Vibration Control for Sensitive Equipment

For most applications, knowing the environmental details is not a requirement - vibration isolation systems will allow your equipment to perform in 99% of all ambient shock and vibration environments. 

What is a Vibration Isolation System?

A vibration isolation system is a setting of isolation devices between the upper structure and the foundation of the equipment - this reduces the transmission of vibration energy. The methods of vibration isolation usually include rubber isolation, sliding isolation, hybrid isolation, etc.

  • Rubber Isolation

Rubber bearing, also known as sandwich (or laminated/multi) rubber isolation pad, consists of rubber and steel planes alternately. Rubber bearings are the most mature and widely used isolation devices. In order to meet the damping requirements of the isolation system, lead plug or high damping rubber is adopted in rubber bearings. The rubber bearing is an ideal device not only having the advantages of strong vertical bearing capacity, small horizontal stiffness and large horizontal allowable displacement, but also withstanding the vertical earthquake excitations with certain strength. However, the device has poor tension properties and the effect of vertical isolation is not obvious. In recent years, some multi-dimensional earthquake isolation devices have been proposed based on the ordinary rubber bearing.

  • Sliding Isolation

Sliding isolation relies on sliding support elements installed between the basement and the upper structure. Sliding support elements can reduce transmission of vibration energy effectively due to energy consumption by relative sliding motion and friction. Theoretical and practical studies show that the sliding isolation system has excellent capacity for vibration isolation. The main advantage of the sliding isolation system is that its isolation effect is affected by the frequency of slight ground motion, and resonance phenomenon does not occur easily. At the same time, the construction of the sliding isolation system is simple and the cost is lower. The sliding isolation system has some drawbacks, such as bad restoring capacity due to no lateral stiffness and an instability of the friction coefficient.

  • Hybrid Isolation

The hybrid isolation system is constituted by two or more isolation systems in a certain way (series, parallel, and series-parallel, etc.) for better vibration isolation effect. A hybrid isolation system makes full use of the advantages of different isolation systems and overcomes shortcomings of different components. For example, when the sliding isolation system and the rubber isolation system are connected in parallel, the former has better load-carrying capacity and can decrease the number of rubber bearings, and the latter can provide restoring force. Hybrid isolation systems have complex hysteresis characteristics due to different isolation components, which can lead to difficult analysis.

When is Vibration Control Required?

In new buildings or facilities, onsite vibration surveys are recommended to define the environment. Results that indicate vibration amplitudes at frequencies exceeding the applicable equipment specification criteria require isolation.

If new equipment is being installed into an existing facility where other equipment is performing successfully with vibration isolation, then isolation should be continued and applied for the new equipment. It is substantially more cost- and time-effective to continue a successful practice rather than take a chance and experiment with a new, unknown situation.

If new equipment is being installed in an existing facility where no other equipment is isolated, you may continue the practice of no isolation. However, new equipment designs generally embody more precision and are therefore more sensitive than the older equipment. Isolation is recommended in this situation as a fail-safe solution, especially if time is a critical factor for going online.