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Time for motors to emerge from their shrouds

17 November 2019

Brith Isaksson outlines some of the key design features that are important for electric motors operating in hygiene areas. 

A food safety recall can cost a company an average £8 million in direct costs alone, according to the 2017 study by the Food Marketing Institute and the Grocery Manufacturers Association (GMA) in the US. A key factor in avoiding recalls is to maintain rigorous hygiene standards. That makes it critical for equipment in food plants to be washed frequently to keep it clean and avoid contamination. 

However, hygienic washdown practices present a major challenge for general purpose motors. They are not designed to withstand frequent sanitation with caustic cleaning agents or being sprayed with water at high temperatures and pressures.  Housings and enclosures corrode, and humid atmospheres cause moisture to form inside the motor casing. In a typical food production environment it is not uncommon for standard motors to fail in less than a month. Protection with painted coatings is not the answer, as paint can chip or peel off and contaminate food products.

Shrouding the motor
A common solution is to place a shroud around the motor. While this does offer some protection, it can create as many problems as it solves. Food particles can accumulate beneath the shroud and the potential for bacteria to grow presents a serious hygiene risk.  The only way to ensure effective cleaning is to remove the shroud, a time-consuming operation that holds up production. 

Instead of covering standard motors, a better approach is to adopt stainless steel motors which are specifically designed for the food and beverage industry and which are able to withstand caustic sanitation chemicals without risk of corrosion. Furthermore, their bright surface makes cleaning easier because any contamination is clearly visible.

It is also important to ensure that the outer surfaces of motors using in food processing applications are completely smooth to prevent food particles from collecting, which would allow micro-organisms to breed. Attention to detail includes laser etching rating information, as name plates are another place that contaminants can collect. The motor should also be self-draining so that liquid will not accumulate on the surface no matter which way the motor is mounted. 

The level of ingress protection is another important consideration. IP69 is the benchmark for motors used in hygienic applications as it confirms protection against high power, high temperature jets of water from all directions. Using motors that are easy to clean can actually help to save time and water.

Epoxy encapsulation for the motor windings is recommended as it provides protection against humid conditions as well as helping to disperse heat. These factors promote longer motor lifetimes.

Finally, it is important to consider the motor efficiency. Motors operating at higher efficiency levels (such as NEMA Premium or IE3) help to reduce energy costs and result in lower running temperatures that contribute to improved reliability.

Depending on the application, a stainless-steel motor can last five times as long as a general-purpose motor.  So, going shroudless will soon deliver a return on investment for food processing companies in terms of enhanced food safety, improved reliability and reduced maintenance costs.

Brith Isaksson is food and beverage global segment manager for ABB’s Motion Business.

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