Choosing a Falk gearbox is no simple task. Dozens of variables must be taken into consideration. A single incorrect calculation can cause costly damage, particularly in the case of thermal horsepower. Thermal horsepower is the actual horsepower (without the service factor) that a drive is able to convey constantly for three or more hours without overheating. Sometimes thermal horsepower is referred to as “true motor load.” It is a key consideration because a drive that creates heat faster than it can be released is bound to suffer severe damage. In today’s blog we’re defining thermal horsepower and explaining why this is such a key element in gearbox selection.
What is Thermal Horsepower, and Why is it Important in Gearbox Selection?
As mentioned above, thermal horsepower describes how much power a gearbox can pass on without overheating when operating non-stop for three hours or more. To be even more specific, this rating describes the amount of work that a drive can perform when working at sea level, at 100° F ambient temperature. (At higher elevations overheating will occur more rapidly.) Another helpful measurement is gear drive operating temperature. Overheating is imminent when sump oil temperature exceeds 200° F.
Exceeding a gearbox’s thermal horsepower rating causes lubrication to overheat. In turn, this can cause gear pitting; rough, discolored bearings; noisy, hot operation; and, sooner or later, failure. As such, engineers must remember to include thermal horsepower in their calculations for gearbox selection. Doing so can prevent the need for costly gearbox replacement and repair.
Offsetting Excessive Heat Caused by High Thermal Horsepower
It is not unusual for a motor’s nameplate rating to exceed the reducer’s thermal horsepower. For instance, let’s say that reducer’s mechanical horsepower rating is 13 HP at 875 RPM, but its thermal horsepower rating at the same speed is 10 HP. In this circumstance, an engineer would require an additional cooling mechanism, such as a shaft-driven fan, to prevent overheating. Oil circulation systems are another cooling approach; they circulate cool oil through the gearbox, and work especially well in locations where the ambient operating temperature is lower than around the gear drive.
With all this said, thermal horsepower isn’t as crucial when lines aren’t running continuously for three hours or more. For example, the gearboxes used in theaters don’t require thermal horsepower calculations because those drives are used only for short bursts.
Ultimately, the operating temperature of a gearbox goes a long way in determining its lifespan. Anything that causes excessive heat will also cause damage and limit efficiency. If you’re looking for expert advice on including thermal horsepower and other key variables in your Falk gearbox selection, call Mar-Dustrial. We’ve been selling and repairing Falk gearboxes for industrial settings for almost thirty years, so we can help you select the best gearbox for your line.
Posted under Tips and Tricks on Monday, June 29th, 2015