What factors compromise a vibration isolator’s performance?

Inadequate Support

Yes, this VertiMount is not vertical and the sheet steel floor behind it is sloping upwards! As there is inadequate structural support, the base on which the VertiMount is ‘supported’ is softer than the vibration isolator, so the vibrational energy is transmitted to the softest part of the system (the base) rather than being absorbed by the vibration isolator.

This was a troubleshooting project for Acoustical Control Engineers, where the VertiMounts purchased from us were initially unable to work properly due to the site conditions, until we were asked to visit the site and rectify the problem.

Uneven supporting structure

If the vibration isolators are not at the same height the load will not be properly distributed resulting in some being overloaded or underloaded. This can be overcome by using height adjustable vibration isolators, which should be used to accommodate the inevitable differences in height that occur with many installations.

Unsuitable/incorrectly selected isolators

Good vibration isolators may be unsuitable for their proposed use for many reasons, including:

  • Incorrect stiffness/deflection
  • Unsuitable fixing type
  • Lack of movement restraint
  • Unsuitable material/finish

Variation in load

If the load imposed on a vibration isolator differs significantly from that for which it was selected, this is likely to overload or underload the vibration isolator.

Dynamic stiffness

For relatively undamped materials such as spring steel, its static and dynamic stiffness are similar. For other materials such as cork, rubber or neoprene, there can be a significant difference. This reduces the actual vibration isolation achieved, compared to that expected, based on the vibration isolator’s static deflection.

Unstable springs

Springs should deflect along their longitudinal axis. However, some springs are laterally unstable (this can depend on the characteristics of the vibration isolator) and at a certain load or deflection the spring can buckle.