IM 178 / Page 31
Adjustment of Seismic Restraints
When a seismic restraint is properly adjusted and the fan
is operating normally, the neoprene center bumper will be
centered within the 2" (51 mm) diameter hole in the restrainer
angle, and the restrainer angle will be centered vertically
between the flanges of the neoprene center bumper. This
results in .25" (6 mm) clearance in all directions. When the fan
is turned off the restrainer angle may come to rest on the
neoprene center bumper.
The seismic restraint is adjustable in all directions. Verti-
cal slots in the restrainer angle and horizontal slots in the
blower base allow the restrainer angle to be adjusted up and
down and back and forth. The neoprene center bumper is
mounted on a slotted hole allowing its adjustment in and out.
Removing the neoprene center bumper bolt allows re-
moval, disassembly, and replacement of the neoprene com-
ponents.
Spring mounted supply air and return air fans may be ordered
with factory installed seismic restraints. The system consists
of four snubbers, one located next to each spring isolator.
These snubbers will allow free movement of the fan assem-
blies during normal operation because normal operation will
not cause fan movements that exceed .25" (6 mm). However,
they will restrain the fan assembly and limit movement to .25"
(6 mm) in any direction if an abnormal condition were to occur.
The position the fan will assume during normal operation
will be determined by actual job site airflow and static
pressure. Therefore, for proper operation the seismic re-
straints must be field adjusted as part of the normal “Check,
Test and Start” procedure. When the fan is operating in a
normal manner there should be no contact between the
snubber restrainer angle and the snubber neoprene bumper.
However, in a “seismic event,” the snubber will limit move-
ment of the spring mounted fan assembly to .25" (6 mm) in
any direction, thereby preventing the fan from being tossed
about and damaged, or causing damage.
Figure 28. Cross section of seismic restraint
Fan Base Channel
Snubber Restrainer Angle
Adjust Up or Down
or Back and Forth
Snubber Neoprene Bumper
Snubber Neoprene Bumper
Adjust In and Out
.25" (6 mm) Gap (Fan Running)
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