ORS - Open Restrained Spring Mountings

Sizes ORS25 & ORS50

The ORS mounting has been designed specifically for applications where transmission of low frequency machinery vibration to a building structure must be reduced to avoid physical damage or annoyance to the occupants.

Vertical and lateral restraint is provided to control movement of the mounted equipment when subjected to external forces. This could otherwise be excessive due to the low stiffness springs required to provide isolation of low frequency vibration.

Equipment located at roof level can be successfully mounted on ORS units as any movement caused by high wind loads will be limited. Cooling towers and chillers which contain large volumes of liquid will benefit from installation on ORS mountings because during 'draining down' upward movement is restricted thus avoiding damage to pipework and electrical connections.

Design Features:
  • High strength all steel construction fully zinc plated after fabrication.
  • Colour coded helical steel springs to BS1726 Class B with nominal deflections of 25 mm and 50 mm and up to 50% overload capacity also O/D equal to at least 80% of working height.
  • Vertical and lateral restraints have rubber inserts to avoid metallic contact and adequate radial clearance ensures isolation efficiency is not impaired.
  • Spring located using rubber sleeved pegs and seated on a rubber washer to reduce high frequency transmission.
  • Working height and vertical limiting stops are fully adjustable.
  • 6 mm thick ribbed rubber seating pad supplied as standard.

Typical Applications:

  • Cooling Towers.
  • Chillers.
  • Large Fans.
  • Air Handling Units.

Application Notes:

  • Isolation Efficiency at Typical Machine Speeds:

    MACHINE SPEEDS (rpm) EFFICIENCY %
    25 mm DEFL. 50 mm DEFL.
    300 34.0 75.2
    500 83.3 92.3
    750 93.2 96.7
    1000 96.3 98.2
    1200 97.4 98.7
    1500 98.4 99.2

    The above figures are theoretical values only based on the vertical natural frequency of the sprung system assuming infinitely stiff structural supports.

    The effects of high frequency spring coil resonances on low frequency performance are also ignored.

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ORS - Open Restrained Spring Mountings - All Variants