Ambient Operating Temperature
Ambient surrounding environmental factors are important to consider when you select a gear drive. What is the maximum ambient operating temperature for a prolonged period of use? A gear drive for an outdoor project in the desert will need to accommodate a higher ambient temperature than a gear drive in icy Northern Canada.
Ambient Air Velocity
It’s important to consider the ambient air velocity as well. A gear drive in a confined area like a factory space may run hotter than a gear drive in the open air. On a conveyer in the outdoors, your gearbox can benefit from natural wind fields (if they’re present) to cool the drive.
In many drive components, there are shaft-attached fans available. These fans work simply and effectively. A fan is affixed to the high-speed shaft, as the motor spins the shaft the fan also spins. The fan blows air over the drive, cooling it down during operation (and improving the thermal rating of the drive).
The man drawback of shaft fan cooling is it’s only so effective. The fan is only capable of blowing so much air to bring down the temperature. Its effectiveness is also tied to the motor speed, so gearboxes with lower input speeds will not benefit as much.
Another option for cooling your gearbox is to add tubes inside the gear drive and pump water through the tubes. As oil heats up, the cool water inside the tubes pulls heat out of the oil sump. While this is a very effective solution, it requires careful engineering to ensure constant access to cool water and to prevent corrosion of the tubes, among other issues. Any leaks in the tubes could quickly contaminate the gearbox oil with water.
Another options for cooling down a gearbox is to use an external shell and tube heat exchanger. This oil-to-water cooling option offers similar benefits to direct water-cooling, without the need to run the water directly through the gearbox.
The drawback of this cooling method is that you need to ensure constant access to cool water, similar to direct water-cooling. You also need to run oil through a pump to the external heat exchanger, which means adding a pump to your gear drive. The pump requires using a separate motor, which creates another point where the gear drive may fail. You also must run electricity to the pump motor—often at a different voltage than the main gearbox motor.
Depending on your application, water accessibility, and external thermal factors, any of these gear drive cooling solutions may be effective. The objective is always to find the most efficient cooling solution with the fewest points of failure, requiring the lowest maintenance.