Pre-Compressed Spring Boxes primarily used for vibration isolation of heavy machine foundation and buildings. The VT4625-serie is used where the requirement for resonance frequency is approximately 3,5 Hz. These isolators consist of nested springs inside reinforced steel boxes, and are pre-compressed with a specific load. The advantages of pre-compressed isolators are:

-The springs are pre-compressed to a deflection that equals a certain percentage (normally 80%) of the mass of the final building. During construction the isolator will be “released” once the pre-compression load has been applied, it will thus only deflect when the final 20% of the load is applied.
-Isolators can also be installed after construction or replaced by the use of hydraulic jacks. To achieve this all isolators must be accessible.
-By the use of nested springs the isolators can be fine tuned to a specific stiffness.
-The springs are design to withstand blocking (complete coil contact) without exceeding stress limits and causing plastic deformation.
-To minimize the effect of coil resonance in the springs the contact surfaces in the steel box are covered with an elastomer layer. Springs in material 51CrV4 manufactured according to DIN 2096.

Finishing: shot peening + black powder coating alternatively Delta Magni Seal Welded steel structure in mild steel S355 painted with primer and top coat. Workmanship and tolerances in accordance with ISO 2768-1 Class M.