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© FANTECH
2016
VIBRATION ISOLATORS
VIBRATION ISOLATORS
I-3
This chart illustrates the theoretical
relationship between isolation efficiency,
disturbing frequency and static deflection
for a simple isolation system on a rigid
foundation. It is also grouped into zones
suggesting isolation efficiency ranges
appropriate to different applications.
To use the chart, determine the lowest
rotational speed of the equipment and
consider this to be the disturbing
frequency. Move vertically to intersect the
diagonal line corresponding to the
percentage isolation required; then move
horizontally left and read the static
deflection required of the mounting.
The table provides a guide to the isolator
type and necessary static deflection for
given values of operating speed and
isolation efficiency. It also suggests
appropriate levels of isolation efficiency
for various operating locations.
To use the table, read the minimum static
deflection directly against machine
disturbing frequency (operating speed)
and required isolation efficiency.
Two static deflection figures appear, one
for basement or on-grade installations;
the other for upper level installations
where some allowance is made for
flexibility of the supporting structure.
Select the appropriate figure.
Note: These figures are to be used as a guide only.
* Double deflection rubber mount required.
Disturbing Frequency, rev/sec (Hz)
Static Deflection, mm
5 6
8 10
20
30
40 50
200
100
60
40
20
10
6
4
2
1
0.6
0.4
0.25
50%
0%
70%
80%
90%
95%
97%
98%
99%
Isolation
efficiency
General
applications
Critical
applications
Non-critical applications
Area of resonance
TO BE AVOIDED
STATIC DEFLECTION GUIDE
ISOLATION EFFICIENCY CHART
Isolation
Efficiency,
80%
Isolation
Efficiency,
90%
Isolation
Efficiency,
95%
Isolation
Efficiency,
98%
Disturbing
Frequency
Ground
Floor
Upper
Floor
Ground
Floor
Upper
Floor
Ground
Floor
Upper
Floor
Ground
Floor
Upper
Floor
rps (Hz)
High Defl.
Springs
5.0
60 90 110 150 -
-
-
-
8.5
-
35 40 50 70 90 -
-
12
-
-
-
-
40 50 100 120
17
-
-
-
-
-
-
50 60
25mm Defl.
Springs
12
11 18 20 25 -
-
-
-
17
-
10 10 15 18 25 -
-
25
-
-
-
-
-
11 20 25
Rubber
Mountings
25
3 5
5 8*
8* -
-
-
33
2 4
4 5
6 8*
-
-
50
1 1.5 1.5 3
4 5
7* 10*
Non-critical
Areas
General
Areas
Critical
Areas
Critical
Areas
Factories,
Workshops,
Garages,
Warehouses,
Laundries,
Basements.
Schools,
Dept. stores,
Super-markets,
Telephone
exchanges,
Hotels.
Multi-storey
buildings,
Offices,
Hospitals -
service area
Churches,
Schools,
Restaurants.
Multi-storey
buildings,
Hospitals -
ward areas,
Broadcasting
studios,
Theatres,
Auditoriums,
Libraries
Isolator Static Deflection, mm