Ongoing refinements in motor technology are making it simpler to deploy dust-tight, washdown motors, the basics covered by IP66 protection, in new designs. But avoiding problems, especially in higher-volume applications, requires careful engineering, understanding how manufacturers are protecting the motors and the issues that could become problems for specific applications.
IP66 provides "ingress protection" in two areas: motors that are totally protected against dust and protection against strong jets of water. The IP67 standards move a step further to motors that are being submerged in water.
"I tell customers that if you want washdown capabilities you want IP66," says Seth Hulst, engineering manager for Groschopp. "Even though the word 'washdown' is not in the standard, that is what people think of it as."
Hulst says standard off-the-shelf catalog motors are commonly IP44, and it is a big step to move to IP66 since there are many joints and mating parts where water and dust can get inside the motor. The obvious areas that need to be addressed are the shaft and the electrical connections for the motor.
To make a motor design rated for IP66, selecting the sealed bearings and the type of seals for the shaft is probably the most important area. Motor manufacturers look at the joints between the bearing and the housing, and the bearing and the shaft. If there is a good press fit, that's acceptable; but typically both races of the bearings can't be press fit so there's a need to seal one of those surfaces.
Some manufacturers use sealants but Groschopp specifies O-rings because they make the motor more serviceable, easier to upgrade and provide more control over the amount of sealing material.
"One of the things we look at is the thermal expansion and what the motor does when it heats up," says Jared Birk, senior electrical engineer for Groschopp. "All of the components expand at different rates, but with an O-ring you know exactly how much rubber there is and you know exactly what the diameter is. You also know what your O-ring groove is, and you can verify that the motor is going to seal both when it is cold and when it is hot."
The single biggest application issue for IP66 motors is a caustic chemical environment, which usually requires a careful review of materials. "The standard IP66 that we offer and that everyone else offers is designed more for water," says Hulst. If the customer has a caustic chemical environment, the motor has to be designed into the application because there are so many different types of chemicals. The customer might know what types of materials work well, and the motor designer has to figure out how to incorporate those materials into the motor.
Hulst says some engineers don't think a fan-cooled motor can be IP66, but that's really not true. With the Groschopp IP66 fan-cooled design, the motor has an extruding housing with cooling channels incorporated into it which have been defined by the motor testers as being outside of the motor. The design basically allows the water and dust to go through the cooling channels.
A final important area is testing. Groschopp IP66 permanent magnet dc series motors have been subjected to rigorous hot/cold tests where the motor is heated to 250F and then immediately submerged into an iced water bath at 33F. But even with these temperature extremes and submersion, post-test evaluations of the seals revealed no water ingress or performance issues.
Click here for OEM Reference Data on Ingress Protection (IP) for motors.
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