Electrical Testing
Tip of the Week: Cool Runnings

Tip of the Week: Cool Runnings

Thermographers provide the data that help you solve motor heating problems most effectively

In our previous article, we looked at the "why" for ventilating motors and saw that thermal imaging lets you avoid guesswork. Now let's look more closely at the "how" part of the plan.

Let’s suppose you’ve replaced the main motor of a process machine several times. Let’s say it’s a hot process (e.g., extrusion of some sort). This means there are sources of heat all around the motor. You know the motor failures were heat-related, partly because it’s so darn hot where that motor sits and partly because the motor repair shop examined a couple of these and reported definite signs of overheating.

Your plant has been very good at “saving money,” so instead of owning a thermographic camera, your maintenance department owns a few contact thermometers.

The motor is situated with one side of the housing facing the aisle and most of its body tucked into the machine. You took readings around the motor and verified that it’s about 150°F in the air on the machine side of the motor and about 120°F on the aisle side. The motor itself is blocking airflow to where cooling air is most needed. A pocket of hot air behind it is keeping the motor from dissipating enough heat.

To solve this problem, you route flexible metal ductwork to the machine side of the motor the next time the machine is down for servicing. The plant manager congratulates you on how neat it looks, all tucked in there and nicely secured.

After the machine has run for a while, you go back out there with your trusty (but cheap) thermometers and see you’ve dropped that machine side temperature to about 145°F. How can this be?

Let’s change the scenario a bit. Your plant has been very good at reducing costs by investing in the test equipment needed for maintenance. Your only problem in this case is deciding which of your thermographic cameras to use.

Your Level II thermographer performs a thermographic survey all around that machine and then presents you with a series of composite heat maps. From these, you decide the best routing for that cooling duct. And that’s really good, because it means you’re going to avoid running that duct over a set of cooling fins that would heat up the “cool” supply air.

The plant manager looks through the thermographic camera and sees the machine side temperature of the motor is about 80°F. He asks if you can duct supply air to the front, as well.

Avoiding heat sources when ducting in cooling air is just an example of how you can use thermography to figure out the “how” when solving a motor heating problem.

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