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Pump Performance, Terminology, and Components
Published in Maurice L. Adams, Power Plant Centrifugal Pumps, 2017
In addition to controlling impeller-eye and interstage leakages, smooth bore bushings also produce a rotor centering force that is (a) proportional to the pressure drop across the bushing, (b) proportional to the rotor-to-bushing radial eccentricity, and (c) inversely proportional to the radial clearance. This is called the Lomakin effect, explained in detail by Adams (2010). Over a period of time the bushing clearances naturally enlarge due to rubbing wear, which not only degrades pump efficiency but also proportionally reduces the beneficial rotor-dynamic centering stiffness Lomakin effect. It is widely recommended that when these bushings wear open to about twice their as-new value, they should be replaced. Thus the three reasons for this recommendation are as follows:
Stability analysis of metro vehicles with adaptive suspension
Published in Maksym Spiryagin, Timothy Gordon, Colin Cole, Tim McSweeney, The Dynamics of Vehicles on Roads and Tracks, 2018
Lai Wei, Jing Zeng, Biao Zheng, Hao Gao
The active primary suspension has been reported in literatures [1–4]. One effective control technique is so-called active yaw damping, which is applicable to the stability control for either solid-axle or independently rotating wheelset. Another aspect is the steering control which is required to achieve equal longitudinal and lateral creepage. A yaw torque is applied so as to eliminate the effect of the primary stiffness which forces the wheelset away from the pure rolling. However, the idea of using active control for the stability or steering control has not been turned from theoretical studies to engineering applications. The radial bogie is another good option to improve both the bogie hunting stability and curving performance [5,6]. The self-steering bogie, forced radial bogie and cross braced bogie,.etc, are the most representative structures of radial bogies. Since elastomeric bushings cannot satisfy the conflict requirements under various excitation frequencies, many fluid-filled bushing designs developed, as evident from some articles and many patents [7–9]. In the field of automotive, engine, wind and other industrial sectors, hydraulic bushings are widely used to improve riding behavior and handling performance and to isolate vibrations. The applications of hydraulic bushings to railway engineering are representative by the products of Schwab, Boge and Conti Tech companies. The primary hydraulic suspension possesses the adaptive ability to different excitation frequencies. The dynamic stiffness of the hydraulic mounted suspension in tangent tracks is stiff enough to enable high running stability, while that in curve becomes soft to allow an easy adjustment of the wheelset.
RCAM Case Reliability and Maintenance Component Modeling
Published in Lina Bertling Tjernberg, Infrastructure Asset Management with Power System Applications, 2018
Periodic inspections and maintenance are made on bushings in order to find potential problems. It is important that the oil level remains on a normal level. If the oil level decreases, it is a sign of a leak in the bushing. If the oil level sinks resulting in exposure of the paper isolated parts, it can lead to a dielectric failure in the bushing. If the leak is on the air side, it can give water an entrance to the bushing [232].
Investigation of Dry Sliding Friction Wear Behavior of CuSn11 Bronze Plain Bearing Applying Impregnated Graphite-Filled PTFE
Published in Tribology Transactions, 2022
Plain bearings are one of the machine elements that support the shafts. They operate at a certain speed and under a certain load. It is desirable that the produced bushings have good lubrication so that they can be used for a longer period of time. This reduces wear and increases the life of the bushing. In order to be used as an additive to PTFE, the additive ratio of graphite with higher lubricating properties was determined. Also, dry friction and wear behavior of the produced composite bushing was examined under different sliding speeds and loads. The study presented here aims to develop a self-lubricating metal–PTFE composite structure, with easy production applicability and long life, by using the porous structure of bronze and the excellent tribological properties of PTFE and graphite. The originality of this work is due to the method of application and the porous structure of bronze, unlike traditional methods. The bronze bushing used in this study has a porous structure and was obtained by powder metallurgy (TM). A self-lubricating structure is used with application of a spray coating method, which differs from other production methods (such as oil soaking or solid lubricant embedding etc.). The study is to find out how much of (and in what proportions) the PTFE + graphite composite with high lubricating properties should be impregnated into the bushing pores. The friction coefficients are determined at the end of different sliding speeds and different load variables that have effects on the friction coefficient. The effect on friction and wear of using a high rate (20% GF) of graphite was also investigated. It is believed that this study contributes to studies examining the dry friction and wear behaviors against steel materials among PTFE composite materials.