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Wednesday, September 3, 2014

Stainless Steel Motors Are the Best Option for Pump Drives in Sanitary Environments

Users of pumps in the food industry and other sanitary environments have choices when it comes to selection of electric motors for their driven equipment. Stainless steel motors, although commanding a premium initial purchase price, have lower total cost of ownership, but many motor buyers still might not realize it.

Since their inception over 100 years ago, the two main types of motors in use have been Open Drip Proof (ODP) and Totally Enclosed Fan Cooled (TEFC). When a motor is operated in a dry environment with little or no exposure to water or contaminants, the ODP motor is a viable choice. Over the decades, when motors have been exposed to moisture or the environment, a TEFC was typically the motor of choice.

Most folks in industry that were around motors had the appreciation that motors were an electrical device that required protection from the elements. As industry demands increased over the latter part of the past century, and as sealing technologies improved, more could be done to protect a motor from its environment. In the food industry, guidelines were put in place to ensure that the apparatus used to produce food was clean and sanitary. Thus the washdown motor was born.

The early washdown motors included painted white motors, which provide a clean appearance and improved sealing over general purpose motors, as well as paint-free motors, which provide a combination of aluminum and stainless parts with no painted surfaces. The more expensive cousin to these motors is the stainless steel motor.

Most motor users buy on price, plain and simple. Although the varieties of washdown motors have grown significantly over the years, many folks who buy motors still buy based on the price tag, whether it’s the maintenance guy on the plant floor or the purchasing agent in the office. “What’s the most cost-effective design available that will provide the best longevity?” they ask. Because of this paradigm, some customers may not be willing to pay 40 to 50 percent more for a stainless steel motor. Only in the past several years have motor users embraced the idea of total cost of ownership, which analyzes cost beyond the initial purchase price.

The greatest portion in the total cost of ownership of an electric motor is not the purchase price at all, but the operating cost. In December 2010, the Energy Independence and Security Act went into effect, mandating that motors in the United States — 1 to 200 hp, 2, 4 and 6 pole — were required to be premium efficient as defined by NEMA (National Electrical Manufacturers Association) MG1 table 12-12. Some exemptions in the law (encapsulated windings, integrally mounted motors, non-standard shaft extensions) currently allow a manufacturer to sell motors that are well below premium levels. Some manufacturers choose to utilize these loopholes to sell lower efficiency motors. However, many customers that demand a high-end stainless product also expect the highest efficiency available. In doing so, they may pay more for their motors up front, but in the end they will reap the benefits of lower operating costs over the life of the motors.

The mixing application (top) is driven by a premium efficient stainless steel motor (above), which provides long-lasting service for this clean environment.

While premium efficient motors are a requirement in the United States and Canada, they are typically not required worldwide. Many countries are raising their Minimum Efficiency Performance Standards (MEPS), but they are several years away from being at premium efficient levels. Because of these low efficiency standards, a large number of lower efficient motors are used in the international marketplace, which may come with lower quality as well.

With total cost of ownership, the word value also comes to the forefront. While white washdown motors are still widely accepted and used much more than stainless motors, the food industry is beginning to recognize the value that comes with spending the extra money on a premium efficient stainless product.

Stainless steel motors continue to gain acceptance, and some of the need for them in the United States is driven by the passage of the Food Safety Modernization Act. This law covers facilities that are registered with the Food and Drug Administration under the Bioterrorism Act of 2002. This law essentially gives the FDA the authority to shut down a food processor or other related facility that indicates by reasonable belief that a hazard exists. This can have far-reaching implications for a food processor if it has to shut down for an indefinite period of time due to negligence. The idea is to make sure beyond any reasonable doubt that all equipment in a facility does not have any risk or even an appearance of risk that would cause a negative FDA inspection. Stainless motors provide this assurance.

One point of contention with electric motors, especially foot-mounted designs, has been the perception that food can collect in crevices. Most motor designs on the market today have crevices around the motor feet that can collect food, which can lead to possible issues related to contamination. Fully welded feet in foot-mounted stainless steel motor designs eliminates opportunity for food buildup to take place, thus removing the perception that contamination can occur. Better use of seals and O-rings has also improved motors over the past few years.

When designing a high-efficiency system, in addition to selecting the best premium efficient motor, one must also consider a more efficient gearbox. A great deal of efficiency gain is available by selecting a gearbox that utilizes helical gearing. Enhancing the total efficiency of the system, in addition to selecting a stainless gearbox, is ideal.

The bottom line is that motor customers still buy on price. While stainless steel designs are more costly, educating customers regarding the value of premium efficient motors and high efficient gearboxes is the key. A winning proposition occurs when a customer can fully appreciate the value of their product lasting longer (which reduces downtime), providing important efficiency gains, and enhancing their clean food environment.


David Steen is product manager for AC motors at Baldor Electric Co., based in Fort Smith, Ark. Baldor’s foot-mounted stainless steel motor design incorporates fully welded feet to prevent food build-up contamination. For more information, visit the company at




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