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))
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.
Unitized assemblies such as chillers with evaporator and condenser, and top
mounted centrifugal compressor or unitized absorption refrigeration
machines, structurally designed with end supports, may be mounted on steel
rails and springs in lieu of steel bases and springs. Where the slab or
deck is less than 100 mm 4 inches thick, provide spring isolation units
with the deflection double that of the vibration isolation schedule, up to
a maximum static deflection of 127 mm 5 inches.
3.1.7.6
Roof and Upper Floor Mounted Machinery
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NOTE: The following table serves only as a
guideline. Delete items that are not applicable.
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SECTION 15070N
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