Glossary F

Face-to-face - When referring to impellers, a face-to-face arrangement is when
two adjacent impellers, in multistage pump, are arranged so that the inlet of the
impellers are facing toward each other.

When referring to ball bearings, face-to-face arrangement is when two adjacent
bearings are arranged so that the face, or low shoulder of the of the outer rings,
are next to each other. The bearing contact angles
converge inward to the shaft.
See definition of
back-to back.

False brinelling -  In ball bearing, it refers to the removal of material from bearing
elements by the fidgeting action between the balls and races due to mechanical
vibration when the bearing is not rotating, such as the occurrence of dents during
handling or transportation. False brinelling can cause a bearing to become noisy.

Fire pump - A pump specifically designed and built for fire protection service and
meets the specifications set forth in a governing code, or standard. In North
America the code is published by the National Fire Protection Association in NFPA
20, and the fire pumps are tested or listed by a third-party agency such as
Underwriters Laboratories, Inc. or FM Global. The use of third-party listed or
approved fire pumps are usually required not only by building codes, or local
regulations, but also by property insurance companies as well.

A fire pump is the main pump unit connected in parallel with a jockey pump in a
fire sprinkler system. When a sprinkler opens in the event of a fire the pressure
drop in the sprinkler system is detected by the automatic controller and the fire
pump is activated. See
jockey pump.

First critical speed - ISO Standard 13709 and API Standard 610 define critical
speed as the "s
haft rotational speed at which the rotor-bearing-support system is
in a state of resonance
." The lowest resonant frequency that produces the first
mode shape is called the first critical speed; the next higher frequency is called
the second critical speed, and so on. The second, or third, critical speed is not a
multiple of the first critical speed - the numbers have no correlation..

Flexible-coupled pump - a pump directly coupled to its driver through a flexible
coupling. The pump and driver  each has its own shaft. See
close-coupled pump.

Flexible rotor - a rotor which operate near, or above, its critical speed, and when
balanced at speed below its critical may lose its balance when it operates above
its critical speed.

Flexible shaft - see flexible rotor.

Floating throat bushing - A tight clearance bushing that can move radially to
compensate for shaft deflection or shaft whip. The bushing is a plain circular ring,
usually made of carbon and is lightly pressed by a spring against the bottom wall
of the stuffing box. Because the bushing can slide radially against the wall to
adjust to the shaft deflection, it can have a tighter clearance than a fixed throat
bushing. A typical range is 0.002" to 0.004" clearance.

Floating throttle bushing - same definition as floating throat bushing. The term
throat bushing usually refers to the bushing on the low pressure stuffing box, and
the term t
hrottle bushing usually refers to the bushing on the high pressure
stuffing box. Also, a throttle bushing usually has a tighter clearance than a throat
bushing because it is subjected to a higher differential pressure.

Fluting - a minor form of electrolysis resulting from leakage of small electrical
current that passes through a bearing that, over a period of time, is accelerated by
the combined effect of vibration and lubricant degeneration due to vibration.
Fluting causes a bearing to become noisy.

R: 0411-GLOF
C: glossary
F: glossary F1

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