Article

Magnetic Bearings and Their Need for Speed (Sensors)

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.

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Reducing Spiral Vibration on a Genset

By Richard Livermore-Hardy, Waukesha Bearings
Published in Turbomachinery International, July/August 2014

An Alstom 450MVA hydrogen-cooled generator operating at 3,600 rev/min and equipped with a brush gear unit showed spiral vibration with a forward rotating unbalance vector.

Spiral vibration, also known as the Newkirk effect, can be observed on various types of turbomachinery and is caused by a vibration-induced hot spot on the shaft surface generated by friction.

Potential modifications were studied by Alstom using hot spot stability analysis with a rotor dynamic model of the generator rotor, and bearing supports. Based on the calculated results, a modification of the generator shaft line was implemented using tilting pad radial bearings at the generator non-drive end and exciter end locations to shift the slip ring shaft critical speeds well above the rated speed.

Read the article in the July/August 2014 issue of Turbomachinery International.

Canned Magnetic Bearings Minimize Corrosion in Oil & Gas Processing

Safely immerse motor compressors in process gas without risking costly damage.

By Richard Shultz, Waukesha Magnetic Bearings
Published in Pumps & Systems, August 2014

Active magnetic bearing (AMB) reliability and availability levels have surpassed oil bearings after 10 years of technological advancements. These advances have made an impact on the industry, drawing attention from major original equipment manufacturers globally.

In 2002, an oil and gas processing company required a bearing for a hermetically sealed integral motor compressor. The natural gas from the well contained hydrogen sulfide, which led the company to pursue a corrosion-resistant canned bearing. Finding a reliable bearing for this hermetically sealed integral motor compressor was a challenge—but one worth the cost.

Read the full article online or in the August 2014 issue of Pumps & Systems.

Active Magnetic Bearings Provide Harsh Conditions Solution

Russian oil & gas company produces a compressor station to maximize pipeline capacity.

By Richard Shultz, Waukesha Magnetic Bearings
Published in Pumps & Systems, April 2014

With more than 20 years of experience in the oil and gas industry, Lukoil, a Russian oil and gas business, aspired to expand its oil and gas fields. For the expansion, Lukoil selected the Bolshekhetskaya depression in West Siberia, where large deposits of cenomanian gas lay.

Developing and constructing a compressor station to connect the fields would increase the total capacity of the pipeline. The compressor design had to produce a high discharge pressure. In addition to the pressure gain required to compensate for the piping frictional losses, the discharge pressure of the compressor also supports a refrigeration process applied to the gas at the plant outlet.

This refrigeration process, based on a throttling principle, is required to cool the gas sufficiently to keep the buried piping temperatures from thawing the permafrost. The permafrost helps maintain a stable support for the buried piping.

The Challenge

Lukoil partnered with Sumy Frunze, an oil and gas equipment manufacturer, to develop centrifugal compressors that could withstand the frigid Siberian conditions. The compressors would allow the station to pump 12 billion cubic meters of gas per year to another station, furthering the central gas pipeline of Russia. Providing such high compressor discharge pressures with reasonable drive power requires compressors with high efficiency.

The high efficiency was achieved with a compressor rotor shaft with a high slenderness ratio. This high slenderness ratio allows high efficiencies but results in a flexible compressor rotor shaft. The Lukoil compressors have the most flexible rotors ever equipped with magnetic bearings. The processing power and advanced control algorithms provided by the bearing manufacturer’s electronic controller were required to make these machines a success.

The bearing manufacturer provided its multiple coordinate control (MCC) algorithm to stabilize all compressor rotor natural frequencies, with robust stability margins.

After installation, the technology performed successfully. Within the centrifugal compressor, the magnetic bearing technology provided savings in energy, ecology and the total cost of ownership for Lukoil.

To read the whole story, download the article below.

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Bearings Reduce Spiral Vibration on Turbo-generators

With the industry trending toward improved efficiency, in both new and existing equipment, higher demands are placed on the equipment and the bearings.

When Alstom Power identified a phenomenon of spiral vibration close to the trip level on one of their 450MVa hydrogen-cooled generators, our proprietary predictive tools and extensive industry experience on equipment of this size made Waukesha Bearings the clear choice to design and manufacture a drop-in bearing replacement.

More than 13 generator sets have been commissioned since the initial phenomenon was detected in 2003. In total, the Maxalign bearings have seen 600,000 cumulative operating hours with these particular Alstom generators.

Read the article at engineerlive.com or download the article below.

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Dover Exec Dishes on New Pearland Manufacturing Plans

Molly Ryan, Reporter, Houston Business Journal

Dover Corp.’s (NYSE: DOV) energy division just broke ground on a new 150,000-square-foot manufacturing and office building in Pearland.

Frank Wierengo is president of Cook Compression, which is one of many of Dover’s businesses moving into the Pearland space. He broke down the details for us about what exactly will happen at the new location.

Illinois-based Dover operates a variety of manufacturing brands throughout the world. The company’s energy division operates numerous facilities throughout Texas, and the new Pearland space is designed to consolidate some of them at one site to increase efficiency.

Normally, the term “consolidation” in manufacturing is associated with layoffs. However, Wierengo explained this is not the case with Dover.

Dover Energy is consolidating three existing Cook Compression facilities now in Stafford, Pearland and Breckenridge, Texas; an existing Bearings Plus facility now in south Houston; and a completely new OPW Midland facility.

Cook Compression will manufacture and repair a variety of compressor components, such as valves and sealing products, at the facility. Meanwhile, at the same Pearland facility, Bearings Plus will mainly work on refurbishing bearings systems and OPW will mainly work on refurbishing and repairing valves. All three of the businesses will predominantly serve the oil and gas industry.

The new Pearland location will initially have close to 200 employees, which Wierengo said is the number of employees the separate facilities have now. However, in the future, Dover hopes to grow the Pearland operations, he said. Not only can the companies add more manufacturing shifts to increase work, but they can also expand the facility onto the 14 acres of land the facility sits on.

By having multiple businesses in one facility, Wierengo said the companies will be able to increase efficiencies by sharing shipping, receiving and material handling functions. The companies are also looking into sharing workers “to collaborate to the highest extent possible,” he added.

Dover is banking on growing the Pearland facility due to the strength of the oil and gas industry, Wierengo said.

Furthermore, for some more insight as to why Dover chose Pearland, city of Pearland documents from December reveal that the city granted a tax abatement agreement to Dover and the city approved a loan agreement between the Pearland Economic Development Corp. and Dover.

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Have a Pump, Motor, Generator, Turbine, Compressor or Gearbox? There’s a Bearing for That!

Waukesha Bearings is known internationally for its capabilities, technology, size and application experience in the rotating (turbo) equipment industry.

Download our article from the October 2012 issue of Power Transmission Engineering for a brief selection guide intended to assist engineers, specifiers, integrators and others in choosing the right bearing—and bearing technology—for the application.

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Executive Outlook 2012: The Regaining of a Home-Court Advantage

Jay Burnette, President of Waukesha Bearings Corporation, shared his outlook with Maintenance Technology magazine:

The “offshoring” of U.S. manufacturing has been going on for years, with China being a major job destination. What’s relatively new is the increased talk about “onshoring” or “reshoring” production back to the U.S.

When I read about companies choosing to offshore (or even onshore), I wonder about their “strategic intent.” Are their decisions based on point-in-time inputs or a longer-term view? Those focused on chasing the lowest cost in the world are often disappointed to learn that many, if not all, of the key inputs change dramatically over time. In China, for example, a strengthened RMB, however slight, has substantially changed the economics of manufacturing over the past two years. Other factors, including rising costs for labor and logistics, intellectual-property protection and lengthy times to market—not to mention the operational challenges of managing a business far from home—have all had an impact on manufacturing in this key region.

Companies with a more strategic view—i.e., the intent to manage cost structure in balance with serving customers locally—have been more successful with offshoring initiatives. Not every organization, however, has the luxury of maintaining this balance. Due to competitive pressures and/or other demands, many must focus solely on lower production costs. Thus, we shouldn’t be surprised that the economic tides now seem to be turning away from China and toward other regions, including the U.S. After all, the U.S. has one of the most sophisticated business infrastructures in the world and one of the most productive.

If—as it appears—reshoring is for real, there will be even more pressure to find and develop key talent from what has become, for various reasons, a diminishing pool of individuals interested in such careers: Much of the U.S. future in manufacturing depends on our ability to replenish our aging workforce with well-trained, younger talent without compromising our productivity advantage.

At Waukesha, our focus has been to continue strengthening our higher-cost manufacturing bases in the U.S. and U.K. (home to our largest facilities) with investments in information technology, more productive machine tools and training. At the same time, we are selectively investing in manufacturing capability in emerging regions. Our overall objective is to operate in our customers’ space and time if value is created in terms of product definition, speed to market, competitive cost structure or other criteria. We hope this balance will pay dividends for our customers, employees and stakeholders over the long term.

The Attraction of Magnetic Bearings for End Users

In the August 2010 issue of International Oil & Gas Engineer, Michael K Swann looks at a solution that turns most aspects of magnetic bearing commissioning and machine troubleshooting over to the OEM and end-user.

The traditional method of installing and commissioning magnetic bearings relies heavily on trained engineers on-site, both at the factory of the Original Equipment Manufacturer (OEM) and at the end-user field location. To this point, the same has held true during routine maintenance of the magnetic bearing systems. This conventional approach adds to the operating expense of using magnetic bearings and encumbers end-users with the logistical headaches of getting the supplier on-site to support maintenance requirements over the life of the turbomachinery.

Waukesha Magnetic Bearings (Waukesha), a division of Waukesha Bearings Corporation – A Dover Company, is challenging the status-quo; offering a solution that turns most aspects of magnetic bearing commissioning and machine troubleshooting over to the OEM and end-user, with specialist support coming primarily via remote condition monitoring and comprehensive training programs. Reduced need for on-site maintenance of the system ultimately increases machine reliability and availability – a significant benefit to end-users and major contributor to the decreased Total Cost of Ownership of magnetic bearing systems.

This fundamental shift to the application of magnetic bearing technology is enabled by Waukesha’s full range of digital controllers featuring remote connectivity capability. The approach leverages both the inherent intelligence of magnetic bearing systems and the remote connectivity capability of third generation controls technology.

The magnetic bearing system intelligence allows for machine commissioning and diagnosing of machine problems using a wealth of output information provided by the system (including information related to rotor forces as well as information regarding the stability of the rotor-bearing system) that is unavailable with mechanical bearings. Remote connectivity enables the performance of these operations on-demand from a remote location with no site visits required for ‘second-in-class’ and subsequent machines.

The third generation controllers available from Waukesha allow for remote connection via TCP/IP to facilitate the measurement of vibration, bearing load and rotor stability. The benefits of these capabilities can be seen in the initial commissioning, subsequent trouble shooting and retuning of the machine after many years of operation.

Third generation technologies also provide the ability to use auxiliary bearings to accommodate transient overloads of the magnetic bearings. This emulates the high load capacity of oil lubricated bearings while assuring rotor stability that can be observed and measured. Moreover, the remote connectivity feature allows automatic clearance checking on demand (while non -rotating) to assure that the auxiliary bearing wear is below the threshold for replacement. As wear is the only failure mode in this bushing-type auxiliary bearing, automatic clearance checking effectively allows for the remote observation of the machine service condition.

The evolution of magnetic bearing technology has shown significant benefits to end-users. End-users not only derive the benefits of lower installed cost, increased energy efficiency and environmental friendliness, but to also see significant enhancements in machine reliability and availability. In fact, Waukesha has recently demonstrated an availability of 99.9% across its fleet of magnetic bearing-equipped motor compressors.

Typical applications for active magnetic bearings include motor-driven gas compression, turbo-expanders and other large high-speed turbomachinery

Waukesha offers three air-cooled digital controllers – Zephyr, Chinook, and Elephanta. Each is optimized for performance in specific applications, including subsea, and designed to accommodate a variety of input power systems. Waukesha’s controller range can accommodate turbomachinery applications from as low as 1 MW to 50 MW and more.

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Advanced Bearing Materials for Process Lubricated Systems

By Jeff Anderson, Waukesha Bearings Corporation, and Kevin Terrasi, Pump Engineering, Inc.
Published in Pumps & Systems, May 2010

Pump manufacturers in a variety of industries are increasingly asked to deliver more with less; they need to handle increased loads with improved system efficiency but reduce envelope, environmental impact and total system cost. As an added challenge, many of these applications are running in low viscosity process fluids. Such applications include chemical processing, mine-dewatering, seawater lift, subsea booster, water injection and desalination pumps.

Process lubricated applications require bearing solutions that can meet (or exceed) the load expectations of oil-lubricated systems while resisting corrosion and swelling, and operating under boundary lubrication conditions. The traditional solution to meet these requirements had been stainless steel pads running against a collar with a graphite insert or ferrobestos pads running against a hard interface; however, ferrobestos is no longer acceptable due to its asbestos content.

As an alternative, Waukesha Bearings, an operating company of Dover Corporation, has developed and validated solid polymer bearing technology to address the many challenges inherent in process lubricated applications. Solid polymer components offer the high load capability and low friction of graphite/stainless steel systems, the wear resistance of ferrobestos and temperature limits double that of standard Babbitt-lined bearings (250 deg C, 482 deg F). Critical to many applications, these components are also resistant to corrosion and capable of embedding particulate (such as salt or dirt) from within the closed system.

A solid polymer, tilting pad thrust bearing is capable of supporting loads up to 10 MPa at typical pump operating speeds. This bearing is engineered to accommodate lubrication by a variety of low viscosity fluids, including water, toluene, mono-ethylene glycol and hexane. The technology was released in 2007 after several years of development and field testing. Since that time, the bearings have been successfully integrated into numerous applications, including those running directly on pumped seawater like swash-plate pumps and high-pressure centrifugal pumps supplying water to reverse osmosis membranes in desalination plants. Original equipment manufacturers (OEM) and end users of these products have noted significant benefits from the ability to use process fluids as a lubricant; one such benefit has been the ability to reduce the size, and subsequently the total cost, of the equipment through the elimination of separate oil lubricating systems and associated seals.

Pump Engineering, Inc., an Energy Recovery Inc company, designs and manufactures high efficiency pumps and energy recovery hydraulic turbochargers for reverse osmosis systems. The company recognized the benefits of using process lubricated bearings and has designed their proprietary pumps to include this technology.

One pump model, an advanced variable speed single-stage pump specifically designed for seawater desalination, has a design point at a capacity of 5,700 gpm at a total developed head of 1,107 feet at 3,600 rpm. Solid polymer bearing technology allowed operation at high loads and very thin films, reducing thrust bearing power losses that can dramatically impact the pump’s overall efficiency. Throughout the development process, the pump achieved efficiencies in the mid to high 80s. Efficiency levels approaching 90 percent are anticipated as the product line is expanded. The high load carrying capability of the bearing solution eliminated the need for a thrust balancing system (traditionally an industry standard), reducing design complexity and areas of maintenance and potential failure.

Another pump model developed from the same manufacturer for RO service that benefitted from this bearing design is a high-efficiency, multistage reverse osmosis pump also designed for seawater desalination; it can deliver flows from 100 to 5,000 gpm at pressures up to 1,200 psi, and can also be used in co-generation, pressure boosting, irrigation and boiler feed water applications. This efficient multistage reverse osmosis pump is designed for in-field hydraulic retrofit if operating conditions change. The bearings are designed with a margin of safety in operating loads and temperatures to allow field retrofit without the need for a bearing change.

These types of pump applications are ideally suited for solid polymer bearing technology. They combine the challenges of hydrodynamic bearing design with the application of advanced polymer materials to deliver optimized performance across a wide range of operating conditions. OEMs are realizing the performance benefit of thrust bearings operating on thinner hydrodynamic films, whether in water, process fluids or oil. Thinner films at optimized temperatures deliver substantially lower power losses within the bearing system, improving the overall efficiency of the rotating machine.

The partnership between the bearing and pump manufacturer led to an exclusive agreement covering desalination applications and has been beneficial for both companies throughout the development of RO pump product lines. Working together, these companies are looking for additional product applications to use the solid polymer bearing technology.

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