Case Studies


Spencer Central Vacuum Systems Improve IAQ in Schools

Spencer Central Vacuum Systems Improve Indoor Air Quality to Protect Student Health Central vacuum systems for schools, available from The Spencer Turbine Company, can provide intensive cleaning power to reduce indoor air pollution and exposure to allergens. Spencer systems are custom-designed for each facility and permanently installed as a “vacuum utility” that can be used […]


Spencer Vortex Blower Enhances Recycling Process

Spencer Supports Non-Profit’s Innovative Program The Spencer Turbine Company blended customer service, know-how and technology to add dividends to a customer’s already award-winning produce recycling program. Connecticut-based Foodshare—which collects donated food and distributes it to people in need—takes in produce along with non-perishables for area shelters, soup kitchens, and pantries. “But some of the produce […]


Spencer Digester Gas Booster Helps Customer Tap Wastewater for Power Generation
Presented at Hunts Point WPC - New York City

Looking for a clean, renewable alternative fuel? The Spencer Turbine Company helped a customer find it in an unlikely place—a wastewater treatment plant. When the Hunts Point Water Pollution Control (WPC) in New York City set out to reduce its energy consumption, the New York Power Authority (NYPA)—which operates the facility— investigated using biosolids to […]


Spencer’s Gas Booster Skid Package Is The Cool Choice For A Rooftop Ice Rink!
Presented at Rooftop Ice Rink - Long Island City, N.Y.

The Spencer Turbine Company is helping to put a client’s dreams on ice. With this particular client, that’s not just a good thing – it’s the whole point. Spencer provided a duplex hermetic gas booster skid package to supply natural gas to chillers that keep the ice frozen in a new rooftop ice skating rink […]


High Speed Bearing Technologies for WWT Applications

High-speed bearing technology is applicable for aeration blowers operating at much higher speeds than the typical 60Hz, 3600RPM for cast multistage units. High Speed Turbo (HST) units are usually single stage (though some utilize multiple cores) and rotate from 15,000 to 50,000RPM. At such high speeds, standard roller bearings cannot offer the industry standard L10 […]


Flour-Processor Cleans Up with Spencer’s Industravac Central Vacuum Systems
Presented at Flour Company - Vermont

The Spencer Turbine Company provides a complete line of Central Vacuum Systems (CVS) for all types of food-processing applications, and one client – a major flour-processing and baking-supply company – has found that an Industravac® CVS makes cleaning easier, more convenient, and even more profitable. Founded in 1790, when America’s first president was elected, the […]

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Bearing Health Monitoring

Only passive temperature monitoring is easily possible with airfoil bearings. Thermocouples can be installed as a specified extra in some cases onto the exterior of the stationary components in the bearing to monitor local temperature. In theory, in the case of localized heating problem on the bearing, if the problem is identified quickly enough, the machine may be turned off to protect itself. However, temperature monitors for the airfoil bearing are not common practice in the field as the response time of such devices must be fast enough to capture the near instantaneous temperature rise. No other health monitoring is available for the airfoil bearing. Unfortunately, this leaves the machine vulnerable to catastrophic failure, as the condition of the shaft coating, imbalances, and center of rotation are not monitored.

Magnetic bearings have active control of the rotating assembly. The bearings continuously offer a detailed picture of the bearing condition. Shaft position can be related to vibration, dynamic imbalances, and internal diagnostics of the bearing. Temperature sensors detect overall condition of the bearing and the control circuitry. Additionally, the above data can be used to analyze system resonances, gyroscopic effects, and overall system stability. If a problem is detected, the machine will automatically shut down to protect itself from costly damage. Finally, the collected data can be retrieved via an internet connection anywhere in the world and analyzed further to see large scale trends, comparison to other machines, etc.

Aeration equipment is a significant investment for any wastewater treatment facility. The ability of the blower to detect any impending damage and to protect itself has the potential to save downtime, repair and replacement costs. Even if a blower fails during a warrantee period, a lengthy shutdown can be a serious disruption for the plant operation. Having the capability to shut down the machine automatically before any damage occurs is a significant long term cost advantage for the plant owner and operator. Additional understanding can be gained from the data being collected by the machine. Maintenance staff for the plant can begin to analyze a machine fault without being on site.


Soft polymer coatings such as Teflon on the foils of an airfoil bearing will tend to wear at the contacting point with the journal at start, stop and low-speed operation (typical liftoff speeds of 2000 to 5000 RPM). A better performer is a hard solid lubricant applied on to the surface of the rotating journal. This eliminates localized wear and distributes it randomly over the circumference of the journal. Endurance tests on PS304 (Korolon) coating have shown the number of start/stop cycles at 5.0 PSI load and 352F to be in excess of 100,000. However, under room temperature conditions, the number of start/stop cycles is reduced by over 50%. Additional consideration must be given to the typical loads seen by the bearings in the wastewater industry. Of the radial and thrust airfoil bearings, thrust bearings are typically more vulnerable to high loads. To minimize loads and extend airfoil bearing life, blower designers will often use thrust balancing lines or employ a “double-ended” motor design in which mirrored blowers are assembled onto both ends of the motor. It should be noted that balancing lines will reduce the overall efficiency of the machine as it reroutes some of the process air to the bearing. Double-ended designs have a larger wetted surface area, and consequently have higher surface drag, compared with typical single stage machines.

Magnetic bearings do not experience contacting under normal operation and therefore do not have physical wear. Contacting is only possible if no power is provided to the bearing. This may happen during a power outage or internal component failure. Back-up systems are typically built-in to commercial magnetic bearings to prevent damage in either scenario. In case of a power loss, the rotating assembly will slow down within seconds and come to a full stop in less than 2 minutes due to the load provided by the back-pressure of an aeration system. For that duration the rotating assembly can be supported in two ways. One commonly used option is a UPS unit which provides power to levitate the bearings until full stop. In case of a UPS failure, the rotating assembly will land on a set of back-up roller bearings. Back-up roller bearings are specially designed to have an internal diameter slightly larger than the diameter of the rotating shaft. During normal operation there is no contact between the rotating assembly and the roller bearings. Additionally, the roller bearings are designed and tested for multiple shaft landings at full load and RPM. Another method of protection against power failure is using the inertia of the rotating assembly after a power loss as a power source for the bearing levitation. With this option, the back-up roller bearings are also employed.

Machines utilizing airfoil bearings are capable of many starts and stops; however, shaft coating will degrade with repeated cycles, ingestion of dust and other contaminants. Coating condition is not easily inspected. Further study may end speculation on the longevity of the airfoil bearing coatings in wastewater treatment applications. Until then, magnetic bearings offer a reliable, long-term solution for aeration blowers.

Failure Modes

It has been demonstrated by the scientific community that many airfoil bearing failures occur as a result of a thermal run-away effect. Because the air bearings rely on viscous shearing of the operating fluid, some heat is generated as part of normal operation. If left unchecked, heat build-up can cause localized hot spots and uneven mechanical heating and may lead to bearing seizure. Failures of this type tend to occur rapidly with little to no warning. Amount of preload between the inner foils of the bearing and the shaft as well as bump foil designs will contribute to this condition. Careful consideration and simulation of these factors is required during machine design as they will affect overall machine longevity. Other failure causes include ambient environment. Ambient dust and salt water moisture can cause significant damage to the coatings on the shaft or foils and can even initiate a catastrophic failure. Typical designs try to limit particulate ingestion with reverse pitot cooling air intakes for the bearings. The working fluid in the radial bearings will not typically circulate and the positive pressure inside the bearing will naturally limit particulate ingestion. However, the thrust bearing tends to accelerate the working fluid radially and will naturally have some flow between the foil and the thrust flange. To eliminate the possibility of damage and extend life of the machine, the air supplied to the bearing must be properly filtered.

Magnetic bearings are much more complex compared to the airfoil bearings and, consequently, have more failure modes. However, the self-protection mechanisms virtually eliminate the possibility for a catastrophic failure. For most problems, the machine will shut down before a failure occurs. Dusty and moist environments do not affect the magnetic bearings as the clearances between the rotating and stationary components are generally large enough to accommodate some particulates. Furthermore, the performance of the bearing is not affected by the particulates in the air as the working medium is electric current.

Protection is offered against costly catastrophic failure by magnetic bearings; however, a simpler system such as the airfoil bearings offers fewer methods to fail. The choice of the bearing technology lies with the plant designer, owner and operator. It is important to consider the effects of failure, time to repair or replace the equipment, cost of the event, and the reputation of the equipment provider before making this key decision.


Cost is often the deciding factor in technology selection. The initial cost of blowers with airfoil bearings is typically significantly less than magnetic bearings. This is due to the complex system the magnetic bearings need for proper operation. However, a direct comparison of the technologies shows that the two are not equal. The added cost of blowers equipped with magnetic bearings offers significant long term advantages over the life of the machine. Selecting airfoil bearings for blowers for your plant will offer a lower upfront cost and fewer failure modes. However, should something go wrong during the typical expected 20-year life span, the possibility of a catastrophic failure and high repair and replacement costs can be expected to be much higher with the airfoil designs. Selecting the bearing technology for your application should take into account capital equipment cost, long term management and maintenance, and considerations for failure modes.


Finally, we can easily point to the significant differences between magnetic and airfoil bearing technologies. Though both bearing types are acceptable for the wastewater treatment industry, they are not equal and should not be compared as such. The simplicity and low cost of the airfoil bearings mean that comprehensive monitoring, active control, and self-protection of the blower is limited at best and in some cases not possible. However, the advantages of remote access to check the status and health of the machine, data trending, multiple fail-safe mechanisms, and many other features come with a higher up-front cost with magnetic bearings.

In some cases airfoil bearings will be the preferred choice for a particular plant design. These may be designs with very low horsepower requirements, continuous operation (few start/stop cycles), and clean air supply. However, it is possible that in most cases magnetic bearings will be the preferred technology due to long term advantages of the technology.

Further Reading

“An Overview of Magnetic Bearing Technology for Gas Turbine Engines”, D. Clark et al. NASA/TM-2001-213177

“Magnetic Bearings at Draper Laboratory”, A.Kondoleon at al. NASA-CP-3336-Pt-1

“Performance and Durability of High Temperature Foil Air Bearings for Oil-Free Turbromachinery”, C. DellaCorte, NASA/TM-2000-209187

“Remaining Technical Challenges and Future Plans for Oil-Free Turbomachinery” C. DellaCorte NASA/TM-2010216762

“Foil Bearing Starting Considerations and Requirements for Rotorcraft Engine Applications”, K. Radil et al. ARL-TR-4873

Figure Credits

Copyright ©2013 A. Irving & J. Ibets

Spencer GasCube with Uninterrupted Power Supply Maximizes Uptime for Mission-Critical Applications

blue spencer gas cube

The Spencer Turbine Company’s innovative GasCube™ natural gas booster skid package is available with an Uninterrupted Power Supply (UPS) unit that can be used as an emergency generator in applications where downtime is not an option. The GasCube with UPS is the ideal solution for boosting natural gas pressure in facilities that provide critical services.

The UPS unit is available for high rise buildings with elevators, computer servers, data centers, telecommunication facilities or other installations where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss.

Spencer’s GasCube natural gas booster skid package with UPS is an extended offering of Spencer’s UL Listed GasCube series, the latest innovation from the air and gas-handling leader that introduced the first UL Listed hermetic gas booster in 1975. It is a ready-to-go solution for boosting pressure for boilers, HVAC, hot water heaters, manufacturing process equipment, or any other mission-critical equipment. The GasCube is shipped prewired, prepiped, and factory tested. It has a compact footprint and has the capability to boost utility street-pressure levels by as much as 83 inches WC with volumes to 240,000 CFH. These are the highest performance ratings available.

The UPS provides instant protection from a momentary power interruption and can also be relied on to power equipment during a longer-term outage until an auxiliary power supply can be turned on, grid power is restored, or equipment is safely shut down. The UPS is UL and CUL Listed and is suitable for indoor use.

The Spencer GasCube series design also provides a continuous flow of incoming natural gas around the UL Listed explosion-proof motor, cooling the motor and extending its life. It is factory assembled and tested before shipping, with set-point adjustments that are made using a pre-engineered PLC control panel with an operator interface terminal (OIT). Spencer’s control panel, in a weatherproof NEMA 4 cabinet, is pre-engineered to monitor actual flow (CFH) based on current (Amps), and monitor motor temperature to prevent overheating. The data is displayed at the OIT. A combination starter is provided for power distribution and protection to the booster motor. The main disconnect switch/circuit breaker combines with a motor starter and overload relay to provide proper motor protection.

In addition, a standard recirculation valve control is included on systems that require lower operating flows than the specified gas booster rated flow. If the gas flow is required to go below the allowable operating range, a modulating recirculation valve with an air-cooled heat exchanger will be installed in the recirculation loop to keep the flow just above the minimum to ensure reliable motor operation.

Simplex and duplex designs of the GasCube series can be provided. All designs are backed by Spencer’s 120 years of technical experience and can be installed and connected to field power and gas lines efficiently. It’s an ideal solution when deadlines are tight, not just for mission-critical installations, but also for industrial, commercial and institutional applications including schools, housing complexes, warehouse/distribution centers, manufacturing plants, healthcare facilities, office buildings, restaurants, and sports arenas.

Spencer’s local sales representatives and in-house sales and engineering groups are always available to provide technical expertise and to assist our customers with product selection and design. They are also available to be on-site to assist with startup. Spencer can provide the GasCube series to meet specific requirements, including outdoor and duplex installations, remote location of the control panel, and other variations.

Additional optional accessories are also available, including check valves, pressure regulators, low- and high-discharge pressure switches, and enhanced control features. To consult with a Spencer representative on natural gas booster needs, call 800-232-4321 or visit

About The Spencer Turbine Company

The Spencer Turbine Company is a privately held, U.S.-owned and -operated provider and servicer of blowers and gas boosters, vacuum systems and other accessory products. Based in Windsor, Conn., Spencer has applied a unique Engineering Edge since 1892 to create innovative solutions for air and gas handling problems. The company is a world leader in addressing wide-ranging energy and environmental solutions across industries and applications that include nuclear, coal, gas, electric and emerging technologies such as fuel cells and hydrogen systems. The company also provides solutions for digester gas and landfill gas recovery and utilization; barge vapor extraction; combustion air delivery; wastewater treatment aeration; soil remediation; emission control; flue gas desulfurization processes, vacuum cleaning for plant-wide cleanliness; and waste material reclamation and recycling.

Flour-Processor Cleans Up with Spencer’s Industravac Central Vacuum Systems

The Spencer Turbine Company provides a complete line of Central Vacuum Systems (CVS) for all types of food-processing applications, and one client – a major flour-processing and baking-supply company – has found that an Industravac® CVS makes cleaning easier, more convenient, and even more profitable.

Founded in 1790, when America’s first president was elected, the upstate Vermont-based client is the country’s oldest flour company. It now operates out of a complex of facilities where it makes, processes, and packages a variety of bakery goods, mixes, and flour.

Spencer’s Industravac is being used by employees in the company’s Grain Room, where ingredients for muffin mixes, scones, pizza dough, and other products are blended, packaged, and then warehoused for distribution to retailers or sale through its website. The integrated vacuum system, with vacuum producer, separator and motor all mounted on a common skid for installation convenience, collects and conveys material through a tubing network. The network feeds to the Industravac unit installed in a room adjacent to the packaging area. The vacuumed material collects into an easy-empty removable can. Installing the Industravac unit in a remote location enhances both safety and cleanliness.

And with convenient hose connections located around the client’s work area – along with proven engineering in the equipment design and its features – the system is ideal for low maintenance, continuous-duty operation. It saves time and labor over other types of systems the client had been using to clean its plant.

woman cleaning up with vacuum
Convenient clean up. Between shifts, employees clean debris from the floor and around equipment by connecting vacuum hoses and tools to inlet valves located in the Grain Room. The vacuumed material is
transported through a tubing system to the
Industravac located in an adjacent room where the vacuumed material is collected.

Spencer designed the system to be used by two operators at one time and also customized it with a static grounded galvanized steel tubing network that includes four ‘drops’ inside the Grain Room. The drops are located conveniently to make it easier to hook up the hose and tools and clean debris that has settled on the floor or around equipment. Natural cotton-twill filter bags were also selected to deal with the extreme fineness of particle size that is inherent to flour processing.

The Industravac CVS also has explosion-proof (XP) design features that help the client deal with the potential for explosion. This is an unlikely occurrence, but it is a hazard that can be associated with flour processing, and the system’s explosion relief vent is ducted to the outside of the building. This way, should there ever be a deflagration, it will be vented safely outside the building. The relief bung’s connection to the outside is specially designed to contain a deflagration, and it is insulated for sound abatement and vibration dampening.

Spencer’s unique design capabilities specifically help to safely mitigate the explosion hazards associated with flour processing. The system is static resistant, as static charge is a potential ignition source of an explosion whenever flour and other baking ingredients are blended and packaged. Grounded hoses, grounded zinc-galvanized steel tubing, and grounded filter bags help to eliminate static electric charges associated with high-velocity industrial vacuum cleaning systems.

employee operating explosion proof features
Explosion proof. Special explosion-proof features, including grounded filter bags and a relief vent safely ducted to the outside, make the Spencer Industravac® a natural for flour-processing operations.

As the Industravac makes the job of cleaning up easier, the client has found additional uses for the Spencer system – including vacuum cleaning dust collection system filters so that they do not have to be replaced as often. This provides additional savings against the client’s operating budget, according to the plant manager.