Environmental Engineering Reference
In-Depth Information
thermometers are installed, they monitor oil thrown from bearings.
Sometimes temperature detectors also monitor bearings with water-
cooled jackets to warn against water supply failure. Pumps with heavy
wall casings may also have casing temperature monitors.
3.3.8.6 Vibration Monitors
Vibration sensors are available to measure either bearing vibration
or shaft vibration direction directly. Direct measurement of shaft vibra-
tion is desirable for machines with stiff bearing supports where bearing-
cap measurements will be only a fraction of the shaft vibration. Pumps
and motors 1000 hp and larger may have the following vibration moni-
toring equipment (Wahren, 1997):
•
Seismic pickup with double set points installed on the pump out-
board housing
•
Proximators with
x
-
y
vibration probes complete with interconnect-
ing coaxial cables at each radial and thrust journal bearing
•
Key phasor with proximator and interconnecting coaxial cables
3.3.8.7 Supervisory Instrumentation
Supervisory instruments are used to monitor the routine operation
of pumps, their prime movers, and their accessories to sustain a desired
level of reliability and performance. Generally, these instruments are not
used for accurate performance tests or for automatic control, although
they may share connections or functions. Supervisory instruments con-
sist of annunciators and alarms that provide operators with warnings
of abnormal conditions that, unless corrected, will cause pump failure.
Annunciators used for both alarm and pre-alarm have both visible and
audible signals.
3.3.9 Centrifugal Pump Modifications
The centrifugal pump can be modified to meet the needs of sev-
eral different applications. If it is necessary to produce higher discharge
heads, the pump may be modified to include several additional impellers.
If the material being pumped contains a large amount of material that
could clog the pump, the pump construct ion may be modified to remove a
major portion of the impeller from direct contact with the material being
pumped. Although numerous modifications of the centrifugal pump are
available, the scope of this text covers only those that have found wide
application in the water distribution and wastewater collection and treat-
ment fields. Modifications presented in this section include:
• Submersible pumps
• Recessed impeller or vortex pumps
• Turbine pumps
