Pump Vibration

Pump vibration measurements and analysis of the ampHtude—frequency spectmm have led to the deterrnination of possible equipment ailments. Examples of frequency relationships to particular pump vibration problems are available (62). Eor example, a one-time (lx) frequency corresponding to a mnning speed usually indicates the presence of rotor unbalance, a 2 x peak may mean a bent shaft, and a - O.dx may be a symptom of an oil whip at the sleeve bearing. 

ASME recommends periodic monitoring of all pumps. Pump vibration level should fall within the prescribed Emits. The reference vibration level is measured during acceptance testing. This level is specified by the manufacturer. 

Figure 10-63 shows an actual pump vibration spectra. In the figure, several amplitude peaks occur at several frequencies. 

Llancock, W. P., How to Control Pump Vibration, Hydrocarbon Processing, March 1974, p. 107. 

To ensure interface-selective detection of the Raman-pumped vibrational coherence, one more incident electric field is required. A fourth-order optical response is thereby generated. The requirement is fulfilled by observing the second harmonic (SH) light generated at the interface, instead of the transmitted fundamental light. 

A tunable mid-IR pulse at frequency >ir pumps vibrational excitations in a polyatomic liquid (all work discussed here is at ambient temperature 295 K). A time-delayed visible probe pulse at frequency >l generates incoherent anti-Stokes Raman scattering. For an instantaneous pump pulse arriving at time t = 0, the change in the anti-Stokes intensity of transition i, with frequency o) the anti-Stokes transient, is (44)... 

Figure 18 Direct and indirect intermolecular vibrational energy transfer in a polyatomic liquid mixture consisting of molecules A and B. In polyatomics, direct transfer does not often compete efficiently with VER. Indirect transfer from A to B occurs when A undergoes VER, which produces phonons, which pump vibrations on B. Indirect transfer is efficient only when the density of excited vibrations is large enough to significantly increase the phonon population.

The idea of this experiment is to excite a single chromophore in a molecule (jet-cooled) and to observe the real energy flow from the optically pumped vibrations of... 

It is also important to use flexible hose, and plastic inlet and outlet fittings. This is because pumps vibrate, and rigid connections do not fare well in this type of environment. Rigid metal fittings can be used at the pump, but if they... 

HI 9.6.4, Centrifugal and Vertical Pumps — Vibration Measurement and Allowable Values ... 

Pump vibrating Low liquid level Suction line plugged Temperature rise in suction line... 

Compressors, pumps Vibration-isolated mounting in enclosed soundproofed rooms. Machines preferably separated from one another by partitions or with individual enclosures. Ventilation or air intake openings of such rooms should have louvred sound attenuators. Intake and outlet silencers for the compressors. Pressure pipelines to have sound-damping expansion joints and acoustically sealed wall inlets. Pressure release pipelines to have silencers. Additional sound insulation for compressed air pipelines to suppress rushing noises. Sound-insulated enclosed portable compressors represent the current "state of the art" for use in quarrying operations. 

Leaks from pumps Number of (detectable) leaks from pumps due to seal failure Number of product pump vibration checks undertaken to schedule. Number of remedial actions raised following vibration monitoring not completed. 

Mechanical seal This is the part of a centrifugal pump that keeps the liquid from squirting out along the shaft. It is often subject to leakage due to pump vibration and cavitation. 

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