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API RP 684-2010 pdf free download

API RP 684-2010 pdf free download.API Standard Paragraphs Rotordynamic Tutorial: Lateral Critical Speeds, Unbalance Response, Stability, Train Torsionals, and Rotor Balancing.
1.3 STANDARD PARAGRAPHS In order to aid turbomachinery purchasers, the American Petroleum Institute’s Subcommittee on Mechanical Equip- ment has produced a series of specifications that define mechanical acceptance criteria for new rotating equipment. Experience accumulated by turbomachinery purchasers over the past ten years indicates that if the API standards are prop- erly applied, the user can be reasonably assured that the installed unit is fundamentally reliable and will, barring prob- lems with the installation and operator misuse, provide acceptable service over its design life. An integral component of these individual equipment spec- ifications is contained in the API Standard Paragraphs, those specifications that are generally applicable to all types of rotating equipment. The criteria associated with lateral and torsional rotordynamics and balancing have been categorized as standard paragraphs. In rotating equipment specifications published by API (for example, API Standard 617— Axial and Centrifugal Compressors and Expander-compressors for Petroleum, Chemical and Gas Industry Services ) there is a section on rotordynamics and balancing. The backbone of those sections are the standard paragraphs augmented by additional information that is applicable only to the type of unit considered in the standard. The Standard Paragraphs relevant to each section of the document are introduced at the end of each section. Limited comments are made to explain the individual paragraphs. Reference is made to the appropriate discussion in the tutorial to describe the background, justification, or application of the paragraph. The complete text of the Standard Paragraphs is included at the end of the document. 1.4 DEFINITIONS AND REFERENCES Definitions are incorporated into each section of the docu- ment. Due to very large number of references employed, they are identified at the end of each relevant section.
This result is called a forced response analysis and is anal- ogous to the unbalance response analysis performed in rotor- dynamics studies. The amplitude ratio depends upon frequency of the excitation and the damping in the system. Figure 1-2 shows the amplitude ratio versus the excitation frequency. Maximum amplitude ratio is seen where the exci- tation frequency equals the natural frequency of the system. Amplitude ratio also increases as damping decreases with the amplitude becoming infinite at zero damping (a situation which is not physically practical). There is a phase difference between the excitation and response. This phase difference is a function of damping and reaches 90 degrees at the natural frequency. Figure 1-3 shows the phase angle versus excitation frequency. If a transient rather than a sinusoidal excitation excites the system, the actual response normally look like that shown in Figure 1-4. In this case, the response is at the natural frequency. It decays with time based on the amount of damping. This response is called “stable”. In Figure 1-5, the response grows with time. In this configuration, the damping causes the response to grow with time. This response is called “unstable”. While the simple, single degree of freedom system described above is useful for examining the general concepts of vibration theory, this system is clearly not representative of a turbomachine. A more accurate representation of a rotating assembly is comprised of lumped masses that are connected by elastic springs. Once the mathematical model of the rotat- ing element is generated, it is connected to ground through elastic stiffness and viscous damping elements that represent the fluid film support bearings, seals, and supports. The major contributor to this analysis occurred in the early 1900’s with the development of the Jeffcott model as shown in Figure 1-6.

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