ISO/TC 108/SC 2/WG 7 - Vibration of machines with active magnetic bearings

This document gives guidelines for identifying: a) The typical architectures of touch-down bearing systems to show which components are likely to comprise such systems and which functions these components provide; NOTE Touch-down bearings are also known as “backup bearings”, “auxiliary bearings”, “catcher bearings” or “landing bearings”. Within this document, the term “touch-down bearings” is used exclusively as defined in ISO 14839‑1. b) The functional requirements for touch-down bearing systems so that clear performance targets can be set; c) Elements to be considered in the design of the dynamic system such that rotordynamic performance can be optimized, both for touch-down bearings and active magnetic bearings (AMBs); d) The environmental factors that have significant impact on touch-down bearing system performance allowing optimization of overall machine design; e) The AMB operational conditions that can give rise to contact within the touch-down bearing system so that such events can be considered as part of an overall machine design. It also considers failure modes within the AMB system that can give rise to a contact event. This ensures that the specification of the touch-down bearings covers all operational requirements; f) The most commonly encountered touch-down bearing failure modes and typical mechanisms for managing these events; g) Typical elements of a design process for touch-down bearing systems including the specification of load requirements, the sizing process, the analytical and simulation methods employed for design validation; h) The parameters to be taken into account when designing a touch-down bearing system acceptance test programme including the test conditions to be specified and the associated instrumentation to be used to ensure successful test execution; i) The condition monitoring and inspection methods that allow the status of in-service touch-down bearings to be evaluated and when necessary identifying the corrective actions to be taken; j) The factors to be considered when designing the maintenance regime for a touch-down bearing system including the actions to be taken after specified events have occurred together with any actions to be performed on a regular basis; k) The factors to be considered regarding other life cycle topics (e.g. obsolescence management, de-commissioning and disposal).

This document defines terms relating to rotating machinery equipped with active magnetic bearings. NOTE General terms and definitions of mechanical vibration are given in ISO 2041; those relating to balancing are given in ISO 21940-2; those relating to geometric characteristics such as coaxiality, concentricity and runout are explained in ISO 1101.

ISO 14839-4:2012: a) indicates a typical architecture of an active magnetic bearing (AMB) system so that users can understand which components are likely to comprise such systems and which functions these components provide; b) identifies the primary similarities and differences between AMB systems and conventional mechanical bearings; c) identifies the environmental factors that have significant impact on AMB system performance; d) identifies the operating limitations that are unique to AMB systems and defines standardized methods of assessing these limitations; e) identifies typical mechanisms for managing these limitations, especially rotor unbalance; f) provides considerations for the design and performance of touchdown bearing systems; g) defines a typical signal set for provision in an AMB system for proper system/process interface as well as condition and diagnostic monitoring; h) details current best practices for monitoring, operation and maintenance to achieve highest operational system reliability; i) identifies typical fault-handling practices; j) recommends inspection and preventive maintenance processes for AMB systems.

ISO 14839-3:2006 establishes the stability requirements of rotating machinery equipped with active magnetic bearings (AMB). It specifies a particular index to evaluate the stability margin and delineates the measurement of this index. It is applicable to industrial rotating machines operating at nominal power greater than 15 kW, and not limited by size or operational rated speed. It covers both rigid AMB rotors and flexible AMB rotors. Small-scale rotors, such as turbo molecular pumps, spindles, etc., are not addressed. ISO 14839-3:2006 concerns the system stability measured during normal steady-state operation in-house and/or on-site. ISO 14839-3:2006 does not address resonance vibration appearing when passing critical speeds. The regulation of resonance vibration at critical speeds is established in ISO 10814.

ISO 14839-2:2004 sets out general guidelines for measuring and evaluating rotating machinery equipped with active magnetic bearings (AMBs) with respect to the following two indices: shaft vibratory displacement measured at or close to the AMBs; and working current and voltage measured in magnetic coils or power supply amplifiers. Both indices are measured under nominal operating conditions in house and/or on site. These guidelines are presented in terms of both steady-state running values of these indices and any magnitude changes which may occur in these steady-state operations. ISO 14839-2:2004 is applicable to industrial rotating machines generating or consuming nominal power greater than 15 kW, and is not limited by size or operational rated speed (i.e. comprising turbo-compressors, turbo-pumps, steam turbines, turbo-generators, turbo-fans, electric drives and other rotors supported by AMBs). It establishes the vibration, current and voltage evaluation of the rotating machinery equipped with AMBs, specified by a comparatively large power capacity as described above, excluding small-scale rotors such as turbo-molecular pumps, spindles and flywheels. ISO 14839-2:2004 covers both AMB-equipped rigid rotors and AMB-equipped flexible rotors.