Axial position

Current histogram of cumulated AE events vs axial position, for each monitored component. 

Figure 6 shows the histogram of localized AE events vs axial position for the same time period as in fig.5. The location of the AE source corresponds, within source location errors (< 10-15 cm), to one of the welds under surveillance. The weld was known by ultrasonic examination to be affected by internal discontinuities. However, the position of the source could also correspond to one of the hangers. The steps observed in EA event accumulation have taken place during steady load operation, which normally corresponds to very low background noise conditions. This type of event, however, has not been observed afterwards. 

Add methyl group to axial position at C 3 so that It IS trans to tert butyl group... 

Bonds 1 and 3 are in axial positions in the helix, with bond 2 oriented equatorially. 

The laminar boundary layer on deforming continuous surfaces with velocity varying with axial position is discussed by Vleggaar... 

Since the higher thermal conduc tivity material (copper or bronze) is a much better bearing material than the conventional steel backing, it is possible to reduce the babbitt thickness to. 010-030 inch. Embedded thermocouples and RTDs will signal distress in the bearing if properly positioned. Temperature-monitoring systems have been found to be more accurate than axial-position indicators, which tend to have linearity problems at high temperatures. 

In local equilibrium theory, fluid and sorbed phases are assumed to be in local equilibrium with one another at every axial position in the bed. Thus, because of uniform concentrations, the overbar on /i is not necessary and we have Cj Cj [note Eqs. (16-52) and (I6-II9)]. 

Here R=r is the parameter for radiative heat transfer in K units, p is a heat of reaction term, in K/atm units tj is the fluid temperature in the j-th axial position e is the particle emissivity 1 is the celt dimension in m 6 is the clock time in minutes... 

Changes in speed or process gas pressure can change the axial position of the turboexpander shaft. Labyrinth seal wear in the turboexpander may also cause thrust force unbalance. To decrease the load... 

Monitoring should include the usual parameters worthy of surveillance in high-speed turbo machinery the temperature of journal bearings, vibration and axial position of the pinions, inlet and discharge temperatures combined with discharge pressure from the individual compressor stages, and various lube oil system devices. Competent manufacturers make sure all measurement locations are completely prewired on the machine and made available at predefined interfaces or in terminal boxes for connection at the plant site. 

API Std 614 Lubrieation, Shaft-Sealing, and Control-Oil Systems for Speeial-Purpose Applieations API Std 670 Vibration, Axial-Position, and Bearing-Temperature Monitoring Systems ASME BPV Seet 11 Materials... 

Provides a purchase specification to facilitate the manufacture, procurement, installation, and testing of vibration, axial position, and bearing temperature monitoring systems for petroleum, chemical, and gas industry services. Covers the minimum requirements for monitoring radial shaft... 

The API Standard 670 covers the minimum requirements for noncontacting vibration in an axial-position monitoring system. 

While the axial position of multistage impellers to their diffusers is not critical, they should line up reasonably well. Impellers are not extremely sensitive to leading-edge dings and minor damage, but anything, such as erosion on the exit tips, that tends to decrease the effective diameter of the impeller is more serious. Front shroud clearance on open impellers should be maintained close to the design values to minimize capacity loss. 

By using the positional information available from a proximity probe, another valuable parameter can be measured. The axial position or axial shift detection can be added to the monitored information. Probes are generally installed at the shaft end in pairs to provide redundancy. Fhe probes, preferably, should be sensing the axial position from two differ ent surfaces. A typical arrangement can be seen in Figure 8-37... 

API Standard 670, Vibration, Axial Position and Bearing Temperature Monitoring System, Third Edition, Washington, D.C. American Petroleum Institute, 1993. 

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