Shafts of high-performing rotating equipment experience a certain mass unbalance distribution resulting from manufacturing tolerances, component assembly and material nonhomogeneities. The residual unbalance generates uneven forces on the rotor as it spins, resulting in vibrations and the transfer of dynamic loads to the bearings and supporting structure.
To limit the negative effects of rotor vibration, ISO and API standards set balancing criteria and acceptance levels for residual rotor unbalance. Whether magnetic or fluid film bearings are used in the machine, there is a prerequisite for spinning a rotor to its rated speed. The rotor must be balanced to meet an acceptable residual unbalance level.
The ability of an active magnetic bearing (AMB) system to tolerate high levels of unbalance on the rotor by applying unbalance force rejection control algorithms does not alter the balancing requirements. Rotors supported by AMBs and rotors supported by fluid film bearings are subject to the same balancing requirements.
In the June 2016 issue of COMPRESSORtech2, Andrea Masala of Waukesha Magnetic Bearings discusses the options and considerations in performing low- and high-speed balancing of active magnetic bearing-supported rotors. Two case studies are also discussed.
By Richard Shultz, Waukesha Magnetic Bearings
Published in Fluid Handling, January/February 2016
Groningen, Europe’s largest natural gas field, was discovered in 1959. Production began in 1963, and by the end of the decade nearly 50% of the field’s reserves were depleted with free-flow operation. Nederlandse Aardolie Maatschappij (NAM), a joint venture between Royal Dutch Shell and ExxonMobil, was created in the mid-1990s to find the most cost-effective way to extract gas from the field and extend the life of its reserves.
By upgrading the field’s equipment, including installation of motors and compressors, the field could supply gas to all of the Netherlands, Germany, and Belgium for an additional 40 years. The challenge was to achieve at least 87% availability and a low total cost of ownership.
Magnetic bearings are a proven technology for large standalone motor compressor strings, like the ones at Groningen, to provide both high availability and a low total cost of ownership, as well as lower power consumption (due to decreased rotating losses), lower maintenance costs, and lower CAPEX costs compared to conventional bearings.
Read the article in the January/February 2016 issue of Fluid Handling, or download it below, for more about the operating principles of magnetic bearings, system design considerations, and the application of the technology at Groningen.
In 2002, a leading oil and gas customer approached Waukesha Magnetic Bearings with the challenge of developing a bearing for a hermetically sealed integral motor compressor. Availability and reliability were the customer’s primary objectives. The end user could achieve a significant cap-ex savings on the installation if the motor compressor could be located outdoors, with no building or enclosure required.
The sealed characteristic the Waukesha bearings and electrical connectors delivered in the end did eliminate the requirement for a costly enclosure for the motor compressor and the end user realized a significant project cap-ex savings.
Read the complete article in the September/October 2014 issue of Oil & Gas Product News, read it online, or download the PDF below.
By Richard Jayawant and Roy Leung, Waukesha Magnetic Bearings
Published in CompressorTech2, August/September 2014
In this article we look at the role of the rotational speed sensor in an active magnetic bearing (AMB) system. The article examines design considerations for obtaining a reliable speed signal, together with the types of sensors that are used, and then looks at the functionality within the AMB system that is dependent on the resulting signals.
Read the article in the print or digital edition of the August/September issue of COMPRESSORtech2 (subscription required), or download a PDF version below.