Bespoke Vibration Isolation Solution for Destoner Machines

Destoner process equipment supported on heavy steel frame with SLFH open spring mounts

It is not every day that we receive an enquiry to isolate a machine that we have are not familiar with. In this case, it was a pair of Destoners. The machines shake material to separate out the larger unwanted stones and other heavy impurities and provide the highest quality product to the following equipment. The shaking motion gives the machines unique movement characteristics that are very substantial in nature. This in turn generated a concerning amount of vibration throughout the building in both the offices and control room on other floors, which was above acceptable level standards.

The Destoners were mounted on a steel frame with feet and fixed into structure

The two machines are situated on the second floor of a steel frame and concrete floor construction within a large open facility. After further testing, the frequency of the structure slab was measured to have resonance between 16 and 18Hz. At an RPM of 1000, the frequency of the destoners was confirmed to be 16.6 Hz. With driving and structural frequencies that are this close together, the vibration was being amplified and transferred through the structure.

The low frequency vibrations were causing problems in the offices and the control room on the fourth level. The vibrations were noted to be above comfortable levels for workers, and at risk of causing damage to the structure. We were approached to work with the acoustic consultants to propose a bespoke solution to mitigate the vibration. The Destoners move back and forth to allow for the functionality of the machine. This movement had to be taken into consideration. They were each mounted on a steel frame with three feet and fixed directly into the structure. The following design is the result of many discussions and iterations to determine the most suitable solution to decouple the machines from the structure and absorb the vibration.

Our recommendation was to install a heavy weight inertia base, however a conventional concrete inertia base was not viable for this project. Therefore, a solid steel frame was designed for each machine. The frames incorporate multiple design aspects such as outriggers for the existing machine feet, multiple heavy steel plates to add significant mass, and height saving spring mount brackets with the option for larger mounts if necessary. The machines could not be lifted a significant amount, hence the frame needed to achieve the lowest lift possible. The solution allowed for a minimal lift of approximately 40mm. Each frame was supplied with separate steel plates to allow for easier manoeuvring and installation. The plates were installed in the frame once in place to add mass, lower the centre of gravity and to aid in the vibration energy absorption. The frames also needed to be very stiff to accept the 900kg machines.

The steel frame was disassembled to allow for easier maneuvering

Fully assembled frame in place and spring mounts adjusted

The dynamic forces produced by the machines were not only in the vertical direction, but horizontal/lateral too. Our SLFH 50mm rated deflection open spring mounts were used. These spring mounts can accept the dynamic forces as the lateral stiffness of the springs is at least 0.8 of the max rated capacity of the spring.

SLFH 50mm rated deflection spring mounts used to absorb vibration (option for large mounts if required).

When the machines were tested before the frames were installed, a low frequency rumble could be felt in your feet (similar to a train passing by). Once the frames were in place and the spring mounts adjusted, it was no longer possible to feel the rumble in your feet. The machine continued to function as intended, and the vibration issue was resolved. This is proof that the solution isolated the vibration very effectively.

Please see a video of the finished results below. Note how the machine is still able to move in the desired manner, however the spring mounts are absorbing the vibration with great efficiency.

If you have a unique vibration issue, we would be happy to design a bespoke solution for you. Please contact our team to discuss your requirements.

Installation photos

See below for further installation photos which include the second frame which was supplied later and in a different colour:

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