Pumps, vibration monitoring

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. 

The use of vibration monitoring to diagnose pump and compressor problems is discussed at the end of the subsection on compressor problems. 

B. The vibration monitoring device furnished on the pump will respond to bearing degradation and allow the operator to shutdown the pump. 

Covers mechanical integrity programs for pumps and compressors, including vibration-monitoring programs ... 

For many smaller pumps, it is not clear how far back on the pump curve the pump can be operated before it is damaged due to low flow. When in doubt, ask the maintenance department to check the pump for vibration before you reduce flow. Then, with the vibration monitor in service, reduce the pumping rate to the desired level. If the indicated vibration amplitude does not increase noticeably, one may safely assume that throttling on the pump discharge will not damage the pump. 

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. 

Vibration signature Turbines and pumps— periodic monitoring Detection of cracks and other distress... 

Approximately 5 to 10 min after the loop B reactor coolant pumps were shut off, the loose-parts monitor again indicated increasing pump vibration. In fact, standing in the control room, the operators said they could feel the vibrations. The operators also reported flow instability, as the loop A flow continued to decrease. At 101 min (1 hr 40 min 40 s), the loop-A reactor coolant pumps were turned off. This action sealed the fate of TMI-2. 

So far we have exclusively discussed time-resolved absorption spectroscopy with visible femtosecond pulses. It has become recently feasible to perfomi time-resolved spectroscopy with femtosecond IR pulses. Flochstrasser and co-workers [M, 150. 151. 152. 153. 154. 155. 156 and 157] have worked out methods to employ IR pulses to monitor chemical reactions following electronic excitation by visible pump pulses these methods were applied in work on the light-initiated charge-transfer reactions that occur in the photosynthetic reaction centre [156. 157] and on the excited-state isomerization of tlie retinal pigment in bacteriorhodopsin [155]. Walker and co-workers [158] have recently used femtosecond IR spectroscopy to study vibrational dynamics associated with intramolecular charge transfer these studies are complementary to those perfomied by Barbara and co-workers [159. 160], in which ground-state RISRS wavepackets were monitored using a dynamic-absorption technique with visible pulses. 

In a vibration analysis, hydraulic instability is displayed at the vane-pass frequency of the pump s impeller. Vane-pass frequency is equal to the number of vanes in the impeller multiplied by the actual running speed of the shaft. Therefore, a narrowband window should be established to monitor the vane-pass frequency of all centrifugal pumps. 

There is a potential for unstable flow through pumps, which is created by both the design-flow pattern and the radial deflection caused by back-pressure in the discharge piping. Pumps tend to operate at their second-mode shape or deflection pattern. This mode of operation generates a unique vibration frequency at the second harmonic (2x) of running speed. In extreme cases, the shaft may be deflected further and operate in its third (3x) mode shape. Therefore, both of these frequencies should be monitored. 

As an example of the importance of process parameters monitoring, consider a process pump that may be critical to plant operation. Vibration-based predictive maintenance will provide the mechanical condition of the pump and infrared imaging will provide the condition of the electric motor and bearings. Neither provides any indication of the operating efficiency of the pump. Therefore, the pump can be operating at less than 50 per cent efficiency and the predictive maintenance program would not detect the problem. 

The above theory is usually called the generalized linear response theory because the linear optical absorption initiates from the nonstationary states prepared by the pumping process [85-87]. This method is valid when pumping pulse and probing pulse do not overlap. When they overlap, third-order or X 3 (co) should be used. In other words, Eq. (6.4) should be solved perturbatively to the third-order approximation. From Eqs. (6.19)-(6.22) we can see that in the time-resolved spectra described by x"( ), the dynamics information of the system is contained in p(Af), which can be obtained by solving the reduced Liouville equations. Application of Eq. (6.19) to stimulated emission monitoring vibrational relaxation is given in Appendix III. 

It is more difficult to perform ultrafast spectroscopy on neat H20 (than it is on H0D/D20 or HOD/H20) since the neat fluid is so absorptive in the OH stretch region. One innovative and very informative technique, developed by Dlott, involves IR pumping and Raman probing. This technique has a number of advantages over traditional IR pump-probe experiments The scattered light is Stokes-shifted, which is less attenuated by the sample, and one can simultaneously monitor the populations of all Raman-active vibrations of the system at the same time. These experimental have been brought to bear on the spectral diffusion problem in neat water [18, 19, 75 77],... 

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