Structural vibrations can be disruptive to sensitive equipment in research labs and medical or healthcare facilities. Our solutions protect your equipment from both interior sources, like walking-induced or mechanical vibrations, and environmental sources such as construction activities, bus lines, or train tracks.
A series of vibration tests investigated a surgical microscope that was experiencing excessive vibrations. On multiple occasions, neurosurgical cases had been disrupted due to the vibrations of the microscope. The task was to determine the source(s) of the vibrations and then propose solutions to eliminate or alleviate unwanted vibration levels.
The microscope manufacturer did not provide any specific vibration limits. Generic vibration criteria available in literature, however, stated that the limit should be 1,000 micro-in/s (mips) in root-mean-square (RMS) for the floors of microsurgery rooms. No vibration criteria specific to the eye of the microscope was found in the literature.
First, potential vibration sources were determined. This included human walking, the internal electronics of the microscope itself, the intensity of the air flow inside, and other medical equipment used in the building. Next, accelerometers were installed on the floor and on the microscope at multiple locations, and vibrations were recorded for one of the vibration sources at a time in a controlled manner.
The largest vibration levels measured at the microscope eye were around 21 Hz. Disruptive vibration levels were observed only when the motor of a condenser water pump operated at 1,260 RPM on the mechanical floor.
The pump controller was reprogrammed to skip the frequencies near 21 Hz which eliminated the resonance problem, hence, the vibration issue was solved with minimal cost.
A structural floor design was reviewed and modified to receive two nuclear medicine imaging equipment installations with stringent vibration criteria.
The manufacturer’s vibration criteria were given in both velocity and acceleration units as root-mean-square, 1/3 octave band spectral values. The equipment was most sensitive in the frequency range of 0.5 Hz to 20 Hz, which is well within the footfall excitation range.
A finite element model of the floor was built, and an enhanced vibration analysis was conducted with consideration for slow walking footfall within the imaging rooms, moderate walking footfall along the ghost corridors and fast walking along the main corridors.
The resulting vibration levels at the equipment base were compared against the vibration criteria, and the structural floor framing was revised to meet required minimum vibration levels.
The project included multiple vibration sensitive equipment at various floors including a vivarium floor, several NMRs, MRIs and other sensitive laboratory equipment.
Floor vibration criteria were selected based on equipment manufacturer’s recommendations. In lieu of such guidance, generic vibration criteria were adapted based on published research.
Each floor that expected to receive a vibration sensitive occupancy was modeled in FEM software and subjected to enhanced footfall vibration analysis.
Calculated vibration levels at the sensitive equipment location were compared against the selected vibration criteria and the structural floor framing was optimized to meet the vibration criteria.
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