these cases, installing a press on spring isolators allows the press to run in closer proximity to both people and other machines so it doesn’t have to be relocated or limited in its production. Press Design and Operation – The design of the press and the operation being run also play a key part in determining whether spring isolators are a good option. Large (400-ton capacity and larger) presses with counter-rotating eccentric drives are often good candidates. These larger presses (and their surroundings) generally benefit from the additional vibration control, yet are balanced enough not to move too much on spring isolators.  On the other end of the spectrum, dynamically-balanced, high-speed presses (greater than 300 SPM) hum along nicely on spring isolators and you should definitely consider them if you have such an installation. Personal Preference – Some metal stampers simply prefer to install presses on spring isolators because they have done so before or want the maximum amount of vibration reduction and are comfortable with a few millimeters of press movement. The use of coil spring isolators is also more common outside the U.S. These users have come to expect the level of vibration isolation provided by spring isolators as well as the press motion they allow. Whatever type of press you have, Vibro/Dynamics will analyze your specific installation and offer the options which are best for your press, whether that be elastomer and/or spring isolators.
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