Machine Design
Explosionproof custom motor keeps sight glass clean

Explosionproof custom motor keeps sight glass clean

Explosionproof custom motor keeps sight glass clean

The wiper assembly for clearing the inside of the sight glass on reactor vessels includes a MICROMO motor and a camera and lights. The 9-W motor is 75% efficient and is housed in an explosionproof casing.

Sight glasses built by the Lumiglas Div. of Papenmeier GmbH & KG in Germany rely on custom-built motors from MICROMO’s Faulhaber Group affiliate in Europe to power wipers that keep the glasses clean. The devices are often installed on large reactor vessels so technicians and supervisors can visually check on processes and cameras can record the action. The MICROMO motor is small enough that it does not block the view but generates enough torque to turn the wiper as it is pushed against the glass. But the motor also had to be explosionproof as volatile gases could be present.

So MICROMO housed its motors inside a custom-made pressure-resistant casing. Other methods of making the motor explosionproof — oil immersion and encapsulation — were not viable with the dc motor. The casing was designed to withstand Class IIC explosions and T5 temperatures. The feed-through on the casing for the motor shaft carries an IP54 rating, while the motor, which can be remote controlled, carries an IP68 rating.

Even with the casing, the 9-W motor measures only 80-mm long with a 35-mm diameter. Attaching a planetary gearhead boosted torque to 10 Nm while only adding another 64 mm to the length. MICROMO also increased the thermal protection on the motor by installing a pair of thermal fuses. One is redundant and lets the motor operate even if the first fuse triggers.


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