TABLE 3A
Vibration Isolator Types and Minimum Static Deflection
(MSD, inches) for 4-8 inch slab on grade and column supported.
Column
Slab on earth
31-40 feet
41-50 feet
Spacing
and 0-30 feet
Equipment
Type
MSD
Type
MSD
Type
MSD
_________
(Note (1))
(Note (1))
(Note (1))
devices.
HR - Thrust restraints
I
- Concrete inertia bases with steel forms.
NM - Neoprene mounts.
NP - Neoprene pads.
R
- Structural steel rail for equipment mounts.
S
- Freestanding spring isolators (floor-mounted equipment).
SV - Freestanding spring isolators (floor-mounted equipment).
SX - Freestanding spring isolators with adjustable cushioned
vertical stops and cushioned horizontal stops
(floor-mounted equipment). Protected spring isolators
SX may be substituted wherever S or SV is specified and
shall meet all requirements.
(2)
Fans
a.
When fan motors are 75 hp or larger, use the deflection
requirements for the next wider column spacing. Except
for building slab on grade a minimum of 2.5 inches
should be used unless larger deflections are
specified in the centrifugal blower table.
b.
Provide sway brace isolators for tubular centrifugal and
axial fans when the fan pressure exceeds 4 inches
water column.
c.
Provide inertia bases for all fans in lieu of
structural steel bases or rails specified above when
the fan pressure exceeds 4 inches water column.
d.
With attaching brackets, suspension spring isolators
bridge between the structure and the thrust-producing
machinery such as high-pressure fan. Both types H and
HR normally provide reaction in tension, while types S,
SV, and SX normally provide reaction in compression.
Thrust restraints are low-cost and effective components
available from manufacturers. Use thrust restraints
to eliminate the need for or reduce the magnitude of
inertia mass when the mass is only used to reduce
the displacement effects of the thrust.
SECTION 15070N
Page 48
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