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Vibration-sensitive facilities — proving the site and the structure are still enough before the tools arrive
Some equipment does not tolerate a floor that moves. Lithography and wafer inspection tools, electron microscopes, MRI scanners, coordinate measuring machines and metrology instruments are specified to operate at vibration levels many times below what a person can feel, on the VC criteria measured in micrometres per second. As Thailand pushes semiconductor and advanced electronics manufacturing in the EEC and the north, the question that comes before the design is whether the plot is still enough: how much vibration the road, the railway, the neighbouring plant and the building's own services deliver to the tool floor, and what structure will meet the criterion the equipment maker has set. These answers are cheapest before the land is bought and most expensive after the slab is poured.
When to call us
- Site selection for a semiconductor, electronics or laboratory facility, where several plots have to be compared with real data
- Floor and foundation design for tool areas, which needs the site vibration environment as an input
- Installation of an MRI, an electron microscope or metrology equipment in an existing building, where the manufacturer requires the vibration level to be confirmed before delivery
- Equipment that gives unstable results or blurred images, where it must be established whether the cause is the floor, the building services or the machine itself
- Construction, piling or a new road next to an operating fab or hospital, which must be monitored so that production or diagnosis is not affected
- Acceptance of a building from the contractor against the VC criterion in the contract
How we help
- A site vibration survey with multichannel high-sensitivity instruments across the 1–80 Hz range the VC criteria define, by day, by night and at the peak traffic periods of any adjacent road or railway.
- Separation of sources — traffic, rail, neighbouring plant, building services and footfall — by simultaneous measurement at several positions and spectral analysis.
- Reporting as one-third-octave spectra against the VC-A to VC-E lines and each equipment maker's own criterion, not as a single figure.
- Design input to the structural engineer for slabs, foundations and the isolation of tool areas from the rest of the building, and a review of the design before construction.
- Assessment of the building's own services — chillers, pumps, air handlers — for the grade of isolation and the positions needed to keep them out of the tool floor.
- Post-construction, pre-installation measurement to confirm the tool floor meets the maker's criterion, reported in the form the maker accepts.
- Continuous monitoring during construction next door, with alert and stop-work levels and real-time alerts to site supervision and production.
- Human-exposure assessment to ISO 2631 and structural assessment to DIN 4150-3 alongside, where the building combines offices and tool areas.
What you get
- A site vibration survey report with spectra against the VC criteria under every condition, and source identification
- A vibration specification for the designers and contractor, with target levels at the tool floor and the acceptance method
- Isolation recommendations for the building services, ordered by effect per baht
- A pre-installation measurement report in the equipment maker's format
- Construction monitoring reports with the event log and the actions taken
Standards applied
VC criteria (VC-A to VC-E, one-third-octave rms velocity 1–80 Hz) · ISO 2631-1/-2 (human exposure) · DIN 4150-3 and BS 7385-2 (structural) · ISO 10816 / ISO 20816 (machinery) · equipment makers' installation criteria as specified
FAQ
What are the VC criteria?
A set of internationally used limit lines for tool floors, expressed as rms vibration velocity in one-third-octave bands from 1 to 80 Hz. VC-A is 50 micrometres per second, and each step halves the limit down to VC-E at 3 micrometres per second. The equipment maker states which line applies to each tool, and all of them are far below what a person can feel.
Why survey before buying the land?
Because a site's baseline vibration comes from things that cannot be changed — the road, the railway, the neighbouring plant. A plot that fails at the outset needs expensive special structure to compensate, and some plots cannot be compensated at all. Comparing candidate plots with real data is the highest-return spend in the project.
When is a measurement representative?
It must cover peak traffic, train or truck passages, the quietest part of the night, and the neighbouring plant's operating periods. So we measure continuously for at least 24 hours at several positions rather than taking one short reading.
How much do the building's own services matter?
Once the site is chosen they are usually the largest remaining source. Chillers, pumps and air handlers on the same structure as the tool area can exceed the VC criterion without anyone feeling it. Their positions and isolation must be fixed at the design stage.
What does the equipment maker want to see?
Typically one-third-octave spectra of vibration velocity at the installation position, in three axes, with the building in normal operation, compared with the maker's stated line. We report in that form and adapt to each maker's template.
Construction is starting next to our operating fab. What do we do?
Install continuous monitoring on the tool floor and at the boundary, agree alert and stop-work levels with the contractor before work begins, and alert in real time so that piling can be stopped before a production lot is lost. See our piling-monitoring case study.
Our instrument gives unstable results. How do we know it is the floor?
By measuring simultaneously on the floor, on the machine base and on the machine, and comparing the spectra with the periods when results go wrong. Frequencies that match the building services or traffic point to the floor; frequencies that match the machine's own components point to the machine. That distinction decides who pays.
What does a hospital installing an MRI need?
The MRI maker sets a vibration criterion and usually requires a survey before approving the installation position. We survey the proposed room, assess the building services and nearby traffic, and report in the maker's form before structural work begins.