2.1.2.4
Balance
The balance for each motor when measured in accordance with NEMA MG 1
paragraph 20.53 shall not exceed the values specified in NEMA MG 1
paragraph 21.54. Each motor's characteristics shall be such that the
maximum vibration requirements of Section 15131A VERTICAL PUMPS, AXIAL-FLOW
AND MIXED-FLOW IMPELLER-TYPE are met.
2.1.2.5
Noise
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NOTE: The Department of Defense considers hazardous
noise exposure of personnel as equivalent to 85 dB
or greater: A-weighted sound pressure level for
eight hours in any one 24-hour period. On the
assumption that pumping plant operating personnel
may be exposed to noise levels approaching or
exceeding that defined by the DOD as hazardous, the
motor noise limit should be specified not to exceed
85 dBA. The additional cost of providing motors
meeting this requirement should be investigated and
weighed against an alternate of providing a room to
isolate these personnel from the noise exposure.
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All motors shall operate at a noise level less than 85 decibels A-weighted
mean sound pressure level (dBA). Noise shall be determined in accordance
with NEMA MG 1 paragraph 21.53.
2.1.2.6
Overspeed Option
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NOTE: NEMA MG 1 paragraphs 12.48 and 21.45 specify
that overspeeds are for emergencies lasting no
longer than one minute. Using this option will
increase costs due to requirements well beyond
standard limits. Designer must do a cost analysis
before selection of this option.
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Each motor shall be designed to withstand indefinitely, without injury, the
maximum overspeed to which the motor will be subjected when the pump to
which it is connected is acting as hydraulic turbine under the maximum head
with the pump discharge pipe open.
2.1.2.7
[Antireverse Device
A self-actuated backstop device or antireversing ratchet, to prevent
reverse rotation of the pump due to loss of power or failure of the
electric prime mover, shall be installed as an integral part of the motor.
The design of the device shall be submitted for approval of the Contracting
Officer and be such that its action is without intentional delay or
excessive backlash. It shall have sufficient capacity to prevent reverse
rotation with a back flow through the pump due to a [_____]-foot
differential head. The device shall be precision machined and be complete
with support housing and oil collector as required. An oil reservoir,
independent of the one used for the thrust bearing, complete with oil-level
gauge and 120-volt ac rated high and low level contacts shall be provided
SECTION 16222A
Page 15
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