API 612 2003 pdf download

API 612 2003 pdf download

API 612 2003 pdf download.Petroleum, Petrochemical and Natural Gas Industries—Steam Turbines—Special-purpose Applications.
8.2 Shafts 8.2.1 Shafts shall be accurately finished throughout their entire length. The surface of the shaft at shrink fit areas and bearing areas shall be finished to a roughness not exceeding 0,8 µm (32 µin.) R a. 8.2.2 The rotor shaft sensing areas to be observed by radial vibration probes shall be concentric with the bearing journals. All sensing areas (both radial vibration and axial position) shall be free from stencil and scribe marks or any other surface discontinuity, such as an oil hole or a keyway, for a minimum of one probe-tip diameter on each side of the probe. These areas shall not be metallized, sleeved, or plated. The surface shall be finished to a roughness not exceeding 0,8 µm (32 µin.) R a . These areas shall be properly demagnetized to the levels specified in API Std 670 or otherwise treated so that the combined total electrical and mechanical runout does not exceed the following: a) For areas to be observed by radial-vibration probes, 25% of the allowed peak-to-peak vibration amplitude or 6,3 µm (0,25 mil), whichever is greater. b) For areas to be observed by axial-position probes, 12,7 µm (0,5 mil). 8.2.3 All shaft keyways shall have fillet radii conforming to ASME B17.1. 8.2.4 Shafts shall be capable of transmitting torque at least equal to the torque determined by potential maximum power. The coupling shaft end design shall conform to the requirements of ISO 10441 or API Std 671. 8.2.5 To prevent the buildup of harmful potential voltage, magnetic flux density of any part of the rotating element shall not exceed 0,000 3 T (3 G). 8.3 Blading 8.3.1 For each blade row, the vendor shall verify by Campbell diagrams, or their equivalent, corrected to actual operating temperatures and speeds, that the excitations do not occur in multiples of up to 15 times the running speed, by nozzle passing frequency and by twice nozzle passing frequency within the specified operating speed range by the following: a) in-phase tangential b) out-of-phase tangential c) axial 8.4 Speed sensing element A dedicated multi-toothed surface for speed sensing shall be provided integral with, or positively attached and locked to the turbine shaft. This surface may be shared by other speed sensors but shall not be used as a gear for driving other mechanical components. The axial width of the multi-toothed surface (the width of the surface being viewed by radial probes) shall be a minimum of one and one-half times the diameter of the probe tip. 9 Rotor dynamics 9.1 General 9.1.1 In the design of rotor-bearing systems, consideration shall be given to all potential sources of periodic forcing phenomena (excitations) which shall include, but are not limited to, the following: a) unbalance in the rotor system; b) oil-film instabilities (whirl); c) internal rubs; d) blade and nozzle passing frequencies; e) gear-tooth meshing and side bands; f) coupling misalignment; g) loose rotor-system components; h) hysteretic and friction whirl; i) boundary-layer flow separation; j) acoustic and aerodynamic cross-coupling forces; k) asynchronous whirl; l) electrical line frequency. NOTE 1 The frequency of a potential source of excitation may be less than, equal to, or greater than the rotational speed of the rotor. NOTE 2 When the frequency of a periodic forcing phenomenon (excitation) applied to a rotor-bearing support system coincides with a natural frequency of that system, the system is in a state of resonance. A rotor-bearing-support-system in resonance may have the magnitude of its normal vibration amplified. The magnitude of amplification and, in the case of critical speeds, the rate of change of the phase-angle with respect to speed, are related to the amount of damping in the system. NOTE 3 API Publ 684 contains additional information on rotor dynamics not covered in this Standard. 9.1.2 For the purposes of this Standard, critical speeds and other resonant conditions of concern are those with an amplification factor greater than 2,5.

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