ETL 1110-2-533
30 Sep 94
(10) A damaged vibration isolation system is
(6) Figure B-5 shows an unanchored charger.
shown in Figure B-6. A cast iron retainer around the
Anchorage provisions are sometimes provided but not
spring failed due to impacts from lateral earthquake-
fully executed. The strength and stiffness of the
induced motions. In this example, the equipment
fabricated channel used to form the anchorage should
shifted about 4 in. to the left. Snubbers restraining
also be checked.
lateral motion should have been added to the system.
Figure B-5. Unanchored battery charger
(7) All systems with back-up batteries should be
Figure B-6. Damaged vibration isolation system
inventoried. The capacity and operating life of each
system under maximum load should be checked
against the demands for safe shutdown. After the
(11) Figure B-7 shows a type of vibration isola-
initial installation, additional equipment is sometimes
tor that frequently fails. The members enclosing the
added, increasing the demand on the batteries. The
spring are made of cast iron, and there are no
availability of battery back-up power to all critical
restraints to limit the motion of the unit if the isola-
systems should be verified. Redundant back-up bat-
tors fail. Failure of the vibration isolators can cause
teries or a means for cross-connecting emergency
the engine generator to move more than a foot. This
batteries should be considered for vital control and
may cause the failure of fuel, water, power, and
communications facilities.
control lines.
(8) Engine generators are another critical element
(12) Simple restraints fashioned from a short
for system protection and safe shutdown. They are
section of heavy angle iron bolted to the floor will
often vibration-isolated to prevent engine vibration
allow the vibration isolation system to operate as
from entering the support structure.
designed (Figure B-8). Snubbers limit the lateral
(9) The vibration isolators are often very vulner-
Rubber bumpers will reduce the effect of impacts,
able to earthquake damage if they are made of cast
although engine generators are generally quite rugged.
iron components and are not designed to withstand
impact loads imposed by earthquake-induced base
(13) The batteries used to start the engine and
motions. Failure of the vibration isolation system can
the daytank (small fuel tank near the engine) must be
cause large displacements of the engine generator,
securely restrained. The integrity of the fuel line
thereby damaging its utilities, such as fuel line, elec-
connecting the main fuel tank to the daytank should
trical connection, control cable connections, and cool-
be evaluated. The engine generator control panel
ing system connections. Generally, engine generators
should be well anchored.
need not be vibration isolated.
B-6
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