Heed Drive-Belt Temperature Limits

By Jim Seffrin, Infraspection Institute

Temperature is frequently used to gauge the condition of motors and power-transmission equipment. The following information applies to flexible drive belts and the temperature limits for them.

Drive belts are an integral component on many types of machines. Despite the critical role they play in machine operation, V-type drive belts tend to be out of sight and out of mind until they fail. In most installations, belt temperature largely influences the life of installed V belts.

As a rule of thumb, properly applied and maintained belts should not exceed 140 F (60 C), assuming an ambient temperature of less than 110 F (43 C). Belt life can be greatly reduced by higher operating temperatures. In fact, for every 18 F-deg. (10 C-deg.) increase in belt temperature, belt life is cut in half. Keeping this in mind, we can see that the life of a drive belt operating at 176 F would be reduced by 75%.

Thermogram shows overheating V-belts. Note castoff in the control photo. Images courtesy of Skip Handlin.

Many factors contribute to high belt-operating temperature, including, but not limited to, ambient air temperature, machine design, installation, alignment, and belt tension. Overheating belts that afford line-of-sight access can be readily detected and documented with an infrared imager.

Issues associated with overheating in drive belts may not be limited to the belts themselves, however. With regard to over-tensioned drive belts, excessive force applied to belts is often transferred to bearings in the driven system. In these situations, it’s not uncommon to see bearings overheat due to the excess force created by the over-tensioned belt(s).

Thermogram shows the effects of an improperly tensioned V-belt. In this example, over-tension causes both the belt and adjacent pillow block bearing to run hot.

It should be noted that the operating temperature of overheating drive belts is not necessarily linear. A worn belt that has reached critical temperature will begin to wear at an accelerated rate, which, in turn, will cause the belt to run hotter and wear even more quickly. This vicious cycle will continue until the belt either breaks or fails to perform its intended task.

Once detected, overheating belts should be investigated for cause and proper corrective measures undertaken as soon as possible. Doing so can help prevent unscheduled downtime and may prolong belt life.

Thermal imaging offers several distinct advantages over other types of inspections for belted systems. Thermal imaging is non-contact and nondestructive. Imaging is performed remotely and requires no shutdown of inspected systems. Because infrared imagers produce real-time data, results are instantaneous and allow rapid inspection. MT

Jim Seffrin, a practicing thermographer with 30+ years of experience in the field, was appointed to the position of Director of Infraspection Institute, Burlington, NJ, in 2000. This article is based on one of his “Tip of the Week” posts on IRINFO.org. For more information on infrared applications, as well details on various upcoming training and certification opportunities, email jim@infraspection.com or visit infraspection.com.