Since their inception more than 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. TEFC is typically the motor choice for equipment exposed to moisture or the environment.
As industry demands increased and sealing technologies improved during the latter part of the past century, manufacturers were able to do more to protect motors from the environment. With the growth of the food industry, guidelines were created to ensure that the equipment used to produce food was clean and sanitary. The washdown motor was the result.
Early washdown motors include painted white motors, which provide a clean appearance and improved sealing (compared with general purpose motors), and paint-free motors, which provide a combination of aluminum and stainless parts with no painted surfaces. The more costly cousin to these first two lines of motors is the stainless steel motor.
Although the varieties of washdown motors have increased over the years, many end users still buy motors based on the price tag, looking for the most cost-effective design that will provide the best longevity. Because of this paradigm, some users may not be willing to pay 40 to 50 percent more for a stainless steel motor. In the past several years, however, motor users have embraced the idea of total cost of ownership, which goes beyond the initial purchase price.
Washdown motors are generally categorized in three categories, listed here in order of price and feature set: painted white washdown, paint-free aluminum and stainless steel. Many end users, particularly those in large food processing facilities, may utilize all three. Painted washdown motors still offer users a good value in that they can use them in a variety of wet or dry applications that see some levels of moisture and some light washdown. Others may upgrade an area of the plant to a paint-free motor, which utilizes a combination of stainless steel and processed aluminum components (no paint). These motors also have better shaft seals and can withstand higher water pressures and some cleaning solutions.
In the most harsh applications, however, the stainless steel motor is the motor of choice, as it uses a number of the best technologies available, such as fully welded conduit boxes, O-rings in endplate to stator joints and enhanced sealing around the shaft exit points. Understanding these feature levels will greatly improve the end user's ability to apply the proper motor to the proper application.
When evaluating total cost of ownership, value is a vital factor. While white washdown motors are still widely accepted and used more than stainless motors, the food industry is beginning to recognize the value of spending the extra money on a premium efficient stainless product.
Stainless steel motors continue to gain acceptance, and much of the need for them in the U.S. is driven by the passage of the Food Safety Modernization Act. This act covers facilities registered with the Food and Drug Administration (FDA) under the Bioterrorism Act of 2002. This law gives the FDA the authority to shut down a food processor or other related facility that indicates by reasonable belief that a hazard exists. A shutdown for an indefinite period of time can have far-reaching implications for a food processor. The purpose of the law is to ensure beyond any reasonable doubt that all equipment in a facility does not pose any risk or even an appearance of risk that would cause a negative FDA inspection. Stainless steel motors can help provide this assurance.
One point of contention with washdown motors, especially foot-mounted designs, has been the perception that food can collect in crevices. Most motor designs contain models that have crevices around the motor feet that can collect food, which can lead to contamination. When selecting a stainless motor, users should consider equipment that has smooth corners and minimal crevices or areas that can collect contamination. Better use of seals around the motor shaft, such as dual seals or labyrinth seals, as well as O-rings used in place of traditional caulk-style materials have also improved washdown motors over the past several years.
While these designs are more costly up front, stainless steel premium efficient motors are key to improved total cost of ownership and a more sanitary environment.