Motor-driven equipment vibrates during operation. The method of reducing vibration transmission to other sensitive areas is to separate the equipment from the supporting structure by vibration isolators. Generally, there are two types of vibration isolators, metal springs and isolation pads that are widely used for vibration isolation.
i) Metal Springs
Springs are particularly applicable where heavy equipment is to be isolated or where the required static deflections exceed 12.5mm. Static deflection of a spring is a value specified by the suppliers. Selection of appropriate springs is important as this may result in poor isolation efficiency or even amplification of vibration, especially in the case that the vibration frequency is extremely low.
The most important feature of spring mounts is to provide good isolation due to its ability of withstanding relatively large static deflection. Metal springs however have the disadvantage that at very high frequencies vibration can travel along the spring into the adhered structure. This is normally overcome by incorporating a neoprene pad in the spring assembly so that there is no metal-to-metal contact. Most commercially available springs contain such a pad as a standard feature. Figure 52 shows some common spring mountings.
Table 17 provides the minimum static deflection required for achieving particular isolation efficiency at different equipment speeds.
ii) Isolation Pads
Isolation pads can be made of rubber, neoprene, glass fibre or combination of them. They are relatively cheap, easy for installation and replacement, and have the advantage of good high-frequencies isolation. However, attention should be given to the life of the isolation pads as some of them can be damaged by overload or low temperature. Figure 53 shows some common isolation pads.